In short, the drug in Viagra, Sildenafil, dilates blood vessels at the entrance to the penis. This helps blood flow into your penis more easily, and helps you get firmer erections that last for longer.
Okay, so a bit of background on erections. When a man gets aroused, the brain sends signals to the body that tell vessels supplying the penis to open up. This lets blood through into the penis, and fills up a stretch of tissue called the corpus cavernosum. It’s a bit like a sponge, and when blood flows into it, it gets full and stiffens up — and this is what gives you an erection. At the same time, the brain tells other vessels near the penis to tighten up, to keep blood in this sponge tissue — and this is what makes an erection last.
When men get ED, it’s because blood can’t flow into the penis. This can be because the signals telling blood vessels to open up aren’t working very well, or because there’s a circulation problem stopping blood moving around the body properly.
Sildenafil is called a PDE5 inhibitor because it blocks an enzyme (PDE5) that tightens up blood vessels. By stopping this enzyme, the drug allows better blood flow into the penis, meaning better erections.
The original ED medication.
