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Sulfone Antibiotic/Antiprotozoal — Dermatitis Herpetiformis Pregnancy: Use with caution — teratogenic risk low; used in pregnancy for DH when benefits outweigh risks; monitor neonatal haemolysis; avoid near term (neonatal methaemoglobinaemia)

Dapsone (Systemic)

Brand names: Dapsone 25/50/100mg Tablets

Adult dose

Dose: 50 mg once daily initially; increase by 50 mg every 2 weeks to effect (typically 50–200 mg/day)
Route: Oral
Frequency: Once daily
Max: 300 mg/day (specialist dermatology)
Treatment of dermatitis herpetiformis (DH — coeliac-associated blistering disease), IgA vasculitis, and other neutrophilic dermatoses (Sweet's syndrome, pyoderma gangrenosum). Dramatic response in DH within 48–72 hours confirms diagnosis. Gluten-free diet is the definitive treatment for DH — dapsone controls symptoms while diet is established.

Paediatric dose

Dose: 1–2 mg/kg/day mg/kg
Route: Oral
Frequency: Once daily
Max: 100 mg/day
BNFc: specialist use for DH in children — rare condition; dose per specialist dermatologist guidance

Dose adjustments

Renal

Use with caution in renal impairment — active metabolite accumulates

Hepatic

Avoid in significant hepatic impairment

Paediatric weight-based calculator

BNFc: specialist use for DH in children — rare condition; dose per specialist dermatologist guidance

Clinical pearls

  • G6PD testing MANDATORY before prescribing — G6PD deficiency causes potentially fatal haemolytic anaemia with dapsone; absolutely contraindicated
  • Dermatitis herpetiformis: intensely pruritic vesicles on extensor surfaces (elbows, knees, buttocks, scalp); IgA deposits at dermal papillae on immunofluorescence; associated with coeliac disease
  • Dapsone response in DH: dramatic improvement within 48–72 hours of first dose is essentially diagnostic — if no response, reconsider diagnosis
  • Methaemoglobinaemia: all patients develop some degree — cyanotic discolouration, fatigue at doses >200 mg/day; ascorbic acid or N-acetylcysteine may help at high doses
  • Dapsone hypersensitivity syndrome (weeks 4–6): fever, morbilliform rash, hepatitis, lymphadenopathy — stop immediately; can be life-threatening
  • Gluten-free diet allows dose reduction and eventual discontinuation of dapsone in DH — takes months to years for full GI healing

Contraindications

  • G6PD deficiency — CONTRAINDICATED (severe haemolytic anaemia)
  • Anaemia
  • Severe renal or hepatic impairment
  • Hypersensitivity to sulfonamides (cross-reactivity)

Side effects

  • Haemolytic anaemia (dose-dependent — all patients; severe in G6PD deficiency)
  • Methaemoglobinaemia (dose-dependent — cyanosis, fatigue)
  • Agranulocytosis (rare — first 3 months)
  • Peripheral neuropathy
  • Dapsone hypersensitivity syndrome (fever, rash, hepatitis — weeks 4–6)
  • Hepatotoxicity

Interactions

  • Trimethoprim — significantly increases dapsone and methaemoglobinaemia risk (avoid combination)
  • Rifampicin — reduces dapsone levels (enzyme induction)
  • Probenecid — increases dapsone levels

Monitoring

  • G6PD screen (before starting)
  • FBC (weekly × 4 weeks, then monthly × 6 months, then every 3 months)
  • Reticulocyte count
  • Methaemoglobin levels (if symptomatic)
  • LFTs

Reference: BNFc; BNF 90; BNFc; BAD Dermatitis Herpetiformis Guidelines 2019; Coeliac UK Clinical Guidance. Verify against your local formulary and the latest BNF before prescribing.

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Curated clinical cross-links plus same-class fallbacks.

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