Adult: In combination with pyrimethamine: 100 mg weekly.
Oral Paucibacillary leprosy
Adult: Recommended regimen by WHO: In combination with rifampicin (2-drug regimen): 100 mg daily for at least 6 months. Treatment duration may vary depending on the therapy regimen (refer to local guidelines for detailed regimen recommendations). Child: 10-14 years Recommended regimen by WHO: In combination with rifampicin (2-drug regimen): 50 mg daily for at least 6 months. Treatment duration may vary depending on the therapy regimen (refer to local guidelines for detailed regimen recommendations); >14 years Same as adult dose.
Oral Dermatitis herpetiformis
Adult: Initially, 50 mg daily, may be increased gradually to 300 mg daily if necessary. Once lesions have started to subside, reduce dose as soon as possible to the usual maintenance dose of 25-50 mg daily. Maintenance dose may be reduced in patients receiving a gluten-free diet.
Oral Prophylaxis of Pneumocystis (carinii) jirovecii pneumonia
Adult: In combination with trimethoprim in immunodeficient patients, particularly AIDS patients: 50-100 mg daily. Alternatively, 100 mg twice weekly or 200 mg once weekly.
Oral Multibacillary leprosy
Adult: Recommended regimen by World Health Organisation (WHO): In combination with clofazimine and rifampicin (3-drug regimen): 100 mg daily for at least 12 months. Treatment duration may vary depending on the therapy regimen (refer to local guidelines for detailed regimen recommendations). Child: 10-14 years Recommended regimen by WHO: In combination with clofazimine and rifampicin (3-drug regimen): 50 mg daily for at least 12 months. Treatment duration may vary depending on the therapy regimen (refer to local guidelines for detailed regimen recommendations); >14 years Same as adult dose.
Topical/Cutaneous Acne vulgaris
Adult: As 5% gel: Apply a thin layer on the affected area bid. As 7.5% gel: Apply a thin layer on the entire face or other affected areas once daily. Reassess treatment if there is no improvement after 12 weeks. Child: As 5% gel: ≥12 years Same as adult dose. As 7.5% gel: ≥9 years Same as adult dose.
Administration
Should be taken with food.
Contraindications
Hypersensitivity to dapsone. Severe anaemia, porphyria, severe G6PD deficiency. Congenital or idiopathic methaemoglobinaemia (topical).
Special Precautions
Patient with history of hypersensitivity to sulfonamides; cardiac disease, pulmonary disease; mild to moderate anaemia, diabetes mellitus; deficiency in G6PD, methaemoglobin reductase or haemoglobin M. Hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Haemolysis, methaemoglobinaemia, haemolytic anaemia; toxic hepatitis, cholestatic jaundice, hyperbilirubinaemia, peripheral neuropathy; fungal or bacterial superinfection with prolonged use (e.g. C. difficile-associated diarrhoea, pseudomembranous colitis). Cardiac disorders: Tachycardia. Gastrointestinal disorders: Nausea, vomiting, abdominal pain, pancreatitis. Hepatobiliary disorders: Hypoalbuminaemia. Investigations: Changes in LFTs. Metabolism and nutrition disorders: Anorexia. Nervous system disorders: Headache; tonic-clonic movements (topical). Psychiatric disorders: Psychoses, insomnia; suicide attempt (topical). Respiratory, thoracic and mediastinal disorders: Sinusitis, severe pharyngitis (topical). Skin and subcutaneous tissue disorders: Photosensitivity, rash, pruritus; application site oiliness or peeling, dryness, erythema (topical). Potentially Fatal: Blood dyscrasias, including aplastic anaemia and agranulocytosis. Rarely, serious dermatologic reactions (e.g. toxic erythema, morbilliform and scarlatiniform reactions, erythema multiforme, toxic epidermal necrolysis, erythema nodosum, urticaria); dapsone syndrome.
Obtain G6PD levels prior to treatment initiation; CBC at baseline, weekly for the 1st month, monthly for 6 months, then semi-annually thereafter; reticulocyte counts; LFTs at baseline then periodically thereafter. Monitor for signs of haemolysis, blood dyscrasias, liver impairment, and dermatologic reactions.
Overdosage
Symptoms: Nausea, vomiting, hyperexcitability, hypoxia, haemolytic anaemia, and methaemoglobinaemia. Management: Supportive treatment. Perform gastric lavage and give activated charcoal to eliminate gastric contents. Administer fluids to maintain renal flow and promote elimination; use oxygen to alleviate hypoxia. In case of methaemoglobinaemia (except in patients with G6PD deficiency), administer 1-2 mg/kg methylene blue via slow IV inj; may be repeated after 1 hour if necessary. For haemolysis, infusion of concentrated human RBC may replace the damaged cells.
Drug Interactions
Plasma concentrations may be increased by probenecid. May reduce the efficacy of oral typhoid vaccine. Increased plasma clearance with rifampicin or rifabutin. May increase the risk of arrhythmia with saquinavir. Elevation of both dapsone and trimethoprim plasma concentrations following concurrent administration in AIDS patients. Topical: May increase the risk of methaemoglobinaemia with methaemoglobin-inducing agents (e.g. oral dapsone, sulfonamides, paracetamol, nitrates and nitrites, chloroquine, primaquine, quinine, phenytoin, phenobarbital). May cause temporary local yellow or orange skin and facial hair discolouration with topical benzoyl peroxide. Increased levels of dapsone and its metabolites with trimethoprim/sulfamethoxazole combination.
Lab Interference
HbA1c may be artificially lowered by reducing the erythrocyte survival time through haemolysis.
Action
Description: Mechanism of Action: Dapsone is a sulfone that inhibits the synthesis of dihydrofolic acid by competing with para-aminobenzoic acid for the active site of dihydropteroate synthetase in susceptible organisms. Its mechanism of action in the treatment of acne vulgaris is still unknown; however, it may be a result from both of its anti-inflammatory and antimicrobial effects. Pharmacokinetics: Absorption: Rapidly and almost completely absorbed from the gastrointestinal tract. Bioavailability: >86%. Time to peak plasma concentration: Within 2-8 hours. Distribution: Widely distributed to organs and fluids (e.g. saliva, sputum, sweat, tears); retained in the skin, muscle, kidneys and liver. Crosses the placenta and blood-brain barrier; enters breast milk. Volume of distribution: 1.5 L/kg. Plasma protein binding: 70-90% (dapsone); approx 99% (metabolite). Metabolism: Metabolised in the liver primarily by N-acetyltransferase via acetylation into monoacetyldapsone (major metabolite), and by CYP3A and CYP2C9 isoenzymes via N-hydroxylation into dapsone hydroxylamine. Undergoes enterohepatic recirculation. Excretion: Via urine (approx 20% as unchanged drug, 70-80% as water-soluble metabolites); faeces (small amount). Elimination half-life: 10-80 hours.
Chemical Structure
Dapsone Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 2955, Dapsone. https://pubchem.ncbi.nlm.nih.gov/compound/Dapsone. Accessed Aug. 26, 2020.
Storage
Tab: Store between 20-25°C. Protect from light. Topical gel: Store between 15-30°C. Do not freeze.
D10AX05 - dapsone ; Belongs to the class of other topical preparations used in the treatment of acne. J04BA02 - dapsone ; Belongs to the class of drugs used in the systemic treatment of lepra.
References
Aczone 7.5% Gel (Allergan, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 05/08/2020.Aczone 7.5% Gel (Almirall, LLC). U.S. FDA. https://www.fda.gov/. Accessed 18/08/2020.Allergan New Zealand Ltd. Aczone 7.5% w/w Topical Gel data sheet 06 September 2018. Medsafe. http://www.medsafe.govt.nz/. Accessed 05/08/2020.Anon. Dapsone (Systemic). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 05/08/2020.Anon. Dapsone (Topical). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 05/08/2020.Buckingham R (ed). Dapsone. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 05/08/2020.Dapsone 100 mg Tablets (Rivopharm UK Ltd.). MHRA. https://products.mhra.gov.uk/. Accessed 05/08/2020.Dapsone 50 and 100 mg Tablets (Actavis). MIMS Hong Kong. http://www.mims.com/hongkong. Accessed 18/08/2020.Dapsone Gel (Northstar Rx LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 05/08/2020.Dapsone Tablet (Alvogen Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 05/08/2020.Dapsone. Gold Standard Drug Database in ClinicalKey [online]. Elsevier Inc. https://www.clinicalkey.com/. Accessed 18/08/2020.Joint Formulary Committee. Dapsone. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 05/08/2020.
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