Something worth pointing out is that no illicit drug can be considered safe.
If you're about to use an illegal drug, its purity and strength hasn't been approved by a regulator. So you really have no idea what you're actually going to put into your body.
I agree, if you need to take a drug illegally then more than likely you're not needing it for medicinal purposes. Dosage and moderation is necessary for any substance, even when it's needed.