• Current Options: This section sets the stage for discussion of new approaches to reversible contraception over the next decade and beyond. The section is organized by categories of methods that are presently available, that is, existing, named formulations that work through a variety of mechanisms and delivery systems. Table 3-1 summarizes these methods, their mechanisms of action, failure rates under typical and perfect use, advantages, disadvantages, side effects, and potential complications.
• Contraceptive Options in the Next Decade, 1995-2005: This section focuses on approaches that are at least in phase I of trials. For the most part, these are either improvements or novel applications of approaches that are already well known. These, too, are considered as methods and are organized in the same way as current options, in order to point more clearly to where improvements are under way. We recognize that, in some categorical instances, the boundary between prospects for the next decade and prospects for the years beyond is often blurred. This is a function of technology and of the degree of advance. In the first instance, a technology that seems promising disappoints in trials. In the second, there may be one or two advances that have become "available methods," but the contraceptive category to which it belongs is otherwise largely empty; good examples are barrier and postcoital methods and contraceptives for men.

Chapter 4 and its appendixes constitute the committee's efforts to respond to its charge to review the state of the relevant basic science and identify a range of potential areas and targets that would provide a foundation for fresh endeavor in contraceptive research and development. The chapter is based not only on the December 1994 workshop but on a set of authored papers found in the appendixes to this report. The chapter has three sections: (1) areas of inquiry or specific targets in the development of contraceptive methods for women, that is, "female methods"; (2) areas of inquiry or specific targets in the development of contraceptive methods for men, that is, "male methods"; and (3) an area that holds promise for the development of various contraceptive methods for both females and males, "immunocontraception," which subsumes the topic of "mucosal immunity'' and its potential for generating new anti-infective and/or contraceptive barrier methods. The internal organization of each of these categories was determined by physiology and by the stage of scientific understanding. Because the stages of the female reproductive cycle are critical from both the technologic and policy perspectives, this particular section is organized according to that cycle. Because of the diversity in the levels of scientific advance, the sections of Chapter 4 that deal with methods for males and with immunocontraception are, necessarily, a mix of specific molecular targets and modes of action.

The reversible contraceptive options that are available today, almost all of