Hey Guys, Someone already touched on the answer, Most every drug used in CP or to treat acute pain whether it's an opiate, muscle relaxer, anti anxiety med or anti siezure meds works on the nervous system. The nervous sytem of a 250 lb man isn't twice the size of a 100 lb woman, therefore twice the amont of drug isn't needed.Few drugs need to be disperseded systemically but in those cases like anti biotics, Paralytic agents, steroids, etc, weight, blood volume and size are factors that need to be considered. But an opiate naive patient is the same whether they way 250 or 100lbs.

There is cetainly a plecebo effect if someone is large and believes they need more or will be in pain, but if the patient wasn't given the info on the actual dose or the patient doesn't have the abilty to convert say a dose of IV dilaudid into an equianelgesic dose of a drug they are familiar with, that effectively takes expectation of relief which is a proven factor in pain management off the table. By removing the psych componant or expectation of relief that may be telling a larger person it only makes sense they would need more of a medication than their 100lb partner people can can stop lookng for reasons whay their meds fail to live up to their expectation and then ned to justify why they need more than their tiny wife recived from a different doc for a complately different condition. Your no longer comparing apples to apples and buying into misinformation.

Hope that makes sense, Take care, Dave