He never stopped using drugs.
I no longer have any of the bios and can't look anything up. I also have other sources over the years. I am correct. You'll see.
There was another good read that I can recommend "Crimes Of The Beats (aka the Unbearables)" that deconstructs the myths of the beatnik authors; satire is a powerful weapon.
I haven't had a chance to dig into The Holy Barbarians yet (I opened it but wasn't ready to go to far before getting caught up in some other book).