Comparative study on the local tolerance and efficacy of benzalkonium chloride, myristalkonium chloride and nonoxynol-9 as active principles in vaginal contraceptives.

Background: Spermicides have been identified as a potentially attractive alternative to hormonal contraceptives and/or intrauterine devices. Thus, this study aimed evaluating the efficacy and local tolerance of benzalkonium chloride (BKC) and myristalkonium chloride (MKC) contained in Pharmatex vaginal formulations and compare them with nonoxynol-9 (N-9), the most common active ingredient in topical vaginal contraceptives.

Methods: Human normozoospermic samples were assessed for motility, viability, acrosome status and penetration ability after exposure to control, N-9 or different BKC and MKC doses for 0 and 10 minutes. Local tolerance on HeLa cells was evaluated by the Trypan-blue and MTT assays.

Results: Exposure to BKC and MKC reduced acrosome integrity while promoting total immobilisation and complete loss of sperm viability ( < .001,  = 15). Both compounds also compromised sperm penetration ability upon exposure ( < .001,  = 15). N-9 induced the same outcomes ( < .001,  = 15); nevertheless, it was more toxic to HeLa cells than BKC and MKC ( < .05,  = 14).

Conclusions: BKC and MKC present strong spermicidal activity at lower doses than N-9 and were better tolerated after immediate exposure than N-9. Available Pharmatex galenic formulations were as effective as products based on N-9.