You think that artificially enriched plutonium should also freely be available
“Enriched plutonium” is not a drug. But I imagine if you had a magical “drug” whose ingestion could make you explode in a mini-Chernobyl, then its access should be restricted.
Again, there is no coherent moral framework to justify criminalizing your use of (ordinary) drugs, medical or otherwise. No arguments exist in defense of this prohibition. It’s a rights violation that does nothing to help victims or protect communities, and in fact makes the situation worse for everyone.
If you have such an argument, please publish it in one of the philosophy journals. There’s no Nobel prize for philosophy, but a bunch of fusty academics will be very impressed with you.

Justifying something — a law, for example, or the civic organization of a nation state — requires a moral standard. For example, laws against slavery can be justified by pointing to harms or rights violations (or whatever framework you have for making ethical judgements). Most people rely on their intuitions, but ethics is a formal system — a bit like mathematics, actually. Such a system has to be consistent to be meaningful (this is called the principle of explosion).
Anyway, many such normative systems have been proposed. Utilitarianism, deontology, and virtue ethics are broad examples.
None of these contains a mechanism to justify a governing body’s criminalization of drugs.
Specifically,
Etcetera.