Major
Ciprofloxacin × duloxetine
Fluoroquinolone antibacterials×SNRI
Mechanism
Ciprofloxacin is a potent CYP1A2 inhibitor, the main duloxetine metabolic route. Duloxetine plasma levels rise 6-fold. Nausea, sedation, and serotonergic effects emerge.
Symptoms
Serotonin syndrome: agitation, confusion, tremor, myoclonus, hyperreflexia. Autonomic features: sweating, tachycardia, hypertension, fever. First signs appear within hours of co-administration.
Management
Avoid the combination. Alternative antibiotics without CYP1A2 effect: a cephalosporin, nitrofurantoin, or fosfomycin. If ciprofloxacin is needed, halve the duloxetine dose.