Multiphasic oral contraceptives. Efficacy and metabolic impact.

The new multiphasic oral contraceptives represent an attempt to maximize contraceptive efficacy while minimizing physical and metabolic side effects. By varying the dose of progestin during the cycle, the total steroid dose per month has been reduced as compared to most fixed-dose preparations. Lowering the progestin dose appears to reduce the incidence of certain cardiovascular complications. Different oral contraceptive formulations may selectively alter lipid and carbohydrate metabolism. Norethindrone-containing multiphasics appear to have the greatest efficacy and the smallest metabolic impact.