I know this is pretty much like flogging a dead horse, but we really don't know what the long term side effects of these drugs are, so perhaps it isn't such a good idea to encourage their use? I understand how some people are willing to take the risk, but really they are somewhat of an unknown from what I understand.
I would stick with natural ganga over the long term but find a way of growing it. Maybe he could use synthetics in the short term but it really should only be a stop gap until he comes up with a more permanent solution, whether it be quitting through concentrating on holistic therapies or actually growing safer, cheaper weed himself.