If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. Take sildenafil at around the same times every day. You can take it in a small dose daily or in a larger dose as needed. These medicines are called PDE5 inhibitors. The following nonprescription or herbal products may interact with sildenafil: cimetidine Tagamet HB , St. The body takes longer to absorb it after a high-fat meal or alcohol. However, if you take sildenafil with a high-fat meal, it will take longer for the medication to start to work. · Is Viagra prescribed in dosages of mg, mg, or mg? The highest recommended Viagra dose for treating erectile dysfunction (ED) is mg per day, according to the drug’s manufacturer. Viagra (sildenafil) as low as. $ View other PDE5 Inhibitors. Sildenafil (Viagra, Revatio) is a moderately priced drug used to treat erection problems in men. It is also used to treat . Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the .