Sulfone Antibiotic/Antiprotozoal — Dermatitis Herpetiformis Pregnancy: In leprosy the benefits of dapsone are generally considered to outweigh any potential risk to the pregnant patient; some leprologists recommend 5 mg folic acid supplementation daily during pregnancy. Excreted into breast milk, with a report of haemolytic anaemia in a breast-fed infant. May reduce sperm number and/or motility.

Dapsone (Systemic)

Brand names: Dapsone 25/50/100mg Tablets

Systemic (oral) dapsone is a sulfone agent used in dermatology for its anti-inflammatory action in dermatitis herpetiformis and other neutrophilic and bullous dermatoses such as linear IgA disease.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Dermatitis herpetiformis: initially 50 mg daily, gradually increasing to 300 mg daily if required

Route: Oral (tablets swallowed whole with a glass of water)

Frequency: Once daily

Max: Up to 300 mg daily in dermatitis herpetiformis (per §4.2); no absolute maximum stated for other indications

UK SPC (Dapsone 100 mg Tablets); posology is stated for adults and children over 12 years of age. Dermatitis herpetiformis: once lesions have begun to subside, reduce the dose to a minimum as soon as possible, usually 25 mg-50 mg daily, which may be continued for a number of years; maintenance dosage can often be reduced in patients on a gluten-free diet. OTHER INDICATIONS: multibacillary leprosy (3-drug regimen) 100 mg daily for at least two years; paucibacillary leprosy (2-drug regimen) 100 mg daily for at least 6 months; malaria prophylaxis 100 mg weekly with 12.5 mg pyrimethamine; Pneumocystis carinii pneumonia, in combination with trimethoprim, 50 mg-100 mg daily, or 100 mg twice weekly, or 200 mg once weekly. PAEDIATRIC: children aged 6 to 12 years — multibacillary leprosy 50 mg daily for at least two years; paucibacillary leprosy 50 mg daily for at least 6 months. Safety and efficacy in children under 6 years has not been established (no data). No per-kg paediatric dose is stated; verify paediatric use against a children's formulary. ELDERLY: dosage should be reduced where there is impairment of hepatic function. Haemolysis and methaemoglobinaemia are dose-related, occurring in most subjects given more than 200 mg daily; doses up to 100 mg daily do not cause significant haemolysis, but G6PD-deficient subjects are affected by doses above about 50 mg daily. Note: the US label retrieved for cross-check was topical dapsone gel 5% (acne) — a different route and indication, so it was not used for this systemic entry.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to dapsone, sulfonamides, sulfones, or to any of the excipients
Severe anaemia
Porphyria
Severe glucose-6-phosphate dehydrogenase (G6PD) deficiency

Side effects

Haemolysis and methaemoglobinaemia (common; dose-related — the most frequently reported effects)
Haemolytic anaemia; agranulocytosis (rare)
Dapsone syndrome (rare) — rash (always present), fever and eosinophilia after 3-6 weeks of therapy; may progress to exfoliative dermatitis, hepatitis, albuminuria and psychosis; deaths have been recorded
Hepatitis, jaundice, changes in liver function tests (uncommon)
Peripheral neuropathy and peripheral motor neuropathy; headache (uncommon)
Severe cutaneous reactions — toxic epidermal necrolysis, Stevens-Johnson syndrome (very rare); photosensitivity, pruritus, rash (uncommon)

Interactions

Oral typhoid vaccine — should not be taken until at least three days after finishing a course of dapsone, as dapsone could make the vaccine less effective
Probenecid — reduces dapsone excretion and increases dapsone plasma concentrations
Rifampicin / rifabutin — reported to increase the plasma clearance of dapsone
Saquinavir — should not be used in combination; could increase the risk of irregular heartbeat
Trimethoprim — increased dapsone and trimethoprim concentrations reported on concurrent administration in AIDS patients

Clinical monograph

How it works

It suppresses neutrophil function, including myeloperoxidase activity and chemotaxis, which underlies its benefit in neutrophil-rich inflammatory skin disease, distinct from its antibacterial sulfone action.

Prescribing in practice

Screen for glucose-6-phosphate dehydrogenase deficiency before starting, as dapsone causes dose-related haemolysis and methaemoglobinaemia that are severe in deficient patients.
Dapsone hypersensitivity syndrome (fever, rash, eosinophilia and organ involvement) is a recognised early reaction that mandates immediate withdrawal.
Agranulocytosis and peripheral neuropathy can occur, so any unexplained infection, bruising or motor weakness must be investigated.

Monitoring

Monitor full blood count frequently in the early months and then periodically, together with reticulocytes, methaemoglobin if symptomatic, and liver function.

Counselling the patient

Report fever, sore throat, unusual bruising, breathlessness or blue discolouration of the lips promptly.
Some breakdown of red blood cells is expected; tell your team if you become unusually tired or breathless.
Do not stop the medicine abruptly without advice as your skin condition may flare.

Evidence & guidelines

Dapsone is the established first-line drug treatment for dermatitis herpetiformis based on long-standing clinical evidence and is recommended in dermatology guidance.

Reference: BAD Dermatitis Herpetiformis Guidelines 2019; Coeliac UK Clinical Guidance; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways