Long-Acting Injectable Antipsychotics in the Elderly

The elderly are at increased risk for psychosis because of age-related deterioration of cortical areas and neurochemical changes, comorbid physical illnesses, social isolation, sensory deficits and polypharmacy. The prevalence of psychiatric and neuropsychiatric disorders requiring treatment with an antipsychotic agent is expected to increase dramatically among people aged >64 years. Antipsychotic agents are effective in the treatment of schizophrenia, schizoaffective disorder, behavioural symptoms in patients with dementia, and mood disorders with psychosis. However, failure to adhere to a prescribed medication regimen by patients with psychosis is one of the most frustrating problems faced by mental healthcare providers, because of the high risk of relapse associated with partial compliance. For patients with psychosis who will not or cannot take oral medications on a regular daily basis or have other characteristics, such as memory, vision or auditory impairment, which contribute to partial compliance, long-acting injectable antipsychotic medication offers a solution.

Older patients are especially at risk of adverse effects associated with traditional antipsychotic agents, such as motor effects, postural hypotension, excessive sedation, and anticholinergic effects because of age-related pharmacokinetic and pharmacodynamic factors, coexisting medical illnesses and concomitant medications. Therefore, drug dosage recommendations in the elderly are much more conservative than in younger patients. The appropriate starting dose of an antipsychotic in older individuals is 25% of the usual adult dose; total daily maintenance doses ranges from 25–50% of the adult dose.

There are few studies regarding the use of depot antipsychotics in elderly patients. Studies that are available indicate that traditional antipsychotic agents given as depot injections are associated with positive outcomes in the elderly. Because the risks for extrapyramidal symptoms and tardive dyskinesia are reduced dramatically with atypical antipsychotics compared with traditional agents, the development of long-acting atypical antipsychotic formulations has been pursued. Of the atypical antipsychotics, risperidone is the first agent to be approved in a long-acting injectable formulation. Unpublished clinical data have revealed that patients treated with long-acting injectable risperidone (25mg, 50mg or 75mg) are more likely to show significant clinical improvement than placebo. In addition, hospitalisation rates decreased continuously and significantly during 1 year of treatment for patients who received long-acting injectable risperidone.

Long-acting injectable antipsychotic medication should be considered for older patients for whom long-term treatment is indicated. The choice of which drug to use should be based on patients’ history of response and personal preference, clinician’s previous experience and pharmacokinetic properties.