Use of Anticholinergic Medications, Adverse Drug Reactions, and Knowledge about Medication Use in Older People

Abstract

Physiological and pathological changes associated with aging directly affect pharmacokinetics—specifically absorption, distribution, hepatic metabolism, and renal excretion—as well as pharmacodynamics, thereby increasing drug sensitivity. These complexities heighten the risk of adverse drug reactions among older adults, particularly with anticholinergic agents,which are widely used for chronic conditions such as Parkinson’s disease, hypertension, and depression. Despite their therapeutic efficacy, the inhibition of acetylcholine may lead to severe anticholinergic burden, manifesting as cognitive impairment, acute delirium, and urinary retention,all of which adversely affect hospitalization and mortality rates. Furthermore, polypharmacy in older adults with multiple comorbidities exacerbates the risk of drug-drug interactions and cumulative adverse effects. However, current research on anticholinergic use is predominantly limited to international contexts, which may not align with the Thai public health landscape due to differences in genetics, lifestyles, and social support systems—notably the prevalence of self-medication and herbal supplement use that may inadvertently potentiate anticholinergic effects.Consequently, this study aimed to investigate anticholinergic medication use behaviors,anticholinergic-related adverse drug reactions, and medication knowledge among older adults,to serve as a guideline for enhancing medication safety and preventing drug-related harm in this vulnerable population.

This descriptive study collected data from a purposive sample of 110 older adults (aged 60 years and older) across four outpatient departments at a tertiary care hospital in Bangkok,Thailand, between November 2020 and 2022. Inclusion criteria required participants to be:using at least one anticholinergic agent, demonstrating Thai language proficiency, and providing voluntary consent. Participants were screened using the Thai version of the 6-Item Cognitive Impairment Test (6-CIT) to assess the absence of cognitive impairment, ensuring the validity of the interview-based data. Exclusion criteria included individuals who withdrew consent or declined to provide information during the data collection process. The research instrumentation comprised five sets of structured interview forms designed to collect demographic data, current medication profiles, and the incidence of anticholinergic-related adverse drug reactions. The Naranjo Scale was used to determine the causality probability of reported adverse drug reactions, alongside data on medication use knowledge. Data were analyzed using descriptive statistics,including frequency distributions, percentages, means, standard deviations, and ranges.

The study findings revealed that the participants’ average age was 68.45 years, witha female majority (68.18%). Most participants presented with 2–4 comorbidities, most notably hypertension and dyslipidemia, respectively. Lorazepam was identified as the most frequently used anticholinergic medication (45.45%), with benzodiazepines as a class accounting for the highest overall usage (56.36%). Adverse drug reactions from the use of anticholinergic medications in the last 2 weeks were reported by 12.73% of the older people, as perceived, with common symptoms including blurred vision, xerostomia (dry mouth), and fatigue. However,the Naranjo Scale used to assess causality categorized these occurrences only as “possible” or "doubtful." Furthermore, the study showed that 29.09% of the sample experienced adverse drug reactions from using this medication group in the past, with the top five symptoms, including nausea/vomiting, rash, blurred vision, dry mouth, and fatigue, respectively. Regarding medication knowledge, although most participants (over 80%) demonstrated an understanding of therapeutic indications, administration, and storage, only 30% were able to identify their medications by name, and 73.64% lacked knowledge about potential adverse effects.

These findings highlight the need to develop comprehensive guidelines for the rigorous assessment and monitoring of anticholinergic medication use, alongside the implementation of systematic surveillance for adverse drug reactions and strategies for enhancing medication literacy.Such measures are essential for ensuring patient safety and reducing drug-related risks among the older population in the Thai healthcare system.

Keywords: Adverse drug reactions, Anticholinergic medications, Knowledge about medication use, Naranjo Scale, Older people

Author Contributions:
PS: Conceptualization, method and design, tool validation, data collection, data analysis, writing and revising the manuscript
NS: Conceptualization, method and design, data analysis, writing, revising, and editing the manuscript, corresponding with the editor-in-chief
MD: Conceptualization, method and design, data analysis, recommendation, revising the manuscript
PM: Conceptualization, method and design, data analysis, conclusion, revising and editing the manuscript