Currently available spermicides containing nonoxynol-9 are ineffective as microbicides, in particular as HIV-preventive measures.17 Thus, spermicides used alone are not recommended to prevent HIV or other STIs. Furthermore, frequent use (more than 2 times a day) of spermicide causes more vulvovovaginal epithelial disruption,18 which theoretically could increase susceptibility to HIV. In a high-risk population using a vaginal gel with nonoxynol-9 more than three applications per day on average, the risk of HIV acquisition was increased compared with placebo.19

Disadvantages and cautions
Local irritation
Temporary skin irritation involving the vulva, vagina, or penis caused by either local toxicity or allergy to the formulation is the most common problem associated with spermicide use... Although vaginal epithelial disruption has been associated with frequent use (twice a day or more) of spermicides containing N-9, this is usually asymptomatic. In a low risk population, long-term use of N-9 containing methods was not associated with epithelial disruption.22

N-9 spermicides are inadvisable if STI/HIV exposure is likely in situations that would involve frequent use defined as 2 times or more a day.