A patient with bipolar disorder on lithium develops coarse tremors, confusion, and ECG changes. Serum lithium level is 2.8 mEq/L. Which early pharmacological intervention reduces lithium absorption from the gut in acute toxicity?

• A Activated charcoal administration
• B Sodium polystyrene sulfonate (Kayexalate) to bind lithium
• C Sodium bicarbonate infusion to alkalinize urine and reduce renal reabsorption ✓
• D Prussian blue to chelate lithium in the gut

Explanation

Activated charcoal does not effectively adsorb lithium (a small monovalent ion). Sodium bicarbonate infusion creates urinary alkalinization and volume expansion; since lithium is reabsorbed by the proximal tubule via the sodium transporter, sodium loading (isotonic saline or bicarbonate) competes with lithium for tubular reabsorption, increasing lithium excretion significantly. Kayexalate is sometimes used for gut binding in sustained-release overdose but is not the primary pharmacological measure. Prussian blue is for thallium or cesium poisoning.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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