When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs. In this case, just leave out the missed dose and take your next dose at the usual time. Sildenafil belongs to a group of medicines called phosphodiesterase 5 PDE5 inhibitors. You are encouraged to report adverse events related to Viatris products by calling U. If you take too much Taking too much sildenafil can cause unpleasant side effects. · How much does Viagra cost online? What dosage is available? Hims: yes: yes – starting at $ per dose of Viagra – starting at $4 per dose of sildenafil, depending on dosage: 25– mg. Viagra (sildenafil) is a prescription drug that’s used to treat erectile dysfunction (ED). The drug comes as a tablet you’ll take by swallowing. It’s usually taken as needed about 1 hour. Generic Viagra (sildenafil) is available as a , , , and milligram (mg) pill and in liquid form. It’s meant to be taken as needed — about an hour before sex — but shouldn’t be.