Five-year, multicenter study of a triphasic, low-dose, combination oral contraceptive.

A total of 4,342 women received a triphasic oral contraceptive combination containing levonorgestrel and ethinyl estradiol (Triphasil in the United States, Trinordiol in Europe) over a 5-year period, for a total of 70,282 cycles. Medication was begun on day 1 in the first cycle, with no backup contraception, and consisted of levonorgestrel (LNg) 50 micrograms + ethinyl estradiol (EE2) 30 micrograms for 6 days, LNg 75 micrograms + EE2 40 micrograms for 5 days, and LNg 125 micrograms + EE2 30 micrograms for 10 days. Twelve pregnancies occurred during the study, resulting in a Pearl Index of 0.22. Medication was missed in an overall total of 5,067 cycles (7.2%), and 9 of the 12 pregnancies were attributed by the investigators to misuse of the drug, resulting in a corrected Pearl Index of 0.06. Cycle control was excellent, bleeding irregularities were minimal, and the incidence of adverse experiences was low (generally less than 1% of total cycles). The results indicate that this triphasic combination, given in pharmacologic doses that are patterned after normal cycles, is a predictable, efficacious, well-tolerated, and accepted means of oral contraception.