Drug response in the elderly--sensitivity and pharmacokinetic considerations

There is now a considerable body of evidence to indicate that response to many drugs changes as people ages. As a result, interest has increased in recent years in the investigation of mechanisms contributing to altered drug responsiveness with age. Significant changes in pharmacokinetics and/or tissue sensitivity have been shown to occur. In the former cases, decreased renal elimination is undoubtedly the most important factor but decreased plasma protein binding and rate of metabolism may also be of clinical significance. In the case of tissue sensitivity, there have been few opportunities so far to determine age-related changes in the number and sensitivity of drug receptors and studies have been largely confined to relating drug effect to plasma levels in patients of different age. Such studies in the elderly have been complicated by alteration in the normal homoeostatic mechanisms and by the presence of disease. Further work in both healthy volunteers and patients is necessary to provide a comprehensive data base from which drug regimens appropriate for elderly patients may be developed.