Follow your doctor’s orders or the directions on the label. For treatment of pulmonary arterial hypertension: For oral dosage forms suspension or tablets : Adults—20 milligrams mg 3 times a day. Tamoxifen This drug was originally licensed for the treatment of breast cancer. If you do not have a plastic syringe or spoon, ask your pharmacist for one. Do not take it more than once a day. Use protective measures and ask your doctor if you have any questions about this. · 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.  · Use only the brand of this medicine that your doctor prescribed. Different brands may not work the same way. Dosing. If you take sildenafil for pulmonary arterial hypertension, do not take Viagra® or other PDE5 inhibitors, including tadalafil (Cialis®) or vardenafil (Levitra®). Viagra® also contains sildenafil. Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, BCGP.