Oral contraceptive steroids play a major role in modern family planning. With the present tendency to decrease the doses of both estrogens and progestogens, any factor that reduces the bioavailability of the lower-dose preparations may have an impact on contraceptive protection. Although ethinyl estradiol, the most commonly used oral estrogen, is liable to an enterohepatic circulation as unchanged drug, the commonly used progestogens are not. At present, no convincing evidence exists in the human subject that disruption of the enterohepatic circulation by antibiotics or antacids does reduce contraceptive efficacy of the pill. Oral contraceptive steroids are mainly absorbed from the small bowel, and contraceptive efficacy depends on its absorptive capacity. Enhanced passage of gastrointestinal contents or impaired absorption may thus contribute to contraceptive failures in patients who have chronic inflammatory disease, diarrhea, ileostomy, or jejunoileal bypass.
PIP: THe recent trend toward decreased dosages of estrogen and progestogen in oral contraceptives (OCs) makes it especially important that attention be directed toward additional factors-- dietary factors, gastrointestinal disturbances or diseases, or drugs that interact with OCs--that may further reduce the bioavailability of steroids and thus compromise contraceptive protection. At present, there is no evidence that antibiotics interfere with OC steroids at the level of enterohepatic circulation; also unlikely is a clinically significant interaction between OCs and antacids. Unlike estrogens, progestogens do not undergo enterohepatic recirculation as unchanged drugs; presumably due to the lack of direct conjugation at the 17 position. Thus, no impact on contraceptive efficacy is produced by disruptions in progestogen metabolism. On the other hand, there is an ample body of research suggesting a link between OCs and chronic inflammatory bowel disease, especially Crohn's disease. The finding of reduced bioavailability of estrogen and progestogen in women who have undergone jejunoileostomy demonstrates that OCs are mainly absorbed in the small bowel and that contraceptive efficacy is related to its absorptive capacity. Overall, it is recommended that careful attention be given to OC acceptors with chronic inflammatory disease, non-colonic diarrhea, ileostomy, and jejunoileal bypass.