The word addiction is based on the latin verb addicer meaning:
1) being propitious to, favour, speak favourably (of).
2) attribute, assign or ascribe something to someone; appoint, designate; award; sentence, condemn.
3) deliver, yield, or resign something to someone; devote, consecrate to, give my support to; give up, sacrifice, abandon, surrender; betray; enslave (to).
4)((of auctions) I adjudge to the highest bidder, knock down (to), strike off, deliver to; sell.
(copied from WordSense.eu)
Your drug is the one you favour. It seems to satisfy a basic urge, but in my opinion only gets rid of some symptoms, for example hurt. Your drug is something you devote to. But addiction is not a weakness of will. You cannot conquer an addiction by just willing to do so. I also believe that you are not able to survive cancer by just willing to do. Just ask Steve Jobs (sorry for this remark). 
An addiction is a chronical desease. Perhaps it opens some information in your genetical code making you an easier target for other substances or addictions, which is called addiction shift. 
I would like to end this page with one word describing a cause for addiction and a way to help:
                                                               "Change"