And almost all of them subclinical or outright bogus in the actual situation. No one, and I mean no one, really knows the secret sauce about most of the modern drug interactions why the chemistry SHOULD spark an interaction but even if it does (and not always or even usually), the interaction is subclinical. Now with the old drugs: phenytoin, theophylline, warfarin, clozapine etc., you bet that those NTI drugs would blow up something but it was that particular drug, not the interaction itself. That's an entire field called pharmacovigilance which pays a bunch of pharmacists to sit around with little effect while we still don't know what exactly makes a drug interaction actually work out badly for a patient.
The best part about modern pharmacology and pharmacy are that both the drugs and systems are designed with low lawsuit potentials in mind such that most people even taking them completely incorrectly or not at all won't permanently harm themselves. It's a difference from the 50s where drugs were approved with the moniker that if they are taken correctly, they should work ok, but we make no guarantees. It's that climate that kept diphenhydramine, aspirin, and phenylpropylamine as OTC agents where irresponsible use would kill you (and even responsible use has risks in certain people), but would possibly not even get through the NDA today for the main indications.
