Follow the manufacturer’s directions to use and clean the oral syringe. Never take 2 doses at the same time. How to take liquid If you or your child are taking sildenafil as a liquid, 1ml is usually the same as taking a 10mg tablet, but it’s important to always check the medicine label. Sildenafil Viagra. If you are taking sildenafil to treat erectile dysfunction, you should know that it does not cure erectile dysfunction or increase sexual desire. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine. · The Answers You Need. Expert-reviewed resources to help you navigate your health journey, from A to Z and everything in between. Compare prescription drug prices . Valid at all major chains including Walgreens, CVS Pharmacy, Target, WalMart Pharmacy, Duane Reade and 65, pharmacies nationwide. No manufacturer promotions could be . 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. For sildenafil to work properly, you’ll need to be sexually excited.