Sex is not a drug.

Orgasms are not a drug.

Physical acts are not a drug. Yes an association to a specific act creates in the person's mind the exact thing to do to achieve a sensation...the act itself though is no drug.

The addiction or pursuit of a specific stimulus...a specific feeling and or sensation is not a drug either. ie...I love roller coasters...can't get enough of the things. It could never be classified as an addiction though. If ti were, it would be my own brain and body's reaction to an outside stimulus that I'd be addicted to. Being as the sensations develop from within, naturally on their own...would be like saying I'm addicted to my nail and hair growth.

Don't confuse naturally occuring positive feelings with addiction. Especially since addiction creates a sense of...need.