The use of multiple drugs administered to the same patient, most commonly seen in elderly patients. It includes also the administration of excessive medication. Since in the United States most drugs are dispensed as single-agent formulations, polypharmacy, though using many drugs administered to the same patient, must be differentiated from DRUG COMBINATIONS, single preparations containing two or more drugs as a fixed dose, and from DRUG THERAPY, COMBINATION, two or more drugs administered separately for a combined effect. (From Segen, Dictionary of Modern Medicine, 1992)