Dapsone

Pronunciation: DAP-sone.

Generic name: dapsone
Drug class: Sulfone antibacterial (antileprosy / anti-inflammatory sulfone)
Form: Tablet (25 mg, 50 mg, 100 mg, depending on market)
Route: Oral
Legal status: Prescription-only

Availability and supply rules vary by country

Trade names by country: United States · Canada

What dapsone is and how it works

Dapsone is a prescription-only oral sulfone antibacterial medicine, used mainly to treat dermatitis herpetiformis (an itchy, blistering skin condition linked to gluten sensitivity) and all forms of leprosy, usually as part of a multidrug regimen. In the UK it is also used for malaria prevention (with pyrimethamine) and to prevent Pneumocystis pneumonia in people with weakened immune systems. (1) (2)

Dapsone is generally taken once a day. It carries real, dose-related risks of haemolytic anaemia and a blood disorder called methaemoglobinaemia, both of which are markedly more likely if you have glucose-6-phosphate dehydrogenase (G6PD) deficiency -- your prescriber may check for this before or during treatment. Rare but serious blood disorders (agranulocytosis, aplastic anaemia) and a specific dapsone hypersensitivity syndrome (fever, rash, and organ involvement appearing 3-6 weeks into treatment) are also real risks that require regular blood tests and prompt reporting of new symptoms.

Mechanism of action: how dapsone works

Dapsone is a sulfone antibacterial whose mechanism of action is believed to be similar to the sulfonamides -- inhibition of folic acid (dihydrofolate) synthesis in susceptible organisms, notably Mycobacterium leprae. Following oral administration it is almost completely absorbed from the gastrointestinal tract (reported bioavailability exceeding 86%), with peak serum concentrations reached within 2-8 hours. (1) (2)

What dapsone is used for

Dermatitis herpetiformis

Used to control the itchy, blistering skin condition dermatitis herpetiformis, with the dose individually titrated to the lowest amount that controls symptoms. (1) (2) (5)

Leprosy (all forms)

Used as part of a combination (multidrug) regimen for both multibacillary and paucibacillary leprosy, together with other anti-leprosy medicines such as rifampicin (and clofazimine for multibacillary disease), except in cases of proven dapsone resistance. (1) (2) (3) (5)

Actinomycotic mycetoma

Used, generally in combination with streptomycin (or sulfamethoxazole/trimethoprim as an alternative), to treat this chronic fungal-like bacterial infection, per Canadian and New Zealand product information. (3) (5)

Malaria prevention and Pneumocystis pneumonia prophylaxis (UK)

In the UK, also used (with pyrimethamine) for malaria prophylaxis, and alone or in combination for prevention of Pneumocystis carinii (jirovecii) pneumonia in immunocompromised patients, including those with HIV/AIDS. (2)

Before taking dapsone

Do not take / not appropriate for

Do not take dapsone if you have had an allergic reaction to it, to sulfonamides, sulfones, or any of its ingredients. (all confirmed markets) (1) (2)
Do not take dapsone if you have severe anaemia (this should be treated first) or porphyria -- dapsone is associated with acute porphyria attacks and considered unsafe in this condition. (United Kingdom, New Zealand) (2) (5)
Do not take dapsone if you have severe G6PD (glucose-6-phosphate dehydrogenase) deficiency. (United Kingdom) (2)
Sulfones, including dapsone, are contraindicated in patients with advanced amyloidosis of the kidneys. (Canada) (3)

Tell your clinician about

Whether you have, or may have, G6PD (glucose-6-phosphate dehydrogenase) deficiency -- this significantly increases the risk of haemolytic anaemia and methaemoglobinaemia with dapsone, and your prescriber may test for it before starting treatment.
Any personal or family history of blood disorders, methaemoglobin reductase deficiency, or haemoglobin M.
Any history of severe anaemia, heart, lung, liver, or kidney disease.
All other medicines you take, especially rifampicin/rifampin, trimethoprim, probenecid, or folic-acid-antagonist medicines (such as pyrimethamine).
Pregnancy, plans for pregnancy, or breastfeeding.
Any history of porphyria.

(1) (2) (3) (5)

How to take dapsone

Take dapsone by mouth exactly as your prescriber directs -- the dose depends on the condition being treated and is often started low and adjusted.
Tablets should be swallowed whole; do not split a tablet if a smaller dose is needed -- a lower-strength tablet should be used instead.
Attend all blood tests your prescriber schedules -- these check for early signs of anaemia or blood-count changes.
Do not stop or change your dose on your own, particularly if you are being treated for leprosy, where treatment is typically combined with other medicines over months to years.

(1) (2) (5)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

If you miss a dose, take it as soon as you remember unless it is almost time for your next dose -- in that case, skip the missed dose and continue your regular schedule. Do not take a double dose. Contact your prescriber if you are unsure, particularly during leprosy treatment where consistent dosing matters.

Overdose

Seek urgent medical attention if too much dapsone may have been taken, or if you develop blue-tinged lips/skin (a sign of methaemoglobinaemia), severe tiredness, shortness of breath, or fainting. Methaemoglobinaemia can be treated with intravenous methylene blue in hospital, but this treatment itself must NOT be given to people with G6PD deficiency -- tell emergency staff if this is known or suspected. (2)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Dose-related haemolysis (breakdown of red blood cells) -- the most common adverse effect, typically causing a small, gradual drop in haemoglobin.

What to notice: Dose-related haemolysis (breakdown of red blood cells) -- the most common adverse effect, typically causing a small, gradual drop in haemoglobin.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Methaemoglobinaemia (a blood disorder reducing oxygen-carrying capacity) -- dose-related.

What to notice: Methaemoglobinaemia (a blood disorder reducing oxygen-carrying capacity) -- dose-related.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (5)

Headache, nausea, and loss of appetite have been reported.

What to notice: Headache, nausea, and loss of appetite have been reported.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Serious warnings

Signs of haemolytic anaemia or methaemoglobinaemia, especially with G6PD deficiency — high caution

Symptoms: Unusual tiredness, pale skin, shortness of breath, rapid heartbeat, or blue-tinged lips/skin.

Action: Contact your prescriber promptly and attend scheduled blood tests. This reaction is dose-related and markedly more likely in people with G6PD (glucose-6-phosphate dehydrogenase) deficiency, methaemoglobin reductase deficiency, or haemoglobin M -- your prescriber may check for this before starting treatment. (1) (2) (5)

Signs of a serious blood disorder (agranulocytosis or aplastic anaemia) — emergency

Symptoms: Sore throat, fever, pallor, unusual bruising or bleeding (purpura), or jaundice.

Action: Seek medical attention immediately. Deaths have been reported from agranulocytosis, aplastic anaemia, and other blood dyscrasias associated with dapsone -- this is why regular complete blood counts are recommended (weekly for the first month, monthly for 6 months, then twice yearly per the US label). (1) (5)

Dapsone hypersensitivity syndrome — emergency

Symptoms: Rash (present in essentially all cases), fever, and swollen glands, typically appearing 3-6 weeks after starting treatment; can progress to widespread skin peeling (exfoliative dermatitis) and liver inflammation (hepatitis).

Action: Seek medical attention immediately if this syndrome is suspected -- it can be fatal if untreated, and your prescriber will need to withdraw dapsone under medical supervision. Cutaneous reactions including toxic erythema, erythema multiforme, and toxic epidermal necrolysis have also been reported and require prompt medical reassessment. (2) (5)

Signs of liver problems — high caution

Symptoms: Yellowing of the skin or eyes (jaundice), dark urine, or unusual fatigue.

Action: Contact your prescriber promptly. Toxic hepatitis and cholestatic jaundice have been reported early in dapsone therapy, and may occur more often in people with G6PD deficiency. (1) (5)

Signs of peripheral neuropathy — moderate caution

Symptoms: New muscle weakness, particularly in the hands or feet (motor loss is the predominant feature).

Action: Tell your prescriber promptly -- dapsone should be withdrawn if muscle weakness appears, as this is a definite though uncommon complication. (1)

Leprosy reactional states (during leprosy treatment) — moderate caution

Symptoms: Increased inflammation, skin changes, nerve pain, muscle weakness, joint pain, or eye pain during leprosy treatment.

Action: These reactional states are not allergic reactions to dapsone and generally do not require stopping anti-leprosy treatment, but should be reported and may need corticosteroids or other management -- discuss with your treating clinician. (3)

Interactions

Rifampicin (rifampin) substantially increases dapsone clearance, lowering its levels by 7-10 fold -- your prescriber will factor this in when the two are combined for leprosy treatment. (1) (2)
Folic acid antagonist medicines (such as pyrimethamine) increase the risk of blood-related side effects when combined with dapsone; agranulocytosis has been reported in patients on weekly pyrimethamine plus dapsone during the second and third months of therapy. (1) (5)
Trimethoprim and dapsone mutually raise each other's blood levels by roughly 1.5 times when combined (relevant in AIDS-related Pneumocystis pneumonia treatment/prevention). (1) (2)
Probenecid reduces dapsone excretion, increasing its plasma concentration. (2)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Dapsone should be given to a pregnant woman only if clearly needed (US Pregnancy Category C). For leprosy treatment specifically, the benefits of continuing therapy generally outweigh the risks, and some clinicians recommend an additional 5 mg of folic acid daily during pregnancy. (1) (2) (3) (4) (5) (6)

Breastfeeding

Dapsone is excreted into breast milk in substantial amounts, and hemolytic reactions have been reported in breastfed infants (including a case report of haemolytic anaemia in a nursing infant) -- discuss feeding decisions with your prescriber, particularly if continuing leprosy treatment during breastfeeding. (1) (2) (3) (4) (5) (6)

Children

Children are treated on the same schedule as adults but with correspondingly smaller, bodyweight-adjusted doses; no data are available for children under 6 years for some indications. (1) (2) (3) (4) (5) (6)

Elderly

No specific dose adjustment based on age alone was identified in the sources reviewed; general caution around blood-count monitoring applies to all patients. (1) (2) (3) (4) (5) (6)

Hepatic_impairment

Use with caution in patients with hepatic disease; toxic hepatitis and cholestatic jaundice have been reported, and liver function should be monitored where feasible, with dapsone discontinued if abnormalities occur until the cause is established. (1) (2) (3) (4) (5) (6)

Renal_impairment

Use with caution in patients with renal disease; sulfones are contraindicated in patients with advanced renal amyloidosis specifically (per Canadian product information). (1) (2) (3) (4) (5) (6)

Source_ids

US-DAILYMED-DAPSONE-TABLETS-2026,UK-EMC-DAPSONE-100MG-2026,CA-HEALTHCANADA-RIVA-DAPSONE-2026,NZ-MEDSAFE-DAPSONE-TABLETS-2026 (1) (2) (3) (4) (5) (6)

Monitoring

Before starting

G6PD (glucose-6-phosphate dehydrogenase) status, where clinically indicated
Baseline complete blood count
Baseline liver function, where feasible
Review of severe anaemia -- treat before starting
Review of all other medicines for interactions (rifampicin, trimethoprim, folic acid antagonists)

During treatment

Complete blood counts: weekly for the first month, monthly for the next 6 months, then every six months (per the US label).
Prompt reporting of sore throat, fever, pallor, unusual bruising/bleeding, or jaundice.
Watching for rash and fever appearing 3-6 weeks into treatment (possible dapsone hypersensitivity syndrome).
Liver function monitoring where clinically indicated.
Monitoring for new muscle weakness (peripheral neuropathy).

(1) (2) (5)

Storage

Store at room temperature, away from moisture and light, out of reach of children.

Professional information

Clinician-facing context only, sourced from the current US, UK, Canadian, and New Zealand labels; verify against the current full label before prescribing. EU status (beyond France's derogatory-access finding) was not independently confirmed live in this session.

United States / United Kingdom / New Zealand

Indication: Dermatitis herpetiformis; leprosy (all forms); actinomycotic mycetoma (Canada/NZ); UK also: malaria prophylaxis with pyrimethamine, Pneumocystis pneumonia prophylaxis

Dose summary: Dermatitis herpetiformis: 50 mg/day titrated to 50-300 mg/day. Leprosy: 100 mg/day (adults, ~1-2 mg/kg) combined with other anti-leprosy agents. Actinomycotic mycetoma: 100 mg twice daily with streptomycin.

Renal context: Use with caution in renal disease; contraindicated in advanced renal amyloidosis (Canada). (1) (2) (3) (5)

Mechanism of action

Hepatic guidance

Toxic hepatitis and cholestatic jaundice have been reported early in therapy; monitor liver function where feasible. Should abnormalities occur, treatment withdrawal pending investigation of the cause is the recommended clinical approach.

Overdose note

Manage methaemoglobinaemia with slow IV methylene blue 1-2 mg/kg where indicated -- contraindicated in G6PD-deficient patients (risk of severe haemolysis instead of benefit). (1) (2)

Frequently asked questions

Does dapsone carry a boxed (black-box) warning?

No. Dapsone's serious risks -- haemolytic anaemia and methaemoglobinaemia (especially with G6PD deficiency), rare but potentially fatal agranulocytosis/aplastic anaemia, dapsone hypersensitivity syndrome, and peripheral neuropathy -- are real and prominently documented in the current US, UK, Canadian, and New Zealand labels, but none of these labels present them as a boxed/black-box warning. They appear as detailed Warnings and Precautions sections instead. (1) (2) (5)

Do I need a G6PD (glucose-6-phosphate dehydrogenase) test before starting dapsone?

Your prescriber will decide based on your individual risk factors and the indication being treated. G6PD deficiency substantially increases the risk of dose-related haemolytic anaemia and methaemoglobinaemia with dapsone, and severe G6PD deficiency is a contraindication in the UK label specifically. Discuss your personal and family history with your prescriber. (2) (1)

Is dapsone available in the European Union?

This could not be fully confirmed. There is no EMA-centralised authorisation for dapsone (expected given how old this medicine is). France was checked specifically and dapsone is available there only through a derogatory/named-patient access framework for imported products lacking a standard French marketing authorisation -- this is a real but limited finding, not evidence of a standard EU national marketing authorisation. Check with a local pharmacist or regulator if you are in the EU. (6)

Why do I need frequent blood tests while taking dapsone?

Dapsone can cause dose-related declines in blood counts, and rare but serious and potentially fatal blood disorders (agranulocytosis, aplastic anaemia) have been reported. The US label recommends complete blood counts weekly for the first month, monthly for the next six months, and every six months thereafter, so problems can be caught early. (1)

What is the mechanism of action of dapsone?

What is the generic name of Dapsone?

The generic name is dapsone. (1) (2)

What class of drug is dapsone?

Dapsone is classed as: Sulfone antibacterial (antileprosy / anti-inflammatory sulfone). (1) (2)

References

Dapsone Tablets USP, 25 mg and 100 mg -- full prescribing information (setid 9cfe5fe7-abc7-4f48-a597-1b1a5c70a354)U.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-30 · source 1
Dapsone 100mg Tablets -- Summary of Product Characteristics (product 13893)UK Medicines and Healthcare products Regulatory Agency / electronic medicines compendium (emc), Summary of Product Characteristics · United Kingdom · accessed 2026-07-30 · source 2
RIVA-DAPSONE (Dapsone Tablets USP, 100 mg) -- Prescribing Information Including Patient Medication Information, dated 24 May 2019Health Canada -- Laboratoire Riva Inc., product monograph · Canada · accessed 2026-07-30 · source 3
Dapsone oral tablets -- ARTG registrations (Dapsomed 50 mg, Link Medical Products dapsone 100 mg, Dapsone Medsurge 100 mg)Australian Therapeutic Goods Administration (TGA), Australian Register of Therapeutic Goods (ARTG) · Australia · accessed 2026-07-30 · source 4
DAPSONE 25 mg and 100 mg tablets -- New Zealand Data SheetNew Zealand Medicines and Medical Devices Safety Authority (Medsafe) · New Zealand · accessed 2026-07-30 · source 5
Referentiel des specialites en acces derogatoire -- DapsoneAgence nationale de securite du medicament et des produits de sante (ANSM), France · France / European Union · accessed 2026-07-30 · source 6

Brand names by country

Single-ingredient dapsone names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

Aczone75 mg/g, 50 mg/g · almirall, llc

Canada

ACZONE

View brands in additional countries.