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Lithium

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Summary

Lithium is a mood-stabilizing drug often used to treat bipolar disorder. It has a narrow therapeutic index, so side effects are commonly seen with its use. Side effects of lithium include hypothyroidism, neuromuscular excitations like involuntary tremors, and nephrotoxicity. Lithium is also teratogenic and may cause birth defects like Ebstein’s anomaly when used in pregnancy.

Key Points

  • Lithium
    • Mechanism
      • Still under investigation; thought to be related to structural similarity to sodium ions
    • Clinical Use
      • Bipolar disorder
        • Used to treat acute mania/mood episodes 
        • Used as maintenance therapy for bipolar disorder
      • Major Depression
        • Used as adjunctive treatment for patients who have failed antidepressants alone
      • SIADH
        • Acts as ADH antagonist to induce diabetes insipidus and intentional fluid volume loss
    • Adverse Effects
      • Acute toxicity
        • Nausea/vomiting, diarrhea, slurred speech, seizures, ataxia
      • Narrow therapeutic index
        • Renally excreted
          • Any drug that affects renal clearance (e.g. diuretics) can cause changes in lithium levels
      • Neuromuscular excitability (involuntary movements)
        • Coarse tremors, fasciculations, ataxia
      • Hypothyroidism
        • Thyroid tests are routinely performed on patients taking lithium
      • Nephrotoxicity
        • May cause chronic interstitial nephritis
        • Creatinine levels are routinely monitored
        • Causes nephrogenic diabetes insipidus (see SIADH above)
      • Teratogenic
        • Causes Ebstein’s anomaly in fetuses
          • Downward displacement of the tricuspid valve → atrialization of the right ventricle
          • Associated with tricuspid regurgitation, accessory conduction pathways, and right-sided heart failure