Dapsone is the backbone antibiotic of leprosy (Hansen disease) treatment, also used in dermatitis herpetiformis and, combined with pyrimethamine, in toxoplasmosis. It is part of WHO multidrug regimens, free in official programmes.
Also known as: DDS, Acnedap
Dexamethasone may reduce dapsone levels, lowering its therapeutic and prophylactic efficacy.
Dexamethasone induces hepatic enzymes that accelerate dapsone metabolism.
Signs of opportunistic infection or relapse.
Fever, respiratory symptoms, skin lesions.
Monitor prophylactic efficacy (Pneumocystis, leprosy) and consider dapsone dose adjustment.
DailyMed — Dapsone Tablet [Macleods] label, Drug Interactions (enzyme inducers): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=839d7440-ba0e-4c56-b648-d374b155cf03
Probenecid increases dapsone levels (reduced renal excretion of the N-hydroxy metabolite), raising toxicity risk (methaemoglobinaemia, haemolysis).
Probenecid inhibits renal tubular excretion of dapsone metabolites.
Oxygen saturation unresponsive to O2, blue-grey skin colour, haemoglobin.
Unexplained cyanosis, extreme fatigue, dark urine.
Watch for cyanosis, fatigue and haemolytic anaemia signs; consider alternative dosing.
DailyMed — Dapsone Tablet [Macleods] label, Drug Interactions (probenecid): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=839d7440-ba0e-4c56-b648-d374b155cf03
Dapsone plus zidovudine increases the risk of anaemia (additive marrow toxicity), especially in advanced HIV patients.
Both can cause haematological toxicity; the dapsone label documents increased anaemia risk with zidovudine.
Full blood count (Hb) at baseline and periodically; anaemia signs.
Progressive fatigue, pallor, exertional dyspnoea, tachycardia.
Monitor full blood count regularly; consider alternative prophylaxis if anaemia develops.
DailyMed — Dapsone Tablet [Macleods] label, Drug Interactions (zidovudine, anaemia risk) + Zidovudine Tablet [Coupler] label: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=437f55b2-f6d9-0065-e063-6294a90ab929
Taking with food or milk reduces nausea, dapsone's most common adverse effect.
Take with food or milk, always at the same time.
EMC-UK — Dapsone SmPC 4.2/PIL (take with food or milk).
Dapsone causes oxidative haemolysis — G6PD screening mandatory before starting (at-risk populations in Angola).
Screen G6PD before starting; discontinue if haemolysis develops.
Site monograph (dapsone — screen G6PD before starting, severe haemolysis).
Dapsone causes dose-dependent methaemoglobinaemia — contraindicated in existing methaemoglobinaemia or NADH-metHb reductase deficiency.
Monitor methaemoglobinaemia if symptomatic (dyspnoea, cyanosis).
Site monograph (dapsone — monitor methaemoglobinaemia).
Dapsone causes rare agranulocytosis and worsens anaemia — caution with prior cytopenias.
Baseline and periodic full blood count.
Site monograph (dapsone — monitor FBC).
Annex 1 records "Neonatal haemolysis and methaemoglobinaemia; administer 5 mg/day folic acid to the mother" (3rd trimester, factor CM). Dapsone is used in malaria (with pyrimethamine) and leprosy in pregnancy when benefit justifies; monitor newborn bilirubin and methaemoglobin.
Use only if clearly necessary; supplement folic acid (5 mg/day, Prontuário) during treatment; avoid near term if possible due to neonatal haemolysis.
Compatible with monitoring: "continue breastfeeding; very small risk for the infant except if G6PD deficient; haemolytic anaemia" (Annex 2, l. 42493). Do not breastfeed if the infant has unknown/deficient G6PD — screen beforehand if possible.
Prontuário Terapêutico INFARMED — Annex 1: "Dapsone — Neonatal haemolysis and methaemoglobinaemia; administer 5 mg/day folic acid to the mother" (l. 39906-07); Annex 2: "Dapsone... G6PD deficiency; haemolytic anaemia" (l. 42493). EMC-UK (MHRA) — Dapsone SmPC.
Clinical and educational support tool. The information does not replace a medical prescription or the opinion of a qualified healthcare professional.
Bacteriostatic sulfone cornerstone of leprosy treatment; the long half-life and low price allow simple WHO MDT regimens. Use requires G6PD screening and hypersensitivity reaction surveillance.
Structural PABA analogue: competitively inhibits Mycobacterium leprae and protozoal (with pyrimethamine) dihydropteroate synthase, blocking dihydrofolate → dTHF → purines and thymine synthesis — bacteriostatic effect dependent on the microorganism's synthetic capacity. Antileprotic action complemented by neutrophil myeloperoxidase inhibition (anti-inflammatory effect in dermatitis herpetiformis).
Almost complete oral absorption (> 90%), peak 2–8 h; wide distribution with high concentrations in skin, muscle, liver and kidneys; partial protein binding. Food does not significantly change extent.
N-acetylation (NAT2 — fast/slow acetylators, no clinical dose relevance) and N-hydroxylation (CYP2C9/3A4) to hydroxylamines — responsible for methaemoglobinaemia and haemolysis; glucuronide conjugation and renal excretion of metabolites. Relevant enterohepatic circulation.
20–30 h — allows once-daily dosing; enterohepatic circulation and high lipophilia prolong exposure. Neonates and renal impairment: longer half-life.
Medicines from the same therapeutic group (ATC classification) or the same pharmacological class.
