Dapsone is indicated in Primary and secondary prophylaxis of Pneumocystis (carinii) jirovecii pneumonia, Multibacillary leprosy, Paucibacillary leprosy, Dermatitis herpetiformis, Acne

Dapsone inhibits folic acid synthesis by preventing normal bacterial utilization of PABA (Para-aminobenzoic acid).

Primary and secondary prophylaxis of Pneumocystis (carinii) jirovecii pneumonia:

• Adult: 50 mg daily, with pyrimethamine 50 mg once wkly. Alternatively, 100 mg with pyrimethamine 50 mg twice wkly.
• Child: 1 mth-18 yr: 2 mg/kg daily (max: 100 mg daily) or 4 mg/kg wkly (max: 200 mg wkly).

Multibacillary leprosy:

• Adult: 100 mg daily with clofazimine 50 mg daily, together with rifampicin 600 mg and clofazimine 300 mg once a mth for 12 mth.
• Child: and child 10-14 yr old: daily doses of dapsone 50 mg, or 1 to 2 mg/kg if their body-weight is low

Paucibacillary leprosy:

• Adult: 100 mg daily with 600 mg rifampicin once a mth, both given for 6 mth.
• Child: Reduce dose as for multibacillary leprosy.

Dermatitis herpetiformis:

• Adult: Initially, 50 mg daily increased gradually to 300 mg daily if required.

Decreased serum conc of dapsone when used with rifampicin. Increased plasma conc with probenecid, trimethoprim. Antagonize clofazimine.

Hypersensitivity. Severe anaemia, porphyria.

Anaemia, peripheral neuropathy, haemolysis and methaemoglobinaemia (dose-related), nephrotic syndrome, psychological changes, hepatitis. Others: Nausea, vomiting, anorexia, headache, maculopapular rash, toxic epidermal necrolysis, Stevens-Johnson syndrome. Topical: Dryness, redness, oiliness and peeling at application site.

Pregnancy Category C. Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

G6PD deficiency, methaemoglobin or Hb M. Perform regular blood counts and monitor liver function regularly. Pregnancy and lactation.

Symptoms: nausea, vomiting, hyperexcitability (within a few min to up to 24 hr later), methemoglobin-induced depression, haemolysis (7-14 days after ingestion), seizures and severe cyanosis.

Treatment: activated charcoal (20g four times daily) and haemolysis may enhance elimination of dapsone and its monoacetyl derivative. For patients without G6PD deficiency, methemoglobinemia may be treated with methylene blue 1-2 mg/kg given by slow IV injection (repeated if methemoglobin reaccumulates) or in less severe cases, 3-5 mg/kg every 4-6 hr orally.

Anti-Leprotic drugs

Tablet: Store between 15-30°C. Protect from light. Topical Gel: Store between 20-25°C. Do not freeze.