This causes the penis to get hard and erect. Unlicensed use Unlicensed use For sildenafil Sildenafil is used for the treatment of digital ulcer, E but is not licensed for this indication. If you’re not sure if you’re taking a nitrate, ask your doctor or pharmacist. Take daily tablets to help you get an erection at any time so you can enjoy those spontaneous moments. They may be able to prescribe an extra medicine to protect your stomach. Check the ingredients listed in the leaflet that comes with the medicine if you know you have specific allergies or intolerances.Medicines A to Z. Sildenafil (Viagra) Who can and cannot take sildenafil. Who can take sildenafil. Most men aged 18 and over can take sildenafil for erectile dysfunction. Most adults and children aged 1 year and over can take sildenafil for pulmonary hypertension. Who may not be able to take sildenafil. Sildenafil is not suitable for some people. Phosphodiesterase type-5 inhibitors. View sildenafil information, including dose, uses, side-effects, renal impairment, pregnancy, breast feeding and contra-indications.  · Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra. Drug classes: Agents for pulmonary hypertension, Impotence agents. Medically reviewed by Kaci Durbin, MD. Last updated on Uses. Warnings. Before taking. Dosage. Side effects. Interactions. FAQ. What is sildenafil?