The deepweb is an option or you should be well connected by someone to get some medicines for bitcoin, its possible for sure.
Yes possible for those illegal medicines/drugs but for those what OP wants is also available in deepweb but its not advisable to buy in that place, you must take the risk before going there.
and there is a chance of getting expired ad bad medicines buying from deepweb and online for bitcoin. medicine is something which should be bought manually from a trusted and verified medical stores. if you want to spend your bitcoin for medicine than the best choice for you is to exchange bitcoins first. I don't think there is any better way than that.