chuckwagon head
A person who will take any kind of drug and/or medicine, whether or not the substance is known, just to see its effect.
Kenny is a chuckwagon head, and will even take pills he finds on the ground.
Chuckwagon Head
A person who will take any drug, without knowing the drug, just to see what it does.
John is such a Chuckwagon Head! He takes any kind of drug that is offered to him!