#1 By: Maggie Koerth-Baker, November 25th, 2013 12:04
#2 By: chgoliz, November 25th, 2013 12:15
I thought one of the reasons why there were so many different makes and models of birth control pills was because they had different dosages, presumably to compensate for weight as well as other variables. We know other medications are tested on men instead of women, but you'd think birth control pills would be tested on women....right?
#3 By: kartwaffles, November 25th, 2013 12:40
I'm neither a woman nor a doctor, but the meds the vet prescribes my animals are often calculated by body weight. Surely human medicine has figured this out, too.
#4 By: Jonas Eggeater, November 25th, 2013 12:57
I think that this only relates to the morning after pill, not regular birth control. As far as I'm aware, there isn't any variety in this particular type of birth control.
#5 By: Jardine, November 25th, 2013 12:57
That's always confused me with drugs. Over the counter stuff never mentions dosage per kg of mass, it's always a set amount. People can be easily two or three times the mass of other adults, but the recommended dose is the same for everyone?
#6 By: Jeff F, November 25th, 2013 12:59
The Mother Jones article (about the morning after pill and the 175# weight limit) clearly states:
It is not clear whether drugmakers can formulate an effective levonorgestrel pill for women who weigh more than 165 pounds. "A dose increase of levonorgestrel is not proven to be a solution for this problem," notes Gajek, the HRA Pharma spokeswoman.
So, yes, this did occur to them, and apparently, something else is going on here.
#7 By: Derek Young, November 25th, 2013 13:01
I wonder if it's because fat cells create estrogen.
#8 By: Humbabella, November 25th, 2013 13:12
If your BMI is over 25, the pill won't work as well for you.
Does BMI actually enter into it? If a little person standing 4 feet tall and weighing 87 pounds has to be worried about getting an underdose because they are too heavy?
#9 By: Jonas Eggeater, November 25th, 2013 13:13
Yeah, that doesn't make sense to me either...
#10 By: Cynthia Bonville, November 25th, 2013 13:50
There is little evidence that BMI affects the effectiveness of birth control pills, the variety of pill and dosage and including ingredients is to address the effectiveness of the prescribee to use the medicine properly and genetics (some people have clotting disorders, some people do poorly on dual hormone medicines, just depends). For example, if you are careful with taking your bcp the same time every day you will do fine on a low dose birth control pill no matter what your BMI is. This is not so true for new mothers or some college women because of their life demands can not ensure they are consistently taking the medicine on time, although it is great in terms of breastfeeding and desiring more children in the future for new moms as it does not interfere with lactation as much as higher dose ones do.
While it is anecdotal as I am one person, low dose birth control pills were completely effective for me for a decade despite always being a large human being and having high fertility when I wanted it (and when I didn't otherwise). So this is a surprise. I doubt it is because fat creates estrogen, the estrogen from fat tends to interfere with ovulation and estrogen peaks with ovulation (the follicle baths the maturing ovum with it) - plan B seems to interfere with both ovulation and sperm effectiveness by creating a more hostile reproductive tract (meaning they don't know for sure how it works). My guess is that plan B is diluted by the body and would be better to place plan B internally in some manner, with a plan B ring for example (placed around the cervix). Remember, BMI describes total weight in relation to height, not necessarily adipose tissue.
#11 By: Jason Andresen, November 25th, 2013 14:02
Depends what the pill is working on. Just because a woman weighs twice as much as some other woman doesn't mean her ovaries are twice as big. It may take longer for a drug to accumulate where it is supposed to be, but theoretically the fat woman should get the same amount of medicine. This assumes the drug won't be taken up by fat cells or some other complication however.
#12 By: Marc, November 25th, 2013 14:03
166 pounds for the average American woman? Isn't that a bit on the high side?
#13 By: Anthony Vicari, November 25th, 2013 14:17
Why yes, yes it is, and the same would apply to the statistics for men. http://en.wikipedia.org/wiki/Obesity_in_the_United_States
Today, the thinnest state in the U.S. has a higher fraction of overweight and obese people than the fattest state had in the year I was born.
#14 By: marco, November 25th, 2013 14:30
Makes sense for why some OTC meds would not mention dosage per kg of body mass - but why do none of them seem to? Surely there are some meds for which body mass is relevant to dosage calculations?
When you get the childrens' tylenol or ibuprofen, there is a table on the side of the bottle for body mass to dosage calculation. And yet, adult dosage is almost always given as a single amount, even though healthy adults' body mass can vary by a tremendous factor.
#15 By: Felix Tannenbaum, November 25th, 2013 14:30
this little fellow is happy to hear it!
he made it past a ripped condom and I think just barely through plan b!
#16 By: Felix Tannenbaum, November 25th, 2013 14:47
I'm curious if the weight limit is tied at all to BMI:
Will it not work on a woman who is 6'2 and who has a low% of body fat but still weighs 175?
#17 By: Jason Andresen, November 25th, 2013 15:12
I think because nobody wants to add that complication to the testing. Most people don't pay careful attention to the dosing recommendations anyway and just take what works for them (which is dangerous for Tylenol!), especially if they're significantly bigger than an average person.
#18 By: Humbabella, November 25th, 2013 15:22
I'm sure it has nothing to do with BMI. People just like to talk about BMI as if it means something. I don't know what that is.
#20 By: Humbabella, November 25th, 2013 16:42
Apparently 27 BMI is maximum life expectency and that is 27 BMI for 5'6". So the fat shaming might be based on unrealistic ideas of what a human is supposed to be.
#21 By: Cary, November 25th, 2013 17:32
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