Spermicide used alone for contraception
Abstract
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
We searched the following computerized databases for randomized controlled trials of spermicides for contraception: CENTRAL, MEDLINE, POPLINE, LILACS, EMBASE, ClinicalTrials.gov, and ICTRP. 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
We located reports from 14 trials. 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
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.
PICOs
Plain language summary
Spermicide used alone for birth control
Spermicides have been used as birth control for thousands of years. Studies have recently looked at how well they work to prevent pregnancy and whether women like them. Spermicides contain an active ingredient (usually nonoxynol‐9) and something to disperse the product, such as foam or vaginal suppository (pessary). This review compared how well different spermicides worked for birth control when used alone.
We did computer searches for randomized trials of spermicides used for birth control. We also wrote to researchers to find other trials.
Trials had to focus on a spermicide used alone for birth control. The product could be compared to a different spermicide, the same spermicide used with a barrier method, another dose of the same spermicide, a different base for the same product, or another type of birth control. Each study must have had data on pregnancy.
We located reports from 14 trials. The largest trial compared five different spermicides. The gel with the smallest amount of nonoxynol‐9 did not prevent pregnancy as well as products with more of the same ingredient. Women liked the gel better than the film or suppository. Few differences were found in the other studies. These trials had problems recruiting women into the studies and then keeping them until the trial ended. Large losses to follow up can bias the results.
