Spermicide used alone for contraception

Cochrane Database Syst Rev; 2013 Sep 30; (9):CD005218; doi:10.1002/14651858.CD005218

Background: Spermicides have been used as contraceptives for thousands of years. Despite this long use, only recently have studies examined the comparative efficacy and acceptability of these vaginal medications. Spermicides contain an active ingredient (most commonly nonoxynol-9) and a formulation used to disperse the product, such as foam or vaginal suppository.

Objectives: This review examined all known randomized controlled trials of a spermicide used alone for contraception.

Search methods: In August 2013, we searched the following computerized databases for randomized controlled trials of spermicides for contraception: CENTRAL, MEDLINE, POPLINE, LILACS, EMBASE, ClinicalTrials.gov, and ICTRP. For the initial review, we examined the reference lists of trials found as well as those of review articles and textbook chapters.

Selection criteria: We included any trial of a commercial product used alone for contraception. Each included trial must have provided sufficient information to determine pregnancy rates.

Data collection and analysis: Two authors independently extracted information from the trials identified. We did not conduct a meta-analysis, since most trials had large losses to follow up. We entered the data into tables and presented the results descriptively.

Main results: We located reports from 14 trials for the initial review, but have not identified any new trials since then. In the largest trial to date, the gel (Advantage S) containing the lowest dose of nonoxynol-9 (52.5 mg) was significantly less effective in preventing pregnancy than were gels with higher doses of the same agent (100 mg and 150 mg). Probabilities of pregnancy by six months were 22% for the 52.5 mg gel, 16% for the 100 mg dose, and 14% for the 150 mg dose. In the same trial, the three different vehicles with 100 mg of nonoxynol-9 had similar efficacy. Interpretation of these figures is limited, since 39% of participants discontinued the method or were lost from the trial. Few important differences in efficacy emerged in other trials.

Authors' conclusions: The probability of pregnancy varied widely in reported trials. A gel containing nonoxynol-9 52.5 mg was inferior to two other products tested in the largest trial. Aside from this finding, personal characteristics and behavior of users may be more important than characteristics of the spermicide products in determining the probability of pregnancy. Gel was liked more than the film or vaginal suppository in the largest trial. Spermicide trials have the dual challenges of difficult recruitment and high discontinuation rates; the latter threatens trial validity.