If you become pregnant while taking sildenafil, call your doctor. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil. If you experience chest pain, dizziness, or nausea during sexual activity, call your doctor immediately and avoid sexual activity until your doctor tells you otherwise. Also tell your doctor if you or any of your family members have or have ever had an eye disease such as retinitis pigmentosa an inherited eye condition that causes loss of vision or if you have ever had sudden severe vision loss, especially if you were told that the vision loss was caused by a blockage of blood flow to the nerves that help you see. If you are looking for an ED drug that works around the clock, Cialis or Tadalafil might be the best option for you. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. The medicine will come with a plastic syringe or spoon to help you take the right amount.AdShop Forhims Online for Great Prices at Store Sale & Clearance. Up To 60% Off Forhims Official SaleK+ visitors in the past month. Sildenafil tablets for erectile dysfunction come in different strengths ranging from 25mg to mg. The usual dose is 50mg, when you need it. Do not take it more than once a day. The dose can be increased to mg or decreased to 25mg depending on its effect. Take sildenafil up to 4 hours before you want to have sex.  · 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.