# Wouldn't pain medication dosages scale with body size **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [May 26, 2011, 12:01am UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226 "2011-05-26T00:01:59Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Shodan](https://avatars.discourse-cdn.com/v4/letter/s/9f8e36/32.png) [@Shodan](https://boards.straightdope.com/u/Shodan)\ **Post date:** [May 27, 2011, 11:58am UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226/21 "2011-05-27T11:58:53Z")
> [@Qadgop\_the\_Mercotan](#): > > It’s an issue with short-acting opiates too, but less of one, due to the fact that receptor sites for the opiates take a while longer to be filled in larger people, due to the volume of distribution of the opiate in the blood and the time it takes to cross the blood-brain barrier. So short-acting opiate dosages would indeed need to be a bit larger to get the same pain relief in a larger person. And with them leaving the receptor sites in a short time, overall the number of opiate receptors activated over time in a larger person could be less. > > In the long-acting opiate situation, it may take a while longer for the medication to take full effect in a larger person, but once the opiates have reached their target, they’ll persist there and the overall number of receptors filled over time will be pretty much the same in smaller and larger folks. > > All of this just points to all the different subtle things that come into play when adding drugs to one’s system. And that’s without even mentioning whether or not the microsomal enzyme oxidizing system has been induced! 🙂 Thanks. Regards, Shodan ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [May 27, 2011, 12:09pm UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226/22 "2011-05-27T12:09:09Z")
> [@BigT](#): > > Well, my doctor has told me the same thing, and I’m going to guess I weigh more than you. Isn’t 800mg just prescription strength? It’s common to take 800mg of Ibuprofen both with and without a doctor’s recommendation. I’ve had 800mg pills prescribed for me, and at other times I just take 4x200mg pills. It’s not really a body weight thing although that might factor into it for especially small people. ---
**Author:** ![Mean\_Mr.Mustard](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mean_mr.mustard/32/3865_2.png) [@Mean\_Mr.Mustard](https://boards.straightdope.com/u/Mean_Mr.Mustard)\ **Post date:** [May 27, 2011, 12:31pm UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226/23 "2011-05-27T12:31:00Z")
> [@horsetech](#): > > As an aside, I don’t know if this exists in human med, but in vet med there are occasionally drugs which are dosed to the patient’s ideal weight rather than actual weight if the patient is obese, the idea being that the extra adipose tissue does not have any effect on the pharmacokinetics of that drug. Insulin is one such drug that is dosed, at least initially, on ideal body weight. > [@GameHat](#): > > Looking at Advil’s site, the standard dosage for an adult is 200 mg. If memory serves, this was one condition of ibuprofen being granted OTC status. > [@needscoffee](#): > > Why dosed according to body surface area? BSA (or meter squared) dosing is used relatively rarely; medications that have a high risk of toxicity - such as chemotherapy (as \*\*horsetech \*\*pointed out) or some IV antibiotics are often dosed based on this calculation. The bottom line is that there are a million variables in how each body responds to each medication. Dosing guidelines - which have been developed as a result of careful, scientific study - are mere starting points, not recipes. mmm ---
**Author:** ![needscoffee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/needscoffee/32/1076_2.png) [@needscoffee](https://boards.straightdope.com/u/needscoffee)\ **Post date:** [May 28, 2011, 5:52am UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226/24 "2011-05-28T05:52:00Z")
> [@Mean\_Mr.Mustard](#): > > BSA (or meter squared) dosing is used relatively rarely; medications that have a high risk of toxicity - such as chemotherapy (as \*\*horsetech \*\*pointed out) or some IV antibiotics are often dosed based on this calculation. Yes, but why calculate based on BSA vs body mass? How is it more accurate? ---
**Author:** ![mnemosyne](https://avatars.discourse-cdn.com/v4/letter/m/c4cdca/32.png) [@mnemosyne](https://boards.straightdope.com/u/mnemosyne)\ **Post date:** [May 28, 2011, 4:44pm UTC](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226/25 "2011-05-28T16:44:48Z")
Total WAG: it yields different dosing amounts than calculation by mass alone, and clinical trials and actual patient treatment data shows that the BSA-calculated dosing has a better treatment success rate. It seems particularly common in cancer treatment protocols, where patients might be experiencing severe weight loss which doesn’t necessarily reflect the way their body will metabolize the drug. [Previous page](https://boards.straightdope.com/t/wouldnt-pain-medication-dosages-scale-with-body-size/583226.md?page=1)