Lithium

Adverse effects

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• Neurologic:
  • Fine hand tremor: Common, dose-dependent, early onset. Treat with dose reduction or Propranolol.
  • Cognitive slowing, ataxia, fatigue.
• Renal & Endocrine:
  • Nephrogenic Diabetes Insipidus (NDI): Li antagonizes ADH/AVP action at collecting duct aquaporin-2 channels.
    • Presentation: Polyuria, polydipsia, low urine specific gravity (< 1.005), low urine Osm (< 300 mOsm/kg).
    • Management: Discontinue Li if feasible. If Li is mandatory, add Amiloride (blocks epithelial Na⁺ channels [ENaC] in collecting duct, preventing Li uptake).
  • Chronic Tubulointerstitial Nephritis / CKD: Seen with long-term therapy (> 10–20 years).
  • Hypothyroidism & Goiter: Inhibits thyroid hormone synthesis and release. c
    • Management: Check TSH; treat by adding Levothyroxine (do not stop Li).
  • Hyperparathyroidism & Hypercalcemia: Stimulates parathyroid hyperplasia. Leading to hypercalcemia. c
• Gastrointestinal: Nausea, vomiting, diarrhea, benign weight gain.
• Dermatologic: Acne exacerbation, new-onset or worsening psoriasis, alopecia.
• Cardiac: Benign T-wave flattening/inversion, sinus bradycardia, sinoatrial (SA) block.

Lithium poisoning

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Etiology

• Excessive intake
  • Increase in prescribed dose (lithium has a narrow therapeutic window)
  • Accidental or intentional overdose
• Decreased excretion
  • Renal insufficiency
  • Hypovolemia (e.g., due to vomiting, diarrhea, or water restriction)
  • Medications that increase the renal absorption of lithium
    • Thiazide diuretics
    • NSAIDs (except aspirin) c
    • ACE inhibitors

Clinical features

• Acute Toxicity:
  • Predominantly GI symptoms: N/V/D, abdominal cramps.
• Chronic Toxicity:
  • Predominantly Neurologic symptoms: Coarse tremor, ataxia, hyperreflexia, clonus, delirium, seizures, coma. c
• Cardiac: Arrhythmias, bradycardia, QT prolongation.

Management

1. Immediate Step: Discontinue lithium.
2. First-Line: IV 0.9% Normal Saline (NS) to restore GFR and drive renal excretion.
   • Note: Activated charcoal does NOT bind lithium.
3. Hemodialysis (Definitive): c
   • Lithium > 4.0 mEq/L (regardless of symptoms).
   • Lithium > 2.5 mEq/L + severe neuro symptoms (seizures, AMS) OR renal failure.
   • Life-threatening symptoms (refractory seizures, fatal arrhythmias) at any level.