191 REVIEW ARTICLE Use of Dapsone in the Prevention and Treatment of Pneumocystis carinii Pneumonia: A Review Walter T. Hughes From the Department of Infectious Diseases, St. Jude Children’s Research Hospital, Memphis, Tennessee Since 1984, when dapsone was first found to have activity against Pneumocystis carinii [1], ú200 publications have addressed the use of this drug in the prevention and treatment of P. carinii pneumonia (PCP). Reports have been limited almost exclusively to clinical studies of patients with HIV infection and to experimental studies of the corticosteroid-treated rat model. These investigations have been adequate to give a reasonable perspective on the use of dapsone in the management of PCP, especially for prophylaxis. The purpose of this article is to review all publications, as well as studies presented at national and international meetings, and to provide pertinent information on the use of this drug for PCP in the immunocompromised host. Antimicrobial Activities of Dapsone Dapsone-USP, 4-4*-diaminodiphenylsulfone, is a synthetic sulfone with bactericidal and bacteriostatic activity against Mycobacterium leprae and is effective in the treatment of patients with leprosy. It is also active in high concentrations (§10 mg/mL) against Mycobacterium tuberculosis and several other species Received 31 October 1997; revised 20 February 1998. Financial support: National Cancer Institute (P01 CA-20180 and P30 CA21765), National Institutes of Allergy and Infectious Diseases (Pediatric ACTG, U01 AI32908), and the American Lebanese Syrian Associated Charities. Reprints or correspondence: Dr. Walter T. Hughes, 332 North Lauderdale, Memphis, Tennessee 38105. Clinical Infectious Diseases 1998;27:191–204 q 1998 by the Infectious Diseases Society of America. All rights reserved. 1058–4838/98/2701–0035$03.00 / 9c51$$jy36 06-16-98 00:27:17 of mycobacteria, including Mycobacterium avium complex. In combination with pyrimethamine, dapsone has been used successfully as chemoprophylaxis for malaria due to chloroquineresistant Plasmodium falciparum and Plasmodium vivax. With or without trimethoprim (TMP) or pyrimethamine, dapsone has been shown in animal and human studies to effectively prevent and treat PCP. Some evidence suggests it has activity against Toxoplasma gondii. Mechanisms of Action Dapsone was first synthesized from para-chloronitrobenzene in 1945 [2] and first marketed in the United States in 1957. The drug is an analog of para-Aminobenzoic acid and acts through the inhibition of folic acid synthesis in susceptible organisms. It is an inhibitor of the dihydropteroate synthetase of P. carinii. Voeller et al. [3] found that a 1.5-mM concentration of dapsone inhibited 50% of P. carinii dihydropteroate synthetase activity. In another study, 0.4 mM of dapsone was effective when tested in an in vitro culture [4]. Dapsone may conceivably affect P. carinii infection by mechanisms other than intervention with folic acid synthesis. In vitro studies have shown that dapsone stimulates neutrophil motility. In a clinical study of healthy individuals [5], dapsone mediated stimulation of polymorphonuclear leukocyte migration. This was related to inhibition of the peroxidase-H2O2halide system in vitro. Other studies indicate that dapsone may inhibit the alternate pathway of complement activation and interfere with the myeloperoxidase-H2O2-halide-mediated cytotoxic system within neutrophils. A recent study of AIDS cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 Dapsone, with or without trimethoprim or pyrimethamine, has strong anti-Pneumocystis carinii activity, as demonstrated by in vitro methods, animal studies, and clinical trials. The drug blocks folic acid synthesis of P. carinii by inhibition of dihydropteroate synthetase activity. Dapsone is efficiently absorbed (70% – 80%) from the gastrointestinal tract, reaches peak serum concentration in 2 – 6 hours, and is adequately distributed to the fluid of the alveolar spaces. Synergistic effects against P. carinii are noted when trimethoprim is combined with dapsone. This combination is recommended for therapeutic use for P. carinii pneumonia (PCP) as an alternative for patients who cannot take trimethoprim-sulfamethoxazole (TMP-SMZ). Evidence from more than 40 studies of dapsone as prophylaxis for PCP in AIDS patients shows that dapsone, either alone or in combination with pyrimethamine, is as effective as aerosolized pentamidine or atovaquone but slightly less effective than TMP-SMZ. Adverse effects include rash, anemia, methemoglobinemia, agranulocytosis, and hepatic dysfunction. Desensitization can be accomplished with many cases. Dapsone is the most cost-effective prophylaxis currently available for PCP. 192 Hughes Metabolism and Pharmacokinetics At least two major metabolites come from biotransformation of dapsone: monoacetyl dapsone (MADDS) and dapsone hydroxylamine. Neither contributes to the therapeutic affect of the drug. Dapsone is acetylated to MADDS by N-acetyltransferase in the liver. MADDS may also be acetylated to dapsone, and an equilibrium may be reached within a few hours after administration. There are no significant differences between slow and fast acetylators in the frequency and type of side effects, plasma concentrations, and therapeutic efficacy in nonPCP conditions. The second major metabolite is N-hydroxylated to dapsone hydroxylamine in the liver by the mixed oxidase system in the presence of oxygen and NADPH. This metabolite has been associated with hematologic toxicity. / 9c51$$jy36 06-16-98 00:27:17 Dapsone is available in 25-mg and 100-mg tablets. No intravenous formulation has been developed for commercial use. In healthy adults dapsone is slowly but efficiently absorbed from the gastrointestinal tract, with 70% – 80% bioavailability in an acidic environment. Peak serum concentrations of 1.7 mg/mL to 1.9 mg/mL are achieved in 2 – 6 hours after a dose of 100 mg. The drug is well distributed throughout total-body water and all tissues. The plasma half-life may vary from 10 to 50 hours, with a mean time of 30 hours, for both dapsone and MADDS. About 70% – 85% of the drug is excreted in the urine. Enterohepatic circulation following biliary excretion of free drug also occurs, accounting for prolonged persistence in the plasma after drug administration is stopped [10]. In children with HIV infection, pharmacokinetic studies show that clearance (CL) and Vss (apparent volume of distribution of steady state) of dapsone are approximately twofold greater than in adults, while the t12 is comparable [11]. The dose of 2.0 mg/kg (not to exceed a total dose of 100 mg/d) administered at the same frequency used in adults may be used for prophylaxis for and treatment of PCP. Dapsone is readily soluble at normal acidic gastric pH and remains insoluble at neutral pH. Because some drugs given concomitantly with dapsone are absorbed best at alkaline pH, such as didanosine, concern has been expressed about the effect of alkalinization on the efficacy of dapsone [12]. In a prospective study in which volunteers were given 100 mg of dapsone plus Maalox C (Novartis Consumer Health, Summit, NJ), the antacid was found to facilitate rather than impair absorption of dapsone [13]. At present there are no sound data to suggest that clinicians need to modify the gastric acidity of patients during the use of dapsone. HIV-infected patients rarely receive dapsone without concomitant medications. The pharmacokinetic interactions of zidovudine, TMP, and dapsone in HIV-infected patients have been studied [14]. Zidovudine did not influence the pharmacokinetic profile of dapsone, and dapsone had no effect on the pharmacokinetic disposition of zidovudine. However, TMP decreased the renal clearance of zidovudine by 58%. There was also a concurrent 54% decrease in urinary recovery of zidovudine. The mean area under the concentration curve from zero to 6 hours of the zidovudine-glucuronide/zidovudine ratio was unchanged. The data indicate that zidovudine, TMP, and dapsone can be given concomitantly to AIDS patients without clinically significant interactions. However, with impaired liver function and impaired glucuronidation, the doses of zidovudine may need to be decreased. In Malaysian leprosy patients, rifampin was found to decrease the plasma t12 of dapsone by 22% – 83%, probably by enhancing hepatic clearance by induction of microsomal enzymes [15]. Because plasma concentrations of dapsone are 0.1 – 7.0 mg/mL with a dose of 200 mg and the MIC (in cell culture) is 0.1 – 10 mg/mL, the concomitant use of rifampin and dapsone could compromise the efficacy of the latter drug [16]. Population pharmacokinetics of dapsone were examined in cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 patients with and without PCP [6] compared the ability of their neutrophils to activate the respiratory burst. When stimulated with P. carinii, neutrophils from the patients with a history of PCP had a significantly lower response than those from the other groups studied. The in vitro experiments of Bozeman et al. [7] suggest that dapsone could prevent myeloperoxidase- and eosinophil peroxidase – mediated tissue injury at sites where the peroxidase enzymes are secreted and diluted into the neutral pH environment of the tissue interstitial space. However, dapsone did not inhibit peroxidase-mediated antimicrobial activity, occurring at high enzyme concentrations in the acid environment of the phagolysosomes. Whether or not dapsone affects neutrophil motility and function to the extent that a discernible therapeutic impact occurs is not known. Some in vitro studies suggest dapsone might have some effect on HIV replication [8]. In phytohemagglutinin P–activated HIV1-infected peripheral blood mononuclear cells, dapsone (2–10 ng/mL) decreased cell proliferation and HIV-1 replication. However, dapsone increased HIV-1 replication in peripheral blood lymphocytes and monocyte-derived macrophages. Dapsone metabolites are potent oxidants that induce glutathione consumption to counteract oxidative processes. It can be speculated that peripheral blood lymphocytes and monocyte-derived macrophages may be able to generate N-hydroxyl-dapsone metabolically upon exposure to dapsone. This may, in turn, induce a glutathione deficit in these cells and an oxidative exhaustion that leads to IL-2dependent proliferation of lymphocytes or enhancement of HIV replication, or both. Duval et al. [8] found these activating effects at concentrations from 1 ng/mL to 10 ng/mL. Dapsone serum concentrations in HIV-infected patients given the drug range from 1.5 ng/mL to 4.2 ng/mL [9]. As with many drugs, the activity of dapsone may not be limited to its effect on a single target in cell replication. Its effect on the dihyhdropteroate synthetase of P. carinii is established. It seems reasonable to expect the anti-inflammatory activity demonstrated in cases of leprosy, dermatitis herpetiformis, and other conditions would also occur in cases of PCP. CID 1998;27 (July) CID 1998;27 (July) Dapsone and P. carinii Pneumonia / 9c51$$jy36 06-16-98 00:27:17 for once-a-week dosing of dapsone for PCP prophylaxis. Unfortunately, no studies of dapsone combined with TMP in weekly doses have been performed. Experimental Studies in Animals Because of the remarkably high incidence of naturally acquired P. carinii infection in rats, the administration of corticosteroid immunosuppression for 4 – 6 weeks or longer results in the provocation of extensive P. carinii pneumonitis from the latent infection in 70% – 100% of animals. This experimental animal model has been used to screen and identify drugs for anti – P. carinii activity [21, 22]. Almost without exception, drugs found effective in rat studies have been effective in humans with PCP. In 1984, Hughes and Smith [1] screened several drugs and found that a 25-mg/(kgrd) dosage of dapsone was totally effective in preventing P. carinii infection. Dapsone was then evaluated at dosages of 5, 25, and 125 mg/(kgrd) and compared with TMP-SMZ given at 50/250 mg/(kgrd) orally. The two highest dosages of dapsone and TMP-SMZ prevented the infection in 100% of animals, and the lowest dosage of dapsone (5.0 mg/[kgrd]) prevented it in 40% of all rats. All of the untreated control animals developed PCP. Therapeutic efficacy was determined by allowing animals to develop extensive PCP and then initiating drug therapy. Based on the extent of residual pneumonitis at the completion of treatment, the frequency of PCP was reduced to 50% by TMP-SMZ and to 25% by dapsone, while all of the untreated controls had extensive PCP. In later studies [23] the efficacies of TMP-SMZ, TMP/dapsone, dapsone, and pentamidine were compared for the prevention of PCP in the corticosteroid-treated rat model. While 11 (73%) of 15 untreated control animals had PCP after 10 weeks of immunosuppression, none of the animals given 125 mg of dapsone per kg daily, weekly, biweekly, or monthly had evidence of infection. Of the 10 rats given a single dose of dapsone 23 and 50 days after immunosuppression was started, five (50%) developed P. carinii pneumonia. When three drugs were given separately to groups of 10 rats in single doses every other week, PCP occurred in 40% of those treated with TMPSMZ, in none of those treated with TMP/dapsone, and in all of those given pentamidine. The experiments showed that dapsone is highly effective in chemoprophylaxis for PCP when given at monthly intervals or more frequently and that dapsone and TMP/dapsone are more effective than TMP-SMZ when given at biweekly intervals. It seems reasonable to expect that at least weekly or even biweekly doses of dapsone or TMP/dapsone would provide an effective and reasonably safe chemoprophylaxis regimen for patients at high risk for PCP. Separate studies of dapsone in the rat model [24, 25] and in a mouse model of severe combined immunodeficiency [26] have also shown dapsone to have potent anti – P. carinii activity. Walzer et al. [27] found dapsone alone to be effective in cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 HIV-infected patients receiving 100 mg of dapsone twice weekly. Rifampin was found to increase the values of clearance/bioavailability (CL/F) and volume of clearance/bioavailability (V/F) by Ç70% (CL/F and V/F were 1.83 L/h and 69.6 L, respectively, in those not taking rifampin) [17]. In AIDS patients successfully treated for PCP, the mean peak dapsone level of 2.1 mg/mL was achieved 6 hours after administration of TMP/dapsone [18]. Dapsone and TMP plasma concentrations were both higher when the drugs were given concomitantly than when given separately. Plasma concentrations of dapsone were 40% higher in patients treated with TMP/dapsone than in those treated with the same dose of dapsone alone (2.1 mg/mL vs. 1.5 mg/mL). The concentration of TMP was 45% higher in patients treated with TMP/dapsone than in those treated with TMP-sulfamethoxazole (SMZ) (18.8 mg/mL vs. 12.4 mg/mL). In a subsequent study the same authors were not able to demonstrate increased concentrations when these drugs were given concomitantly [14]. However, the former study evaluated a larger group of patients receiving treatment for PCP, while the latter study involved only six asymptomatic patients. Until more definitive data are available, the extent of drug interaction is unclear. One can conclude at least that no antagonistic effects are at play. Because infection with P. carinii and the disease it causes are located almost exclusively in the lung, it is critical that drug activity and concentration be maximal in the lung parenchyma and alveolar space. Cruciani et al. [19] studied the penetration of dapsone into epithelial lining fluid of HIV-infected patients receiving prophylaxis with dapsone (100 mg twice weekly). The bronchoalveolar lavage (BAL) fluid and plasma samples were studied for dapsone concentrations. The mean concentrations in BAL fluid at 2, 4, 12, 24, and 48 hours after the dose of 100 mg were 0.9, 0.7, 1.55, 0.23, and 0.45 mg/L, respectively. These concentrations were 76%, 79%, 115%, 65%, and 291% respectively, of those observed in plasma at the same times. This study suggests that dapsone is well distributed into the epithelial lining fluid and that administration of 100 mg of dapsone twice a week provides sustained concentrations in the tissue compartment. The pharmacokinetics and safety of weekly dapsone and dapsone plus pyrimethamine in adults with AIDS were studied [20]. Of three doses — 100 mg, 200 mg, and 300 mg of dapsone weekly — 200 mg weekly was established as the maximum tolerated dose. This dose was then found to be well tolerated in combination with pyrimethamine (25 mg). In another study [9], median plasma concentrations of dapsone and pyrimethamine during day 1 after ingestion of 200 mg of dapsone and 75 mg of pyrimethamine were 1.04 mg of dapsone and 0.36 mg of pyrimethamine per mL. By day 6 – 7 the dapsone concentration decreased to õ20 ng/mL, but the pyrimethamine level remained elevated at 0.13 mg/mL. Concurrent administration of didanosine did not decrease the drug concentrations. These data tend to support the potential 193 194 Hughes murine PCP and that Ro 11-8958, an analog of TMP, enhanced the efficacy of dapsone. In an animal model with dual infections of PCP and toxoplasmosis, Brun-Pascaud et al. [28] found the drug combination of pyrimethamine (3 mg/kg) plus dapsone (25 mg/kg or 50 mg/kg) administered daily totally prevented both infections. In another study, a diformyl derivative of dapsone, 4-4*-sulfonylbisformanilide, was found to have efficacy equal to that of dapsone [29]. This compound has not been evaluated in clinical trials for PCP. Clinical Trials: Treatment / 9c51$$jy36 06-16-98 00:27:17 Although the numbers of patients studied were small, the 100% successful response rate with dapsone/TMP suggested the combination was more efficacious than dapsone alone (61% successful response rate). Furthermore, it is noteworthy that major toxicity was noted in none of the patients treated with dapsone alone, in 13% of those treated with dapsone/TMP, and in 51% of recipients in the comparable study with TMP-SMZ. Whether or not TMP plays a role in the toxicity profile is not known. Such a role might come from a direct adverse effect of TMP or might be due to an associated increase in the plasma concentration of dapsone, as shown in one of the studies by Lee et al. [14] and discussed herein in the section on metabolism and pharmacokinetics. In a small randomized (2:1) double-blind study [32], 18 HIV-infected patients with moderate or severe PCP (D[A-a] O2 of 35 – 55 mm Hg) received either trimetrexate, leucovorin, and dapsone or TMP-SMZ. Ten (77%) of the 13 patients given trimetrexate/leucovorin/dapsone and 3 (60%) of the 5 treated with TMP-SMZ had responded favorably by day 21 of treatment. Adverse reactions occurred in 85% and 80% of the patients, respectively. In 1991 Safrin et al. [33] concluded that a high-dose, singleagent regimen of dapsone was not suitable for further study or as therapy for PCP and that this therapy should not be clinically employed. Their study was a prospective one of seven patients with mild PCP. Patients were treated with 200 mg of dapsone daily. None of the seven patients successfully completed a full course of treatment with dapsone; two patients died, and four experienced major side effects. There was no explanation for these poor responses in comparison with those in other studies. In 1996 a randomized, double-blind study (ACTG [AIDS Clinical Trials Group] 108) was reported by Safrin et al. [34] that involved 181 AIDS patients with cytologically documented PCP, who were randomized to receive treatment with one of three drug regimens: dapsone plus TMP, TMP-SMZ, or clindamycin plus primaquine. Dapsone was used at a dosage of 100 mg/d. Treatment was given over a period of 21 days. The results showed no significant differences among the groups with respect to therapeutic failure (P ú .2), survival during therapy or for 2 months thereafter (P ú .2), and treatmentlimiting toxicity (P Å .2) (figures 1 and 2). However, elevation of serum aminotransferase levels to more than five times the baseline levels was more frequent in the TMP-SMZ group (P Å .003), and one or more serious hematologic toxic effects (neutropenia, anemia, thrombocytopenia, or methemoglobinemia) occurred more frequently in the clindamycin/primaquine group (P Å .01). Of the 8 deaths (4.4%) during the 81-day period of observation, 4 were in the TMP-SMZ group, 2 in the dapsone/ TMP group, and 2 in the clindamycin/primaquine group. While this is the largest trial evaluating the therapeutic efficacy of dapsone, the limited sample size prevented unequivocal demonstration of the equality of these three regimens. Several single case reports describe the successful treatment of PCP with dapsone, with and without TMP [35 – 38]. At cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 The first clinical trials to evaluate dapsone in humans with PCP were done in 1984 and 1985. The plan was to first evaluate dapsone plus TMP in an open-label study for efficacy in the treatment of PCP. If this was successful a second study would be undertaken with dapsone alone. This approach stemmed from the animal studies showing the combination of dapsone/ TMP to be more effective than dapsone alone [21]. The initial study by Leoung et al. [30] included adult patients with AIDS and first-episode PCP at the San Francisco General Hospital between November 1984 and April 1985. Dapsone (100 mg/d) and TMP (20 mg/[kgrd]) were given orally. Fifteen patients were studied. The pretreatment arterial oxygen tension ranged from 48 to 82 torr (median, 68.1 torr) in 14 of the patients, and one patient’s value was 104 torr. The conditions of all 15 patients improved clinically and radiographically within 3 – 10 days after the start of dapsone/TMP therapy. Continued improvement was noted at the end of 3 weeks of treatment. Fourteen of the patients had adverse reactions (nausea and vomiting in 6, maculopapular rash in 8, decrease in hematocrit (ú5%) in 7, neutropenia in 1, and thrombocytopenia in 1). Two patients had to be withdrawn from the therapy because of rash. Six patients had an increase in hepatic transaminase levels. The observed 100% initial response rate (95% CI, 78% – 100%) and 87% overall efficacy (95% CI, 58% – 98%) were equal to or better than the values noted in a comparable study with TMP-SMZ and pentamidine. Because of the success of the initial study with use of both dapsone and TMP, the second planned study was undertaken to evaluate dapsone alone [31]. As shown in animal studies, the single-drug therapy was effective but not as effective as the combination. The 18 patients with AIDS and PCP admitted to San Francisco General Hospital between April 1985 and July 1985 were given dapsone (100 mg/d) orally for 21 days. The conditions of 7 (39%) of the 18 patients worsened during dapsone therapy, and these cases were considered treatment failures; the conditions of the remaining 11 (61%) improved within 3 – 10 days after administration of dapsone was started. Adverse reactions were noted in 6 of the 11 patients whose dapsone therapy was maintained (rash in 6 patients and abnormal liver enzyme levels in 2). However, no toxic effect necessitating termination of treatment occurred. CID 1998;27 (July) CID 1998;27 (July) Dapsone and P. carinii Pneumonia present one may conclude that dapsone, with or without TMP, is effective in the treatment of PCP, but the drug combination is most effective. TMP/dapsone is probably similar in efficacy to TMP-SMZ for mild and moderately severe PCP. Dapsone alone is not indicated for treatment. Some but not all patients who have experienced adverse reactions to TMP-SMZ will be able to tolerate TMP/dapsone. once a day orally; (2) dapsone, 50 mg daily, plus pyrimethamine, 50 mg once a week, and leucovorin, 25 mg once a week orally; or (3) dapsone, 200 mg, plus pyrimethamine, 75 mg, and leucovorin, 25 mg once a week orally. The dapsone dose recommended as PCP prophylaxis for children is 2.0 mg/(kgrd), not to exceed 100 mg daily. In the early years of the AIDS epidemic, before PCP prophylaxis became established as standard practice, PCP occurred in 80% of persons with AIDS and was the AIDS-defining illness in ú60% of patients [83]. Effective chemoprophylaxis and more effective primary treatment for HIV infection have brought about an impressive reduction in PCP among patients with HIV infection. Unfortunately, despite these effective prophylactic regimens, PCP continues to be a significant opportunistic infection in AIDS. A longitudinal cohort study in the Multicenter AIDS Cohort Project, reported in 1995 [84], identified factors associated with failure of PCP prophylaxis in patients prescribed TMP-SMZ, dapsone, or aerosolized pentamidine. The main predictor of failure of prophylaxis was profound lymphopenia affecting CD4/ lymphocyte counts. Of the 476 patients receiving prophylaxis, 92 (19%) had breakthrough PCP. PCP occurred more rapidly among patients receiving aerosolized pentamidine (14.5% of patients per year) and dapsone (13.5% per year) than among those given TMP-SMZ (9.8% per year) as the initial regimen. Although more than 40 studies involved the use of dapsone as prophylaxis for PCP, these investigations have varied greatly Clinical Trials: Prophylaxis The greatest use of dapsone in the management of PCP has been as prophylaxis for patients at high risk for this infection. The efficacy demonstrated in animal studies has also been demonstrated in at least 41 clinical trials involving HIV-infected individuals (table 1). Two major advantages of dapsone are its long halflife, allowing infrequent dosing, and low cost. Some evidence suggests dapsone in combination with pyrimethamine may prevent mycobacterial infections [81] and toxoplasmosis [62]. Efficacy with regard to the successful prevention of PCP has been demonstrated in clinical trials of four drugs: TMP-SMZ, dapsone, aerosolized pentamidine, and atovaquone. TMP-SMZ is considered the first choice for those who can tolerate the drug. Dapsone was recommended in the ‘‘1997 USPHS/IDSA Guidelines for the Prevention of Opportunistic Infections in Persons Infected with Human Immunodeficiency Virus’’ [82] for those who are unable to take TMP-SMZ. The dosage schemes suggested are: (1) dapsone, 50 mg b.i.d. or 100 mg / 9c51$$jy36 06-16-98 00:27:17 Figure 2. Time until dose-limiting toxicity, according to treatment regimen for Pneumocystis carinii pneumonia. Logrank test, P ú .2. TS Å trimethoprim-sulfamethoxazole; DT Å dapsone/trimethoprim; CP Å clindamycin/primaquine. Figure reprinted from [34] with permission. cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 Figure 1. Time until therapeutic failure, according to treatment regimen for Pneumocystis carinii pneumonia. Logrank test, P ú .2. TS Å trimethoprim-sulfamethoxazole; DT Å dapsone/trimethoprim; CP Å clindamycin/primaquine. Figure reprinted from [34] with permission. 195 196 Hughes CID 1998;27 (July) Table 1. Data from dapsone prophylaxis studies described in the literature. Percentage of patients with Prophylaxis Reference, year, type of study [39], 1984, PO [40], 1989, CR [41], 1989, PO [42], 1990, PO [43], 1990, RO [45], 1991, RO [46], 1991, O [47], 1991, RO [48], 1991, PO [49], 1991, O [50], 1991, PO [51], 1991, RO [52], 1992, RO [53], 1992, CR [54], 1992, RO [55], 1992, PO [56], 1992, RO [57], 1992, PO [58], 1993, RO [59], 1993, CR [60], 1993, RO [61], 1993, RO [62], 1993, RO Dapsone TMP-SMZ None Dapsone None Dapsone Dapsone Dapsone Dapsone Dapsone Dapsone Dapsone / Pyrimethamine Dapsone Expected Dapsone Pentamidine (a) Dapsone Dapsone Dapsone / Pyrimethamine Dapsone Dapsone / Pyrimethamine Dapsone None Dapsone Fansidar Dapsone Pentamidine (a) Dapsone TMP-SMZ Pentamidine (a) Dapsone Prior TMP-SMZ: With AEs Without AEs Dapsone / Pyrimethamine TMP-SMZ Dapsone TMP-SMZ Dapsone / Pyrimethamine Pentamidine Dapsone / Pyrimethamine TMP-SMZ Dapsone Dapsone / Pyrimethamine Pentamidine (a) TMP/SMZ Dapsone Pentamidine (a) Dapsone / Pyrimethamine Pentamidine / 9c51$$jy36 Dosage* No. of patients 100 mg/d Daily ... 100 mg/w ... 50 – 100 mg/d 50 mg/d 100 mg/d 100 mg/w 200 mg/w 300 mg/w 200 mg/w 25 mg/w 100 – 300 mg/w (Calculated) 100 mg 2 1 w 400 mg/m 100 mg 2 1 w 200 mg/w 200 mg/w 25 mg/w 100 mg 2 1 w 100 mg 2 1 w 25 mg 2 1 w 50 mg 2 1 w ... 50 mg/d 500 mg 1 1 w 100 mg 2 1 w 400 mg/mo 50 mg/d 31w 300 mg/mo 100 mg 3 1 w 100 mg 3 1 w 25 mg 3 1 w 312 100 mg/d Daily 100 mg/w 25 mg/w 300 mg/mo 100 mg/w 25 mg/w 31w 100 mg 3 1 w 100 mg/w 25 mg/w 300 mg/mo 31w 100 mg 2 1 w 100 mg q2w 50 mg/d 50 mg/w 300 mg/mo 06-16-98 00:27:17 cida Time observed Break-through PCP AEs 173 48 23 16 46 24 20 10 5 7 9 5 9.4 mo 8.2 mo 9.6 mo ND 190 d 108 d 19 w 19 w ND ND ND ND 1 0 100 6.3 34.8 4 ND ND 4 0 0 0 10 38 ... ND ... 20 7 ND ND 23 ND ND 61 ... 50 46 22 23 22 9 mo ... 11.3 mo Same 34 w 40 w 37 w 2 23 16 15.2 4.5 4.3 4.5 13 ... 16 4 18 13 18 2.3 1.8 3.1 2.7 10 80 0 2 18 17 6.5 0 3.6 0 0 ... 10 10.8 12 17 55 55 2 33 128 109 12 – 18 mo 16 mo 10 10 65 51 50 46 77 133 125 79 12 mo 6 mo 6 mo 6 mo 18 mo 18 mo 5.7 mo 7.4 mo 9.3 mo 23 w 54 25 142 16 ND 12 ND 84 47 39 58 ND 862 pm 776 pm 21 mo 2 2 2 12 ND 70 64 ND 29 85 10 mo 380 d 2 15.3 ND 42 81 23 116 380 d 126 pm 304 d 3.7 14 6.9 67 39 7.8 108 107 126 152 173 299 339 42 43 539 4.6 2.8 18 14 5.8 1.09 9.0 10.7 2.0 24.3 176 Same 5.7 1.7 UC: CID d d w w d Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 [44], 1990, PO Drug CID 1998;27 (July) Dapsone and P. carinii Pneumonia 197 Table 1. (Continued ) Percentage of patients with Prophylaxis Reference, year, type of study [63], 1993, CR (children) [64], 1993, PR [65], 1993, CR [66], 1994, RO [69], 1995, RO [70], 1995, RO [71], 1995, RO [72], 1995, RO [73], 1995, CR [74], 1995, RO [75], 1995, RO [76], 1996, CR [77], 1996, CR [78], 1996, RO [79], 1997, RO [80], 1997, O Dosage* Dapsone Dapsone / Pyrimethamine Fansidar Dapsone / Pyrimethamine Pentamidine Dapsone / Pyrimethamine TMP-SMZ Pentamidine (a)/ Pyrimethamine Sulphamethopyrazine/ Pyrimethamine Dapsone Dapsone TMP-SMZ Pentamidine (a) Pentamidine iv Dapsone Pentamidine (a) Dapsone / Pyrimethamine TMP-SMZ Pentamidine (a) Dapsone / Pyrimethamine TMP-SMZ Dapsone / Pyrimethamine Pentamidine (a) Dapsone TMP-SMZ Pentamidine Dapsone TMP-SMZ Pentamidine Dapsone / Pyrimethamine TMP-SMZ Dapsone TMP-SMZ Clindamycin / primaquine Dapsone TMP-SMZ Pentamidine Dapsone / Pyrimethamine TMP-SMZ Dapsone Atovaquone Dapsone 1 mg/(kgrd) 100 mg 2 1 w 25 mg 2 1 w ND 100 mg/w 12.5 mg q4d 300 mg/mo 100 mg/w 25 mg/w 31w 300 mg/mo 25 mg daily 500 mg 2 1 w 25 mg 2 1 w 100 – 350 mg/w 1 mg/(kgrd) 31w 300 mg/mo 4 mg/(kgrmo) 50 mg/d 300 mg/mo 100 mg/w 25 mg q.o. w q.o.d. 300 mg/mo 100 mg 2 1 w 50 mg 2 1 w 31w 200 mg/w 75 mg/w 300 mg/mo ... ND ... 100 mg/d Daily 300 mg/mo 100 mg 2 1 w 50 mg 2 1 w 31w ND ND ND 50 mg/d Daily 300 mg/mo 100 mg 2 1 w 25 mg 2 1 w 31w 100 mg/d 1500 mg/d 50 mg/(m2rw) No. of patients Time observed 20 21 7.3 mo 12 mo 29 56 Break-through PCP AEs 12.5 9.8 15 9.5 14 mo 3.6 12.5 20 8.7 13 14 16 mo 11 mo 15.4 7 5.3 20 15 15 10 mo 11 mo 0 0 0 14 14 12 mo 0 21 52 71 225 76 48 93 103 63 25 w ND 6 21 6 20 25 5.7 11.7 14.3 4 ND ND ND ND 20 11.7 11.1 1.5 5.8 6.3 10.6 4.4 9 ND 0 4.1 10 30 242 45 178 253 288 276 278 105 505 d (per py) Same Same 36 mo (accumulated risk) Same Same 24 mo 5.4 13 9.8 14.5 17.5 18 21 9.4 4 ND ND ND 75 79 12 3 115 62 147 24 45 129 20 137 Same 63.4 py 176.2 py 22.8 py 418 pm 1110 pm 164 pm 20 mo 6.9 11.0 3.4 30.7 13 0.9 14 5.8 8 16 44 38 ND ND ND 8.5 157 521 536 32 20 mo (per 100 py) Same 1y 2.6 18.3 15.5 0 7 27.5 26.8 0 ND ND ND ND 12.4 mo 13.4 mo 160 d 66 68 96 275 211 d 430 d 104 291 449 d NOTE. AEs Å adverse events; C Å clinical; ND Å not determined or not reported; O Å open label; P Å prospective not randomized; PCP Å Pneumocystis carinii pneumonia; pm Å patient-months; py Å patient-years; R Å randomized. * TMP-SMZ dose: 160 – 320 mg of TMP and 800 – 1,600 mg of SMZ. / 9c51$$jy36 06-16-98 00:27:17 cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 [67], 1994, CR [68], 1994, CR Drug 198 Hughes / 9c51$$jy36 06-16-98 00:27:17 occurred in 55% of patients given 50 mg of dapsone daily, whereas in another study [39] only 10% of patients had adverse reactions when given double this dose (100 mg). However, general comparison of adverse reactions to dapsone and to other drugs can be made within each study. From review of all the studies (table 1), one can generally conclude that adverse reactions occur more frequently with dapsone than with aerosolized pentamidine and that no striking differences are seen between dapsone and TMP-SMZ. Some perspective on the relative efficacy of dapsone with respect to TMP-SMZ and aerosolized pentamidine can be gleaned from the studies reported. Among the 16 studies in which dapsone, with and without pyrimethamine, was compared with TMP-SMZ, the rate of break-through PCP was greater with dapsone in 11 of the studies [53, 55, 58, 60, 66, 68, 70, 71, 76 – 78], and in 5 [39, 56, 73 – 75] the break-through rates were similar. In 15 studies dapsone was compared with aerosolized pentamidine [45, 52, 53, 57, 60 – 62, 65, 68 – 70, 72 – 74, 77], and no statistically significant difference in rates of break-through PCP were discernible, although in one study [70] PCP occurred in 14.3% of those receiving dapsone and pyrimethamine and 5.8% of those receiving pentamidine. Salmon-Ce´ron et al. [69] found lower survival among AIDS patients taking dapsone than among those receiving aerosolized pentamidine for prophylaxis. This European study randomized 196 AIDS patients to receive either aerosolized pentamidine (300 mg monthly) or dapsone (50 mg daily). After a follow-up (mean { SD) of 13 { 6.4 months, the study was prematurely terminated because of excessive mortality in the dapsone group; 21% of the 103 patients in the pentamidine group vs. 42% of the 93 receiving dapsone had died. The mean CD4 cell count during the study was lower in the dapsone group. The dapsone preparation used in this study contained 200 mg of iron protoxalate per tablet. Weinberg [85] suggests the increased iron burden from this formulation might have contributed to the lower survival rate. He has shown that iron chelators inhibit the growth of P. carinii in cell culture and are effective in the treatment of PCP in animals [86, 87]. Bucker et al. [88] utilized a meta-analysis to examine the efficacy of dapsone (and dapsone plus pyrimethamine), TMPSMZ, and aerosolized pentamidine in patients with HIV infection. The analysis included 4,832 patients in 22 trials. For the 1,548 patients given dapsone, with or without pyrimethamine, and the 1,800 patients receiving aerosolized pentamidine, the risk ratio for PCP was 0.90 (95% CI, 0.71 – 1.15). For the 1,484 patients given TMP-SMZ vs. the dapsone group, the risk ratio of PCP was 0.49 (95% CI, 0.26 – 0.92). For TMP-SMZ vs. aerosolized pentamidine, the risk ratio of PCP was 0.59 (95% CI, 0.45 – 0.76). The report by El Sadr et al. [79] shows atovaquone to be as effective as dapsone in PCP prophylaxis. Future studies will place this drug in perspective for PCP prophylaxis. cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 in experimental design, dapsone dosages, and intervals of administration. Dosages ranged from 50 to 300 mg/d, with and without pyrimethamine, and at intervals from daily to weekly. Dapsone prophylaxis has been compared to that with TMPSMZ, aerosolized pentamidine, fansidar, clindamycin/primaquine, and atovaquone in retrospective and prospective studies and in randomized and nonrandomized studies. Unfortunately, no study has been blinded, and most of the studies have not had a sufficient number of subjects or time of observation to allow statistically sound conclusions to be drawn. In addition, studies of TMP plus dapsone, shown to be synergistic in animals [21], have not been done in humans. Instead, pyrimethamine has been used in combination with dapsone, intended in most studies to extend the spectrum of coverage to T. gondii. However, there are no studies and little rationale to suggest that TMP would be less effective than pyrimethamine in combination with dapsone against T. gondii. Only three studies have compared dapsone prophylaxis with no prophylaxis. None of these were randomized studies. However, these comparisons are convincing evidence of the anti–P. carinii activity of dapsone. Metroka et al. [39] found that 100% of 23 high-risk AIDS patients not given prophylaxis developed PCP over a period of 9.6 months, whereas only 2 (1.0%) of 173 patients given 100 mg of dapsone daily had PCP over the same period of time. Lucas et al. [40] noted PCP in 16 (35%) of 46 patients not receiving prophylaxis and in 1 (6.3%) of 16 patients taking 100 mg of dapsone once a week. Penco [50] reported the occurrence of PCP in 8 (80%) of 10 patients not receiving prophylaxis during a 6-month period, while only 1 (10%) of 10 AIDS patients given 50 mg of dapsone twice weekly had PCP during a 12month period of observation (table 1). There are no conclusive data to support or to discount the use of pyrimethamine with dapsone as prophylaxis for PCP because adequate comparative studies have not been done. In the small randomized study of 55 patients by Lavelle et al. [47], dapsone (200 mg/w) was compared with the same dose plus 25 mg of pyrimethamine per week. Break-through PCP occurred in 4.3% and 4.5% of the groups, respectively. Adverse reactions occurred in 13% and 18% of the respective groups. When the confounding variables in the clinical trials are considered, no specific dose or schedule of administration can be selected as more effective than others (see table 1). In studies with 100-mg daily doses of dapsone alone, rates of break-through PCP of 1% [39], 0 [42], 2% [56], 12% [63], 17% [74], 18% [79], and 21% [68] were encountered. When 100 mg of dapsone was given once a week, breakthrough rates were 2% [44], 4% [43], and 6% [67]. When dapsone was used alone at a dosage of 50 mg/d, breakthrough PCP occurred in 0 [51], 5% [42], 5.7% [69], 6.5% [53], and 13% of patients [77]. Accurate comparison of adverse reaction rates among the clinical trials reported is not possible because of the variations in the definitions for adverse events, periods of observation, and other factors. For example, in one study [53] adverse reactions CID 1998;27 (July) CID 1998;27 (July) Dapsone and P. carinii Pneumonia It seems reasonable to conclude that dapsone is not superior to any drug as prophylaxis for PCP, is somewhat less effective than TMP-SMZ, and is equal to aerosolized pentamidine in efficacy. Several factors must be considered in choosing between dapsone and aerosolized pentamidine for patients who cannot take TMP-SMZ. For example, infants, children, and some adults may not be able to take aerosolized pentamidine, and aerosol administration may be hazardous when the patient has a contagious respiratory tract infection. Cost is also a major factor. Cost of Prophylaxis Adverse Effects Adverse effects of dapsone include a dose-related hemolysis seen in most patients receiving high dosages of §200 mg/d. Methemoglobinemia may occur at symptomatic and asymptomatic levels. Peripheral motor weakness may also occur with high doses. Adverse reactions unrelated to dosage include agranulocytosis, aplastic anemia, a variety of cutaneous reactions, and a ‘‘sulfone syndrome’’ (fever, exfoliative dermatitis, jaundice, lymphadenopathy, anemia, and methemoglobinemia) believed to be a hypersensitivity reaction occurring after 6 – 8 weeks of treatment. Although adverse reactions are fairly common with dapsone, fatalities are rare. Useful information on toxicity has come from studies of a patient without AIDS who consumed a single 2,500-mg dose of dapsone, 25 times the usual daily dose [91]. The next day he was noted to have blue skin. Twenty hours post-dose the methemoglobin concentration was 2.5 g/dL (25% of total hemoglobin). The plasma dapsone level was 18.8 mg/L. The patient had an uneventful recovery without specific therapy. / 9c51$$jy36 06-16-98 00:27:17 Balestrini et al. [92] studied the adverse events in 261 HIVinfected patients taking dapsone as prophylaxis for PCP. Seventy-one patients (27%) stopped taking the drug; 23 had rash; 10 had hematologic toxicity; 10 had malaise or nausea; and 10 died of causes not related to dapsone. Because of the doubleblind, randomized design of the study by Medina et al. [93], a valid comparison of adverse effects from dapsone/TMP and TMP-SMZ can be made. Patients with known allergy to any of the drugs were excluded from the study. The drugs were given for the treatment of PCP. Dosages used were 20 mg of TMP plus 100 mg of SMZ/(kgrd) and 20 mg of TMP/(kgrd) plus 100 mg (total dose) of dapsone daily. Major toxic effects that required a change to another drug occurred in 9 (30%) of 30 patients receiving dapsone/TMP and in 17 (57%) of 30 patients receiving TMP-SMZ (P õ .025). Abnormally high liver transaminase levels occurred in 1 and 6, neutropenia (õ750 neutrophils/mm3) in 1 and 5, thrombocytopenia in 1 and 1, severe rash in 3 and 3, nausea and vomiting in 2 and 2, a decline in hematocrit by §25% in 0 and 0, and methemoglobinemia (ú20%) in 1 and 0 of the patients receiving dapsone/TMP and TMP-SMZ, respectively. Therapeutic efficacy was similar in the two groups. Beumont et al. [94] assessed the safety of dapsone prophylaxis in patients who had previously been found intolerant of TMPSMZ. Of 75 patients subsequently given dapsone, the overall incidence of adverse events was 39%. Rash (16%) and anemia (23%) were the most common events. However, when each case was evaluated critically, only three cases of anemia (4%) and two cases of rash (3%) were considered ‘‘likely related’’ to dapsone. Only five (6.7%) of the 75 patients had the same adverse event as previously experienced with TMP-SMZ. A retrospective review of 89 patients receiving dapsone because of prior adverse reactions to TMP-SMZ showed 56% experienced single or multiple adverse reactions (maculopapular rash in 27 patients, CNS symptoms in 15, gastrointestinal symptoms in 8, and anemia in 12) [95]. Few HIV-infected patients who receive PCP prophylaxis take only the drug or drugs prescribed for this purpose. The concomitant use of several drugs adds to the complexity in sorting out the adverse effects of one specifically. Moore et al. [96] attempted to quantify the incidence of these effects in clinical practice. They calculated the overall adverse event rates from the use of dapsone, TMP-SMZ, zidovudine, didanosine, and zalcitabine in an observational cohort of 1,450 HIV-infected patients with CD4/ lymphocyte counts of £500/mm3. The rates are given in table 2. The adverse events from dapsone were not related to CD4/ lymphocyte count, race, gender, age, or injection drug use. A desensitization scheme has been evaluated by Metroka et al. [97] for patients with hypersensitivity-like reactions to dapsone. Fourteen patients who had fever (ú397C) and diffuse erythematous maculopapular rash that appeared 8 – 14 days after initiation of dapsone therapy were desensitized over a period of 42 days. Daily doses of dapsone escalated from cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 A dapsone regimen is the most economical currently available for prophylaxis for both individual and population use. The annual cost (in $U.S.) of PCP prophylaxis for an adult is $8,190 for atovaquone, $1,200 for aerosolized pentamidine, and $30 for TMP-SMZ (3 days a week), in comparison with $70 for daily dapsone and $10 for weekly dapsone [89]. However, efficacy and safety must be factored into the cost equation. Using a decision-analytic model, Freedberg et al. [90] assessed the effectiveness and costs of dapsone, TMP-SMZ, and aerosolized pentamidine as initial prophylaxis for PCP in HIV-infected individuals with CD4/ lymphocyte counts of õ200/mm3. Each strategy increased life expectancy by about 18%, compared with that with no prophylaxis. Annual per-person costs were $400 for dapsone, $700 for TMP-SMZ, and $1,680 for aerosolized pentamidine. They estimated that for 100,000 people receiving prophylaxis with TMP-SMZ or dapsone (and switching to aerosolized pentamidine if oral therapy is not tolerated), the savings in medical costs is between $8 million and $124 million per year. 199 200 Hughes Table 2. Adverse effects associated with drugs used in the treatment of 1,450 HIV-infected men with CD4/ cell counts of £500/mm3. Adverse event rate (per 100 person-years) Drug Dapsone Didanosine Zidovudine Trimethoprim-sulfamethoxazole Zalcitabine 16.2% 24.1% 26.3% 26.3% 37.0% NOTE. Data are from [96]. / 9c51$$jy36 06-16-98 00:27:17 Single cases of symptomatic methemoglobinemia have been reported [103 – 105]. Specific and effective therapy is the infusion of methylene blue (1.0 mg/kg). Theoretically, inhibition of N-acetyl-transferase (NAT) – dependent acetylation of dapsone could increase the plasma concentration of dapsone, shifting the biotransformation pathway to the P450-mediated formation of hydroxylamine, a toxic metabolite of dapsone. In in vitro studies of human liver cytosol and clinically relevant concentrations of drugs used in the management of AIDS patients, pyrimethamine modestly (by 30%) inhibited MADDS formation [106]. No inhibition was observed with atovaquone, sulfadiazine, clarithromycin, TMP, ketoconazole, and fluconazole. This experiment suggests that NAT-2 is the predominant liver NAT isoform acetylating dapsone in vivo and that coadministration with other anti – opportunistic infection drugs should not inhibit this acetylation pathway. Studies to elucidate the mechanism of increases in serum creatinine level, sometimes associated with the administration of pyrimethamine plus dapsone, show this abnormality is due to the renal tubular secretion of creatinine by pyrimethamine. The inhibition is reversible and does not affect the glomerular filtration rate [107]. Wu and DuBois [108] demonstrated that dapsone inhibits oxidation of pyruvate in rat and mouse tissues by interfering with the pyruvate oxidase system. Because thymine pyrophosphate is needed for normal function of pyruvic oxidase and because thymine deficiency is associated with symptoms of dapsone poisoning, an animal study was done to supplement dapsone administration with thymine hydrochloride. The results showed that the LD50 for control rats given dapsone alone was 233 mg/kg, whereas if dapsone were given with thymine hydrochloride the LD50 was 425 mg/kg. No clinical studies have evaluated the use of thymine in dapsone toxicity. One case of dapsone toxicity with megaloblastic pancytopenia associated with vitamin B12 deficiency has been reported [109], suggesting that supplemental folic acid might be indicated when this is likely to occur. Conclusion Dapsone is effective in the prevention of PCP and in combination with TMP is effective in the treatment of this pneumonitis. It is not the drug of first choice for either prophylaxis or treatment for patients who can take TMP-SMZ. The data currently available are adequate to consider it as a drug of second choice for patients who have experienced adverse effects from TMP-SMZ. Most but not all patients with such effects will be able to take dapsone safely. The most serious adverse effects from dapsone are dose-related hemolytic anemia, peripheral motor weakness, and methemoglobinemia as well as dose-unrelated granulocytopenia, aplastic anemia, and cutaneous reactions such as the sulfone syndrome. Although the number of studies to clearly define the optimal dose and schedule for administration is limited, the following cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 0.01 mg initially to 90 mg by day 37. Thirteen of the 14 patients were successfully desensitized and once again were given dapsone prophylaxis for up to 7 months at the full dosage of 100 mg/d. The 14th patient developed a recurrent diffuse rash on day 42. Holtzer et al. [98] studied 60 HIV-infected patients who had hypersensitivity reactions (anaphylaxis, rash, hives, pruritis, or drug fever) to TMP-SMZ and were subsequently given dapsone as prophylaxis for PCP. Thirteen (22%) of the 60 patients also had hypersensitivity reactions to dapsone. Four (30.8%) of the 13 patients were able to continue receiving dapsone despite the adverse reaction. Thus, up to 85% of patients with adverse reactions to TMP-SMZ might be expected to tolerate prophylaxis with dapsone. The classic sulfone syndrome (fever, hemolytic anemia, and fulminant hepatitis) was reported in the first fatal case of dapsone toxicity [99]. Mole-Boetani et al. [100] reported the first case of the sulfone syndrome involving a patient with AIDS and reviewed the 22 cases of sulfone syndrome in non-AIDS patients reported in the literature. The AIDS patient’s syndrome resolved, and he was discharged after 10 days in the hospital. Methemoglobinemia in HIV-infected patients receiving dapsone has been reported infrequently, although this is wellknown as a toxic effect from its early use in non-AIDS patients. Sin et al. [101] described five AIDS patients who had symptomatic methemoglobinemia while taking either primaquine or dapsone alone or in combination. Two cases resulted from intentional overdoses of dapsone, and three cases developed within a few days of starting primaquine while the patients were receiving dapsone. Four cases required iv methylene blue, supplemental oxygen, and RBC transfusion. It is well-known that the risk of methemoglobinemia is increased greatly if two or more drugs, such as primaquine and dapsone, known to cause this condition, are combined [102]. Blood gas studies and pulse oximetry may not be affected by methemoglobinemia in the usual concentrations encountered with dapsone toxicity. However, with a normal cardiorespiratory system and 100% methemoglobinemia, an oxygen saturation of 85% may be expected with use of conventional pulse oximetry [96]. Co-oximetry, which measures all major hemoglobin species, is accurate in this setting. CID 1998;27 (July) CID 1998;27 (July) Dapsone and P. carinii Pneumonia References 1. Hughes WT, Smith BL. Efficacy of diaminodiphenylsulfone and other drugs in murine Pneumocystis carinii pneumonitis. Antimicrob Agents Chemother 1984; 26:436 – 40. 2. Windholz M, ed. The Merck index. 9th ed. Rahway, NJ: Merck and Co, 1976:370. 3. Voeller D, Kovacs J, Andrawis V, et al. Interaction of Pneumocystis carinii dihydropteroate synthase with sulfonamides and diaminodiphenylsulfone (dapsone). J Infect Dis 1994; 169:456 – 9. 4. Cushion MT. In vitro studies of Pneumocystis carinii. J Protozool 1989; 36:45 – 52. 5. Anderson R, Gatner MS, van Rensburg CE, et al. In vitro and in vivo effects of dapsone on neutrophil and lymphocyte function in normal individuals and patients with lepromatous leprosy. Antimicrob Agents Chemother 1981; 19:495 – 503. 6. Lawrsen AL, Rungby J, Anderson PL. Decreased activation of the respiratory burst in neutrophils from AIDS patients with previous Pneumocystis carinii pneumonia. J Infect Dis 1995; 172:497 – 505. 7. Bozeman PM, Learn DB, Thomas EL. Inhibition of the human leukocyte enzymes myeloperoxidase and eosinophil peroxidase by dapsone. Biochem Pharmacol 1992; 44:553 – 63. 8. Duval X, Clayette P, Dereddre-Bosquet N, et al. Dapsone and HIV-1 replication in primary cultures of lymphocytes and monocyte-derived macrophages. AIDS 1997; 11:943 – 4. 9. Opravil M, Joos B, Luthy R. Levels of dapsone and pyrimethamine in serum during once-weekly dosing for prophylaxis of Pneumocystis carinii pneumonia and toxoplasmic encephalitis. Antimicrob Agents Chemother 1994; 38:1197 – 9. 10. USP dispensing information — volume I: drug information for health care professionals. 15th ed. Rockville, MD: The United States Pharmacopeial Convention, 1995:1041 – 4. / 9c51$$jy36 06-16-98 00:27:17 11. Gatti G, Casazza R, Miletich F, Cruciani M, Bassetti D. Pharmacokinetics of dapsone in human immunodeficiency virus – infected children. Antimicrob Agents Chemother 1995; 39:1101 – 6. 12. Metroka CE, McMechan MF, Andrada R, Laubenstein LJ, Jacobus DP. Failure of prophylaxis with dapsone in patients taking dideoxyinosine [letter]. N Engl J Med 1991; 325:737. 13. Mirochnick M, Cooper E, McIntosh K. Pharmacokinetics of daily and weekly dapsone in HIV-infected children. In: Program and abstracts of the 3rd Conference on Retroviruses and Opportunistic Infections. Alexandria, Virginia: Infectious Diseases Society of America, 1996: 159. 14. Lee BL, Safrin S, Makrides V, Gambertoglio JG. Zidovudine, trimethoprim, and dapsone pharmacokinetic interactions in patients with human immunodeficiency virus infection. Antimicrob Agents Chemother 1996; 40:1231 – 6. 15. Peters JH, Murray JF, Gordon GR, et al. Effect of rifampicin on the disposition of dapsone in Malaysian leprosy patients [abstract]. Fed Proc 1997; 36:996. 16. Horowitz HW, Jorde UP, Wormser GP. Drug interactions in use of dapsone for Pneumocystis carinii prophylaxis. Lancet 1992; 339:747. 17. Gatti G, Merighi M, Hossein J, et al. Population pharmacokinetics of dapsone administered biweekly to human immunodeficiency virus – infected patients. Antimicrob Agents Chemother 1996; 40:2748 – 58. 18. 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Antimicrob Agents Chemother 1986; 20:509 – 10. cida UC: CID Downloaded from http://cid.oxfordjournals.org/ by guest on September 9, 2014 recommendations are probably adequate: for prophylaxis, (1) 100 mg of dapsone daily or dapsone (50 mg daily) plus pyrimethamine (50 mg once weekly) plus leucovorin (25 mg once weekly) or (2) dapsone (200 mg) plus pyrimethamine (75 mg) plus leucovorin (25 mg) once weekly, orally, for adults. The dose recommended for children is 2.0 mg/(kgrd), not to exceed 100 mg daily. For treatment of PCP, TMP (20 mg/[kgrd]) plus dapsone (200-mg [total dose] daily) is adequate. As with any drug, attention should be given to the use of concomitant medication. Information is limited with regard to drug interactions with dapsone. Especially for patients with impaired hepatic and renal function, the use of drugs such as the antiretroviral nucleosides, antacids, and rifampin should be carefully monitored. The combination of TMP with dapsone for prophylaxis has been essentially unexplored in human studies, although prophylaxis studies in animals and treatment studies in humans suggest a synergistic effect on efficacy. In circumstances where economy is an issue, dapsone is the least expensive effective prophylaxis available. Forty years after dapsone was first marketed in the United States for the treatment of leprosy, indications for its use have changed dramatically to include PCP, an obscure and insignificant disease in 1957. It is within reason to expect that this old drug will remain with us for a long time and perhaps find new indications in the future. 201 202 Hughes / 9c51$$jy36 06-16-98 00:27:17 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. of the 7th International Conference on AIDS (Florence). Florence: Institute Superiore di Sanita`, 1991:239. Cruciani M, Danzi MC, Perri G, et al. Dapsone in secondary prophylaxis of P.C.P. [abstract no W.B.2208]. 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