Mood Stabilizers in Bipolar Disorder — Comprehensive Notes

Overview

• Mood stabilizers (anti-manic medications) are used to treat a patient with unstable mood, particularly in bipolar disorder (mania or hypomania, rapid cycling, and mixed episodes).
• Goal of treatment: remission versus stabilization. Remission means the mood symptoms have resolved; stabilization means improvement, but not necessarily full remission.
• Mood stabilizers can be used as adjuncts to antidepressants and antipsychotics.
• They can also be used to promote abstinence in alcoholism and to treat aggression and impulsivity in other conditions (dementia, intoxication, mental retardation, personality disorders, and other general medical conditions).
• Examples of mood stabilizers include: Lithium, Carbamazepine, Valproic acid, and Lamotrigine.

Lithium (Lithium carbonate)

• Lithium is the drug of choice for treating acute mania and serves as prophylaxis against further manic and depressive episodes in bipolar disorder; considered the gold standard for mania.
• Pharmacokinetics: Lithium is primarily eliminated by the kidneys (renally metabolized/excreted); unlike most drugs that are hepatically metabolized, lithium's blood levels correlate with efficacy.
• Therapeutic window: the serum level must be maintained in a narrow range for efficacy and safety.
  • Therapeutic range: $0.7 \leq \text{Li} \leq 1.2 \text{mEq/L}$
  • Levels below this range are subtherapeutic; levels above this range increase risk of toxicity.
  • Toxicity risk rises significantly with levels above $2.0 \text{mEq/L}$, and levels above $3.0 \text{mmol/L}$ may necessitate hemodialysis.
• Drug interactions that increase lithium levels (be cautious when co-prescribing): $\text{NSAIDs}, \text{tetracyclines}, \text{metronidazole}, \text{ACE inhibitors}, \text{diuretics}, \text{theophylline}, \text{osmotic diuretics}, \text{acetazolamide}$.
• Mechanism: alters neuronal sodium transport; not primarily hepatic metabolism.
• Monitoring: baseline kidney function and thyroid function; regular monitoring of serum lithium levels and thyroid hormones.
• Pregnancy: lithium is contraindicated in pregnancy due to risk of Ebstein's anomaly (a congenital cardiac defect).
• Side effects (common): fine tremor, sedation, ataxia, thirst or metallic taste, polyuria, edema, weight gain, GI problems, benign leukocytosis, thyroid enlargement.
• Nephrogenic diabetes insipidus can occur.
• Toxicity signs and progression: coarse tremor, ataxia, slurred speech; dizziness, weakness, nystagmus, GI upset; can progress to stupor, coma, seizures, arrhythmias, and death if not treated.
• Management of toxicity:
  • Mild toxicity: correct electrolyte disturbances, provide IV hydration, discontinue lithium.
  • Severe toxicity (level > $3.0 \text{mEq/L}$) often requires hemodialysis.
• Monitoring plan: routinely check serum lithium level, kidney function, and thyroid function during therapy.

Anticonvulsants as mood stabilizers

• Carbamazepine

  • Indications: useful for bipolar disorder with mixed episodes and rapid cycling; also used for trigeminal neuralgia (poduced analgesic effect).
  • Mechanism: blocks voltage-gated sodium channels and inhibits action potentials.
  • Time to onset: usually around one week.
  • Notable side effects: skin rash, drowsiness, ataxia, slurred speech, leukopenia, hyponatremia.
  • Serious hematologic/LFT risks: aplastic anemia, agranulocytosis, elevated liver enzymes, thrombocytopenia.
  • Pregnancy: fetal anomalies, including spina bifida.
  • Monitoring: baseline CBC and LFTs prior to starting therapy.

• Valproic acid

  • Indications: useful in treating bipolar mood episodes with mixed features and rapid cycling.
  • Mechanism: not fully understood; increases CNS levels of GABA.
  • Side effects: weight gain, alopecia, hemorrhagic pancreatitis, hepatotoxicity, thrombocytopenia, and teratogenic risks (including spina bifida).
  • Monitoring: pregnancy test; baseline CBC and LFTs.

• Lamotrigine

  • Indication: particularly indicated for bipolar depression; helps stabilize mood and prevent depressive episodes.
  • Important safety note: can cause Stevens–Johnson syndrome (a potentially fatal rash).
  • Dosing strategy: start at a very low dose and wait two weeks before making small incremental increases to dosing to monitor for rash.

Adjunctive and other treatments

• Antipsychotic medications, benzodiazepines, and electroconvulsive therapy (ECT) can be helpful in mood disorders including bipolar disorder.

Treatment goals, definitions, and emergency considerations

• Remission: resolution of mood symptoms; if psychotic features occur with manic episodes, treat psychosis first.
• Reasonable response: improvement in the number, frequency, duration, and/or intensity of symptoms when full remission is not achieved.
• Bipolar mania and bipolar depression can be medical emergencies due to risk-taking behavior or suicidality; require assessment of level of care and urgency of intervention.

Levels of care and decision-making in treatment planning

• Inpatient hospitalization: indicated if the patient is not safe for themselves or others or cannot meet basic needs.
• Partial hospital program: daytime hospital-based care with the patient returning home at night; provides intensive treatment while preserving some independence at home.
• Outpatient: appropriate when the patient has good insight and judgment, plus strong support at home; suitable if safety and functioning are manageable.

Monitoring and safety practices

• Baseline tests before initiating mood stabilizers: kidney function, thyroid function (for lithium); CBC and LFTs as applicable; pregnancy testing for women of childbearing potential.
• Ongoing monitoring: regular labs for kidney function, thyroid function, CBC, and LFTs depending on the mood stabilizer used; monitor for side effects and adherence.

Key takeaways

• Mood stabilizers are central to bipolar disorder management: aim for remission; monitor safety; consider comorbid conditions and patient-specific factors when choosing therapy.