This leads to shortness of breath when exercising or completing regular daily activities. This medicine is available only with your doctor’s prescription. Its effects might last longer if you have mild to moderate ED. Do not use in larger or smaller amounts or for longer than recommended. B No evidence of risk in humans Based on FDA pregnancy categories Do not start or stop taking tadalafil during pregnancy without your doctor’s advice. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Without physical action to the penis, such as that occurring during sexual intercourse, tadalafil will not work to cause an erection.Brand Cialis. Generic Tadalafil. No data.. Form. Bottle. Box. Disp Pack. Tablet. No data.. Dosage. mg. 5mg. 10mg. 20mg. No data.. Quantity. 5. 6. 90 . The four main medicines taken by mouth for erectile dysfunction are: Avanafil (Stendra). Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes muscles in the penis, called nitric oxide. Tadalafil Prices, Coupons and Patient Assistance Programs , over-the-counter drugs and pet prescriptions. Print Free Discount Card. Note: This is a drug discount program, not an insurance plan. Valid at all major chains including Walgreens, CVS Pharmacy, Target, WalMart Pharmacy, Duane Reade and 65, pharmacies nationwide.