be effective, but were in many cases worthless. There were no methods for evaluating such claims until rational therapeutic concepts were established in medicine, starting at about the end of the 19th century. The development of receptor theory at the start of the 20th century and later developments led to better understanding of how medicines act and the development of many new medicines that are both safe and effective. Expansion of the scientific principles of pharmacology and clinical pharmacology continues today. See also Dormant therapy References External links International Union of Basic and Clinical Pharmacology (IUPHAR) European Association for Clinical Pharmacology and Therapeutics (EACPT) Dutch Society on Clinical Pharmacology and Biopharmaceutics (NVKF&B) American Society for Clinical Pharmacology and Therapeutics (ASCPT) American College of Clinical Pharmacology (ACCP) British Pharmacological Society (BPS) Korean Society for Clinical Pharmacology and Therapeutics (KSCPT) Japanese Society for Clinical Pharmacology and Therapeutics (JSCPT) Pharmacology