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PubMed1989

Relationship between neutrophil-mediated oxidative injury during acute experimental pyelonephritis and chronic renal scarring.

Previous experiments with rats have suggested that pyelonephritic scarring after acute ascending Escherichia coli pyelonephritis partly results from excessive polymorphonuclear leukocyte (PMN) infiltration and activation in the kidney parenchyma. We have studied the role of PMN oxidative metabolism in generating tissue injury during acute pyelonephritis. Rats with acute pyelonephritis were treated with dapsone (25 mg/kg twice daily for 3 days), a compound known to prevent PMN oxidant damage. In vitro, levels of dapsone easily achieved in vivo inhibited myeloperoxidase (MPO)-mediated reactions involving the oxidation of halides to reactive cytotoxic hypohalites (such as MPO-mediated iodination and luminol-enhanced chemiluminescence). In contrast, dapsone had no effect on superoxide production, lysosomal enzyme release, or bacterial killing by activated PMN. In vivo, dapsone treatment had no significant effect on acute pyelonephritis with respect to (i) bacterial counts, (ii) inflammatory swelling, and (iii) PMN infiltration. However, dapsone-treated animals sacrificed 2 months after acute pyelonephritis had a 65% reduction of renal scars when compared with controls. Since dapsone had no antibacterial effect, this protection is compatible with the hypothesis that dapsone prevented oxidant-generated tissue injury due to the extracellular release of the MPO system by activated PMN during acute suppurative pyelonephritis.

Acute Disease↗
PubMed2001

Decreases in mean hemoglobin and serum albumin values in erythema nodosum leprosum and lepromatous leprosy.

Changes in hemoglobin (HGB) and serum albumin (SA) concentration associated with the onset of symptomatic erythema nodosum leprosum (ENL) were studied by comparing the values obtained on the day thalidomide or prednisone therapy commenced, with each patients' preceding values. In three groups of ENL patients mean HGB values fell with statistical significance: 1) in 38 patients who had been begun on thalidomide in the decade of the 1990s and who had been receiving dapsone for a minimum of 6 months, mean HGB values fell from 13.19 gm/dl to 12.27 gm/dl, or 7.0%, p = 6.0 x 10(-6); 2) in 8 patients who were in the active patient file not overlapping with the preceding group, and who had been on dapsone for a minimum of 6 months, mean HGB values feel from 13.40 gm/dl to 11.96 gm/dl, or 10.7%, p = 0.0015; and 3) in 8 patients not overlapping with the preceding groups, who were treated with rifampin and minocylcine or clarithromycin mean HGB values fell from 13.25 gm/dl to 12.48 gm/dl, or 5.8%, p = 0.0035. In two groups of ENL patients SA values also fell with statistical significance: 1) in 34 patients who were begun on thalidomide in the decade of the 1990s and who had been on dapsone for a minimum of 6 months, mean SA values fell from 4.14 gm/dl to 3.77 gm/dl, or 8.9%, p = 1.2 x 10(-5); and 2) in 10 patients from the active file not overlapping with the preceding group, and who had been on dapsone for a minimum of 6 months, mean SA values fell from 4.45 gm/dl to 4.06 gm/dl, or 8.8%, p = 0.039. A brisk fall in HGB values was often accompanied by a fall in SA concentration, and vice versa. Recovery from extreme falls in HGB and SA values was complete in 13 weeks. Recovery occurred in the presence of continued dapsone treatment. The falls could be rapid, occurring too soon to be the result of decreased erythropoiesis or hepatic SA synthesis. This study provides no direct evidence as to the mechanism responsible for the fall in these two parameters, but an interleukin-6 mediated hemodilution is an attractive hypothesis. The ENL-associated fall in HGB values was distinct from dapsone-induced hemolysis and the anemia of chronic disease. The ENL-associated anemia is not a good reason to discontinue dapsone therapy.

Anemia↗
PubMed1986

Intra-adipose administration of monoacetyldapsone to healthy volunteers.

The pharmacokinetics of intra-adiposely administered monoacetyldapsone (particle size less than 20 micron) were investigated in 11 male and 11 female healthy volunteers. Dapsone and monoacetyldapsone concentrations in serum were determined by high-pressure liquid chromatography (HPLC). Injection of 1175 mg monoacetyldapsone, which is equivalent to 1000 mg dapsone, resulted in dapsone concentration/time profiles in all the volunteers characterized by peak concentrations ranging from 0.14 to 0.85 mg/l, and by averaged dapsone concentrations after 28, 42, and 56 days of 0.33, 0.19, and 0.10 mg/l, respectively. Areas under the curves ranged from 6.7 to 25.3 mg X day/l. Detectable concentrations (greater than 6 ng/ml) of dapsone were achieved for 56 days in most of the subjects. An estimation of the mean concentration after repeated injection every 4 weeks ranged from 0.24 to 0.90 mg/l. No differences in dapsone concentration/time course were detectable between men and women or between rapid and slow acetylators. The injection was generally well tolerated by the subjects. This, combined with the excellent sustained release properties, makes it a promising injection. In the future, it might contribute to combat noncompliance among leprosy patients, which is believed to be one of the main causes of dapsone resistance.

Acetylation↗
PubMedDate not supplied

Interaction of anti-leprosy drugs with the rat serum complement system.

Dapsone, clofazimine and rifampicin, the three most important constituents of multidrug therapy against leprosy, were studied with respect to their effects on the rat serum complement system, in vitro as well as in vivo. Of the three drugs only dapsone and clofazimine exhibited significant in vitro anti-complement activity and only at a very high, non-therapeutic dose of 0.24 mg/ml. On the contrary, rifampicin could not induce significant in vitro complement consumption. Furthermore, dapsone and clofazimine could reduce rat-serum-mediated rabbit erythrocyte haemolysis in the presence of Mg2+-EGTA, indicating that they could also affect the alternative pathway of complement activation. However, the latter pathway of complement consumption by these drugs seems to be insignificant because the factor-B-mediated complement-consumption system is minimal in rat sera. Immunoelectrophoretic study of mixtures of fresh rat sera and anti-leprosy drugs against specific anti-rat-C3 antisera demonstrated that dapsone and clofazimine could not cleave the C3 complement component. In a separate experiment we attempted to reconstitute the haemolytic complement activity consumed by dapsone and clofazimine by adding Crat-EDTA sera (a source of C3, C5, C6, C7, C8 and C9), but at most only 12% reconstitution of haemolytic activity could be achieved. We thus conclude that both dapsone and clofazimine could affect the complement system, predominantly through the earlier complement components and at very high, non-therapeutic doses. On the contrary, in-vivo experiments in rats showed that a combination of these three drugs, when given at a therapeutic dose or at 10 times the therapeutic dose for three months, did not affect the complement system.

Animals↗
PubMed2003

Activation of cytochrome P450 2C9-mediated metabolism: mechanistic evidence in support of kinetic observations.

Studies were designed to investigate the possible mechanisms associated with the kinetic observation of CYP2C9 activation by dapsone and its phase I metabolite, N-hydroxydapsone. Kinetic studies suggested that dapsone activated CYP2C9-mediated flurbiprofen 4(')-hydroxylation by decreasing the K(m) (alpha=0.2) and increasing the V(max) (beta=1.9). Interestingly, N-hydroxydapsone also activated flurbiprofen 4(')-hydroxylation by increasing V(max) (beta=1.5) but had no effect on K(m) (alpha=0.98). To study the effects of these modulators on the binding affinity of flurbiprofen, spectral binding studies were performed. In the presence of dapsone, the spectral binding constant (K(s)) for flurbiprofen was reduced from 14.1 to 2.1 microM, while in the presence of N-hydroxydapsone, the K(s) remained unchanged (14.0 microM), which suggests that dapsone causes an increase in the affinity of flurbiprofen for CYP2C9, whereas N-hydroxydapsone does not. Additionally, stoichiometry measurements under activation conditions in the presence of dapsone resulted in a doubling of both NADPH and oxygen consumption for flurbiprofen 4(')-hydroxylation, with an overall increase in metabolite formation and a decrease in formation of peroxide and excess water. Interestingly, the presence of N-hydroxydapsone generally caused the same effects on stoichiometry as those of flurbiprofen 4(')-hydroxylation but failed to reduce excess water formation, which suggests that, while N-hydroxydapsone activates CYP2C9, it does so less efficiently and possibly through a mechanism different from that of dapsone.

Aryl Hydrocarbon Hydroxylases↗
PubMed1995

Brown recluse spider envenomation of the eyelid: an animal model.

The authors developed a rabbit model of the brown recluse (BR) spider envenomation of the human eyelid. The spider bite causes cutaneous necrosis and systemic toxicity in human eyelids, possibly leading to disseminated intravascular coagulation, hemolysis, and death. The treatment has been controversial. The animal model evaluated the effects of single- and combined-agent therapy in four phases: venom dose response, time course, therapeutic effectiveness (steroid vs. dapsone vs. antivenom), and optimal therapy (steroid and dapsone; steroid and antivenom; and dapsone and antivenom combination groups). The combination dapsone and antivenom treatment group was the optimal animal regimen, although not completely effective in eliminating microscopic necrosis. The authors also report dramatic clinical improvement in human inflammatory response with dapsone therapy and recommend immediate dapsone therapy combined with specific BR venom, if available, in humans.

Animals↗
PubMed1978

IgA and C3 complement in the uninvolved skin in dermatitis herpetiformis after gluten withdrawal.

IgA deposits in the skin in 53 patients with dermatitis herpetiformis (DH) have been studied in relation to treatment. In 19 patients the disorder was controlled by a gluten-freen diet (GFD) alone, in 13 patients by dapsone and GFD and in 18 by dapsone alone. In 3 patients the skin disorder became insignificant and required no treatment. Of the patients taking a GFD alone, six had been clear of skin lesions for 7 years, 5 for 3--5 years, and 8 for periods of 6 months--3 years. IgA deposits were found in all patients in an initial biopsy in a second biopsy after treatment for periods varying from 1 to 7 years. There was no difference in the quantity of IgA, as assessed by the amount of fluorescence, whether patients were controlled with a GFD alone, GFD and dapsone, dapsone alone, or in those in clinical remission. The C3 component of complement was present in the skin in 3 of the 19 patients (16%) controlled by a GFD alone, 6 of the 13 patients (46%) of those controlled by a GFD and dapsone, and in 12 of 18 (66%) of the patients taking dapsone alone, and in one of the patients in clinical remission.

Adult↗
PubMed1970

Experimental and clinical studies on rifampicin in treatment of leprosy.

Rifampicin showed high activity against experimental leprosy, inhibiting the multiplication of dapsone-sensitive and dapsone-resistant strains of Mycobacterium leprae in mice fed 5 mg./kg. body weight. In a formal pilot-type trial on six previously untreated patients with active lepromatous leprosy, rifampicin (600 mg. daily by mouth) was as effective as standard treatment with dapsone. Myco. leprae, however, appeared to be killed more rapidly by rifampicin than by dapsone or other antileprosy drugs so far studied. This was confirmed on a further 10 patients, including two with dapsone resistance, and from the infectivity in mice of bacilli recovered from patients during treatment with rifampicin or dapsone. These results are consistent with the bactericidal activity of rifampicin against other micro-organisms, which could be important to the chemotherapy of leprosy, since all antileprosy drugs in current use are bacteriostatic.

Animals↗
PubMed1986

Selective inhibition of human neutrophil chemotaxis to N-formyl-methionyl-leucyl-phenylalanine by sulfones.

The therapeutic efficacy of the sulfones, dapsone, and sulfoxone in neutrophilic dermatoses may be related to the effects of these drugs on neutrophil function. Therefore we determined whether neutrophil chemotactic migration to various chemoattractants could be inhibited by sulfones in vitro. The chemotactic responses of human neutrophils from healthy donors were tested by using N-formyl-methionyl-leucyl-phenylalanine (F-met-leu-phe), purified human C5a, and leukocyte-derived chemotactic factor (LDCF). Therapeutic concentrations of sulfones selectively inhibited neutrophil chemotaxis to F-met-leu-phe, but did not affect neutrophil chemotaxis to LDCF or C5a. Inhibition of neutrophil chemotaxis to F-met-leu-phe was induced by both dapsone and sulfoxone at a concentration of 10 micrograms/ml without affecting random migration, and the inhibition was reversed by washing the neutrophils. When dapsone- and sulfoxone-treated neutrophils (100 micrograms/ml) were stimulated with F-met-leu-phe, neutrophil superoxide generation was not inhibited. Sulfapyridine (10 micrograms/ml) also selectively inhibited neutrophil chemotaxis to F-met-leu-phe; however, sulfamethoxazole and sulfisoxazole did not affect chemotaxis. The inhibitory effects of dapsone, sulfoxone, and sulfapyridine could not be demonstrated with granulocytes from rabbits or guinea pigs nor with human monocytes. Experiments with radiolabeled dapsone showed rapid, nonspecific, and reversible binding of dapsone to human neutrophils. These data suggest that a mechanism of action of sulfones in neutrophilic dermatoses may be a selective inhibition of neutrophil migration to as yet undefined chemoattractants in the skin.

Animals↗
PubMed1989

An electron microscopic study of alterations in the morphology and permeability of purified Mycobacterium leprae.

This communication reports the association of changes in ultrastructure of Mycobacterium leprae with alterations in its permeability. To study morphologic changes of the organisms under different conditions (of temperature and exposure to NaOH and trypsin), ultrathin sections of the bacteria were cut and examined in an electron microscope. In the untreated bacilli and those washed with trypsin, the cytoplasmic membrane and the cell wall (peptidoglycan layer) remained intact; dapsone showed little effect on diphenoloxidase of the bacteria. M. leprae is unique among mycobacteria in possessing an unusual form of the enzyme diphenoloxidase. The antileprosy drug dapsone is a potent inhibitor of the enzyme, but it does not readily penetrate the bacteria where the cell envelope remains intact. The cell wall of M. leprae exposed to -80 degrees C or washed with NaOH was partially detached from the cell membrane; dapsone readily penetrated these organisms and inhibited the bacterial enzyme. In the above preparations, the cytoplasmic membrane appeared undamaged and the bacteria remained viable, as evidenced by multiplication in mouse foot pads. At 50 degrees C, the peptidoglycan layer became completely separated from the membrane and the cytoplasm was partially denatured. These organisms were permeable to dapsone, but were no longer viable. At 100 degrees C, the structural organization of the bacilli was completely destroyed, and of course, they lost their enzyme activity as well as viability. Evidently, the intact cell wall layer mediates the exclusion of dapsone from M. leprae, and there is no correlation between its viability and permeability. The ultrathin sections also reveal the internal organization and cytoplasmic inclusions of M. leprae, as never before seen.

Catechol Oxidase↗
PubMed1984

Dermatitis herpetiformis: effects of sulfones and sulfonamides on neutrophil myeloperoxidase-mediated iodination and cytotoxicity.

The effects of sulfones and sulfonamides on neutrophil myeloperoxidase-mediated iodination and cytotoxicity were studied using in vitro assays to measure these parameters. Leukocyte iodination was documented using a quantitative assay to measure the iodination of protein by human neutrophils undergoing phagocytosis. Cytotoxicity for the tumor cell line LSTRA by human neutrophils activated by exposure to phorbol myristate acetate was measured by a 51Cr release assay. Dapsone, diasone, and sulfapyridine, at concentrations comparable to serum levels obtained by therapeutic doses of drug, effectively inhibited iodination and cytotoxicity mediated by human neutrophils. Other sulfonamides showed little inhibition of either iodination or cytotoxicity. The amount of inhibition was comparable to that seen with the inhibitors azide or cyanide and occurred in a dose dependent manner with all three drugs. A cell-free cytotoxic system using myeloperoxidase, iodide, a H2O2 generating system, and target cells also showed inhibition by dapsone, diasone and sulfapyridine in a similar fashion. The active drugs inhibited both the intra- and the extracellular myeloperoxidase-H2O2-halide cytotoxic systems. Serial iodination studies of four dermatitis herpetiformis patients, evaluated while taking dapsone or sulfapyridine, showed inhibition of iodination by either drug. Levels of IgA immune complexes, as measured by the Raji cell radioimmune assay adapted for IgA, did not change when medication was withheld. These studies demonstrate that dapsone, diasone, and sulfapyridine inhibit both neutrophil iodination and cytotoxicity for tumor cells, while other sulfonamides have no effect. This confirms previous studies showing inhibition by myeloperoxidase mediated iodination by dapsone. Furthermore, the effect on neutrophils is quickly reversible; in vivo administered drug has no effect on in vitro function. The active drugs inhibit both intra- and extracellular cytotoxic systems. This may represent an important mechanism by which these drugs produce their therapeutic effects when used to treat inflammatory skin diseases.

Antigen-Antibody Complex↗
PubMed2001

N-acetyltransferase polymorphism in patients with Behçet's disease.

OBJECTIVES: The objective of our study was to investigate the possible role of human arylamine N-acetyltransferase 2 (NAT2) polymorphism in susceptibility to Behçet's disease. METHODS: Eighty-five patients with Behçet's disease gave their written informed consent to participate in the study. Seven point mutations (G191A, C282T, T341C, C481T, A803G, G590A, G857A) in the NAT2 gene were analysed using polymerase chain reaction/restriction fragment length polymorphism techniques. In addition, each patient received 100 mg dapsone orally to determine their NAT2 phenotype. Dapsone and its metabolite monoacetyl-dapsone were measured in 3-h plasma samples using high-performance liquid chromatography. Subjects with an acetylation ratio (monoacetyl-dapsone/dapsone) less than 0.4 were defined as slow acetylators. RESULTS: Of 85 patients with Behçet's disease, 54 (63.5%) were identified as genotypically slow acetylators. However, 60% (51 of 85) of patients were diagnosed as slow acetylators according to monoacetyl-dapsone/dapsone ratio. Thus, a low incidence of genotype/phenotype discrepancy (3.5%) was observed in Turkish patients with Behcet's disease. When we compared our results with previous phenotyping and genotyping studies in the Turkish population, frequencies of slow and rapid acetylators were not statistically different in patients with Behçet's disease. The frequency of the *5B allele was found to be slightly higher in patients with Behçet's disease than historic controls (44.7 vs 35.6%, P = 0.039). However, there was no significant difference in the frequency of the overall genotypes and alleles of NAT2 between patients and controls. CONCLUSION: Although the frequency of the NAT2*5B allele, responsible for slow acetylation, was slightly higher in patients than historic controls, our results failed to show an association between NAT2-acetylator status and risk for developing Behçet's disease.

Acetylation↗
PubMed2002

Effect of chronic disulfiram administration on the activities of CYP1A2, CYP2C19, CYP2D6, CYP2E1, and N-acetyltransferase in healthy human subjects.

AIMS: Short-term disulfiram administration has been shown to selectively inhibit CYP2E1 activity but the effects of chronic disulfiram administration on the activities of drug metabolizing enzymes is unclear. The purpose of this study was to evaluate the effects of disulfiram given for 11 days on selected drug metabolizing enzyme activities. METHODS: Seven healthy volunteers were given disulfiram 250 mg daily for 11 days. Activities of the drug metabolizing enzymes CYP1A2, CYP2C19, CYP2D6, CYP2E1 and N-acetyltransferase were determined using the probe drugs caffeine, mephenytoin, debrisoquine, chlorzoxazone, and dapsone, respectively. Chlorzoxazone was administered before disulfiram administration and after the second and eleventh doses of disulfiram, while the other probe drugs were given before disulfiram administration and after the eleventh disulfiram dose. RESULTS: Disulfiram administration markedly inhibited chlorzoxazone 6-hydroxylation by more than 95%, but did not affect metabolism of debrisoquine or mephenytoin. Caffeine N3-demethylation was decreased by 34% (P < 0.05). Monoacetyldapsone concentrations were markedly elevated by disulfiram administration resulting in a nearly 16-fold increase in the dapsone acetylation index, calculated as the plasma concentration ratio of monoacetyldapsone to dapsone. CYP-mediated dapsone N-hydroxylation was not significantly altered. CONCLUSIONS: These data suggest that disulfiram-mediated inhibition is predominantly selective for CYP2E1. The magnitude of CYP2E1 inhibition was similar after both acute and chronic disulfiram administration. The effects on caffeine N3-demethylation (CYP1A2) and dapsone metabolism suggest that chronic disulfiram administration may affect multiple drug metabolizing enzymes, which could potentially complicate the use of chronically administered disulfiram as a diagnostic inhibitor of CYP2E1.

Adult↗
PubMed1995

A randomized trial of three antipneumocystis agents in patients with advanced human immunodeficiency virus infection. NIAID AIDS Clinical Trials Group.

BACKGROUND: We evaluated the effectiveness of three treatment strategies for the prevention of a first episode of Pneumocystis carinii pneumonia in patients infected with the human immunodeficiency virus (HIV). METHODS: In an open-label trial, 843 patients with HIV infection and fewer than 200 CD4+ cells per cubic millimeter received zidovudine plus one of three randomly assigned prophylactic agents, beginning with trimethoprim-sulfamethoxazole, dapsone, or aerosolized pentamidine and followed by a defined sequence of other drugs to be used in cases of intolerance. RESULTS: The estimated 36-month cumulative risks of P. carinii pneumonia were 18 percent, 17 percent, and 21 percent in the trimethoprim-sulfamethoxazole, dapsone, and aerosolized-pentamidine groups, respectively (P = 0.22). The difference in risk among treatment strategies was negligible in patients entering the study with 100 or more CD4+ lymphocytes per cubic millimeter. In those entering with fewer than 100 CD4+ cells per cubic millimeter, the risk was 33 percent with aerosolized pentamidine, as compared with 19 percent with trimethoprim-sulfamethoxazole and 22 percent with dapsone (P = 0.04). The lowest failure rates occurred in patients receiving trimethoprim-sulfamethoxazole, and failures were more common with 50 mg of dapsone than with 100 mg. Toxoplasmosis developed in less than 3 percent of patients. Of the patients assigned to the two systemic therapies, only 23 percent were receiving their assigned drug and dose when they completed the study. The median survival was approximately 39 months in all three groups, and the mortality attributable to P. carinii pneumonia was only 1 percent. CONCLUSIONS: In patients with advanced HIV infection, the three treatment strategies we examined have similar effectiveness in preventing P. carinii pneumonia. Strategies that start with trimethoprim-sulfamethoxazole or with high-dose dapsone, rather than aerosolized pentamidine, are superior in patients with fewer than 100 CD4+ lymphocytes per cubic millimeter.

AIDS-Related Opportunistic Infections↗
PubMed1996

Clindamycin/primaquine as prophylaxis for Pneumocystis carinii pneumonia.

The records of 206 patients with advanced infection due to human immunodeficiency virus type 1 who were receiving prophylaxis with clindamycin/primaquine (C/P), trimethoprim-sulfamethoxazole (TMP-SMZ), or dapsone to prevent Pneumocystis carinii pneumonia (PCP) were retrospectively examined. Two hundred sixty-two patient-years of prophylaxis were accrued (176.2 of TMP-SMZ, 63.4 of dapsone, and 22.8 of C/P). The rates of PCP in the TMP-SMZ, dapsone, and C/P groups were 3.4, 11.0, and 30.7 per 100 patient-years, respectively. Pairwise comparisons showed C/P to be less effective than TMP-SMZ (relative risk [RR], 9.02; 95% confidence interval [CI], 3.03-26.83). A similar trend was apparent for C/P vs. dapsone (RR, 2.78; 95% CI, 0.98-7.93). When only those receiving primary prophylaxis were analyzed, C/P recipients remained at greater risk than TMP-SMZ recipients (RR, 13.19; 95% CI, 3.54-49.12) and dapsone recipients (RR, 3.85; 95% CI, 1.12-13.31). Failure of C/P prophylaxis could be due, at least in part, to underdosing (clindamycin, 300 mg/d; primaquine, 15 mg/d). C/P recipients had more nonspecific diarrhea than did TMP-SMZ recipients (RR, 2.99; 95% CI, 1.61-5.55).

Adult↗
PubMed2000

Acetylator phenotype and genotype in patients infected with HIV: discordance between methods for phenotype determination and genotype.

The acetylator phenotype and genotype of AIDS patients, with and without an acute illness, was compared with that of healthy control subjects (30 per group). Two probe drugs, caffeine and dapsone, were used to determine the phenotype in the acutely ill cohort. Polymerase chain reaction amplification and restriction fragment length polymorphism analysis served to distinguish between the 26 known NAT2 alleles and the 21 most common NAT1 alleles. The distribution (%) of slow:rapid acetylator phenotype seen among acutely ill AIDS patients differed with the probe substrate used: 70:30 with caffeine versus 53:47 with dapsone. Phenotype assignment differed considerably between the two methods and there were numerous discrepancies between phenotype and genotype. The NAT2 genotype distribution was 45:55 slow:rapid. Control subjects, phenotyped only with caffeine, were 67:33 slow:rapid versus 60:40 genotypically. Stable AIDS patients, phenotyped only with dapsone, were 55:45 slow:rapid versus 46:54 genotypically. Following resolution of their acute infections, 12 of the acutely ill subjects were rephenotyped with dapsone. Phenotype assignment remained unchanged in all cases. The distribution of NAT1 alleles was similar in all three groups. It is evident from the amount of discordance between caffeine phenotype and dapsone phenotype or genotype that caution should be exercised in the use of caffeine as a probe for NAT2 in acutely ill patients. It is also clear that meaningful study of the acetylation polymorphism requires both phenotypic and genotypic data.

Acetylation↗
PubMed2006

Population pharmacokinetic and pharmacodynamic modelling of the antimalarial chemotherapy chlorproguanil/dapsone.

AIMS: To determine the population pharmacokinetics of chlorproguanil, dapsone and the active metabolite of chlorproguanil, chlorcycloguanil; and to estimate the duration of parasitocidal activity for chlorpoguanil/dapsone against Plasmodium falciparum isolates of varying sensitivity. METHODS: Rich and sparse pharmacokinetic data were collected prospectively from: healthy volunteers (n=48) and adults (n=65) and children (n=68) suffering from P. falciparum malaria. All subjects received 2.0 mg kg-1 of chlorproguanil and 2.5 mg kg-1 of dapsone. RESULTS: The population pharmacokinetic parameter estimates for chlorproguanil were ka=00.09 h-1 (intersubject variability was 44%), CL/F=51.53 l h-1 (57%), CLD/F=54.67 l h-1, V1/F=234.40 l (50%) and V2/F=1612.75 l; for dapsone were ka=00.93 h-1, CL/F=1.99 l h-1 (72%) and V/F=76.96 l (48%); and for chlorcycloguanil were CLm/Fm=3.72 l h-1 kg-1 (67%) and Vm/Fm=12.76 l kg-1 (64%). For dapsone, CL/F and V/F were both significantly positively correlated with body weight. For a 10-kg child, the mean duration of parasitocidal activity for chlorproguanil/dapsone against the three most susceptible P. falciparum strains was 4.5 days [5th and 95th percentiles 2.4, 7.3] for W282; 5.9 days (3.6, 9.7) for ItG2F6; and 6.1 days (3.7, 10.1) for K39. For an isolate with the ile-164-leu mutation, V1/S, activity ranged from 0.8 days (0.0, 3.3) for a 10-kg child to 1.8 days (0.0, 4.0) for a 60-kg adult. CONCLUSIONS: Plasmodium falciparum malaria has no effect on the pharmacokinetic parameters for chlorproguanil, dapsone or chlorcycloguanil. Chlorproguanil/dapsone will probably prove to be ineffective against parasite strains with the mutation ile-164-leu, were these to become prevalent in Africa.

Adolescent↗
PubMed1989

Sulphamethoxypyridazine for dermatitis herpetiformis, linear IgA disease and cicatricial pemphigoid.

One-hundred and sixty-eight cases of dermatitis herpetiformis were reviewed to compare the clinical response to and incidence of side-effects from dapsone and sulphamethoxypyridazine. Thirty-seven received sulphamethoxypyridazine (0.25-1.5 g/day) as a single agent therapy at some stage during their care and 161 had dapsone only (50-450 mg/day). Thirty of these patients received both drugs, but at different times. Both were highly effective in controlling the skin disease in 97% of patients on dapsone and 89% on sulphamethoxypyridazine. While 36 (22%) of dapsone-treated subjects had intolerable side effects warranting a change in therapy, this occurred in only five (13.5%) of those treated with sulphamethoxypyridazine. Sulphamethoxypyridazine was also effective as a single agent in three patients with linear IgA disease who had suffered adverse effects from dapsone, and in 10 out of 15 patients with oral and cutaneous lesions of cicatricial pemphigoid.

Adolescent↗