Genetic Implications: Genetic Implications


Trade Name(s)

  • Aczone

Ther. Class.
leprostatic agent


  • PO 
    • Treatment of leprosy (in combination with other agents)
    • Treatment of dermatitis herpetiformis.
  • Topical Treatment of acne vulgaris.

Unlabeled Use(s):

PO Prevention (as monotherapy) and treatment of Pneumocystis jirovecii pneumonia (with trimethoprim or other agents).


Interferes with folate synthesis in susceptible organisms.

Therapeutic Effect(s):

Bacteriostatic action.


Active against:

  • Mycobacterium leprae,
  • Pneumocystis jirovecii.


Absorption: Slowly absorbed (70–80%) following oral administration; acidic environment promotes absorption.

Distribution: Widely distributed; crosses the placenta and enters breast milk in significant concentrations.

Protein Binding: Dapsone 70–90%;  MADDS– 99%.

Metabolism and Excretion: Mostly metabolized by the liver to monoacetyl dapsone (MADDS), its major metabolite, which is then metabolized back to dapsone.

Half-life: 10–50 hr.

TIME/ACTION PROFILE (blood levels)



Contraindicated in:

  • Hypersensitivity (cross-sensitivity with sulfonamides may occur)
  • Genetic implication Congenital or idiopathic methemoglobinemia;
  • Lactation: Lactation (can cause hemolytic reactions in infants).

Use Cautiously in:

  • Severe anemia
  • Genetic implication G6PD deficiency (↑ risk of severe hemolysis or methemoglobinemia)
  • Impaired hepatic function
  • OB:  Use during pregnancy only if potential maternal benefit justifies potential fetal risk.

Adverse Reactions/Side Effects

Derm: STEVENS-JOHNSON SYNDROME, exfoliative dermatitis, hypersensitivity reactions (including erythema nodosum leprosum), photosensitivity, systemic lupus erythematosus

EENT: blurred vision, tinnitus, pharyngitis (topical)

GI: HEPATOTOXICITY, PANCREATITIS, abdominal pain, nausea, vomiting

Hemat: AGRANULOCYTOSIS, METHEMOGLOBINEMIA, hemolytic anemia, reticulocytosis

Neuro: peripheral neuropathy, headache, insomnia, mood changes, tonic-clonic movements (topical), vertigo

* CAPITALS indicate life-threatening.
Underline indicate most frequent.



  • Concurrent administration with  didanosine  or  antacids  may ↓ absorption of dapsone (separate administration times by 2 hr).
  • Blood levels may be ↑ by amiodarone,  fluconazole,  ketoconazole,  itraconazole,  clarithromycin,  erythromycin,  quinidine,  verapamil,  or  diltiazem.
  • Blood levels may be ↓ by rifampin,  phenytoin,   phenobarbital,  or  carbamazepine.
  • Coadministration with  trimethoprim  results in ↑ levels of both agents.
  • Concurrent use with  rifampin,  anticonvulsants, or  pyrimethamine  may ↑ the risk of hemolysis.
  • Concomitant use of topical dapsone with  benzoyl peroxide  may result in yellow/orange discoloration of skin and facial hair
  • Concurrent use of  acetaminophen,  chloroquine,  isosorbide dinitrate,  isosorbide mononitrate,  nitrofurantoin,  nitroglycerin,  nitroprusside,  phenobarbital,  phenytoin,  primaquine,  quinine, and  sulfonamides  may ↑ risk of methemoglobinemia

Drug-Natural Products:

 St. John's wort  may ↓ blood levels of dapsone.



PO (Adults): 50–100 mg/day for 3–10 yrs.

PO Children: 1–2 mg/kg/day, up to 100 mg/day.

Dermatitis Herpetiformis

PO (Adults): Initiate therapy with 50 mg/day, up to 300 mg/day may be required.

Acne Vulgaris

Topical (Adults and Children  ≥12 yrs): 5% gel– Apply small amount twice daily.

Topical (Adults and Children ≥9 yr): 7.5% gel– Apply small amount once daily.

Pneumocystis jiroveciiPneumonia

PO (Adults): Prophylaxis– 100 mg/day; Treatment– 100 mg/day (in combination with trimethoprim) for 21 days.

PO (Children >1 mo): Prophylaxis– 2 mg/kg/day (up to 100 mg/day) once daily, or 4 mg/kg once weekly (up to 200 mg/dose).

Availability (generic available)

Tablets: 25 mg, 100 mg

Gel: 5%, 7.5%


  • Leprosy: Assess skin lesions prior to and periodically throughout therapy.
  • Assess skin for new or toxic dermatologic reactions during therapy. Unless dermatologic reaction is leprosy reactional state, dapsone should be discontinued promptly. Large doses of corticosteroids should be given if severe reactions or neuritis occurs.
  • Pneumocystis jirovecii pneumonia: Assess for infection (vital signs, sputum, WBC) and monitor respiratory status (rate, character, lung sounds, dyspnea, sputum) at beginning of and throughout therapy.
  • Obtain specimens for culture and sensitivity prior to initiating therapy. First dose may be given before receiving results.
  • Acne: Assess lesions periodically during therapy.

Lab Test Considerations:

Monitor AST and ALT prior to and periodically during therapy. Discontinue dapsone if there is evidence of progressive hepatic damage.

  • Genetic implication Monitor patients for hemolysis. Screen patients at higher risk for G6PD deficiency (patients of African American or Mediterranean ancestry) prior to oral therapy. If hemolysis occurs, discontinue and do not restart dapsone.
  • Monitor CBC and reticulocyte counts prior to treatment, then weekly for 1st mo, then monthly for 6 mo, and then semiannually thereafter. In patients with HIV, monitor counts every 2–3 days for the first 2–3 wk of therapy. Discontinue dapsone and monitor patient closely if significant reduction in leukocytes, platelets, or hematocrit occurs or if there is an increase in reticulocyte count.
  • Obtain serum methemoglobin in patients with slate-grey cyanosis in buccal mucous membranes, lips and nail beds, lightheadedness, fatigue, headache, or shortness of breath. Patients with G6PD deficiency (patients of African American or Mediterranean ancestry) using topical dapsone are at increased risk. Discontinue if signs and symptoms occur.

Potential Diagnoses


  • PO 

    May be taken with food if GI upset occurs.

    • Do not administer concurrently with alkaline drugs (e.g. antacids, didanosine); separate administration times by 2 hrs.
  • Topical Apply to clean, dry skin and rub in thoroughly. Wash hands after application. Do not freeze.

Patient/Family Teaching

  • Instruct patient to take dapsone as directed, at the same time each day, for full course of therapy, even if feeling well. Take missed doses as soon as possible if not time for next dose; do not double doses.
  • Advise patients to stop dapsone gel and notify health care professional if signs and symptoms of methemoglobinemia occur. May occur hours after exposure.
  • Instruct patient to notify health care professional immediately if rash, sore throat, fever, chills, persistent fatigue, yellow eyes/skin, bruising, or bleeding occur.
  • Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications.
  • Rep:  Advise patient to notify health care professional is pregnancy is planned or suspected. Avoid breastfeeding during therapy.
  • Emphasize the importance of regular follow-up and blood work to check progress. Advise patient to notify health care professional if no improvement is seen in 2–3 mo in patients with leprosy, 1 wk in patients with Pneumocystis jirovecii pneumonia, or within a few days in patients with dermatitis herpetiformis.

Evaluation/Desired Outcomes

  • Healing of skin lesions in patients with leprosy or dermatitis. May require 6 mo–3 yr or more in patients with indeterminate and tuberculoid leprosy, 2–10 yr in borderline (dimorphous) leprosy, and 2 yr to life in lepromatous leprosy.
  • Prevention and resolution of symptoms of Pneumocystis jirovecii pneumonia.
  • Decrease in acne lesions. If no improvement after 12 weeks, reassess treatment.
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