27 Nov, 13 | by EBM
a disturbing story today that morning-after pills may not be as effective in overweight women (see http://in.reuters.com/article/2013/11/26/us-fda-morningafter-idINBRE9AP02B20131126 for story). basically, European health regulators found that a French morning after pill marketed as Norlevo had decreasing effectiveness in women over 165 pounds and was not effective at all in those over 176 pounds, prompting the Europeans to order a label change. turns out that Plan B in the US is basically the same composition. there was a comment in Physician’s First Watch that “According to the CDC, the average American woman weighs 166.2 pounds, which may raise concern about the efficacy of this type of emergency contraception among many U.S. women. The battle to make emergency contraception available has been long and arduous. Hopefully, this recent information will not discourage users, as this may still be the best option available.”
a couple of comments:
1. it is pretty surprising to me that if the average US woman weighs in the “decreasing effectiveness” group, and that there are lots in the “not effective at all” group, that failure rates in the US would have been pretty apparent before this.
2. seems that BMI would be more useful than weight per se, since (i would assume) the issue is the amount of fat present, with its effects on hormone metabolism (ie and the amount of adipose tissue in a 6 foot tall woman weighing 176# is pretty different from a 5 footer of same weight)
2. there was a recent article in ObGyn journal (see DOI: http://10.1097/AOG.0b013e31828317cc) which assessed efficacy of oral contraceptive pills, patches, and vaginal rings in 7500 women of varying BMIs followed 2-3 years. no difference in failure rates in those with BMI <25 (8.5%), BMI 25-30 (11%), or BMI >30 (9%). this was an observational study with self-reported outcomes. dose of ethinyl estradiol in the pills ranged from 20-35 micrograms (though no information on whether the higher dose pills were taken more by the more overweight women). other observational studies have had mixed results.
so, quite concerning finding in Europe. i would assume that the Food and Drug Admin will assess this aggressively to see, for example, what the US experience is and if the morning after pill should have differing hormonal content based on BMI (or weight).