Dapsone (topical)

No formal drug-drug interaction studies were conducted with ACZONE Gel, 7.5%. Trimethoprim/sulfamethoxazole (TMP/SMX) increases the systemic level of dapsone and its metabolites ( 7.1 ). Topical benzoyl peroxide used at the same time as ACZONE Gel, 7.5% may result in temporary local yellow or orange skin discoloration ( 7.2 ).

7.1 Trimethoprim-Sulfamethoxazole A drug-drug interaction study evaluated the effect of the use of dapsone gel, 5% in combination with double strength (160 mg/800 mg) trimethoprim-sulfamethoxazole (TMP/SMX). During co-administration, systemic levels of TMP and SMX were essentially unchanged, however, levels of dapsone and its metabolites increased in the presence of TMP/SMX. The systemic exposure from ACZONE Gel, 7.5% is expected to be about 1% of that from the 100 mg oral dose, even when co-administered with TMP/SMX.

7.2 Topical Benzoyl Peroxide Topical application of dapsone gel followed by benzoyl peroxide in patients with acne vulgaris may result in a temporary local yellow or orange discoloration of the skin and facial hair.

7.3 Drug Interactions with Oral Dapsone Certain concomitant medications (such as rifampin, anticonvulsants, St. John’s wort) may increase the formation of dapsone hydroxylamine, a metabolite of dapsone associated with hemolysis. With oral dapsone treatment, folic acid antagonists such as pyrimethamine have been noted to possibly increase the likelihood of hematologic reactions.

7.4 Concomitant Use with Drugs that Induce Methemoglobinemia Concomitant use of ACZONE Gel, 7.5% with drugs that induce methemoglobinemia such as sulfonamides, acetaminophen, acetanilide, aniline dyes, benzocaine, chloroquine, dapsone, naphthalene, nitrates and nitrites, nitrofurantoin, nitroglycerin, nitroprusside, pamaquine, para‐aminosalicylic acid, phenacetin, phenobarbital, phenytoin, primaquine, and quinine may increase the risk for developing methemoglobinemia [see Warnings and Precautions ( 5.1 )] .

8.1 Pregnancy Risk Summary There are no available data on ACZONE Gel, 7.5%, use in pregnant women to inform a drug-associated risk for adverse developmental outcomes. The systemic absorption of ACZONE in humans following topical application is low relative to oral dapsone administration [see Clinical Pharmacology ( 12.3 )] . In animal reproduction studies, oral doses of dapsone administered to pregnant rats and rabbits during organogenesis that resulted in systemic exposures more than 400 times the systemic exposure at the maximum recommended human dose (MRHD) of ACZONE Gel, 7.5%, resulted in embryocidal effects.

When orally administered to rats from the onset of organogenesis through the end of lactation at systemic exposures approximately 500 times the exposure at the MRHD, dapsone resulted in increased stillbirths and decreased pup weight [see Data ] . The estimated background risks of major birth defects and miscarriage for the indicated population are unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Data Animal Data Dapsone has been shown to have an embryocidal effect in rats and rabbits when administered orally daily to females during organogenesis at dosages of 75 mg/kg/day and 150 mg/kg/day, respectively. These dosages resulted in systemic exposures that represented approximately 1407 times [rats] and 425 times [rabbits] the systemic exposure observed in human females as a result of use of the MRHD of ACZONE Gel, 7.5%, based on AUC comparisons. These effects were probably secondary to maternal toxicity.

Dapsone was assessed for effects on perinatal/postnatal pup development and postnatal maternal behavior and function in a study in which dapsone was orally administered to female rats daily beginning on the seventh day of gestation and continuing until the twenty-seventh day postpartum. Maternal toxicity (decreased body weight and food consumption) and developmental effects (increase in stillborn pups and decreased pup weight) were seen at a dapsone dose of 30 mg/kg/day (approximately 563 times the systemic exposure that is associated with the MRHD of ACZONE Gel, 7.5%, based on AUC comparisons).

No effects were observed on the viability, physical development, behavior, learning ability, or reproductive function of surviving pups.