Some medications should not be taken with sildenafil. Take sildenafil as needed before sexual activity. Use the oral syringe provided with your medication to measure and take your dose. Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient. It works for up to 36 hours. Neither Sildenafil nor drugs in the same class are appropriate or safe for women. In psychogenic erectile dysfunction, psychological issues prevent maintaining or getting an erection — nothing physical.Sildenafil oral tablet is a prescription medication used to treat erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). Sildenafil can be taken . Sildenafil is in a class of medications called phosphodiesterase (PDE) inhibitors. Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual . Products and services Erectile dysfunction: Viagra and other oral medications By Mayo Clinic Staff Medicines that you take by mouth are called oral .