Methemoglobinemia
Cases of methemoglobinemia, with resultant hospitalization, have been reported postmarketing in association with twice daily dapsone gel, 5% treatment. Patients with glucose-6-phosphate dehydrogenase deficiency or congenital or idiopathic methemoglobinemia are more susceptible to drug-induced methemoglobinemia. Avoid use of dapsone gel, 7.5% in those patients with congenital or idiopathic methemoglobinemia.
Signs and symptoms of methemoglobinemia may be delayed some hours after exposure. Initial signs and symptoms of methemoglobinemia are characterized by a slate grey cyanosis seen in e.g., buccal mucous membranes, lips, and nail beds. Advise patients to discontinue dapsone gel, 7.5% and seek immediate medical attention in the event of cyanosis.
Dapsone can cause elevated methemoglobin levels particularly in conjunction with methemoglobin-inducing agents [see Drug Interactions (7.4)].
Hemolysis
Oral dapsone treatment has produced dose-related hemolysis and hemolytic anemia. Individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency are more prone to hemolysis with the use of certain drugs. G6PD deficiency is most prevalent in populations of African, South Asian, Middle Eastern, and Mediterranean ancestry.
In clinical trials, there was no evidence of clinically relevant hemolysis or hemolytic anemia in subjects treated with topical dapsone. Some subjects with G6PD deficiency using dapsone gel, 5%, twice daily developed laboratory changes suggestive of hemolysis [see Use in Specific Populations (8.6)].
Discontinue dapsone gel, 7.5%, if signs and symptoms suggestive of hemolytic anemia occur. Avoid use of dapsone gel, 7.5% in patients who are taking oral dapsone or antimalarial medications because of the potential for hemolytic reactions. Combination of dapsone gel, 7.5%, with trimethoprim/sulfamethoxazole (TMP/SMX) may increase the likelihood of hemolysis in patients with G6PD deficiency [see Drug Interactions (7.1)].
Risk Summary
There are no available data on dapsone gel, 7.5%, use in pregnant women to inform a drug-associated risk for adverse developmental outcomes. The systemic absorption of dapsone 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 dapsone 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 to 4% and 15 to 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 1,407 times [rats] and 425 times [rabbits] the systemic exposure observed in human females as a result of use of the MRHD of dapsone 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 dapsone 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.
Risk Summary
There is no information regarding the presence of topical dapsone in breastmilk, the effects on the breastfed infant or the effects on milk production. Orally administered dapsone appears in human milk and could result in hemolytic anemia and hyperbilirubinemia especially in infants with G6PD deficiency. Systemic absorption of dapsone following topical application is low relative to oral dapsone administration.
The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for dapsone gel, 7.5% and any potential adverse effects on the breastfed child from dapsone gel, 7.5% or from the underlying maternal condition.
In Vivo Activity: No microbiology or immunology studies were conducted during dapsone gel, 7.5% clinical studies.
Drug Resistance: No dapsone resistance studies were conducted during dapsone gel clinical studies therefore there are no data available as to whether dapsone treatment may have resulted in decreased susceptibility of Propionibacterium acnes, an organism associated with acne, or to other antimicrobials that may be used to treat acne. Therapeutic resistance to dapsone has been reported for Mycobacterium leprae, when patients have been treated with oral dapsone.
Hematological Effects