If you are taking sildenafil for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Sildenafil usually should not be taken more than once every 24 hours. If you become pregnant while taking sildenafil, call your doctor. Take sildenafil at around the same times every day. Do not take a double dose to make up for a missed one. Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors such as tolbutamide, warfarin , CYP2D6 inhibitors such as selective serotonin reuptake inhibitors, tricyclic antidepressants , thiazide and related diuretics, ACE inhibitors, and calcium channel blockers. The products discussed in this site may have different product labeling in different countries.The cost for sildenafil oral tablet mg is around $10 for a supply of 2 tablets, depending on the pharmacy you visit. Quoted prices are for cash-paying customers and are not . VIAGRA does not protect against sexually transmitted diseases, including HIV. The most common side effects of VIAGRA: headache; flushing; upset stomach; This Savings Offer is limited to 50% savings off the amount of your co-pay or your out-of-pocket cost, whichever is less, with a maximum savings of $ off each prescription for up to Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial hypertension (PAH; high blood pressure in the vessels carrying blood to the .