Diurex PMS contains the pain reliever acetaminophen, the diuretic pamabrom, and the antihistamine pyrilamine maleate. The combination of medicines in Diurex PMS treats minor aches and pains, bloating, water-weight gain, and irritability. On the other hand, Diurex Water Pills combines caffeine with the nonsteroidal anti-inflammatory drug (NSAID) magnesium salicylate. The diuretic function of caffeine is similar to pamabrom in that it helps the body flush out excess fluid. Magnesium salicylate relieves pain and can be used to treat symptoms such as cramps, backache, and headache.Ask your doctor or a pharmacist which Diurex brand best suits your needs.