The reason marijuana lessens the effectiveness of lidocaine is that it alters the pH of the tissues. Lidocaine works best at a certain pH (I forget exactly what pH that is, though) and marijuana interferes with that reaction.

Habitual smokers will often have trouble getting numb at the dentist. Try to refrain ahead of time for a few days at least if you know you'll be getting worked on.
TheSmokingMonkey Reviewed by TheSmokingMonkey on . Question for the dentists So some time ago i went to the dentist (high, of course), and the anesthesia worked only weakly, even after two shots. The dentist said that when people are nervous, the adrenaline hinders the effects of the anesthesia, possibly because it binds to the same receptors the anesthesia does (thats what she said). I wasnt even a bit nervous, but i was high, and so i thought maybe the cannabinoids also bind to the same receptors the anesthesia does and that would be the reason because it didnt work Rating: 5