Lindane is excreted into breast milk after ingestion of the agent from treated foods (2). Concentrations in milk ranged from 0 to 113 parts per billion.

One report describing the use of lindane in lactating women has been located. In a TIS prospective study, topical lindane was applied by nine women who were breastfeeding, and irritability was reported by one mother (10).

Based on theoretical considerations, a manufacturer estimated the upper limit of lindane levels in breast milk to be approximately 30 ng/mL after maternal application (E.D. Rickard, personal communication, Reed & Carnrick Pharmaceuticals, 1983). A nursing infant consuming 1000 mL of milk/day would thus ingest about 30 mcg/day of lindane. This is in the same general range that the infant would absorb after direct topical application (E.D. Rickard, personal communication, 1983). These amounts are probably clinically insignificant. Waiting at least 24 hours after discontinuing lindane lotion, however, should prevent exposure of a nursing infant to any drug in the milk (3).

Lindane (and other isomers) is used topically for the treatment of lice and scabies for those who have failed or are not candidates for other approved therapies (1, 2, 3, 4). Small amounts (approximately 10%) are absorbed through the intact skin and mucous membranes (2, 3, 4, 5). It has an elimination half-life of about 18 hours (1,3,4).

Animal Data: Animal reproduction studies have been conducted with rats, mice, rabbits, pigs, and dogs. Animal studies have not shown a teratogenic effect (6,7), and in one, lindane seemed to have a protective effect when given with known teratogens (8). Multigeneration reproduction studies in mice, rats, rabbits, pigs, and dogs at oral doses up to 10 times the human dose have revealed no evidence of impaired fertility or fetal harm (2, 3, 4). In rats, oral lindane exposure at doses 2 times the estimated human exposure (HE) from gestational day 6 through lactational day 10 resulted in decreased pup survival, decreased weight, and decreased weight gain during lactation, increased motor activity, and decreased motor activity habituation. In rabbits, an increased number of stillborn pups and pup mortality were observed with doses about 10 times the HE (assuming 50% rabbit oral bioavailability and 10% human bioavailability) (3,4).

An increased incidence of neoplasms was observed after oral and topical application of lindane and other isomers in mice and rats. This was not clearly related to lindane. Multiple assays for mutagenicity were negative. In male rats, oral lindane was associated with decreased number of spermatids in the testes (3,4).

Placental Transfer: It is not known if lindane crosses the placenta. The molecular weight (about 290) and long elimination half-life suggest that the drug will cross the placenta, but the low absorption after topical application should limit exposure.

Human Data: No published reports linking the use of this drug with toxic or congenital defects have been located, but one reference suggested that it should be used with caution because of its potential to produce neurotoxicity, convulsions, and aplastic anemia (9).

In a surveillance study of Michigan Medicaid recipients involving 229,101 completed pregnancies conducted between 1985 and 1992, 1417 newborns had been exposed to topical lindane during the 1st trimester (F. Rosa, personal communication, FDA, 1993). A total of 64 (4.5%) major birth defects were observed (60 expected). Specific data were available for six defect categories, including (observed/expected) 17/14 cardiovascular defects, 4/2 oral clefts, 0/0.7 spina bifida, 1/4 polydactyly, 2/2 limb reduction defects, and 7/3 hypospadias. Only with the latter defect is there a suggestion of a possible association, but other factors, including concurrent drug use and chance, may be involved.

The manufacturer reports a case of intrauterine fetal demise after the mother was exposed to lindane multiple times during the pregnancy. No other information is provided (3).