Yes, NSAIDs Can Significantly Increase Lithium Levels
NSAIDs increase serum lithium levels by reducing renal lithium clearance, which can lead to lithium toxicity, and this interaction requires close monitoring and potential dose adjustment. 1, 2
Mechanism and Clinical Significance
NSAIDs decrease renal lithium elimination by reducing lithium clearance, leading to increased tubular reabsorption of lithium 2, 3. This occurs in patients with normal renal function and is not primarily mediated by prostaglandin inhibition, as aspirin (which inhibits prostaglandins) does not cause this interaction 4, 3.
The clinical impact is substantial:
- Indomethacin is the most potent, decreasing renal lithium elimination by 23% and increasing steady-state plasma lithium levels by 40% 3
- Ibuprofen and naproxen can significantly increase serum lithium levels, though with marked interindividual variation 2
- Diclofenac, ketoprofen, mefenamic acid, niflumic acid, and piroxicam have all been reported to cause this interaction 4
A recent retrospective study of 501 psychiatric inpatients confirmed that NSAIDs independently increase lithium levels in routine clinical practice 1.
Critical Exceptions
Aspirin does NOT significantly affect lithium levels and may be the preferred anti-inflammatory option for patients on lithium therapy 2, 3. Despite suppressing prostaglandin E2 excretion by 65-70%, aspirin increased renal lithium elimination by only 6% and had no effect on steady-state plasma lithium levels 3.
Sulindac also appears safe, with no convincing evidence of clinically significant effects on serum lithium levels 2.
Monitoring and Management Algorithm
When NSAIDs must be used with lithium:
- Check serum lithium levels every 4-5 days until the extent of drug interaction is assessed 2
- Reduce lithium dosage as needed based on serum levels 2
- Inform all patients on lithium about the risk of interaction with over-the-counter NSAIDs 1
- Consider aspirin or sulindac as safer alternatives when anti-inflammatory therapy is needed 2, 3
Common Pitfalls
The most dangerous pitfall is over-the-counter NSAID use that patients may not report 1. Patients often self-medicate with ibuprofen or naproxen without realizing the risk of lithium toxicity. This is particularly concerning because lithium has a narrow therapeutic index (optimal range 0.6-0.8 mmol/L) 5.
Another critical caveat: neurological deficits from lithium toxicity may not correlate with serum lithium levels during recovery 6. Clinical improvement may lag behind normalization of lithium levels, so don't assume the patient is safe just because levels have normalized.
Additional Risk Factors
The interaction is compounded when NSAIDs are combined with other medications that affect renal function, including ACE inhibitors, angiotensin receptor blockers, and diuretics 7, 5. These combinations create additive effects on lithium clearance and increase toxicity risk 1.