Lithium

Overview

• Psychiatric medications can be broken down into the following categories
  • antidepressants
  • antipsychotics
  • mood stabilizers
    • include lithium
• anxiolytics

Mechanism

• Mood stabilizer
• Mechanism
  • unknown
• may be related to inhibition of phosphoinositol recycling in neurons

Indications

• Clinical use
  • mood disorders
    • bipolar disorder 
      • for acute treatment of mood episodes and maintenance therapy (prevention of future episodes) 
    • major depressive disorder (MDD)
      • adjunctive treatment for some patients who have failed treatment with an antidepressant alone
    • reduces suicide risk in bipolar disorder and MDD 
• SIADH

Toxicity and Side Effects

• Toxicity 
  • very narrow therapeutic index
    • requires blood monitoring
    • toxicity may be seen at levels higher than 1.5 mEq/L
    • increased risk in patients who are volume depleted or hyponatremic
    • caution if adding hydrochlorathiazide, NSAID, or ACE-inhibitor
    • loop diuretics do not increase toxicity 
  • tremor (coarse tremor indicates likely toxicitiy)
  • sedation
  • ataxia
  • acne
  • edema
  • heart block
  • exclusively excreted by the kidneys (reabsorbed at the proximal convoluted tubule with Na+) and long term use may cause a glomerulopathy
  • hyperparathroidism 
  • hypothyroidism 
  • polyuria  
    • ADH antagonist resulting in nephrogenic diabetes insipidus
    • reason for use in SIADH
  • leukocytosis
  • teratogenesis if given in pregnancy
    • cardiac malformations including Ebstein anomaly in first trimester