You can take Viagra daily, but because the medication stays in your system for four to six hours, it will not be effective all day. Cialis stays in your system for up to 36 hours and may provide support for erections during that entire time. Stop taking VIAGRA and call your healthcare provider right away if you have any sudden vision loss sudden hearing decrease or hearing loss. How long does it take for Cialis to peak? Cialis reaches its maximum effectiveness two hours after you take it.Depending on your symptoms and needs, you may be prescribed Viagra, sildenafil, Cialis, tadalafil, Stendra, paroxetine, or a combination of tadalafil and sildenafil, available as mints or pills. Prices range from $3 to $ per dose or $82 to $ for a monthly supply, depending on the medication. The Savings Offer and Program expire on 12/31/ For further information, call , visit , or write: Viatris Inc., P.O. Box , Mission, KS See risks & benefits. Learn more about what VIAGRA® (sildenafil citrate), a prescription treatment for ED. Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its effects often last for 4 to 5 hours. It might work longer if you have mild to moderate erectile dysfunction. Vardenafil.