I would generally advise against drug consumption, but as Lysander Spooner wrote in Vices are not Crimes,
I think this type of situation is the essence of libertarianism. People mistake it to mean that if you're libertarian, you support drug use. In actuality, libertarians are against the use of violence, specifically state violence, to stop drug use. This carries through to all issues.
The question isn't so much "Should X action be allowed?" but moreso "Should lethal state violence be used to stop people from doing such action?"
Precisely. If there is no victim, there is no crime. You have the right to pursue happiness, and make mistakes in the process, even if it is self-destructive. I recommend against drugs, sexual promiscuity, drunkenness, etc. but I won't call for you to be robbed, kidnapped, or executed for consenting exchanges.