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.
The problem with buying medicine in the deep web is you don't know what someone is selling to you, may be it is not what you thought it was, maybe the medicine was adulterated in some way or form and you will never know that.
That is the main problem when you plan to buy medicines online specially on darknet and you wont really know if those medicines are legit or fake ones and its really risky to depend your medicines on buying online instead its better to buy offline because our health is important and maybe in the future we could able to use our bitcoins directly on paying our medicines on pharmacies that accepts bitcoin as payment.