What is the therapeutic serum lithium level range for acute mania, and at what level does toxicity typically begin?

Explanation

## Lithium Therapeutic and Toxic Levels **Key Point:** The therapeutic window for lithium is narrow (0.6–1.2 mEq/L for acute mania), and toxicity typically begins at levels > 1.5 mEq/L. This narrow margin requires careful monitoring. ### Therapeutic Serum Levels **High-Yield:** Lithium dosing is individualized based on serum levels, which should be measured 5 days after initiation or dose change (steady state): | Clinical Indication | Target Serum Level (mEq/L) | | --- | --- | | **Acute mania** | 0.8–1.2 | | **Maintenance/prophylaxis** | 0.6–0.8 | | **Bipolar depression** | 0.6–1.0 | ### Toxicity Threshold **Mnemonic:** **LITE** toxicity levels - **L**evel > 1.5 mEq/L → mild toxicity (tremor, nausea, diarrhea) - **I**ncreased level > 2.0 mEq/L → moderate toxicity (confusion, ataxia, coarse tremor) - **T**oxic level > 2.5 mEq/L → severe toxicity (seizures, arrhythmias, coma) - **E**mergency > 3.0 mEq/L → life-threatening (renal failure, death) ### Timing of Serum Level Measurement **Clinical Pearl:** Lithium levels must be drawn: 1. **At steady state** — 5 days after initiation or dose change 2. **12 hours post-dose** — standardized timing to avoid false elevation 3. **Baseline** — before starting therapy (renal function, thyroid function) 4. **Periodically** — every 3–6 months during maintenance; more frequently if renal function declines ### Factors Affecting Lithium Levels **Warning:** Lithium is renally cleared (95%) and has no protein binding. Conditions that increase levels: - Dehydration, sodium depletion - NSAIDs, ACE inhibitors, thiazide diuretics - Renal impairment - Hypothyroidism (reduced metabolism) - Pregnancy (especially third trimester) ### Monitoring Protocol **Tip:** Standard monitoring includes: - Serum lithium level (baseline, 5 days post-initiation, then 3–6 monthly) - Renal function (serum creatinine, eGFR) — baseline and annually - Thyroid function (TSH, free T4) — baseline and annually - Urinalysis — baseline and annually (for proteinuria) - Pregnancy test in women of childbearing age (lithium is teratogenic) [cite:KD Tripathi 8e Ch 12; Stahl's Essential Psychopharmacology 4e Ch 12]