Which Is More Effective? Which Lasts Longer? Phosphodiesterase type 5 PDE5 inhibitors. Cialis and Viagra are equally effective. If you experience chest pain, dizziness, or nausea during sex, seek immediate medical help. Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient. This site is intended only for U. · 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. 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 . The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 minutes to 4 hours before sexual activity. And you.