Pharmacology is a branch of medicine that deals with the interaction of drugs with the systems and processes of living animals, in particular the mechanisms of drug action as well as the therapeutic and other uses of the drug. Important basic pharmacological research is carried out in the research laboratories of pharmaceutical and chemical companies. The work of pharmacologists in industry deals with the exhaustive tests that must be made before new drugs can be introduced into medical use. The effects of drugs in patients is done only after exhaustive tests on animals and is usually conducted by physicians to determine the clinical effectiveness of new drugs. Constant testing is also required for the routine control and standardization of drug products and their potency and purity.