USMLE

Lithium

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Mental Health Drugs
  1. Tricyclic Antidepressants
  2. SSRIs
  3. SNRIs
  4. Benzodiazepines
  5. Barbiturates
  6. Typical Antipsychotics
  7. Atypical Antipsychotics
  8. Extrapyramidal Symptoms
  9. Lithium
  10. MAOIs
  11. Bupropion
  12. Buspirone
  13. Trazodone
  14. Zolpidem
  15. Amphetamines

Summary

Lithium is a mood stabilizing drug used to treat bipolar disorder. It has a narrow therapeutic range, and toxicity symptoms start to show up above a blood level of 1.5. Things that can cause lithium toxicity include fluid loss like dehydration and diuretics, low sodium levels, decreased kidney function, or the specific use of NSAIDs or thiazide diuretics. Early signs of lithium toxicity include GI distress, which includes nausea, vomiting, and diarrhea. Late signs of toxicity are neurological problems, like loss of coordination, sedation, confusion, or seizures. Lithium is also teratogenic and should not be given during pregnancy.

Key Points

  • Mechanism
    • Mood stabilizer
      • Alteration of ion transport in muscle and nerve cells
      • Increased receptor sensitivity to serotonin
    • Excreted through the kidneys
    • Clinical Use
      • Bipolar disorder
        • Effective in controlling the manic phase (flight of ideas, hyperactivity
        • Desired effect may take up to 3 weeks
    • Side Effects and Adverse Reactions
      • Narrow therapeutic range of 0.6-1.2 mEq/L
        • Toxicity symptoms generally start above 1.5 mEq/L
        • Patient will require regular blood work to monitor lithium levels
          • Twice weekly during initial treatment, and then every 2 months during maintenance
      • Toxicity caused by
        • Fluid loss
          • Dehydration
          • Diuretics
          • Diarrhea/vomiting
          • Make sure patient has adequate fluid intake of 1-2 L/day
        • Hyponatremia
          • Make sure patient has adequate sodium intake
        • Drug-drug interactions
          • NSAIDS and Thiazide Diuretics
            • Should not be taken with lithium
            • Use acetaminophen for pain relief
        • Decreased renal function
          • Lithium is excreted through the kidneys, so with kidney damage, more drug stays in the body
      • Early/acute signs
        • GI Distress
          • Nausea, vomiting, diarrhea, loss of appetite
          • If patient is experiencing these symptoms hold lithium, notify provider, and anticipate an order for a stat serum lithium level
      • Late/chronic signs
        • Neurological Symptoms
          • Confusion
          • Ataxia
          • Muscle tremors/twitching
          • Sedation
          • Seizures
          • Diabetes Insipidus (polyuria, polydipsia)
        • Blurred vision
        • Severe hypotension
        • Cardiac dysrhythmias
      • Levels above 3.5 will often result in coma and/or death
      • Teratogenic
        • Pregnancy Category D
      • Caffeine can lower lithium levels and induce a manic state
      • Weight gain
      • Drowsiness
      • Dry mouth