This medicine works best when you take it on an empty stomach an hour before sex. Is my electronic health record kept private? Different brands may not work the same way. Remove the syringe from the bottle. Sildenafil should not be used with any other medicine or device that causes erections.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. 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. Learn about uses, how it works, and more for Viagra (sildenafil). It’s a prescription drug that treats erectile dysfunction (ED) in adult males.