Factors affecting drug binding in plasma of elderly patients.

The binding of salicylate, sulphadiazine and phenylbutazone to plasma proteins has been studied in young and elderly subjects. Elderly patients had significantly reduced concentrations of plasma albumin, compared with subjects under 40 years of age. Sifnificant increases in free levels of all three drugs were found in elderly patients receiving multiple drug therapy, and a correlation obtained with the number of drugs being taken. It is suggested that because of their low albumin levels, elderly patients may be more susceptible to the effects of multiple drug therapy on drug binding. The clinical implications of these observations are discussed.