Viagra (sildenafil) may increase eyebrow hair growth and potentially help prevent androgenetic alopecia by promoting vasodilation and improving scalp blood flow.

“There's also studies with Viagra that significantly, which is also known as sildenafil as the generic now, it can increase eyebrow hair growth. So potentially what it does is it helps vasodilate and relax the veins, especially in older men. And when those veins are relaxed, you have better blood flow. That's one of the proposals or theories behind why older men get the androgenetic alopecia more. You're having less blood flow in the scalp. So theoretically it can also help prevent that, but it's not going to-”