Amlodipine is a dihydropyridine calcium channel blocker that lowers blood pressure by arterial vasodilation, and co-administration with sildenafil can cause a modest additional drop in blood pressure. However, this effect is usually mild and is not the well‑known, potentially catastrophic interaction seen with another class of drugs. The timeline and severity point to a different drug as the culprit. 

Please go back and reconsider.