Oral medicines for ED usually work well and cause few side effects. Take care to ensure they are legit before buying anything. And whilst most have been studied for their efficacy as a Viagra alternative, the results have been largely inconclusive. This can knock your ability to get it up. It is used by the body to make nitric oxide, a chemical that widens your blood vessels and improves blood flow — something similar to the PDE5 inhibitors like Sildenafil.7th January Manual Health Centre. In 30 seconds. Viagra was the first pill to be approved to treat erectile dysfunction (ED). Yet, over twenty years on, the market is . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or Missing: aftermarket.