From Elite Wiki

A commodity found on the F8 markets screen (if you have installed SW Economy OXZ).

Traded in kilogrammes (just like Gold & Platinum), and hence kept in the ship's safe - and thus salvageable when you blast off in your Escape Pod!

It is only produced in agricultural worlds with a minimum TL of 8.

It is cheap in agricultural worlds, and expensive in industrial worlds.

There is a large illegal trade in narcotics in our Ooniverse - just for fun - and there is no trade in medicine at all!

OK, medicine trade can be regulated. You can’t trade medicine without a proper license. Just like you can’t trade firearms for the same reason. And, listen, some narcotics CAN be medicine, but most of medicine goods are NOT narcotics. And we already have alcohol trading without any license.

There are two possible opposite assumptions setting the economy gradient for medicine.

       A. Medicines are formulated from plants, so they are an agricultural product.
       B. Modern pharmacology is based mostly on chemical synthesis, so it is high TL industry.

In reality we have a mixed approach – we have a pharmaceutical industry, using raw plants, synthetic drugs and biotechnology.

Option B seems highly probable for our Ooniverse's futuristic setting, but I prefer option A. It gives a nice symmetry. Industrial worlds trade luxury for medicine. Medicine is an agricultural item, but it is high tech agriculture. Don’t expect to find medicine exported from low tech agricultural worlds (specific filter again). Like redefined luxuries, medicine is measured in kilograms, so it is a nice addition to the regular goods in the cargo hold. And, the market for Medicine is volatile not due to unpredictable harvests, but due to unpredictable demand.