“Hot as a hare, blind as a bat, dry as a bone, red as a beet and mad as a hatter” is a very common mnemonic taught to medical students while in school to help them identify the common side effects of anticholinergic medications. This mnemonic explains each side effect respectively: increased body temperature, dilated pupils, dry mouth, dry eyes, decreased sweat, flushed face and delirium. Anticholinergics are a common drug class used to treat multiple disorders such as an overactive bladder, motion sickness, symptoms for Parkinson’s disease, schizophrenia and seasonal allergies. Common medications with anticholinergic properties include Benadryl, meclizine, atropine, oxybutynin, amitriptyline and many other medications.
Problems with anticholinergic medications
While they are meant to help alleviate certain symptoms, anticholinergic medications can have adverse effects when misused. Anticholinergic toxicity is very common in elderly people because they have a much slower metabolism than younger individuals. “In 2013, the American Association of Poison Control Centers (AAPC) National Poison Data System Annual Report documented 8,729 single exposures to anticholinergic drugs. Unintentional ingestions accounted for 8,208 presentations, intentional ingestions accounted for 332 presentations, and adverse reactions occurred in 151,” according to Medscape. Specific antidotes can be administered in a medical setting to individuals who present with anticholinergic toxicity.
Besides acute toxicity, anticholinergic medications have been shown to have chronic effects over time. One of the most well-researched effects is cognitive blunting, most specifically dementia. A study performed at Indiana University School of Medicine used brain imaging techniques to demonstrate that individuals taking anticholinergic medications had reductions in their brain size and lower metabolisms.
“The study looked at 451 people, with an average age of 73. Sixty of them were taking at least one medication with medium or high anticholinergic activity,” a CNN article reported. “To identify physical and physiological changes that could be associated with the reported effects, researchers assessed the results of memory and cognitive tests; PET scans, to measure brain metabolism; and MRI scans, to assess brain structure.”
Short-term memory and executive functioning, such as verbal reasoning and problem solving, were all decreased in patients who were taking anticholinergics. Many individuals can relate to these side effects after taking a Benadryl, which is known to cause drowsiness. Many of these medications have warnings regarding driving motor vehicles and operating heavy machinery. These studies also tested brain metabolism in individuals using anticholinergic medications. Brain metabolism is often tested through glucose uptake. By using this technique, researchers in this study found that individuals taking anticholinergics had reduced brain metabolism overall and in the hippocampus, an area in the brain responsible for memory. Additionally, these individuals had enlarged ventricles and reduced brain volumes, which signify a decrease in white matter and cognitive decline.
The importance of awareness
Unlike prescription painkillers, such as opioids, and illegal substances — which are constantly portrayed in the media and have become well-known to the general public for their abuse potential and severe side effects — anticholinergics are not widely publicized and as a result many people are unaware of the acute and chronic effects these medications can portray, especially in the elderly population. Health care professionals are taught to educate their patients on these medication side effects, and it’s also important that consumers take time to educate themselves on medications they consume.
Kristen Fuller, M.D., is a medical writer at Sovereign Health, who enjoys writing about evidence-based topics in the cutting-edge world of medicine. She is a physician and author, who teaches, practices medicine in the urgent care setting and contributes to medicine board education. She is also an outdoor and dog enthusiast. For more information and other inquiries about this article, contact the author at firstname.lastname@example.org.