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.

 

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.

 

摘要

背景

單獨使用殺精劑作為避孕方式

殺精劑已使用數千年。儘管歷史悠久，一直到最近才有研究比較這些陰道藥物的效果以及接受度。殺精劑含有一種活性成分(大多數是nonoxynol−9)以及用來驅散藥物的賦形劑，像是泡沫或陰道塞劑。

目標

本評論檢視所有單獨使用殺精劑作為避孕方式的相關隨機對照試驗。

搜尋策略

我們在下列已上線的資料庫中，搜尋2004年7月以前所有使用殺精劑來避孕的隨機對照試驗:Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, POPLINE, LILACS,及EMBASE。我們也檢視了每一個試驗、評論文章以及教科書章節的參考文獻。

選擇標準

我們納入所有使用上市殺精劑作為唯一避孕方式的試驗。每一個試驗都必須能夠提供足夠的資訊來判斷懷孕率。有14個試驗的報告被採用。

資料收集與分析

2個審查員獨立從上述試驗摘取資訊。我們沒有做統合分析，因為大部分試驗都有很多受試者失去追蹤。我們把資料鍵入表格並以敘事方式呈現結果。

主要結論

在最大的試驗中，含有最低劑量nonoxynol−9(52.5mg)的膠狀殺精劑(Advantage S)，避孕效果明顯比其他兩種含同成分但劑量較高(100 mg及150 mg)的膠狀殺精劑要差。使用6個月的懷孕率如下: 52.5mg為22%，100mg為16%，150mg為14%。同樣在這個試驗中，三種皆含有100 mg nonoxynol−9但不同賦形劑的殺精劑，其效果是差不多的。要判讀這些數據是有困難的，因為39%的參與者不再繼續使用殺精劑或中途離開了試驗。其他試驗有顯示出一些效果上的重大差異。

作者結論

在已報告的試驗中，懷孕的機率差異甚大。在最大的試驗中，含有52.5mg nonoxynol−9的膠狀殺精劑效果比其他兩種產品要差。除此之外，個人差異以及使用方式也許相較於殺精劑產品的差異，更能影響懷孕率。在最大的試驗中，膠狀殺精劑比薄膜狀或陰道塞劑更為使用者喜愛。殺精劑試驗的兩大挑戰在於受試者招募困難以及使用中斷率高；後者尤其容易影響試驗的效度。

翻譯人

本摘要由臺灣大學附設醫院陳芊彣翻譯。

此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。

總結

因為試驗品質不佳，各種殺精劑的避孕效果從而不明。陰道殺精劑已使用數千年。這篇評論比較了各種殺精劑單獨使用時的避孕效果。在最大的試驗中比較了五種殺精劑。含有最少nonoxynol−9的膠狀殺精劑相較於其他含有較多此成分的劑型，避孕效果較差。女性喜愛膠狀殺精劑更勝於薄膜狀或陰道塞劑。這些試驗都有受試者招募困難以及受試者中途離開試驗的問題。