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To The Editor:
I am writing to provide important details from the Today contraceptive sponge worldwide Phase III clinical trial that were not presented in your recent article in Contraceptive Technology Update, "Wider access eyed for contraceptive sponge, April 2007". I would also like to clarify some important effectiveness data from this trial, specifically these data surrounding effectiveness of the Today contraceptive sponge on parity.
First, missing from this article on the Today contraceptive sponge was a review of the results from the worldwide Phase III clinical trial, which was the basis for FDA approval.1 This year-long clinical trial was conducted in 20 centers (13 U.S., seven international) and included more than 1,800 women. In this trial, the method effectiveness rate of the Today contraceptive sponge per 100 women for an entire year of intercourse was determined to be 89% to 91%.1 Since these effectiveness rates were derived from clinical trial participants' entire year of intercourse, these effectiveness rates equate to approximately one pregnancy for every 1,250-1,500 acts of intercourse. Additionally, 103 women in a subset of U.S. centers in this same clinical trial continued to use the Today contraceptive sponge for a second year, and the method effectiveness rate was found to increase to greater than 96%.1,2
The levels of efficacy quoted in the April issue were taken from a substantially smaller trial (N=249)3 and from a trial in which the Today contraceptive sponge was allowed to be used for longer than the labeled indication (i.e., left in place for up to two days vs. labeled restriction of 30 hours).4,5 The method effectiveness rates for one year of use (89% to 91%), taken from the Phase III global clinical trial, were reviewed by the FDA and approved by the Non-Prescription Drug Advisory Committee and are currently found within the Today contraceptive sponge label.
Lastly, a statistical comparison as it relates to the effectiveness of the Today contraceptive sponge in nulliparous and parous women was also missing from the same April 2007 article. When reviewing these data contained within the worldwide Phase III clinical trial, the 12-month method pregnancy rates per 100 women were nine for nulliparous and 10.2 for parous sponge users.1 Most importantly, the method pregnancy rates were found to be similar between these groups, with no statistically significant differences noted.
We believe the readers of Contraceptive Technology Update should be provided with a comprehensive review of the effectiveness of the Today contraceptive sponge that includes the efficacy results from the Phase III worldwide clinical trial that supported the approval of this product by the FDA.
Ron Spangler, PhD
Chief Scientific Officer
SYNOVA Healthcare Inc.
The statistics included in the April 2007 article came from a 2003 systematic review of randomized controlled trials by Cochrane Collaboration reviewers that compared the vaginal contraceptive sponge with the diaphragm used with a spermicide. The McClure DA (1985) and North BB (1985) studies referenced above were not included in the Cochrane review.
The Today contraceptive sponge package insert carries an adaptation of the contraceptive effectiveness table published in Contraceptive Technology. (See the table from the upcoming 19th edition. The figures quoted for the sponge are the same as those included in the Today sponge package insert.) Sixteen percent of nulliparous women and 32% of parous women are estimated to experience an unintended pregnancy during the first year of typical use of the sponge.