Low-dose monophasic and multiphasic oral contraceptives: a review of potency efficacy and side effects.

This literature review compares the potency efficacy cardiovascular risk carbohydrate metabolic effects cycle control and drug interactions of low dose monophasic and triphasic oral contraceptives. Contraceptive efficacy is comparable in these pills. Assessment of progestogenic and androgenic potency is problematical. Levonorgestrel- containing pills may have a lower dose but a higher androgenic effect. The estrogen may raise HDL-C while the norgestrel-containing pills may lower it more than estrone progestins. The clinical significance of these findings is uncertain. While the estrogens increase procoagulants slightly the overall effect is fibrinolytic except in smokers where antithrombin III and prostacyclin are decreased significantly greatly enhancing clotting tendency. No significant effects on blood pressure have been reported. The only documented effect of low dose pills on carbohydrate metabolism is on the subtle euglycemic clamp test in certain subgroups of diabetics. The incidence of breakthrough bleeding is a matter of great controversy between pill manufacturers. Possibly a womans geographical origin age weight contraceptive history and smoking habit may determine bleeding patterns more than type of pill the contraceptive efficacy of low dose pills may be compromised by intake of certain antibiotics rifampin and phenytoin. There are nonmedical reasons for selecting any type of low dose pill over another. Generic monophasic pills are now available at reduced cost.