Which medications should be avoided when a patient is taking lithium?

Medications to Avoid with Lithium

Thiazide diuretics, NSAIDs (especially indomethacin), and ACE inhibitors must be avoided or used with extreme caution in patients taking lithium due to their high risk of precipitating lithium toxicity. 1, 2

High-Risk Drug Classes That Increase Lithium Levels

Diuretics (Highest Risk: Thiazides)

• Thiazide diuretics increase lithium concentrations by 25-40% after initiation and carry the greatest risk of lithium toxicity among all diuretic classes. 1
• Loop diuretics and potassium-sparing agents have minor, variable effects on lithium levels and are safer alternatives if diuretic therapy is necessary. 1
• Osmotic diuretics and methylxanthines actually increase lithium clearance and have historically been used as antidotes for lithium toxicity. 1

NSAIDs (Variable Risk by Agent)

• Indomethacin is the most potent NSAID for increasing lithium levels and should be strictly avoided. 3, 4
• Ibuprofen and naproxen can significantly increase serum lithium levels, but with marked interindividual variation requiring close monitoring. 3
• Aspirin and sulindac do NOT significantly affect lithium levels and are safe alternatives for pain management. 3
• When NSAIDs must be used, check lithium levels every 4-5 days until the extent of interaction is assessed, and reduce lithium dosage if needed. 3

Antihypertensive Agents

• ACE inhibitors impair lithium elimination and warrant concern, though further investigation is needed to identify specific at-risk patients. 1, 2
• Renin-angiotensin system inhibitors predict lithium toxicity in regression analyses, independent of baseline lithium or creatinine levels. 2
• Female sex and older age significantly predict severity of lithium intoxication when combined with certain antihypertensive classes. 2

GLP-1 Receptor Agonists (Emerging Risk)

• Tirzepatide may enhance lithium absorption through delayed gastric emptying or other pharmacokinetic changes, leading to toxicity even without changes in renal function or hydration. 5
• A case report documented lithium levels rising from 0.9 mEq/L to 1.7 mEq/L within days of switching from semaglutide to tirzepatide. 5
• Increased monitoring of lithium levels is warranted when initiating, changing doses, or switching between GLP-1-modulating agents. 5

Medications Associated with Neurotoxicity (Without Pharmacokinetic Changes)

• Antipsychotics, anticonvulsants, and calcium channel blockers have all been implicated in neurotoxicity when combined with lithium, though the relative risk appears low given their common co-administration. 1
• These combinations warrant caution and close clinical monitoring despite the absence of clear pharmacokinetic interactions. 1

Critical Monitoring Requirements

• Mandatory monitoring of serum lithium levels and clinical status is required after introducing any antihypertensive drug, diuretic, or renin-aldosterone system inhibitor. 2
• The true incidence of lithium intoxication is unknown but likely underestimated, making vigilant monitoring essential. 2
• 40.4% of patients with high lithium levels or intoxication were taking at least one risk medication with relative contraindication for concurrent lithium treatment. 6

Common Pitfalls

• Feverish infections are significantly associated with severe lithium intoxications and require immediate lithium level assessment. 6
• In 37.5% of hospitalized cases, no psychiatrist was involved in managing high lithium levels, resulting in less frequent dose adjustments (37.3% vs 64.7% when psychiatrists were involved). 6
• Patients and physicians should be aware that intoxication risk exists even within the high therapeutic range (≥1.1 mmol/L), with 11.1% of high therapeutic levels showing moderate to severe intoxications. 6