Iatrogenesis and neurological manifestations in the elderly

Older people are often exposed to polypharmacy in a multimorbidity context. Inappropriate polypharmacy is often harmful, increasing the risk of inappropriate prescriptions and therefore adverse drug events (ADEs). Five to 20% of all hospital admissions are related to ADE in older people, among which 40 to 70% could be prevented. However, identifying ADEs and drug-related admissions in the elderly is challenging because ADEs often present as common geriatric problems such as falls, delirium, which might be due to the aging process, underlying diseases, and/or medications. In the pharmacovigilance database of the World Health Organization, drug-related neurological manifestations are the third reported cause of ADEs in the elderly, and neurological drugs are the third leading class of medications involved in ADEs. We must therefore be particularly vigilant, both in our prescriptions but also in our diagnoses to avoid prescribing inappropriate treatments and detect ADEs. Even though multiple pharmacologic changes occur in the elderly (absorption, distribution, drug metabolism and excretion), most of medications are still often prescribed at the same daily dosage as in young adults. When prescribing any drug for old patients, we should remember that daily intake should be adapted to these specificities, keeping in mind the old well-known aphorism "start low, go slow". In this review, we describe the main drug-related neurological manifestations (drug-induced movement disorders, falls, seizures, delirium, hypoglycemia, stroke, hyponatremia, peripheral neuropathy and myopathy, and serotonin syndrome) and the main drugs associated with neurological manifestations (dopamine receptor blocking agents, antithrombotics, anticholinergics, beta-lactams, antidepressants, benzodiazepines, mood stabilizers).