21.   Then the scientists blocked the enzyme that churns out the gas, which prevented erections in the rats.

22.   These drugs were designed to do one thing -- to block an enzyme that is needed to manufacture cholesterol.

23.   This class of drug works by blocking enzymes that are known to cause a breakdown of a chemical in the brain that is essential for communication.

24.   Trusopt, applied topically, works by blocking an enzyme that causes the buildup of excess fluid within the eyes of glaucoma patients.

25.   Until recently, the only drugs that blocked this enzyme also had a troublesome side effect.

26.   Viagra works by blocking an enzyme that breaks down the chemical GMP, which increases the blood flow and helps compress the veins shut.

27.   Viagra, whose chemical name is sildenafil, works by blocking an enzyme called phosphodiesterase which causes erections to subside.

28.   What statins do in the body, researchers found, is block an enzyme called HMG CoA reductase that helps the liver process cholesterol.

29.   While Propecia works by blocking one enzyme responsible for making DHT, Dutasteride would work by blocking two.

30.   He said drugs designed to block the enzyme could enter clinical trials within three years.