Dapsone

Uses

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

Dapsone is also used to associated treatment for these conditions: Acne Vulgaris, Bullous Systemic Lupus Erythematosus, Bullous dermatitis herpetiformis, Hansen's Disease, Pemphigus Vulgaris (PV), Relapsing Polychondritis, Mild Pneumocystis pneumonia, Mild Toxoplasma gondii encephalitis, Moderate Pneumocystis pneumonia, Moderate Toxoplasma gondii encephalitis, Refractory Idiopathic thrombocytopenic purpura

How Dapsone works

Dapsone acts against bacteria and protozoa in the same way as sulphonamides, that is by inhibiting the synthesis of dihydrofolic acid through competition with para-amino-benzoate for the active site of dihydropteroate synthetase. The anti-inflammatory action of the drug is unrelated to its antibacterial action and is still not fully understood.

Dosage

Dapsone dosage

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.

Side Effects

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.

Toxicity

Overdosage might be expected to produce nasal congestion, syncope, or hallucinations. Measures to support blood pressure should be taken if necessary.

Precaution

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

Interaction

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

Food Interaction

• Take with or without food. The absorption is unaffected by food.

Dapsone Drug Interaction

Moderate: hydroxychloroquine, hydroxychloroquineUnknown: mycophenolate mofetil, mycophenolate mofetil, duloxetine, duloxetine, furosemide, furosemide, pregabalin, pregabalin, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol, ondansetron, ondansetron, cetirizine, cetirizine

Dapsone Disease Interaction

Major: bone marrow suppressionModerate: liver disease

Elimination Route

Bioavailability is 70 to 80% following oral administration.

Half Life

28 hours (range 10-50 hours)

Elimination Route

Renal

Pregnancy & Breastfeeding use

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.

Contraindication

Hypersensitivity. Severe anaemia, porphyria.

Acute Overdose

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.

Storage Condition

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

Innovators Monograph

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