![]() Physicians may not realize that eye drops can be a significant factor in anticholinergic toxicity. 6,21-23 This results in these medications being prescribed without the realization that an additive anticholinergic load is occurring. Many of these medications, such as anticholinergic eye drops, furosemide, digoxin, cimetidine, and prednisolone, are not commonly thought to have systemic anticholinergic effects. Examples of such classes of medications that frequently cause strong anticholinergic effects include antiemetics, antispasmodics, bronchodilators, antiarrhythmics, antihistamines, various analgesics, antihypertensives, antiparkinsonian agents, corticosteroids, skeletal and smooth muscle relaxants, antiulcer drugs, and psychotropics 1,20,21 ( Table II). Many of the medications used to treat chronic conditions cannot be readily stopped and/or are needed to prevent potential life-threatening conditions. ![]() 4-6,8,20 In a study by Remillard8 using the health insurance databases of the province of Saskatchewan, Canada, it was found that 25% of the elderly persons prescribed anticholinergic medication were receiving doses in the “high to excessive dose range.” 20 Studies focused on the elderly have found a prevalence of 10-40% of community-dwelling elderly and 30-60% of nursing home residents who are taking at least one medication with significant anticholinergic properties, and that approximately 7% of community-dwelling elderly and 10-17% of nursing home residents routinely use multiple anticholinergic medications. 6,10 It has been estimated that 51% of the general population use some medication with anticholinergic properties on a regular, if not a daily, basis. 6 Nursing home residents report significantly more chronic illnesses and take more medications than the community-dwelling elderly. More than 80% of the elderly population report at least one chronic disease, with the average community-dwelling elderly individual reporting three to five chronic medical conditions. Many medications with anticholinergic properties are used to treat diseases in older persons (eg, urinary incontinence, emphysema). Why Older Persons Are Susceptible to Anticholinergic Toxicity The correct diagnosis of anticholinergic toxicity depends on the treating physicians’ awareness of the condition, recognition of its symptoms, appreciation of the various autonomic processes affected by the neurotransmitter/hormone acetylcholine, and an understanding of the potential additive anticholinergic effects of various medications. 16-19 The degree of anticholinergic toxicity can range from producing minor symptoms, which may be mistaken as the “normal changes of aging” (eg, minor cognitive impairment), to the common benign side effects of medications (eg, constipation, dry mouth) to severe symptoms (eg, acute agitated delirium with hallucinations, hyperthermia, coma, death). It may also appear similar to other medication-induced symptoms such as neuroleptic malignant syndrome (NMS) and central serotonin syndrome. Identifying a patient with anticholinergic toxicity can be difficult since its presentation is often similar to the delirium caused by other conditions (eg, infections, benzodiazepine withdrawal, metabolic disturbance). 3,7,12 In addition, patients can be exposed to the anticholinergic effects of street drugs, over-the-counter medications, and herbal products/medication. 3,6-11 Currently, there are over 600 medications identified as having some degree of serum anticholinergic activity (SAA). ![]() 3-6 Due to the large number of medications used by the elderly (average, 5-10 prescriptions), it is often the additive effects of these medications that lead to acute anticholinergic toxicity. They are also at a higher risk for developing an anticholinergic toxicity syndrome. The decreased cholinergic reserve in older persons results in them being more susceptible to the side effects of anticholinergic medications, which include cognitive decline, impaired homeostatic regulation, and delirium. The prescription of medications with anticholinergic properties to older patients must be undertaken judicially since the elderly have decreased cholinergic reserves and are prone to dementias (vascular, multi-infarct, and Alzheimer’s) and other conditions that are often worsened by anticholinergic medication 1-4 ( Table I).
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