Drug reference

Dapsone

Sulfone antibacterial / anti-inflammatory · Antileprotic

Also known as Diaminodiphenyl Sulfone, DDS

START

Test G6PD first; leprosy/PCP prophylaxis 100 mg PO daily; DH 50 mg/day titrate

TYPICAL MAX

~300 mg/day (DH short-term highest); leprosy/PCP 100 mg/day

STOP IF

Dapsone hypersensitivity syndrome (DRESS), severe haemolysis/methaemoglobinaemia, agranulocytosis, motor neuropathy

WATCH

G6PD before therapy, FBC/reticulocytes (weekly early then periodic), methaemoglobin if cyanosis, LFTs, DRESS in first 8 weeks

CDSCO approvedSchedule HJan AushadhiNPPA price-controlledATC J04BA02

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 4h · absorption
PEAK: 4h · Cmax
t½: 1.1d · plasma t½
DURATION: 1d · once-daily

EXCRETION

Hepatic acetylation/CYP; ~80% renal metabolites

route + CYP

INTERACTIONS

9 major

SEVERE in our sources

PREGNANCY

Use if clearly needed (leprosy, PCP prophylaxis) — generally continued; monitor for haemolysis (give folate)

FDA category + note

Top interactionssee all 12 →

Aminolevulinic AcidSevereDatabaseDDInter
CladribineSevereDatabaseDDInter
ClozapineSevereDatabaseDDInter
DeferiproneSevereDatabaseDDInter

Available in India

6 branded formulations and 4 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Inhibits bacterial dihydropteroate synthase (folate synthesis — antibacterial vs M. leprae, Pneumocystis); separately suppresses neutrophil myeloperoxidase/oxidant function (anti-inflammatory in dermatologic disease).

Indications

Leprosy (multidrug therapy component)Pneumocystis jirovecii pneumonia treatment/prophylaxis (alternative)Dermatitis herpetiformisOther neutrophilic dermatoses (off-label); toxoplasmosis prophylaxis (with pyrimethamine)

Dosing

Adult: Leprosy: 100 mg PO daily (with rifampicin ± clofazimine). PCP prophylaxis: 100 mg PO daily (or 50 mg + others). Dermatitis herpetiformis: 50 mg/day, titrate to 100–300 mg/day to control then minimise.
Pediatric: 1–2 mg/kg/day (per indication; G6PD-tested).
Renal adjustment: No specific adjustment; caution in severe impairment (metabolite accumulation).
Hepatic adjustment: Caution; monitor (hepatic metabolism; hepatotoxicity).
Geriatric: No specific adjustment; monitor haematology.
Max dose: ~300 mg/day (dermatitis herpetiformis, short-term highest)

Pharmacokinetics

Onset

Antibacterial over weeks; dermatologic response days–weeks

Peak effect

Cmax ~2–8 h

Duration

Once daily

Half-life

~20–30 h (variable; enterohepatic recirculation)

Bioavailability

~70–80%

Protein binding

~70–90%

Metabolism

Hepatic N-acetylation (acetylator status) + CYP-mediated N-hydroxylation (→ haemotoxic hydroxylamine)

Excretion

Renal (~70–85%, metabolites; some unchanged) and biliary

Contraindications

Severe G6PD deficiency (test before — haemolysis)
Severe hypersensitivity / prior dapsone hypersensitivity syndrome
Significant pre-existing anaemia (relative — correct/monitor)

Side effects

Common

Dose-related haemolysis (especially G6PD deficiency)Methaemoglobinaemia (cyanosis, fatigue, headache)Nausea/anorexiaHeadache, dizziness

Serious

Severe haemolytic anaemia (G6PD)
Severe methaemoglobinaemia
Dapsone hypersensitivity syndrome (DRESS: fever, rash, hepatitis, eosinophilia — potentially fatal)
Agranulocytosis
Peripheral motor neuropathy; hepatotoxicity

Pregnancy & lactation

Pregnancy

Use if clearly needed (leprosy, PCP prophylaxis) — generally continued; monitor for haemolysis (give folate)

Lactation

Excreted in milk → infant haemolysis risk (esp. G6PD); monitor infant or avoid

Drug interactions

Aminolevulinic Acid

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Cladribine

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Clozapine

Severe

Database

Drug interaction classified as: synergy

Source: DDInter

Deferiprone

Severe

Database

Clinical effect not specified

Source: DDInter

Nitrous Acid

Severe

Database

Clinical effect not specified

Source: DDInter

Other Oxidant

Severe

Database

Additive haemolysis/methaemoglobinaemia

Avoid combination; especially with G6PD deficiency

Source: Kimi deep-research + Cla

Prilocaine

Severe

Database

Clinical effect not specified

Source: DDInter

Saquinavir

Severe

Database

Clinical effect not specified

Source: DDInter

Trimethoprim

Severe

Database

Mutual level increase → enhanced haematologic toxicity (methaemoglobinaemia)

Monitor closely if combined (PCP regimens); check methaemoglobin

Source: Kimi deep-research + Cla

Rifampin

Moderate

Textbook

Synergism in leprosy.

Source: KDT 7e · p699

Folic Acid Antagonists

Moderate

Database

Additive marrow suppression

Monitor blood counts

Source: Kimi deep-research + Cla

Paracetamol

Moderate

Database

Increased risk of methemoglobinemia.

Monitor for signs of methemoglobinemia (e.g., cyanosis, dyspnea). Avoid co-administration in G6PD deficient patients. Consider alternative analgesics.

Source: DDInter

Related guidelines

Leprosy

ICMR · Dermatology · 2021

Community-acquired pneumonia

IDSA · Pulmonology · 2019

Community-acquired pneumonia

ICMR · Pulmonology · 2022

Inflammatory bowel disease

OTHER · Gastroenterology · 2015

Venous thromboembolism prophylaxis

ASH · Haematology · 2018

Ask House about Dapsone

Continue into a citation-backed clinical answer with the drug context already attached.

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Sources: KD Tripathi 7e, Goodman & Gilman 14e, Harrison 22e, Katzung·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19