Toward developing a once-a-month pill: a double-blind, randomized, controlled trial of the effect of three single doses of mifepristone given at midcycle on the pattern of menstrual bleeding.
OBJECTIVE
To test the feasibility of timing the administration of mifepristone as a once-a-month contraceptive pill on the 12th day before the next menses, as calculated from the length of the previous menstrual cycles.


METHODS
Double-blind, randomized, controlled trial.


METHODS
Five family planning centers across the world.


METHODS
Three hundred ninety-nine women attending family planning clinics.


METHODS
Randomized to receive 10, 25, or 200 mg of mifepristone or a placebo.


METHODS
Lengthening or shortening of the normal menstrual cycle length following administration of the drug by at least 5 days.


RESULTS
The menstrual period came within 5 days of the predicted date in 88% of women receiving the placebo, 84% of women receiving 10 mg, 72% of women receiving 25 mg of mifepristone, and only 48% of women treated with 200 mg of mifepristone. Increasing the dose of mifepristone was associated with an increased chance of having a delayed period (P<.001). Only 45% of women were in the peri-ovulatory phase of the cycle according to LH and P measurements on the day of drug administration. Women treated before ovulation were more likely to have delayed menses with all three doses of mifepristone.


CONCLUSIONS
Because of the disruption in cycle length, it appears unlikely that mifepristone administered once a month, at a calendar-based time, would provide a reliable method of contraception.
Narvekar
Nitish
N
Contraceptive Development Network, Centre for Reproductive Biology, Edinburgh, Scotland.
Glasier
Anna
A
Dada
Kai
K
Van der Spuy
Zephne
Z
Ho
Pak C
PC
Cheng
Linan
L
Baird
David T
DT
D000293:Adolescent; D000328:Adult; D015897:Comorbidity; D003280:Contraceptives, Oral, Synthetic / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D038622:Internationality; D008183:Luteal Phase / Q000187:drug effects*; D008597:Menstrual Cycle / Q000187:drug effects; D008598:Menstruation / Q000187:drug effects*; D015735:Mifepristone / Q000008:administration & dosage*; D010060:Ovulation / Q000187:drug effects*; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016896:Treatment Outcome
D003280:Contraceptives, Oral, Synthetic; D015735:Mifepristone