Embryotoxicity of benzalkonium chloride in vaginally treated rats

The effects of the spermicide benzalkonium chloride (BKC) were studied on the conceptus of rat. Single doses (0, 25, 50, 100 or 200 mg kg −1 ) of aqueous solutions of BKC were administered intravaginally (1 ml kg −1 ) on gestational day 1. The vulval metallic clips, used to prevent leakage of the solution, were removed 24 h post‐treatment. Fetuses were obtained and examined for malformations on day 21 of gestation. Slight to copious amounts of vaginal discharge and vaginitis were noticed in rats treated with the two largest doses of BKC. A dose‐related increase in resorptions and fetal death, reduction in litter size and weight were observed in BKC‐treated dams. The conceptus loss seemed to occur both before and after implantation. BKC did not cause any discernible visceral malformations, although minor sternal defects occured in fetuses exposed to 100 and 200 mg kg −1 of the spermicide. These results suggest that single vaginal application of BKC is embryo‐ and fetocidal in the rat at a dose about 143 times higher than that recommended for controlling conception in women.