If you are drugged by someone ELSE you can’t give consent.
If you arrange to dose yourself, you are waiving your consent.
While I agree that for an adult there must be responsibility in intoxication (don’t get behind the wheel, think of safety BEFORE you imbibe, etc), I do not believe that because you are under the influence you deserve sexual assault. I also don’t think your belief is legal. It is still a felony in most places to rape an unconscious or drunk person.