Rogue pharmacies are not licensed to sell in the United States and put you at risk of counterfeit or tainted drugs How Many Online Pharmacies Are There? Do I have to provide all of the information asked during my telemedicine consultation? If you need emergency medical care for a heart problem, it is important that your doctor knows when you last took sildenafil. Take sildenafil exactly as directed. Refills: See if you can set up automatic refills or order as needed. Do not press on the plunger of the syringe. The generic versions are just as effective and much less expensive.To treat erectile dysfunction-ED, take this drug by mouth as directed by your doctor, usually as needed. Take sildenafil at least 30 minutes, but no more than 4 hours, before sexual activity (1. This means that 4 hours after you take a dose, your body has cleared half of the dose. In most cases, it takes about 5 half-lives for your body to completely remove a drug from your system. So.  · Call your doctor right away if you believe you’ve taken too much Viagra. Another option is to call the American Association of Poison Control Centers at or use its online tool.