Pharmacokinetic variability of contraceptive steroids is a relatively under-explored area of contraceptive research, and hardly a common point of discussion among those who plan and deliver family planning services. Nevertheless, numerous independent studies over the last 15 years have indicated that women in different regions of the world vary in their pharmacokinetic response to contraceptive steroids. The causes of such variability are not known, but it has important consequences for contraceptive effectiveness. It may also offer insight to the basis of contraceptive side-effects. The impetus for this volume was to collect documentation of pharmacokinetic variability of contraceptive steroids, and to explore both the possible causes and implications of these data. Factors known to affect steroid pharmacokinetics, such as concurrent use of specific medications, are reviewed by Back and Orme. Other factors known to affect endogenous steroid dynamics are presented in chapters by Bradlow, Longcope, Goldin and Snow, because of their possible role in contraceptive steroid pharmacokinetics.

Why Pharmacokinetics? An Introduction and Overview.- Why Pharmacokinetics? An Introduction and Overview.- Experience with Contraceptive Side Effects.- Selection of a Contraceptive: What Guides a Woman?.- Contraceptives and Women's Complaints: Preliminary Results from the Post-Marketing Surveillance of Norplant®.- Regional and Individual Variation in Bleeding Patterns Associated With Steroid Contraception.- Variability in Menstrual Bleeding Patterns: Comparing Treated and Untreated Menstrual Cycles.- Contraceptive Use and Discontinuation: The Social Meaning of Side-Effects.- Variability in Steroid Pharmacokinetics.- Population and Delivery Systems: Variability in the Pharmacokinetics of Long-Acting Injectable Contraceptives.- Pharmacology of Ethynl Estrogens in Various Countries.- Pharmacokinetics of Norplant® Implants.- Pharmacokinetic Drug Interactions with Oral Contraceptives.- A Critical Evaluation of the Pharmacokinetics of Contraceptive Steroids.- A Short Review on the Sources of Variability in Pharmacokinetic Parameters of Sex Steroids: Comment on the Paper by K. Fotherby.- Lessons from Endogenous Metabolism.- Diet and Estrogen Metabolism.- Diet, Circulating Estrogen Levels and Estrogen Excretion.- Variations in Estrogen Metabolism: Commentary on B. Goldin.- Body Fat, Fat Topography and Endogenous Steroid Metabolism.- Implications for Policy and Programs.- Steroid Contraceptives and Women's Response: Program Considerations from the Quality of Care Perspective.- Bringing a Client and Life-Cycle Perspective to Scientific Evidence.- Commentary on Presentation of Dr. Pramilla Senanayake.- A Clinician's Perspective.- Future Research Directions.- Regional Population Differences and Population Pharmacokinetics of Steroidal Contraceptives.- Variability in SteroidPharmacokinetics: Needs for Future Research.- Experimental Design for Future Research.- Looking Forward: New Research Priorities.- Contributors.