Major
Lithium × naproxen
Psycholeptics. Lithium×NSAID, propionic acid derivative
Mechanism
NSAIDs reduce renal lithium clearance via prostaglandin-dependent renal blood flow blockade. Lithium plasma levels rise 1.5- to 2-fold with toxicity risk.
Symptoms
Tremor, muscle twitching, nausea, diarrhoea, confusion, ataxia. Symptoms emerge when serum lithium exceeds 1.2 mmol/L.
Management
Avoid prolonged combination. If naproxen is needed for a short course, reduce lithium by 25–30% and check lithium level at 5–7 days. For chronic analgesia: paracetamol or celecoxib (with lithium monitoring).