A great many drugs are grossly unsafe if you even minorly exceed the clinical dosage threshold, but are still regularly used by people because we haven't found

A great many drugs are grossly unsafe if you even minorly exceed the clinical dosage threshold, but are still regularly used by people because we haven't found better replacements. A much larger set of drugs fall into a gradient of "as far as we can tell you'll just excrete it if you take too much" to "it's probably not _good_ if you unnecessarily take it, but it won't really be detectable in 4 weeks" to "oh god why would you ever prescribe that". So if we were purely grading on safety, we'd be out quite a lot of pharmacology.