M05.10.10 Mood stabilizers

Mood stabilizers are a class of medications used to treat bipolar disorder, a condition characterized by episodes of mania (elevated mood) and depression. They help to prevent future episodes and stabilize mood swings. This section provides an overview of some commonly used mood stabilizers, their mechanisms of action, side effects, and important considerations for medical students.

Lithium

• First-line treatment for bipolar disorder.
• Mechanism of Action (proposed): Blocks inositol-1-phosphate, a second messenger involved in cellular signaling.
• Absorption: Rapidly absorbed from the gastrointestinal tract.
• Protein Binding: Not significantly bound to plasma proteins.
• Metabolism: Not metabolized by the liver.
• Excretion: Primarily eliminated by the kidneys (95%).

Important Considerations:

• Therapeutic Index: Narrow. Requires close monitoring of blood levels to avoid toxicity.
• Monitoring: Regular monitoring of serum lithium levels is crucial due to the narrow therapeutic index. If levels exceed 2.5 mEq/L, consider dialysis as the primary treatment for lithium intoxication.
• Electrolytes and Hydration: Good kidney function and adequate salt and fluid intake are essential for lithium use.
• Side Effects:
  • Common: Tremor, thirst, anorexia, gastrointestinal distress, polyuria (frequent urination), polydipsia (excessive thirst), edema (fluid retention), acne.
  • Less common: Hypothyroidism, nephrotoxicity (kidney damage), teratogenicity (birth defects, especially Ebstein’s anomaly of the heart valve), diabetes insipidus (imbalanced water regulation).
  • Toxic effects: Ataxia (incoordination), seizures, confusion.

Points to Remember:

• Lithium is a highly effective mood stabilizer but requires careful monitoring due to its narrow therapeutic index and potential side effects.
• Maintaining adequate hydration and electrolyte balance is crucial for safe lithium use.
• Be aware of potential teratogenic effects and counsel women of childbearing potential about the risks.

Valproic Acid

• Used to treat bipolar disorder, particularly rapid cycling bipolar disorder.
• Mechanism of Action: Increases levels of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter, in the central nervous system.

Important Considerations:

• Side Effects: Sedation, weight gain, tremors, hair loss (alopecia), gastrointestinal distress, and teratogenicity (especially neural tube defects).
• Hepatotoxicity: Can cause liver damage. Monitor blood levels to assess for potential liver function impairment.
• Toxicity: Confusion, coma, or cardiac arrest can occur in severe cases.

Points to Remember:

• Valproic acid is effective for bipolar disorder but carries a risk of teratogenicity and hepatotoxicity.
• Close monitoring of blood levels and liver function is essential during treatment.
• Not recommended for women of childbearing potential unless other options are ineffective.

Carbamazepine

• Used to treat bipolar disorder.
• Mechanism of Action: Blocks sodium channels in neurons, affecting the transmission of nerve impulses. Additionally, it may alter central GABA receptors.

Important Considerations:

• Side Effects: Gastrointestinal distress, rash, mild decrease in white blood cell count (leukopenia), potentially life-threatening agranulocytosis (severe decrease in white blood cells), and aplastic anemia (bone marrow failure).
• Toxicity: Hypotension (low blood pressure), rapid heart rate (tachycardia), respiratory depression, or coma can occur in severe cases.
• Monitoring: Monitor blood cell counts and signs of rash during treatment.

Points to Remember:

• Carbamazepine is an effective mood stabilizer but carries a risk of serious blood cell abnormalities.
• Regular monitoring of blood cell counts and prompt evaluation of any rash are essential.
• Consider alternative medications for patients with a history of blood cell disorders.

Lamotrigine

• Used to treat bipolar disorder, particularly for maintenance treatment and to prevent depressive episodes.
• Mechanism of Action: The exact mechanism is not fully understood, but it may involve effects on glutamate and sodium channels.

Important Considerations:

• Side Effects: Associated with an increased risk of Stevens-Johnson syndrome, a severe allergic skin reaction.
• Monitoring: Patients should be monitored for signs and symptoms of Stevens-Johnson syndrome, such as a painful rash, blistering, and mucosal involvement.

Points to Remember:

• Lamotrigine is a valuable option for bipolar disorder but carries a risk of Stevens-Johnson syndrome.
• Careful monitoring for potential allergic reactions is necessary.

Bibliography:

• American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: Author.
• National Institute of Mental Health