Erection pills only work when you are sexually aroused. They don't just give you an erection out of nowhere. They help your body get and maintain an erection.
Here's how it works:
Blood vessels relax: The medication blocks a specific enzyme in your body, PDE5. This enzyme normally breaks down a substance that causes the blood vessels in your penis to relax. By inhibiting the enzyme, the blood vessels remain relaxed for a longer period.
Improved blood flow: Because the blood vessels are relaxed, more blood flows to your penis when you become aroused. That helps you get an erection.
The effect is temporary: The effect of the medication is temporary. The duration varies per product. For example, Sildenafil works for 4 to 6 hours, while Tadalafil can be active for up to 36 hours.