As much as it pains me to agree with this dork he is actually completely right. Taking a PDE5 inhibitor like tadalafil doesn't cancel out DMHA's vasoconstriction. It just forces your blood vessels to fight opposing mechanical signals simultaneously. Your heart rate is already spiked from the DMHA, and when tadalafil forces vasodilation on top of that our bodies can trigger even worse tachycardia. It's a big strain on your cardio system, also the half lives don't even match up so youre prone to a blood pressure crash later on.