Tell your doctor if any of these symptoms are severe or do not go away: headache. The frequency of patients reporting improvement of erections in response to a global question in four of the randomized, double-blind, parallel, placebo-controlled fixed dose studies patients of 12 to 24 weeks duration is shown in Figure 7. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. While the sale remains subject to a consultation with a pharmacist, the other restrictions from the trial have been removed, allowing customers over the age of 18 to purchase an unlimited number of pills. This is consistent with ritonavir’s marked effects on a broad range of P substrates. How should this medicine be used?Sildenafil oral tablet is available as a brand-name drug and as a generic drug. Brand names: Viagra, Revatio. Sildenafil comes in three forms: an oral tablet, an oral suspension (liquid), and an. Brand names for sildenafil include Viagra, Revatio, and Liqrev. The cost for sildenafil oral tablet mg is around $10 for a supply of 2 tablets, depending on the pharmacy you . Cialis lasts up to 36 hours in the body, while Viagra lasts 4–6 hours in the body. Both are taken 30 minutes before sex. Cialis can cause limb pain, while Viagra can cause vision change, rash.