Abstract

Microdose norethindrone (0.35 mg taken each day without interruption) was used as an oral contraceptive agent by 168 women for 4,264 months over a five-year span. Seven pregnancies occurred with regular use and two with irregular use, resulting in a drug-effectiveness rate of 1.9 and a use-effectiveness rate of 2.5 per 100 woman-years. Cycle length was variable. During the five years of study, there was a tendency toward weight gain, but no definite trend in blood pressure changes was noticed; however, there were no comparable control groups for these latter two observations. Results of metyrapone tests done after 27 to 33 months of treatment were normal.