Dapsone
Synonym :
Diaminodiphenylsulfone
Mechanism :
Dapsone is a sulfone for the primary treatment of Dermatitis herpetiformis and an antibacterial drug for susceptible cases of leprosy. Dapsone is bactericidal as well as bacteriostatic against Mycobacterium leprae. As an antibacterial, dapsone inhibits bacterial synthesis of dihydrofolic acid, via competition with para-aminobenzoate for the active site of dihydropteroate synthetase.
Indication :
- Leprosy
- Pneumocystis carinii pneumonia (off-label)
Contraindications :
Avoid use in cardiac or pulmonary disease, anemia, G6PD deficiency.
Methemoglobin reductase deficiency.
Hypersensitivity to dapsone or any of its components.
Dosing :
Oral
Leprosy:
Oral 1-2 mg/kg/day as single dose in combination with
rifampicin. Maximum Dose: 100 mg/day.
Pneumocystis Pneumonia Prophylaxis:
>1 month:
2 mg/kg/day (up to 100 mg) orally once a day OR 4 mg/kg orally once weekly Maximum dose = 200 mg
Adolescents:
100 mg once orally or in two divided doses in single drug treatment OR 50 mg once every day in combination therapy.
Adverse Effect :
Dose-related hemolysis, agranulocytosis, especially in combination with pyrimethamine, peripheral neuropathy, nausea, vomiting, abdominal pain, pancreatitis, vertigo, blurred vision, tinnitus, insomnia, fever, headache, psychosis, phototoxicity, pulmonary eosinophilia, tachycardia, albuminuria, nephrotic syndrome, hypoalbuminemia without proteinuria, renal papillary necrosis, male infertility, drug-induced lupus erythematosus, infectious mononucleosis-like syndrome, methemoglobinemia, erythema nodosum leprosum.
Interaction :
Rifampin: Plasma concentration reduced as Dapsone is a substrate of cytochrome P-450 3A4.
Probenecid: Reduces dapsone excretion, increased risk of side-effects.
Pyrimethamine: May increase the likelihood of hematologic reactions.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Dose as in normal renal function |
| 10-20 | Dose as in normal renal function, use with caution |
| <10 | 50–100mg daily, use with caution. No dose reduction is required for malaria prophylaxis. |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Likely dialysability. Dose as in GFR<10 mL/min |
| HD | Dialysed. Dose as in GFR<10 mL/ min |
| HDF/High flux | Dialysed. Dose as in GFR<10 mL/ min |
| CAV/VVHD | Likely dialysability. Dose as in GFR=10–20 mL/min |
Hepatic Dose :
Dapsone can cause toxic hepatitis and cholestatic jaundice. Monitor LFT before starting and during treatment.