Comparison of the potency of d-propranolol, chlorhexidine and nonoxynol-9 in the Sander-Cramer test

Abstract

The potency of two new candidate spermicides, d-propranolol and chlorhexidine, was compared with an established agent nonoxynol-9 by the Sander-Cramer test. The lowest concentrations of nonoxynol-9, d-propranolol and chlorhexidine which consistently inhibited progressive forward sperm motility within twenty seconds were found to be 0.12, 0.44, and 4.81 mg/ml, respectively. These relative potencies and other properties of d-propranolol and chlorhexidine indicate that they should be further investigated as alternatives to nonoxynol-9 in spermicidal preparations.

PIP: 3 spermicides with different types of activity -- d-propranolol, chlorhexidine, and nonoxynol-9 -- were compared by examining their potency in abolishing sperm motility within 20 seconds. The Sander-Cramer test involves finding by visual observation the lowest concentration of a spermicide that will abolish sperm motility within 20 seconds. In this test 200 mcl of freshly ejaculated semen is mixed with 500 mcl of drug solution. These volumes were halved to permit a greater number of tests with each ejaculate. Nonoxynol-9 and d-propranolol hydrochloride were dissolved in phosphate buffered saline (PBS), and chlorhexidine diacetate was dissolved in 5.25% dextrose. Tables I and II show the results of Sander-Cramer tests on 6 successive ejaculates. Testing in duplicate confirmed results in all 18 serial dilution experiments. The lowest spermicide concentrations which consistently abolished sperm motility within 20 seconds were as follows: nonoxynol-9, 0.12 mg/ml (relative potency 1.0); d-propranolol, 0.44 mg/ml (relative potency 0.27); and chlorhexidine, 4.81 mg/ml (relative potency 0.025). Nonoxynol-9, chlorhexidine, and d-propranolol all rapidly inhibited sperm motility at concentrations likely to be achieved after placement in the vagina, suggesting that the variation in potency found may have little clinical significance.