What is an average medication? Its an extremely broad generalization that doesnt make much sense. It includes everything from chemotherapeutic agents over Fentanyl over Aspirin to coal tablets. There are quite a few medications that are a lot more dangerous than the drugs on your list. And they are more dangerous for a reason, as they still have fewer side effects then the illness they are trying to combat.

Unless you are talking about the purity of the product, i dont see a sensible case for the comparison of street drugs with pharmaceuticals.