DapsoneRx

Trade Names: Generic

Drug Class: Sulfone bacteriostatic

Preparations: 25- and 100-mg tablets

Dose: 25 mg/day initially, increased by 25- to 50-mg increments to as high as 200 mg/day
For prophylaxis of Pneumocystis in patients unable to tolerate trimethoprim/sulfamethoxazole, dapsone 100 mg once daily  or dapsone 50 mg daily with pyrimethamine and leucovorin has been used.

Indications: Sometimes tried for skin lesions of systemic or discoid lupus erythematosus, urticarial vasculitis, pemphigus, aphthous ulcers and pyoderma gangrenosum. Nonrheumatologic uses include leprosy, malaria, prophylaxis of Pneumocystis carinii, and dermatitis herpetiformis.

Mechanism of Action: Immunomodulatory mechanism unknown; has sulfonamide-like action competing for p-aminobenzoic acid and preventing bacterial synthesis of folic acid

Contraindications: Hypersensitivity to dapsone, G6PD deficiency

Precautions: Use caution in patients allergic to sulfonamides, check for G6PD deficiency, and severe anemia.

Monitoring: Determine G6PD status before treatment of patients from ethnic groups at greater risk. Monitor CBC in all patients initially weekly, then monthly, and then every 2–3 months. Monitor LFTs at intervals. Check for jaundice and hemolysis.

Pregnancy Risk: C

Adverse Effects
Common: Rash, dose-related hemolysis, and methemoglobinemia
Less common: GI intolerance, leukopenia, agranulocytosis, exfoliative dermatitis, hepatitis, cholestatic jaundice

Drug Interactions
Rifampin: Decreased effect of dapsone
Folic acid antagonists (trimethoprim, sulfonamides): Increased toxicity

Patient Instructions: Regular blood monitoring is required. May cause photosensitivity.

Comments: The incidence of hemolytic anemia may be reduced by using concomitant antioxidant therapy (vitamin E or C). HLA-B*1301 may be  a risk factor  for dapsone hypersensitivity syndrome; the allele is present in approximately 1-12% of Asian populations but is extremely rare in Europeans and Africans.

Clinical Pharmacology: Well absorbed; acetylated in the liver.  Acetylator phenotype (slow or fast) does not affect clinical use. Cytochrome P-450–mediated hydroxylation; renal elimination of metabolites; half-life 30 hours

Cost: $$

BIBLIOGRAPHY

National Institutes of Health and CDC Recommendations for prevention and treatment of Pneumocystis pneumonia (PCP) http://aidsinfo.nih.gov/guidelines/ accessed 8/19/2014