Well, I've missed a lot. First off, human trials actually ARE done, but you have to get animal testing done first to make sure it isn't toxic to mammals in general. That's actually a sensible precaution. Once you demonstrate that, say, rats don't get cancer and die from taking sensible doses of the stuff, you move up to limited human trials before it's released on the market. IIRC, most drugs tend to spend a decade or two in testing before they're released for general consumption, so there's plenty of time. So it's a pretty silly example you've brought up.
Secondly, there's possibly some argument that, in the absence of significant population pressure or exterior competition, a lot of (generally highly developed, economically speaking) human populations aren't experiencing natural selection. But I don't want to argue about that; neither of us has the data to back that up, and the Idiocracy argument is pretty damn stupid, if you're trying to go down that road. More importantly, natural selection is a horribly unethical way to run society. If you want natural selection to operate the way you're expecting it to, then you basically have to stop people from sharing knowledge. If you can't figure out antibiotics on your own, sucks to be you. Don't know how to farm? Hope you're a good scavenger! Knowledge isn't genetic on any level, but intelligence is, but knowledge is what provides the selective advantage, so you have to force everyone who wants high knowledge to be highly intelligent, which means removing easy ways for stupid people to benefit.
This is especially ridiculous at a point in time where humanity is approaching the ability to modify itself. Evolution is slow, inefficient, and incapable of producing certain results. Just go straight to genetic engineering, etc., if you think that natural selection is necessary to produce a better humanity. You'll get better results, faster, and there's no significant difference, morally speaking.