Age-dependency of the risk for tricyclic antidepressant-associated anticholinergic adverse reactions

Introduction: Due to affinity to peripheral and central muscarinic cholinergic receptors of varying degree, tricyclic antidepressants (TCA) can cause anticholinergic adverse reactions (ADRs) such as dry mouth, blurred vision, constipation, urinary retention, increase of intraocular pressure, and tachycardia. Central side effects include impaired cognitive functions, confusion and delirium. Because of high sensitivity to anticholinergic effects and polypharmacy, elderly patients are more susceptible to these events. The aim of this study was to further determine the importance of risk factors such as age, sex and concomitant medication for the occurrence of TCA-induced anticholinergic ADRs. Methods: Databases of the spontaneous ADR reporting system AGATE (Arbeitsgemeinschaft Arzneimitteltherapie bei psychiatrischen Erkrankungen) which systematically surveys and assesses psychotropic drug-induced adverse events. The risks for anticholinergic ADRs were corrected for the prescription numbers of drugs estimated on two reference days per year. Results: In comparison to younger patients, patients 51 to 65 and over 65 years-old had an about 3 or 5 times higher risk for all TCA-associated anticholinergic ADR. Compared to younger patients, 51 to 65 and over 65 year-old patients were about 6 or 10 times more likely to develop a TCA-associated delirium. The risk for anticholinergic ADRs was not sex-dependent. In average, patients suffering from anticholinergic ADRs got 3.0 (18–50 year-old), 4.0 (51–65 year-old), and 4.5 (>65 year-old) drugs, respectively. Conclusions: The risk for anticholinergic ADRs increases already in middle age. It is therefore advisable to pay attention to the risks of anticholinergic drugs and drug interactions within this age group.