The short answer is no. The longer answer is that there's actually a decent case that he never did. Here's the thing-- he used weaponized hallucinogens in a number of his stories, thereby making a subtle "drugs are dangerous" statement. Then in 1971, he did this explicitly anti-drug comic called "The Block" (which is actually pretty good, and isn't any more preachy than it needs to be). But then there's his whole misspent youth to take into consideration...
My gut feeling is that he was probably never into drugs (though he may have tried some), but he knew people who were and he saw them fall apart, which thus motivated him to stay pretty straight-edge. (Basically, read The Block; he's Leroy). Thus making his work a case of What Do You Mean, It Wasn't Made On Drugs?
(Frankly, once you get really into his work, it becomes pretty clear his drug of choice is beautiful women)