ABSTRACT
CONTRACEPTIVE DEVELOPMENT Contraceptive development is a long, slow, expensive, uncer-
tain process (Figure 15.1). Thousands of chemical entities
need to be screened before any are found to be effective, even
in experimental animals. Of those methods which pass
laboratory testing, very few are safe enough to be tested on
human volunteers. In phase I clinical trials, a few tens of indi-
viduals in carefully controlled situations are given the candi-
date drug or device for short-term use. In phase II clinical
trials a few hundred volunteers may use the method, primar-
ily to discover any short-term hazards. In phase III clinical
trials of a contraceptive, an aggregate of at least 600 woman-
years of exposure is achieved and the goal is to measure effec-
tiveness and gather additional information on short-term side
effects. Once a drug has been approved for marketing, it is
essential to continue postmarketing surveillance (sometimes
called phase IV clinical trials). If, for example, the drug has a
serious adverse effect in one in 10 000 or one in 100 000,
then it may require several million woman-years of exposure
before the risk is observed and measured. In today’s world, it
may cost US$200 million or more to bring a drug from a
laboratory to the market place (Figure 15.2).
