Amitriptyline × celecoxib

Additive anticholinergic effect (amitriptyline pronounced, celecoxib mild). In older patients, side-effect severity intensifies.

Dry mouth, constipation, urinary retention, accommodation disturbance, tachycardia. In older patients: delirium and confusion risk.

On the combination, reassess the celecoxib benefit — for osteoarthritis, alternatives: topical NSAIDs or paracetamol up to 2 g/day. Avoid the combination in older patients. If unavoidable, cap amitriptyline at 25 mg/day. For constipation: fibre and adequate fluid intake (1.5 L/day).