Benzalkonium chloride (BZK) has been shown in in vitro and in vivo studies to immobilize sperm, to be active against STD-causing organisms, and to penetrate and thicken cervical mucus. A US clinical study of a sponge containing 60 mg BZK showed life table pregnancy rates at 6 and 12 months of 11.7 and 18.9 per 100 women, respectively. BZK is not currently marketed in the US as a contraceptive. The present study aimed to assess 1) the ability of a new contraceptive vaginal film containing either of two doses of BZK to prevent the penetration of sperm into midcycle cervical mucus; 2) the effect of the film on the vaginal epithelium; and 3) the acceptability of the film. All results were compared with VCF, a currently marketed film containing nonoxynol-9 (N-9). Ten women underwent two baseline cycles of postcoital testing in which no film was used, followed by three test cycles in which Allendale-BZK film, a new film containing either 19 or 25 mg BZK, or VCF, containing 70 mg N-9, was used. The sequence of testing cycles was randomized. In each cycle, condoms were used prior to midcycle, then a midcycle cervical mucus specimen was examined to ensure midcycle characteristics and the absence of sperm. Each woman then had intercourse using either no film (baseline cycles) or a test film (test cycles) and returned 2-3 h afterwards. Cervical mucus was again assessed for adequacy and the presence of sperm. Each woman also underwent colposcopy, using a protocol developed by the World Health Organization. The average number of progressively motile sperm seen per high power field was as follows: first baseline cycle, 22.2; second baseline cycle, 22.1; test cycle with film containing 19 mg BZK, 0.2; test cycle with film containing 25 mg BZK, 0.0; and test cycle with VCF containing 70 mg N-9, 0.0. There was no significant difference between baseline cycles or among test cycles in the average number of progressively motile sperm seen (p = 0.78 and p > or = 0.75, respectively). The average number of progressively motile sperm seen in each test cycle did, however, differ significantly from the average number seen in either baseline cycle (p < 0.01). Colposcopy showed superficial de-epithelialization without underlying inflammation in 15-20% of baseline cycles, regardless of whether colposcopy was done before or after coitus; in 50% of cycles in which either dose of BZK was used; and in 69% of cycles in which VCF was used. In all cases women were asymptomatic. Erythema and petechiae were also seen on colposcopy although at a lower frequency than de-epithelialization. There was no difference in the acceptability of the films. A vaginal contraceptive containing either 19 or 25 mg BZK in a new film base appears to be comparable with VCF in preventing sperm from entering midcycle cervical mucus and may be somewhat less disruptive to the vaginal epithelium.
PIP: Both in vitro and in vivo studies have confirmed the capability of benzalkonium chloride (BZK) to immobilize sperm, protect against sexually transmitted pathogens, and penetrate and thicken cervical mucus. In this Phase I study, 10 US women underwent 2 baseline cycles followed by 3 experimental cycles in which either a new contraceptive vaginal film containing 19 or 25 mg of BZK or a currently marketed film containing 70 mg of nonoxynol-9 (N-9) was used. After a midcycle cervical mucus specimen was analyzed, each woman had intercourse using either no film or a test film and was evaluated 2-3 hours later. The average number of progressively motile sperm seen per high power field was as follows: first baseline cycle, 22.2; second baseline cycle, 22.1; test cycle with film containing 19 mg BZK, 0.2; test cycle with film containing 25 mg BZK, 0.0; and test cycle with film containing 70 mg N-9, 0.0. Colposcopy revealed superficial de-epithelialization without underlying inflammation in 15-20% of baseline cycles, 50% of BZK test cycles, and 69% of cycles in which the N-9 film was used. Women rated both films as neutral or pleasant in terms of appearance, smell, and feel. These findings suggest that contraceptive vaginal films containing either 19 or 25 mg of BZK are as effective as N-9 containing films and may be somewhat less disruptive to the vaginal epithelium. However, since each woman used each BZK film only once, the effects of multiple use on the vaginal epithelium and microflora require further study.