The contraceptive action of lynestrenol phenylpropionate.
The efficacy of lynestrenol phenylpropionate as a once-monthly injectable contraceptive was assessed. 89 nonlactating fertile women were treated with 75 mg/month by deep im injection through 382 cycles. No change in cycle pattern was seen during the 1st treatment cycle but, thereafter, there was a decrease or increase in the length of cycles and periods. Endometrium revealed an estrogenic effect in 9 out of 10 cases studied. These results suggest that the action was mainly estrogenic. The mode of action may be explained by the knowledge that carbon-19 steroids can be converted to estrogens. It is suggested that the main indication be hypoestrogenic conditions that require contraception and treatment for less than 6 months.