Erectile dysfunction medication is now widely available through online questionnaires, and increasingly through products sold without any prescription at all. That is genuinely good for access. It also means a growing number of men take a PDE5 inhibitor without anyone systematically checking the one interaction that can kill them.
Nitrates are the reason. They are common after a cardiac event, they appear in forms people do not think of as medication — a spray in a drawer, a patch, recreational ‘poppers’ — and combined with any drug in this class they can cause a catastrophic drop in blood pressure.
The other items here are less dramatic but matter: alpha-blockers need dose separation, strong CYP3A4 inhibitors need dose reduction, and a previous episode of NAION rules the class out entirely. None of that is obscure — it is all in the prescribing information. It just rarely gets asked.
The full detail is in our medication safety guide.