Drugs and Aging

The brain has millions of brain cells called neurons (i.e., its working units). Neurons operate using various substances called neurotransmitters, examples of which include acetylcholine and dopamine. For proper brain function there needs to be a balance of these neurotransmitters. Imbalances in or marginal deficits in certain neurotransmitters can lead to symptoms or disorders that could have serious consequences.

In older people, two major changes in neurotransmitters are of importance. There is a decrease in the number of cholinergic and dopaminergic neurons, which leads to a relative state of deficiency of acetylcholine and dopamine (Drachman). This reduces the reserve capacity of the brain and makes the balance between neurotransmitters more delicate. The end result is that medication-related problems are more common, and of serious consequence in seniors. Commonly used medications that can be problematic include antipsychotics (e.g., haloperidol), benzodiazepines (e.g., diazepam), and medications with anticholinergic properties (e.g., diphenhydramine or Benadryl). For example, the incidence of drug-induced Parkinsonism (a condition that mimics Parkinson's disease) is much higher in seniors. This condition can cause significant problems due to problems in moving, walking, performing every day tasks with their hands, and can lead to falls, which can have disastrous consequences. Seniors who take benzodiazepine drugs are also at risk for drug-induced cognitive impairment. This means that they may suffer from memory loss, decreased ability to think, and present with other characteristics that may mimic Alzheimer's disease. Lastly, medications with anticholinergic effects such as diphenhydramine (Benadryl, Tylenol PM), dimenhydrinate (Dramanine), and other commonly used medications present a particular problem in older people. In older people they should be avoided, as they are a common cause of cognitive impairment and delirium.