Choice of ethinyl estradiol as a postcoital pill

Abstract

In the article Interception: The use of postovulatory estrogens to prevent implantation (Am. J. Obstet. Gynecol. 115: 101 1973) Morris and van Wagenen show that postovulatory administration of estrogens in a high dosage seems to be an effective method of lowering the pregnancy rate to the .3 to .03 per cent range after unprotected intercourse. They call their technique Most investigators quoted in this article have used the estrogen diethylstilbestrol (DES) as a postcoital pill. DES may have harmful effects on the fetus if the woman is pregnant at the time of its administration. Clear cell vaginal and cervical adenocarcinoma were reported in daughters of women treated with DES during pregnancy. The Food and Drug Administration has advised that a pregnancy test be taken before DES is prescribed and if the test is positive no DES should be given. At the time of the prescription the patients should be offered the option of a voluntary termination of pregnancy in the event of failure. In view of the suspected risk associated with DES it seems preferable to substitue ethinyl estradiol (EE) which differs from DES chemically and has a different biological effect while apparently it is quite as effective for interception. No fetal abnormalities were found in infant macaque monkeys whose mothers had been treated with marginal doses of various estrogens including DES and EE. In human subjects no instance of the adenosis-carcinoma syndrome was observed in the offspring of mothers treated with EE during pregnancy. Haspels in a large series and Doring in a small pilot study found EE a highly effective drug for interception. My own experience in private practice with EE for interception started in February 1967 and presently comprises a total of 133 cases. In the beginning I prescribed small dosages of EE for 3 days only or a total of 6 to 10 mg. Since December 1970 I have increased the dosage to 5 mg. of EE daily for 5 days or a total of 25 mg. administered in 10 tablets of .5 mg. distributed evenly over the day with the recommendation that it be taken after meals. This method of administration has the advantage that it reduces the incidence and intensity of side effects. Only 10 per cent of the women in my series complained of headaches; 10 per cent nausea; and 2 per cent vomiting. Other investigators have reported side effects in up to 50 per cent of their patients on interception therapy when using DES or EE in single daily dosages. The follow-up in my series was 100 per cent. One pregnancy was observed in the early stages of this investigation. It occurred in a woman who had started treatment 8 days after exposure. More recently under the 25 mg. regimen an instance of possible left ectopic pregnancy was seen in a woman who had started EE medication 24 hours after exposure. When the usually regular period of this woman was delayed for 5 days and the left adnexa were enlarged I did an endometrial aspiration which revealed decidua. The pregnancy test was negative. Since then the patient has had three normal menstruations. The use of EE for interception in preference to DES is suggested. Continued investigation of this method is indicated. (Full text)