Show me data that says approximately how long it takes THC to no longer affect a person or how long it takes to metabolize and we can discuss it. Alcohol has a relatively know rate of being metabolized by the body, and there are limits to what is tolerated in your system while at work. Also, alcohol has a relatively known effect on judgement and motor abilities. Can the same be said of THC?
And don't our patients have the right to be treated by somebody who is not under the influence of anything?
The general consensus is that the effects of marijuana depend on the dose and method of ingestion. However, in the case of a standard dose (i.e. a joint) that is smoked, multiple studies generally agree that the "acute intoxication" phase or "high" lasts 2-4 hours with some lingering effects (including motor impairment) may last up to eight hours. Heavier use or ingesting marijuana in food may make the intoxication stronger and longer lasting. Metabolites may be present for 2 weeks to 3 months, depending on body fat, kidney function and amount of use, but the metabolites do not get you "high" or in fact have any effect on cognitive function.
While the effects of marijuana vary from user to user (just like with alcohol, mind you) there are a collection of symptoms that are generally the same with most users. They include euphoria, loss of coordination or reaction time, memory impairment, dry mouth, bloodshot eyes, disorientation, impaired judgement, difficulty problem solving, increased appetite and somnolence. Uncommon side effects include paranoia, racing heart rate and acute psychosis (generally in those predisposed to mental illness).
>>>TL : DR VERSION: We know how pot affects people and roughly how long it lasts if you're smoking it.
There are tests being developed to more accurately determine whether a user is under the influence of marijuana, but one commonly being used is the oral swab. LAPD is now using one that can determine use within three hours.
http://www.scpr.org/news/2013/12/27/41219/la-dui-checkpoints-will-expand-testing-of-drug-imp/
I agree that nobody should drive under the influence, let alone practice medicine while high. However if it is used responsibly, I don't see this being an issue. Most, if not all, companies out there have policies stating no alcohol 8-12 hours before shift, and a similar policy should be in place for marijuana.