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Anti-inflammatory / Antimicrobial Pregnancy: Caution — used in pregnancy for DH; neonatal haemolysis if G6PD-deficient neonate

Dapsone

Brand names: Aczone (topical), Dapsone (oral — systemic indications)

Adult dose

Dose: Dermatitis herpetiformis (oral): 25–50 mg OD. Titrate to minimum effective dose (often 50–100 mg OD). Apply BD–TDS (topical acne — Aczone 7.5% gel).
Route: Oral (systemic) or topical
Frequency: OD (oral); BD (topical)
Max: 300 mg/day oral; minimal topical
Oral dapsone: for dermatitis herpetiformis and pemphigoid. G6PD testing mandatory before starting — haemolysis risk.

Paediatric dose

Dose: 1 mg/kg
Route: Oral
Frequency: Once daily
Max: 100 mg per dose
Concentration: 25 mg, 50 mg, 100 mg tablets mg/ml
BNFc paediatric (specialist initiation): 1–2 mg/kg orally once daily for dermatitis herpetiformis and selected dermatoses. G6PD testing mandatory before starting (haemolysis risk in deficiency). Monitor FBC, LFTs, methaemoglobin. Topical dapsone gel (Aczone) for acne is NOT weight-based — fixed-dose.

Dose adjustments

Renal

Reduce dose in renal impairment

Hepatic

Avoid in hepatic impairment

Paediatric weight-based calculator

BNFc paediatric (specialist initiation): 1–2 mg/kg orally once daily for dermatitis herpetiformis and selected dermatoses. G6PD testing mandatory before starting (haemolysis risk in deficiency). Monitor FBC, LFTs, methaemoglobin. Topical dapsone gel (Aczone) for acne is NOT weight-based — fixed-dose.

Clinical pearls

  • G6PD testing mandatory before prescribing — can be fatal in G6PD-deficient patients
  • Dermatitis herpetiformis: dapsone dramatically improves symptoms; gluten-free diet is definitive treatment (allows reduction of dapsone over time)
  • Methaemoglobinaemia: characterised by cyanosis not responding to oxygen — treat with methylene blue 1–2 mg/kg IV
  • Dapsone hypersensitivity syndrome (first 6 weeks): fever + rash + systemic involvement — stop immediately

Contraindications

  • G6PD deficiency (high risk of haemolysis)
  • Severe anaemia
  • Sulfonamide allergy (cross-reactivity)

Side effects

  • Haemolytic anaemia (G6PD-dependent)
  • Methaemoglobinaemia
  • Peripheral neuropathy (prolonged)
  • Agranulocytosis (rare)
  • Nausea
  • Dapsone hypersensitivity syndrome (rash, fever, hepatitis — first 6 weeks)

Interactions

  • Probenecid — increases dapsone levels
  • Rifampicin — reduces dapsone levels
  • Pyrimethamine — increased myelosuppression

Monitoring

  • FBC (haemolysis, metHb)
  • G6PD before starting
  • LFTs
  • Peripheral neuropathy symptoms

Reference: BNFc; BNF; BAD Dermatitis Herpetiformis Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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