Effect of Ovral, a combination type oral contraceptive agent, on vitamin A metabolism in rats

When a typical combination-type oral contraceptive agent (Ovral, which contains 0.5 mg norgestrel and 0.05 mg ethinyl estradiol per tablet), is given to young female rats at 50 x the human dosage for an extended period, plasma vitamin A levels are elevated about 50%. The increase is mainly due to a higher steadystate level of retinol binding protein, and not to the presence of more lipoprotein-bound retinyl ester. In Ovral treated rats, the depletion of vitamin A from the liver, calculated as a linear rate, as a linear rate per unit body weight, or as a half-life, tends to be greater, although the differences are only marginally significant. The absorption, storage and short-term excretion patterns of a dose of radioactive vitamin A are not demonstrably affected by Ovral treatment.