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Anti-inflammatory / Antimicrobial Pregnancy: ORAL tablets (UK SPC section 4.6), pregnancy: 'It is generally considered that the benefits of dapsone in the treatment of leprosy outweigh any potential risk to the pregnant patient. Some leprologists recommend 5 mg folic acid supplementation daily for leprosy patients receiving dapsone during pregnancy.' Breast-feeding: dapsone is excreted into breast milk and there has been a report of haemolytic anaemia in a breast-fed infant; there is an opinion that dapsone should not be used in lactating mothers, although in general therapy for leprosy is continued in such patients. Fertility: limited information; it may reduce the numbers and/or motility of sperm. TOPICAL gel 5% (US label section 8.1): 'There are no available data on dapsone gel, 5%, use in pregnant women to inform a drug-associated risk for adverse developmental outcomes.' In animals, oral dapsone given to pregnant rats and rabbits during organogenesis at systemic exposures more than 250 times the exposure at the maximum recommended human dose of the gel was embryocidal; given orally to rats from the onset of organogenesis through the end of lactation at approximately 400 times that exposure it produced increased stillbirths and decreased pup weight. The retrieved text of the US pregnancy section ends at the source-fetch limit, so it is not complete, and no lactation statement for the gel was retrieved.

Dapsone

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

Topical dapsone is a gel formulation of the sulfone antibacterial applied to the skin for inflammatory acne vulgaris.

Adult dose

Dose: Two regimens, one per route. (1) Dermatitis herpetiformis - ORAL dapsone tablets (UK SPC; adults and children over 12 years): initially 50 mg daily, gradually increasing to 300 mg daily if required; 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. (2) Acne vulgaris - TOPICAL dapsone gel 5% (US labelling): apply approximately a pea-sized amount in a thin layer to the acne-affected areas twice daily.
Route: Oral (tablets, swallowed whole with a glass of water) for dermatitis herpetiformis; topical (gel 5%, acne-affected skin) for acne vulgaris. The gel is for topical use only - not for oral, ophthalmic or intravaginal use.
Frequency: Oral: daily (maintenance often reducible with a gluten-free diet). Topical gel: twice daily; reassess treatment if there is no improvement after 12 weeks.
SOURCES: the oral regimen is from the UK SPC for Dapsone 100 mg Tablets; the topical regimen is from US prescribing information (DailyMed, dapsone gel 5%) - no UK SPC for a topical dapsone gel was available, so verify the gel regimen against a UK source before treating it as UK practice. Strength: the only topical strength in the source is gel 5% (each gram contains 50 mg of dapsone). The UK SPC says maintenance dosage can often be reduced in patients receiving a gluten-free diet. The oral tablet SPC also licenses leprosy, malaria prophylaxis and Pneumocystis prophylaxis; those regimens are not part of this dermatology page and are not listed here. The gel is not recommended in patients under 12 years (safety and efficacy not studied) and is not weight-based. Rub the gel in gently and completely; it is gritty with visible drug particles; wash hands after application. Children: use a children's formulary.

Dose adjustments

Renal

No renal dosing statement is given in the UK SPC section 4.2 (oral tablets) or the US gel label dosage section.

Hepatic

Oral tablets, UK SPC section 4.2 (elderly population): 'Dosage should be reduced in the elderly where there is an impairment of hepatic function.' No other hepatic dosing statement in the retrieved sections.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • ORAL tablets (UK SPC section 4.3): hypersensitivity to dapsone, sulfonamides, sulfones or any excipient
  • ORAL tablets: severe anaemia
  • ORAL tablets: porphyria
  • ORAL tablets: severe glucose-6-phosphate dehydrogenase deficiency
  • TOPICAL gel 5% (US label section 4): the label lists no contraindication ('None.'); however, avoid use in patients with congenital or idiopathic methaemoglobinaemia (section 5.1), and G6PD-deficient patients are more susceptible to drug-induced methaemoglobinaemia and haemolysis (labelled warnings, not contraindications)

Side effects

  • ORAL (UK SPC): haemolysis and methaemoglobinaemia are the most frequently reported adverse effects and are dose related - they occur 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. Haemolytic anaemia and agranulocytosis are also listed (agranulocytosis is rare when dapsone is used alone)
  • ORAL (UK SPC): tachycardia; anorexia, nausea, vomiting; hepatitis, jaundice, changes in liver function tests; hypoalbuminaemia; headache, peripheral neuropathy, peripheral motor neuropathy; insomnia, psychoses; photosensitivity, pruritus, rash, maculopapular rash, exfoliative dermatitis, toxic epidermal necrolysis, Stevens-Johnson syndrome, fixed drug eruptions
  • ORAL (UK SPC): dapsone syndrome (rare) - may follow 3-6 weeks of therapy; rash (always present), fever and eosinophilia; if dapsone is not stopped immediately it may progress to exfoliative dermatitis, hepatitis, albuminuria and psychosis, and deaths have been recorded
  • TOPICAL gel (US label): most common adverse reactions (incidence 10% or more) are oiliness/peeling, dryness and erythema at the application site
  • TOPICAL gel: methaemoglobinaemia - cases with resultant hospitalisation have been reported postmarketing; signs and symptoms may be delayed some hours after exposure and are characterised by a slate-grey cyanosis seen in, e.g., buccal mucous membranes, lips and nail beds
  • TOPICAL gel: some subjects with G6PD deficiency using dapsone gel developed laboratory changes suggestive of haemolysis
  • TOPICAL gel: serious adverse reactions reported in clinical trials included but were not limited to suicide attempt and tonic-clonic movements (nervous system/psychiatric); abdominal pain, severe vomiting and pancreatitis (gastrointestinal); severe pharyngitis
  • TOPICAL gel: depression was reported in 12 of 4032 subjects across the clinical trials (3 of 1660 treated with vehicle and 9 of 2372 treated with dapsone gel 5%); psychosis was reported in 2 of 2372 subjects treated with dapsone gel 5% and in 0 of 1660 treated with vehicle
  • TOPICAL gel: temporary local yellow or orange discoloration of the skin and facial hair when topical benzoyl peroxide is applied after dapsone gel (reported by 7 out of 95 subjects in a clinical study; resolved in 4 to 57 days)
  • TOPICAL gel: combined contact sensitisation/irritation studies in 253 healthy subjects resulted in at least 3 subjects with moderate erythema; dapsone gel 5% did not induce phototoxicity or photoallergy in human dermal safety studies
  • NOTE: the US gel label sections on warnings, adverse reactions, interactions and pregnancy end at the source-fetch limit, so the topical safety content is what was retrieved, not the whole of those sections

Interactions

  • ORAL (UK SPC section 4.5): oral typhoid vaccine should not be taken until at least three days after finishing a course of dapsone, because dapsone could make the vaccine less effective
  • ORAL: probenecid - concurrent administration reduces dapsone excretion and increases dapsone plasma concentrations
  • ORAL: rifampicin / rifabutin - reported to increase the plasma clearance of dapsone
  • ORAL: saquinavir - should not be used in combination, as this could increase the risk of irregular heartbeat
  • ORAL: trimethoprim - increased dapsone and trimethoprim concentrations reported following concurrent administration in AIDS patients
  • TOPICAL gel (US label section 7): trimethoprim/sulfamethoxazole increases the level of dapsone and its metabolites (dapsone AUC 0-12 increased by about 40% and N-acetyl-dapsone by about 20%; dapsone hydroxylamine more than doubled), although exposure from the topical dose is about 1% of that from the 100 mg oral dose even when co-administered
  • TOPICAL gel: topical benzoyl peroxide used with dapsone gel may cause temporary local yellow or orange skin discoloration
  • TOPICAL gel: dapsone can cause elevated methaemoglobin levels, particularly in conjunction with methaemoglobin-inducing agents

Monitoring

  • ORAL (UK SPC section 4.4): regular blood counts during dapsone therapy are recommended
  • ORAL: use with caution in cardiac or pulmonary disease, and in anaemia - severe anaemia should be treated before starting dapsone
  • ORAL: patients deficient in glucose-6-phosphate dehydrogenase or methaemoglobin reductase, or with haemoglobin M, are more susceptible to the haemolytic effects of dapsone
  • ORAL: stop dapsone immediately if dapsone syndrome is suspected (rash, fever, eosinophilia, typically 3-6 weeks into therapy)
  • TOPICAL gel (US label): discontinue dapsone gel if signs of methaemoglobinaemia occur; advise patients to stop the gel and seek immediate medical attention in the event of cyanosis - signs may be delayed some hours after exposure
  • TOPICAL gel: in G6PD deficiency, watch for laboratory changes suggestive of haemolysis; review concomitant medicines that induce methaemoglobin
  • TOPICAL gel: reassess treatment if there is no improvement after 12 weeks

Clinical monograph

How it works

Applied locally it exerts anti-inflammatory and antimicrobial effects, attenuating the neutrophilic inflammation that characterises inflammatory acne lesions.

Prescribing in practice

  • A transient yellow-orange skin or hair discolouration can occur where the gel contacts benzoyl peroxide, so the two should not be applied at the same time.
  • Systemic absorption is low, so the haematological risks seen with oral dapsone are not generally expected with topical use.
  • Confine application to the affected skin and avoid the eyes, lips and mucous membranes.

Monitoring

Routine blood monitoring is not required for topical use; assess the treated skin for irritation and therapeutic response at review.

Counselling the patient

  • Apply a thin film to clean, dry affected skin and wash your hands afterwards.
  • Do not use benzoyl peroxide products at the same time of day, as together they may temporarily stain skin or hair orange.
  • Mild dryness, redness or stinging may occur initially and usually settles.

Evidence & guidelines

Topical dapsone gel has demonstrated efficacy for inflammatory acne in randomised controlled trials underpinning its licence.

Reference: BAD Dermatitis Herpetiformis Guidelines; 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).

Related

Curated clinical cross-links plus same-class fallbacks.

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