The Pharmacology of Contraceptive Agents

Abstract

Some aspects of the pharmacology and physiology of contraceptive agents administered to women are reviewed. Hormonal events during the normal menstrual cycle are described. Contraceptive compounds in addition to modifying the hormonal control of ovarian function also may act on later stages of fertility (i.e. sperm entry and postconception events up to and including implantation). The contraceptive drugs in clinical use for women are all either combinations of or singly administered estrogens and/or progestogens. There are combination estrogen-progestogen contraceptives progestogens estrogens sequential estrogen plus progestogen preparations postcoital contraceptives and steroid administration from silastic preparations. IUDs have been increasingly used as antifertility agents. Copper wire-bearing IUDs have been used since 1967 and the most recent innovation in IUDs has been the steroidal releasing devices. Certain metabolic and systemic effects have been attributed to oral contraceptive (OC) therapy. The retrospective studies of the British Research Council were the first to demonstrate an increased risk of thromboembolic phenomena in oral contraceptive use. Prospective studies however have not borne out the association between OC use and thromboembolism. There is evidence for a definite association between cerbrovascular disease and OC use. Combination OCs have been reported to affect the coagulation process in several ways and have been found to induce a mild to moderate deterioration of glucose tolerance in many women. Serum triglycerides have been found to be elevated in 60%-96% of women taking combined oral contraceptives. Both prospective and retrospective studies have generally agreed on a definite association between combined OC use and the development of hypertension in some women although there are some dissenters. There have been conflicting reports on the effects of combined OC use and lactation amenorrhea depression and hepatic dysfunction. Melasma is the most common skin complication and occurs in 5%-8% of OC users within 1-20 months of start of therapy. Side effects condition the rate of patient acceptance and the reliability of use.