Clathrates between cyclodextrin and an estrogen in pharmaceutical compositions conferred an increased stability to said estrogen. The estrogen ethinyl estradiol had an increased resistance to oxidative degradation when part of the inclusion complex as measured at an array of temperatures and relative humidity levels. Compositions formulated to limit the amount of oxidants also increased the stability of the estrogen. Pharmaceutical compositions comprising an estrogen for female contraception, hormone replacement therapy, menopause, or acne have longer storage lives and may require less amounts of the active substance.
