lithium and diclofenac

Diclofenac and other non-steroidal anti-inflammatory drugs (NSAIDs) reduce renal blood flow by inhibiting prostaglandin synthesis, which decreases the renal clearance of lithium. This leads to elevated serum lithium concentrations and a risk of lithium toxicity.

The interaction is clinically significant because raised lithium levels can cause symptoms of lithium toxicity, including nausea, vomiting, diarrhoea, tremor, ataxia, confusion, and slurred speech. Severe toxicity can progress to seizures, arrhythmias, renal impairment, and death. Toxicity may occur within days of initiating diclofenac, even at usual doses.

Avoid concurrent use if alternatives exist. If co-prescription is necessary, monitor serum lithium levels closely before and during therapy, and after stopping diclofenac. Adjust lithium dose based on levels. Monitor renal function and watch for signs of toxicity. Consider a non-NSAID analgesic such as paracetamol if appropriate. Advise patients to seek medical attention if symptoms develop.

This interaction is well established and is documented in international drug interaction databases and guidelines. Clinical case reports and pharmacokinetic studies consistently show that NSAIDs increase lithium levels. However, the magnitude of effect varies between patients.