Moderate
Amitriptyline × Cetirizine
Tricyclic antidepressants (TCA)×Second-generation antihistamines
Mechanism
Additive anticholinergic effect and sedation. Cetirizine is a second-generation antihistamine with minimal central activity, but the effect adds up with amitriptyline. Older patients: high delirium risk.
Symptoms
Dry mouth, constipation, urinary retention (anticholinergic effect). Drowsiness, ataxia. Older patients: delirium and fall risk.
Management
In older patients, an alternative antihistamine with minimal anticholinergic load: fexofenadine or bilastine. Take cetirizine during the day, not at bedtime. Monitor cognition in prolonged therapy.