A metabolic assessment of different oral contraceptives

Abstract

Summary The demonstration in the late 1960s that the risk of developing thrombo-embolic disease was increased in women using oral contraceptives and that the magnitude of the risk was correlated with the oestrogen dose, led to the withdrawal of formulations of oral contraceptives containing more than 50 μg of ethinyloestradiol. At about the same time the demonstration that some progestagens caused the development of breast nodules in certain experimental animals led to these progestagens no longer being used in contraceptive formulations. Thus at the beginning of the 1970s the choice of an oral contraceptive was considerably narrowed. During the past decade the introduction of formulations containing less than 50 μg of oestrogen, which now account for more than 50 percent of oral contraceptives in use and in which the dose of progestagen is also reduced, the development of new formulations in which the daily dose of the oestrogen and progestagen components are varied, as in the triphasic and biphasic pills, or formulations containing new progestagens, has again increased the available choice. At present more than 25 oral contraceptive preparations are available in the United Kingdom and although some of these contain the same components in the same doses, it is obvious that there is still a wide choice.