Board Review: Lithium Monitoring

 Board Review: Lithium Monitoring

Subtitle: Labs, Toxicity Signs, and Board Alerts

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 🔍 Introduction

Lithium is a cornerstone mood stabilizer in the treatment of bipolar disorder. However, due to its narrow therapeutic window, it carries significant risk of toxicity. Boards frequently test your knowledge of labs, side effects, and drug interactions. This guide breaks down what you need to master for both patient safety and board success.

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 🧪 Core Concepts: Dosing and Monitoring

* Baseline labs: BMP, TSH, CBC, pregnancy test (in women), ECG (if age >40 or cardiac risk)
* Therapeutic range:

* Acute mania: 0.8–1.2 mEq/L
* Maintenance: 0.6–1.0 mEq/L
* Toxic levels:

* Mild: >1.5 mEq/L (GI symptoms)
* Severe: >2.0 mEq/L (neurologic toxicity)
* Monitoring schedule:

* Check lithium level 5–7 days after dose change
* Then every 3 months when stable
* TSH and creatinine every 6–12 months

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 ☠️ Lithium Toxicity – Must-Know Clues

* Early signs: Nausea, vomiting, diarrhea, fine tremor
* Later signs: Confusion, ataxia, fasciculations, coarse tremor, myoclonus, seizures, coma
* Board Favorite: Elderly patient on lithium + NSAID presents with confusion → Think lithium toxicity!

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⚠️ Drug Interactions to Memorize

💧 Hydration status matters: Dehydration ↑ lithium concentration and risk of toxicity.

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 🧠 Mnemonic – LITHIUM

* L – Levels monitored
* I – Interactions (ACEi, NSAIDs, diuretics)
* T – Tremor/toxicity signs
* H – Hypothyroidism
* I – Increased urination (DI risk)
* U – Urea/creatinine for renal function
* M – Monitor in pregnancy

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🧪 Clinical Scenario

A 56-year-old woman with bipolar disorder presents with nausea, slurred speech, tremor, and confusion.
She recently began lisinopril for hypertension. Labs show lithium level 2.3 mEq/L.

Diagnosis: Lithium toxicity
Cause: ACE inhibitor-induced decreased clearance
Management: Stop lithium + lisinopril, administer IV fluids, consider hemodialysis if symptoms are severe

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🚫 Mistakes to Avoid

❌ Not monitoring *TSH** – Lithium-induced hypothyroidism is a common board-tested complication.
❌ Forgetting *renal monitoring** – Lithium can lead to chronic nephrogenic diabetes insipidus.
* ❌ Ignoring medication changes – Always reassess lithium levels when adding NSAIDs or antihypertensives.

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 📦 Rapid Review Summary Box