The usual dose of sedatives given in procedures such as endoscopy is less effective in patients who regularly smoke or ingest recreational cannabis, researchers warn. 

Patients may be exposed to higher doses of these drugs and run a greater risk of dose-dependent side effects, they say.

US internists reviewed 250 patients who underwent endoscopic procedures at a Colorado clinic after the state legalised recreational cannabis.

They found that patients who used the drug weekly required 14% more fentanyl, 20% more midazolam, and 220% more propofol than non-users for optimum sedation.