The absolute oral bioavailability of dapsone in dogs and humans

The absolute oral bioavailability of dapsone (DDS) was established in dogs and healthy volunteers by comparing AUC's after oral and intravenous administration. Five female inbred beagles each received 100 mg DDS orally and intravenously as a bolus injection in a randomized cross-over study. DDS serum concentrations were determined using HPLC. After both routes of administration, linear pharmacokinetics were observed, the elimination half-life (t1/2) amounting between 5.8 and 10.2 h. After oral administration, AUC values between 56.1 and 99.2 mg X h X l-1 were found, while after intravenous administration AUC's were between 63.5 and 98.1 mg X h X l-1. The absolute oral bioavailability, corrected for differences in t1/2, averaged 107 +/- 9% (SD). A similar study was carried out in 2 female and 3 male healthy volunteers. The intravenous dose was reduced to 50 mg and given as an infusion. Pharmacokinetics were linear after both routes of administration. The t1/2 values amounted between 15.6 and 30.4 h. AUC's ranged from 24.0 to 75.4 mg X h X l-1 after oral administration and from 13.3 to 37.5 mg X h X l-1 after intravenous infusion of half of the oral dose. The absolute, t1/2-corrected oral bioavailability was calculated to be 86 to 104%. Complete bioavailability of DDS was demonstrated in dogs and healthy volunteers. The method used in this study might help to detect possible DDS malabsorption in leprosy and dermatitis herpetiformis patients.

Acetylation and oxidation phenotypes in malignant lymphoma

101 white British adults with Hodgkin's disease or non-Hodgkin's lymphoma were phenotyped for acetylation status using dapsone and for oxidation status with debrisoquine prior to treatment. The frequencies of acetylation and oxidation phenotypes in these patients were compared with reference populations of normal subjects. No significant difference in phenotype frequency was found in the lymphoma patients. This suggests that neither of these metabolic polymorphisms for exogenous compounds is strongly associated with these malignancies. Owing to the small size of the study, however, an effect of these phenotypes could not be excluded.

Excretion of chloroquine, dapsone and pyrimethamine in human milk

The concentration of chloroquine (CQ), dapsone (DDS) and pyrimethamine (PYR) in plasma and milk were measured following the coadministration of a single dose of chloroquine and Maloprim to lactating women. The milk to plasma area under the concentration-time curve (AUC) ratio ranged from 1.96 to 4.26 for CQ, 0.22 to 0.45 for DDS and 0.46 to 0.66 for PYR. Assuming a daily milk ingestion of 1 l by the infant, the maximum percentage of the maternal dose for CQ, DDS and PYR in milk was 4.2%, 14.3% and 45.6%, respectively, over a 9 day period.

The pharmacokinetics of dapsone after oral administration to healthy volunteers

After oral administration of 100 mg dapsone (DDS) to 25 healthy volunteers peak serum DDS concentrations between 1.10 and 2.33 mg l-1 were reached within 0.5 to 4 h. AUCs varied from 20.3 to 75.4 mg l-1 h, while the elimination half-lives ranged from 11.5 to 29.2 h. The apparent volumes of distribution were 0.84 to 1.26 l kg-1 body weight, assuming complete bioavailability. Statistically significant differences in peak drug concentration, peak time and AUC existed between males and females. Absorption and elimination of DDS appeared to be faster than reported in other studies, suggesting differences in DDS kinetics between healthy volunteers and patients.

Sustained release properties of an intra-adiposely administered dapsone depot injection

A dapsone depot injection, consisting of dapsone crystals of bipyramidal shape with a particle size of 38 micron-63 micron suspended in an aqueous vehicle, appeared to result in different concentration/time profiles in men and women when delivered "intramuscularly." This phenomenon can be explained by the larger skin-to-muscle distance in women than in men. Injections intended to be delivered intramuscularly are, in fact, administered into subcutaneous fatty tissue in most of the women. Because sustained release properties were more satisfactory in women than in men, in this study the absorption of dapsone was investigated after administration of the same injection into gluteal fatty tissue. Via this route of administration, for which the term intra-adipose is used, 12 female and 15 male healthy volunteers received 1000 mg dapsone, after which blood samples were taken at regular intervals for 35 days to determine dapsone and monoacetyldapsone concentrations in serum using high-pressure liquid chromatography with fluorometric detection. No important differences between men and women appeared to exist at any time point after injection. The peak concentrations were 0.69 +/- 0.40 mg/l in men and 0.84 +/- 0.31 mg/l in women. No important side effects were observed, either locally or systemically. Volunteers who previously received an intramuscular injection preferred the intra-adipose administration. The good depot properties and better acceptance of intra-adipose dapsone administration are reasons to prefer this route of administration.

Blood dapsone levels in leprosy patients treated with acedapsone

The metabolism of the repository drug acedapsone (DADDS,4,4'-diacetyldiaminodiphenyl sulfone) was studied in 15 individuals receiving 225 mg of DADDS, intramuscularly for a period of 75 days. Plasma levels of DDS were determined on the 2nd, 7th, 15th, 30th, 60th and 75th day after administration of the drug by spectrophoto-fluorometric technique. The mean peak levels of DDS (85.36 ng/ml) were noticed on 7th day followed by a gradual decrease in DDS concentration. The mean half-life level (44.53 ng/ml) of DDS were observed around the 15th day. The mean DDS level for the entire period of observation after one dose was 41.95 ng/ml. On the 75th day, the DDS level reached the minimum value of 14.76 ng/ml which was still about 5 times more than the minimal inhibitory concentration (MIC) level of DDS against M. leprae (3 ng/ml). The results are discussed.

Reduced albumin binding of MADDS--a measure for bilirubin binding--in sick children

The reserve albumin concentration for binding of MADDS (monoacetyldiaminodiphenyl sulphone) in plasma is used as a measure of the reserve albumin concentration for binding of unconjugated bilirubin. The aim of the present study was to investigate whether a reduction in the reserve albumin concentration for binding of MADDS could exist in sick children after 5 months of age, where the bilirubin binding properties of the albumin has reached the adult level. The material included 75 children, 1-15 years of age with mild infections, severe bacterial infections, acute viral hepatitis, chronic hepatic diseases or uraemia, and a control group of 22 healthy children. The reserve albumin concentration was significantly lower in children with severe bacterial infections, acute viral hepatitis, and uraemia, than in healthy children (p less than 0.01), while the reserve albumin concentration in children with mild infections and chronic hepatic diseases did not differ significantly from that of the control group (p greater than 0.05). The total albumin concentration in plasma in either of the groups of sick children did not differ significantly from that of the healthy children. The plasma concentration of unconjugated bilirubin was elevated in the group of children with acute viral hepatitis, but not enough to influence the concentration of reserve albumin for binding of MADDS to a significant degree. The reserve albumin concentration was significantly lower in children with acute viral hepatitis than in children with severe bacterial infections (p less than 0.05).

Race-linked differences in serum concentrations of dapsone, monoacetyldapsone and pyrimethamine during malaria prophylaxis

Serum concentrations of dapsone (DDS), monoacetyldapsone (MADDS), the principal acetylated metabolite of DDS, and pyrimethamine (PYR) were measured in 55 Caucasian adults (31 males, 24 females) and 159 Papua New Guinean adults (140 males, 19 females) following the oral administration of Folaprim (100mg DDS; 12.5mg PYR). Blood samples were collected at mean sampling times of eight hours after medication and 18 hours before the next weekly dose for malaria prophylaxis. Clearance of DDS and MADDS from serum were significantly faster (p less than 0.001) in Caucasians than in Papua New Guineans. Significantly lower (p less than greater 0.001) serum concentrations of PYR were found in Papua New Guineans than in Caucasians at both sampling times, an observation which may reflect differences in the bioavailability of PYR between the two racial groups. The theoretical implications of these results are that Caucasians may be more susceptible to PYR-resistant Plasmodium falciparum malaria than Papua New Guineans whilst Papua New Guineans may be more susceptible to P. vivax; malaria than Caucasians.

Armadillo as a model for studying chemotherapy of leprosy: preliminary studies

In order to determine the suitability of the armadillos as a model of human leprosy for chemotherapeutic studies, especially in evaluating newer anti-leprosy drugs, uninfected Armadillos were used to study the metabolic disposition of DDS. Serum DDS levels ranged from 500 ng/ml at 3 hours to 13 ng/ml at 96 hours after intravenous administration of DDS (1 mg/kg). In an ad libitum feeding trial of DDS it was found that the level of serum DDS varied according to the dose of DDS, and even at a dose of 0.0001%, the animals maintained MIC of DDS against M. leprae. Finally, it was demonstrated that armadillos acetylate DDS to MADDS and 7-9% of DDS is acetylated by armadillos.

Albumin binding of bumetanide

Bumetanide binding to human serum albumin was studied using ultrafiltration. The first stoichiometric binding constant for bumetanide is 6.4 X 10(4) M-1. Bumetanide competes with bilirubin for human serum albumin binding, having a KDispl (displacement constant) of 6.2 X 10(3) M-1 measured by the peroxidase method. This displacement effect is also observed using pooled umbilical cord serum and pooled adult serum employing a dialysis rate method. Bumetanide competes to a lesser degree with diazepam binding to human serum albumin. No competition with diazepam occurs using umbilical cord or adult serum. Pharmacologic concentrations of bumetanide would not significantly affect bilirubin-albumin binding and should not increase the risk of bilirubin encephalopathy in newborn infants.

Simultaneous estimation of serum concentrations of dapsone, monoacetyldapsone, and pyrimethamine in Chinese men on maloprim for malaria prophylaxis using reversed-phase high performance liquid chromatography

A reversed-phase high performance liquid chromatography method was developed to simultaneously estimate serum concentrations of dapsone (DDS), monoacetyldapsone (MADDS), and pyrimethamine (PYR) in 34 young adult Chinese men after they had taken the sixth weekly dose of Maloprim for malaria prophylaxis. Serum concentrations of DDS, MADDS, and PYR after 24 h were (mean +/- SEM) 374 +/- 31.3, 310 +/- 30.4, and 121 +/- 7.9 ng/ml, respectively. The 72-h serum concentrations of DDS, MADDS, and PYR were (mean +/- SEM) 134 +/- 21.6, 115 +/- 17.9, and 80 +/- 7.2 ng/ml, respectively. Serum concentrations of DDS and MADDS in many subjects after 120 h were less than 20 ng/ml, while mean +/- SEM concentration of PYR was 53 +/- 5.6 ng/ml. Acetylator phenotyping of the subjects showed that there were 31 (91%) fast acetylators, three (9%) intermediate acetylators, and no slow acetylators.

Fusidic acid binding to serum albumin and interaction with binding of bilirubin

Sodium fusidate, an antibiotic used in staphylococcal infections, is strongly bound to human serum albumin, competitively with bilirubin. It is given in molar amounts sufficient to occupy a considerable fraction of circulating albumin. In order to avoid a risk of bilirubin encephalopathy, induced by displacement of bilirubin, fusidate should be given with caution to newborn infants, particularly if patients are prematurely born, icteric or acidotic. Fusidate does not interfere with albumin binding of warfarin or diazepam.

Chemical drug delivery systems: I. Preparation and evaluation of prodrugs of dapsone

Several prodrugs of dapsone have been prepared and evaluated in vivo for the release of parent drug. The prodrug: 4,4'-dibutyrylaminodiphenyl sulfone gave blood levels above 0.5 micrograms/ml of DDS for about 34 days in rabbits injected intragluteally. The results have been compared with DDS and DADDS.

Binding of dapsone and its analogues to human serum albumin

The binding of dapsone, 4,4'-sulfonylbis(aniline)(1), and its diacetylated derivative, 4,4"'-sulfonylbis(acetanilide)(2), to human serum albumin is reported. To assess the ability of these compounds to displace 4'-[(4-aminophenyl)sulfonyl]acetanilide (3) from albumin, a dialysis rate technique was used. Competition for the bilirubin binding site on albumin was measured with the peroxidase assay. Compounds 1 and 2 strongly displaced both 3 and bilirubin from human serum albumin. The association constants for 1 and 2 with respect to bilirubin binding were 1.29 X 10(3) and 1.15 X 10(4) M-1, respectively. These results suggest that the binding site for 3 and the bilirubin binding site are similar with respect to 1 and 2 and that the binding of dapsone and its derivatives probably does not involve the amino function.

Hematin and bilirubin binding to human serum albumin and newborn serum

In jaundiced newborn infants, hemolytic disease is considered a risk factor for kernicterus due to the suspected competition between bilirubin and other hemoglobin breakdown products for albumin binding. We have studied the effect of hematin on bilirubin-albumin binding using the peroxidase assay and a light-scattering technique for measuring unbound bilirubin. Our results show that hematin does not affect bilirubin-albumin binding. To determine if other albumin binding functions are affected by hematin, we used a microdialysis rate technique employing two ligands, diazepam and monoacetyldiaminodiphenyl sulfone (MADDS). Hematin does not utilize the diazepam binding function of albumin, but does decrease the albumin binding of MADDS. The results of this study indicate that the MADDS and bilirubin binding functions are not identical. The clinical usefulness of reserve albumin equivalent determination using MADDS is discussed.

Inadequate prophylaxis of malaria with dapsone-pyrimethamine

The dapsone-pyrimethamine combination (100 mg of dapsone, 12.5 mg of pyrimethamine [Folaprim; Maloprim, one tablet a week) is considered to provide adequate prophylaxis for Plasmodium falciparum malaria, but to be inadequate for the prevention of P. vivax malaria. Field trials and case reports, however, have shown the comparable efficacy of this combination in the suppression of parasitaemias caused by both parasites. In Lae, Papua New Guinea, 12 patients with clinical signs of malaria had serum concentrations of dapsone-pyrimethamine which were consistent with appropriate weekly use of this combination. The fact that 10 of these patients had P. vivax malaria supports the hitherto unsubstantiated view that dapsone-pyrimethamine can be ineffective in suppressing parasitaemias caused by this parasite. In the two patients with P. falciparum malaria, host factors rather than parasite resistance to dapsone-pyrimethamine were implicated in the development of the parasitaemias.

A rapid method for determination of acetylation phenotype using dapsone

A rapid, simple one-stage protein precipitation method for the estimation of plasma dapsone (DDS) and monoacetyldapsone (MADDS) concentration by high-pressure liquid chromatography (h.p.l.c.) is described. Its performance in the assignment of acetylator phenotype was compared with a reference h.p.l.c. method utilising an extraction procedure and internal standard. The rapid h.p.l.c. technique combined with measurement of the plasma MADDS/DDS ratio is, in our opinion, the method of choice for the determination of the acetylator phenotype in population studies.

Acute dapsone intoxication: a case treated with continuous infusion of methylene blue, forced diuresis and plasma exchange

A case of massive dapsone poisoning (15 g) in a 26 year old man is reported. The patient exhibited high plasma dapsone concentration, marked methemoglobinemia, and signs of hemolysis. He recovered completely after intensive treatment with methylene blue, activated charcoal, forced diuresis, and plasma exchange. In order to avoid overdosage of methylene blue it is concluded that this substance should be given by continuous intravenous infusion in cases with severe methemoglobinemia. This way of administration caused a steady decrease in the methemoglobin concentration compared to intermittent administration. Plasma exchange was of minor benefit, probably due to the large distribution volume of dapsone.

Successful treatment of acute dapsone intoxication using charcoal hemoperfusion

A 22 year old female was admitted to hospital two hours after ingesting 4 g of dapsone. Over the next 15 h she developed progressive hemolysis and methemoglobinemia. Charcoal hemoperfusion and sequential dialysis were performed because of the serious risk of fatality following such a massive dose of dapsone. Charcoal hemoperfusion led to rapid clearing of dapsone from the circulation. This resulted in clinical improvement and controlled the progression of hemolysis and methemoglobinemia.

Pharmacokinetic observations on dapsone in dermatitis herpetiformis

The pharmacokinetics of dapsone (DDS) and monoacetyldapsone (MADDS) following an oral dose of 150 mg DDS were studied in sixteen patients with dermatitis herpetiformis and seven normal subjects. No differences in DDS disposition were observed between the two groups. The maintenance dose of DDS for individual patients was not significantly correlated with jejunal biopsy morphology, DDS or MADDS half-lives, or the area under the plasma concentration-time curves for DDS or MADDS. DDS plasma protein binding was normal in patients and did not apparently determine the concentration of DDS in skin biopsies, for which the skin/plasma DDS concentration ratio was approximately unity. There was no undue representation of acetylator phenotype in the patient group and no correlation between maintenance dose and MADDS/DDS ratio was noted. The determinants of the maintenance DDS dose have not been found. This may relate to pharmacodynamic differences, but alternatively the concentration of oxidative metabolites rather than DDS or MADDS could be responsible for the therapeutic activity in dermatitis herpetiformis.