Dapsone

Trade Names:Aczone- Gel 5%

Trade Names:Dapsone- Tablets 25 mg- Tablets 100 mg

Pharmacology

Mechanism of action is unknown; however, dapsone is bactericidal and bacteriostatic against Mycobacterium leprae .

Pharmacokinetics

Absorption

Rapidly and nearly completely absorbed from the GI tract, reaching peak plasma concentrations in 4 to 8 h. Administration of 200 mg/day for 8 days achieves plateau levels of 0.1 to 7 mcg/mL.

Distribution

Approximately 70% to 90% bound to plasma protein. The main metabolite, monoacetyl dapsone, is nearly 100% protein bound.

Metabolism

Dapsone is acetylated in the liver, the degree of which is genetically determined.

Elimination

The plasma t _½ ranges from 10 to 50 h. Approximately 70% to 85% is excreted in the urine as conjugates and unidentified metabolites. Enterohepatic circulation accounts for appreciable tissue levels 3 wk after discontinuation of therapy.

Indications and Usage

Treatment of dermatitis herpetiformis; leprosy.

Treatment of acne vulgaris.

Contraindications

Standard considerations.

Dosage and Administration

Topical Apply an approximately pea-sized amount in a thin layer to the acne-affected areas twice daily. Rub in gently and completely.

PO Start with 50 mg/day in adults and correspondingly smaller doses in children. If full control is not achieved with 50 to 300 mg/day, higher doses may be tried. Reduce dose to minimum maintenance level as soon as possible. The time for dosage reduction is 8 mo (range, 4 mo to 2½ yr of age) and, for dosage elimination, 29 mo (range, 6 mo to 9 yr of age).

PO 100 mg/day in adults and correspondingly smaller doses in children without interruption in therapy with at least 1 antileprosy drug.

General Advice

• Topical
• Gently wash and pat skin dry prior to application.
• Wash hands after application.
• For external topical use only; not for oral, ophthalmic, or intravaginal use.

Storage/Stability

Store tablets at 68° to 77°F. Protect from light.

Store gel at 59° to 86°F. Protect from freezing.

Drug Interactions

Absorption of dapsone may be decreased, resulting in a loss of efficacy.

Risk of hematologic reactions may be increased.

Dapsone levels may be reduced 7- to 10-fold.

Topical application of dapsone followed by topical benzoyl peroxide may cause temporary local yellow or orange discoloration of the skin and facial hair.

Plasma concentrations of both dapsone and trimethoprim may be elevated, increasing the pharmacologic and toxic effects.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Tachycardia.

CNS

Headache, insomnia, peripheral neuropathy, psychosis, vertigo.

Headache (4%); pyrexia (1%); suicide attempt, tonic-clonic movements.

Dermatologic

Bullous and exfoliative dermatitis, erythema multiforme, erythema nodosum, morbilliform and scarlatiniform reactions, phototoxicity, toxic epidermal necrolysis (TEN), urticaria.

Application-site reaction (18%); dryness (16%); erythema, oiliness/peeling (13%); burning, pruritus (1%).

EENT

Blurred vision, tinnitus.

Nasopharyngitis (5%); pharyngitis (2%); severe pharyngitis.

GI

Abdominal pain, nausea, pancreatitis, vomiting.

Abdominal pain, pancreatitis, severe vomiting.

Genitourinary

Albuminuria, male infertility, nephrotoxic syndrome, renal papillary necrosis.

Hematologic-Lymphatic

Agranulocytosis, hemolysis, hemolytic anemia.

Musculoskeletal

Joint spasm (1%).

Respiratory

Pulmonary eosinophilia.

Upper respiratory tract infection (3%); cough, sinusitis (2%).

Miscellaneous

Fever, hypoalbuminemia without proteinuria, infectious mononucleosis–like syndrome, lupus erythematosus.

Influenza (1%).

Precautions

Pregnancy

Category C .

Lactation

Excreted in breast milk.

Undetermined.

Children

Children are treated on the same schedule as adults, but with correspondingly smaller doses. Dapsone is generally not considered to have an effect on the later growth and functional development of children.

Safety and efficacy not established in children younger than 12 yr of age.

Hypersensitivity

Serious cutaneous reactions (eg, erythema multiforme, TEN) resulting from hypersensitivity may occur. In addition, sulfone syndrome, a potentially fatal hypersensitivity with symptoms of exfoliative dermatitis, fever, hemolytic anemia, jaundice with hepatic necrosis, lymphadenopathy, malaise, and methemoglobinemia, may occur.

Hepatic Function

Toxic hepatitis or cholestatic jaundice have been reported and hyperbilirubinemia may occur more frequently in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency.

Hematologic

Deaths caused by agranulocytosis, aplastic anemia, and other blood dyscrasias have occurred. Treat severe anemia prior to initiation of dapsone therapy.

Hemolysis

Because hemolysis and Heinz body formation may be exaggerated in individuals with G-6-PD deficiency, hemoglobin M, or methemoglobin reductase deficiency, give dapsone with caution to patients with these conditions or patients exposed to other agents or with conditions capable of producing hemolysis (eg, diabetic ketosis).

Peripheral neuropathy

Has been reported with oral treatment.

Overdosage

Symptoms

Hyperexcitability, methemoglobin-induced depression, nausea, seizures or severe cyanosis, severe anoxia (with retinal and optic nerve damage), vomiting.

Patient Information

• Oral
• Review dosing schedule and prescribed length of therapy with patient.
• Advise patient that medication may be started at a low dose and then gradually increased to provide max benefit.
• Instruct patient to continue to take other prescribed medications while taking dapsone.
• Emphasize to patient that treatment will be lengthy and that the entire course of treatment must be completed to avoid relapse or development of resistance.
• Advise patient to take each dose with food if GI upset occurs.
• Instruct patient to stop using and notify health care provider immediately if any of the following symptoms occur: fever, muscle weakness, paleness, purple discoloration of skin, skin rash, sore throat, yellowing of skin or eyes.
• Advise patient that drug may cause blurred vision or dizziness and to use caution while driving or performing other tasks requiring mental alertness until tolerance is determined.

• Topical
• Instruct patient to report any signs of adverse reactions to health care provider.

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