The toxicology and biological properties of laureth 9 (a polyoxyethylene lauryl ether), a new spermicidal agent

Abstract

Laureth 9, and ethoxylated lauryl ether, is a light yellow, viscous liquid soluble in water. It was lethal to human spermatozoa within 20 seconds in a final concentration of 1:2000. The acute oral LD 50 ± SE of laureth 9 for Swiss mice was 3050 ± 480 mg/kg, and the acute intravenous LD 50 ± SE was 100 ± 7 mg/kg. The 5-day oral subacute LD 50 ± SE for albino rats was 1190 ± 146 mg/kg. Laureth 9 was well tolerated by albino rats when administered intragastrically at dose levels of 195 and 390 mg/kg once daily 18 times in 22 days. Laureth 9 produced no cutaneous irritation when applied as 15 and 20% aqueous solutions to normal and abraded skin of rabbits. The undiluted material produced slight irritation of intact skin and moderate irritation of unbraded skin. Undiluted laureth 9 failed to induce vaginal or cervical irritation in dogs when introduced in 5-ml quantities once daily, 5 days a week for 2 weeks. Neither immediate nor delayed irritant effects or sensitivity reactions were observed in seven guinea pigs which received ten daily intracutaneous prechallenge injections followed by a challenge injection 2 weeks later. Repeated patch tests indicated that aerosol preparations containing 10, 15, and 20% laureth 9 were as well tolerated by 53 subjects as a commercially available contraceptive foam formulation, and they were better tolerated than a commercially available contraceptive vaginal cream. Repeated application of all five preparations induced a mild erythema reaction in most subjects. This type of reaction was interpreted as the “skin fatigue” described by Draize (1955). It occurred most frequently with the commercially available vaginal cream which has had an acceptable seven-year market history. None of the 51 subjects challenged with the five preparations tested reacted with edema, vesiculation, eczematization, or pruritus indicative of sensitization.