Adverse effects

---

• Renal
  • Nephrogenic diabetes insipidus
    • Pathophysiology: lithium interferes with ADH signaling → ↓ aquaporins (water channels) on the collecting duct cell’s surface → ↓ water molecules are reabsorbed and kidneys are unable to concentrate urine → ↑ free water excretion
    • Clinical features: polyuria, nocturia, and polydipsia → ↑ risk of dehydration and subsequent lithium toxicity

Lithium poisoning

---

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)
    • ACE inhibitors

Clinical features

---

• Gastrointestinal: nausea, vomiting, and diarrhea
• Neurological
  • Altered mental status, confusion
  • Somnolence, coma
  • Delirium, encephalopathy, psychomotor impairment
  • Coarse tremors, seizures, fasciculations, myoclonus
  • Ataxia, slurred speech, nystagmus
  • Hyperreflexia