DES as postcoital contraception
Oestrogens increase uterine secretion rate, contractility of tubal and uterine muscle, and closure of the isthmo-ampullar and uterotubal junctions. It may cause either “tubelocking” or accelerated transport, depending on the time the oestrogens are given, and on their dosage.
In 72 women, either victims of rape, or woman whose partners had used condoms that failed, oestrogens were given within 48 hours of coitus.
The dosage was either 5 mg of stilboestrol 5 times daily for 5 days, or 1 mg of ethinyloestradiol twice daily for 5 days.
About 1/2 the women had been exposed to the possible effects of unprotected coitus between 12 and 16 days before the time of their next expected period. No pregnancies were seen with the above dosages. There were 2 pregnancies where the doctor had prescribed 1 mg of ethinyloestradiol daily instead of the 2 mg advised.
Nearly all the women developed nausea at 1st, and 3 of them vomited up their tablets. These were given daily injections of 2 ampoules of 12.5 mg of dimenformon forte instead.
At present patients are advised, as a routine, to take an antiemetic, such as 1/2 a tablet of avomine, 1/2 an hour before taking the oestrogen. A gynaecologist has been one ectopic pregnancy in a patient for whom he had prescribed 25 mg of stilboestrol daily for 8 days.
By inhibiting oestrogen synthesis, oestrogens given as described here may act as antioestrogens and so interfere with the delicate hormone balance required in the regulation of the isthmo-ampullar junction of the tube. Which dosage will accelerate ovum transport and hence premature arrival in the uterus, resulting in ovum degeneration, and which dosage will produce delayed ovum transport (“tube locking”) is not yet clear. Other mechanisms may be withdrawal bleeding or interference with implantation.
- The “morning-after pill”–a preliminary report, IPPF medical bulletin, NCBI PubMed PMID: 12275493, 1969.
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