Antipsychotic drug use in older adults

Abstract

The pharmacology, pharmacokinetics, drug interactions, adverse effects, indications for use, efficacy, dosage, and pattern of use of antipsychotics in adults older than 65 years are reviewed. Most available antipsychotic agents block dopamine type 2 postsynaptic receptors. Antipsychotics also bind to cholinergic, alpha-adrenergic, histamine type 1, and serotonin receptors. The affinities of a given agent for receptors determine its adverse effects and probably its efficacy. There are many obstacles to therapeutic drug monitoring. Many antipsychotics are metabolized into multiple active compounds. Drug clearance from brain tissue may be slower than from plasma. Therapeutic steady-state concentrations are difficult to define. Age-related physiological changes alter the pharmacokinetic and pharmacodynamic characteristics of antipsychotics, placing the elderly adult at heightened risk for adverse effects. Agents that may interact with the antipsychotics include carbamazepine, phenytoin, phenobarbital, tricyclic antidepressants, and lithium. Adverse effects frequently observed in the elderly are orthostatic hypotension, anticholinergic effects, pseudoparkinsonism, and tardive dyskinesia. Neuroleptic malignant syndrome is a rare but potentially fatal reaction. The antipsychotics carry approved labeling for use in treating psychotic disorders; many antipsychotics are approved for use in treating other conditions as well, such as behavioral problems. The Omnibus Budget Reconciliation Act of 1987 established dosage and documentation guidelines for antipsychotic drug use in residents of nursing homes. The guidelines specify that antipsychotics should not be used in this population if the only indication is a problem behavior like wandering. Although antipsychotics are often prescribed for behavioral control in older adults, most studies show only modest efficacy, while some show worsening of symptoms. As-needed orders for antipsychotics are controversial. Antipsychotics can relieve symptoms in the older adult, but lower dosages and more frequent assessments are necessary than for younger adults.