Drugs and the aging

The elderly use a significant share of nonprescription medications. Each individual's pharmacokinetic and pharmacodynamic response is dependent on his individual physiological and psychosocial state. Drug bioavailability may be modified. Changes in gastric motility due to anatomical-physiological modification or anticholinergics can affect the absorption of hematinics, vitamins, and some drug molecules. However, it is rarely necessary to alter drug dosage in the aged because of impaired absorption, in the absence of a disease state. Although lipophilic and lipophobic drugs may be handled somewhat differently as an individual ages, important effects on the treatment of a disease or symptom are rarely seen with nonprescription medicines. Age-related changes in drug tolerance are extremely variable among subgroups in the general population due to hereditary factors, nutritional state, and general health status. The elderly may transform and eliminate most drugs as efficiently as do younger persons. Only a decrease in renal glomerular filtration rate is a consistent feature in aging with a concomitant slowing of the kinetics of excretion of water-soluble drugs or metabolites. The individualization of drug dosage should be performed on the basis of physiology and medical history. Modified pharmacodynamics in the elderly may be expressed as a decreased binding of specific drugs at tissue receptor sites or functional changes in the responsive cells. Anticholinergics must be used with caution in persons with glaucoma and prostatic hypertrophy; nonprescription antihistamines are labeled to alert such individuals. Reports of altered pharmacodynamics in the aged leading to significant side effects or ineffectiveness for the condition being treated generally refer to prescription drugs. Further gerontological research may shed further light on these important issues.