NCLEX Review Guide: Psychiatric Medications - Mood Stabilizers

Definition and Purpose

• Mood stabilizers are medications primarily used to treat bipolar disorder, controlling the extreme highs (mania) and lows (depression) characteristic of the condition. These agents work by regulating neurotransmitters in the brain to prevent mood swings and maintain emotional stability.
• While primarily indicated for bipolar disorder, certain mood stabilizers are also used for other conditions including epilepsy, migraine prophylaxis, and as adjunctive therapy for treatment-resistant depression or schizophrenia.

Lithium

• Lithium (brand names: Lithobid, Eskalith) is the oldest and most established mood stabilizer, considered the gold standard for bipolar disorder treatment. It works by altering sodium transport in nerve and muscle cells and affects neurotransmitter release, particularly affecting second messenger systems.
• Lithium has a narrow therapeutic index, requiring careful monitoring of serum levels (therapeutic range: 0.6-1.2 mEq/L). Levels above 1.5 mEq/L can lead to toxicity, while below 0.6 mEq/L may be ineffective.

Anticonvulsants as Mood Stabilizers

• Several anticonvulsant medications have demonstrated mood-stabilizing properties and are FDA-approved for bipolar disorder. These include valproic acid (Depakote), carbamazepine (Tegretol), and lamotrigine (Lamictal).
• These medications work through various mechanisms including sodium channel blockade, enhancement of GABA activity, and glutamate antagonism, which helps stabilize neuronal hyperexcitability associated with mood episodes.

Atypical Antipsychotics with Mood Stabilizing Properties

• Several second-generation (atypical) antipsychotics have received FDA approval for bipolar disorder treatment, including olanzapine (Zyprexa), quetiapine (Seroquel), risperidone (Risperdal), aripiprazole (Abilify), and lurasidone (Latuda).
• These medications primarily work through dopamine (D2) and serotonin (5-HT2A) receptor antagonism, with varying affinities for other neurotransmitter receptors, providing mood stabilization while addressing psychotic features that may accompany severe mood episodes.

Absorption and Distribution

• Lithium is rapidly absorbed from the GI tract, with peak plasma levels occurring 1-4 hours after oral administration. It distributes throughout total body water with minimal protein binding and crosses the blood-brain barrier slowly, explaining the delayed onset of therapeutic effects.
• Anticonvulsant mood stabilizers have variable absorption rates and protein binding characteristics. Valproic acid is highly protein-bound (90-95%), while lamotrigine has moderate protein binding (55%). These characteristics affect drug interactions and dosing requirements.

Metabolism and Elimination

• Lithium is not metabolized and is excreted unchanged by the kidneys, with a half-life of 18-24 hours. Renal impairment significantly increases the risk of lithium toxicity, requiring dose adjustments and more frequent monitoring in patients with reduced kidney function.
• Most anticonvulsant mood stabilizers undergo hepatic metabolism via the cytochrome P450 system. Carbamazepine is a potent inducer of CYP3A4, leading to numerous drug interactions and potential decreased efficacy of other medications including oral contraceptives.

Dosing Considerations

• Lithium is typically initiated at low doses (300mg BID or TID) and gradually titrated upward based on serum levels and clinical response. Extended-release formulations may improve adherence and reduce GI side effects but should not be crushed or split.
• Lamotrigine requires an extremely slow titration schedule to minimize the risk of serious rashes, including Stevens-Johnson syndrome. The standard titration begins with 25mg daily for 2 weeks, then 50mg daily for 2 weeks, with subsequent increases of 50-100mg every 1-2 weeks to a target dose of 200mg daily.

Lamotrigine Titration Schedule

1. Weeks 1-2: 25mg once daily
2. Weeks 3-4: 50mg once daily
3. Week 5: 100mg once daily
4. Week 6: 150mg once daily
5. Week 7 and beyond: 200mg once daily (target dose)

Common Side Effects

• Lithium commonly causes fine tremor, polyuria (increased urination), polydipsia (increased thirst), nausea, diarrhea, and weight gain. These side effects are often dose-dependent and may improve with time or dose adjustment.
• Valproic acid frequently causes gastrointestinal disturbances, sedation, tremor, weight gain, hair loss, and thrombocytopenia. Taking the medication with food and using extended-release formulations may reduce GI effects.

Serious Adverse Effects

• Long-term lithium use can cause nephrogenic diabetes insipidus, hypothyroidism (in up to 20% of patients), and chronic interstitial nephritis. Baseline and regular monitoring of thyroid and kidney function is essential throughout treatment.
• Valproic acid can cause rare but serious hepatotoxicity (especially in children under 2 years), hyperammonemia, and pancreatitis. Lamotrigine can cause life-threatening skin reactions including Stevens-Johnson syndrome, particularly during initial titration or after dose increases.

Drug Interactions

• Lithium levels can be increased by NSAIDs, thiazide diuretics, and ACE inhibitors, potentially leading to toxicity. Conversely, caffeine, theophylline, and sodium loading can decrease lithium levels, potentially reducing efficacy.
• Carbamazepine induces the metabolism of many medications including oral contraceptives, warfarin, and other mood stabilizers, potentially reducing their effectiveness. It also has a significant interaction with grapefruit juice, which can increase carbamazepine levels.

Assessment and Monitoring

• For lithium therapy, obtain baseline and periodic monitoring of renal function (BUN, creatinine, GFR), thyroid function (TSH, free T4), electrolytes (especially sodium), and ECG (particularly in older adults or those with cardiac risk factors).
• For valproic acid, monitor complete blood count, liver function tests, and ammonia levels at baseline and periodically throughout treatment. For lamotrigine, careful assessment for any skin changes is essential, especially during titration periods.

Procedure for Lithium Level Monitoring

1. Draw blood samples 12 hours after the last dose (trough level)
2. Ensure patient has been on a stable dose for at least 5 days
3. Maintain consistent sodium intake and hydration before testing
4. Check more frequently during dose adjustments or with signs of toxicity
5. Monitor more frequently in elderly patients or those with medical comorbidities

Patient Education

• Educate patients on the importance of medication adherence, as abrupt discontinuation can lead to relapse or withdrawal symptoms. Emphasize that therapeutic effects may take several weeks to become apparent, but side effects may occur earlier.
• Teach patients to maintain adequate hydration and consistent sodium intake while on lithium therapy. Instruct on recognition of early signs of toxicity and the importance of seeking immediate medical attention if these occur.

Special Populations

• Pregnancy considerations are crucial for mood stabilizer therapy. Valproic acid is contraindicated due to high risk of neural tube defects. Lithium has a lower but still significant risk of cardiac malformations (Ebstein's anomaly). Lamotrigine may have a more favorable risk profile but still requires careful risk-benefit assessment.
• Elderly patients require lower initial doses and more frequent monitoring due to age-related changes in pharmacokinetics, particularly decreased renal function affecting lithium clearance. They are also more susceptible to side effects including cognitive impairment and falls.

Critical Concepts

• Mood stabilizers are the cornerstone of bipolar disorder treatment, working to prevent both manic and depressive episodes. The major classes include lithium, anticonvulsants (valproic acid, carbamazepine, lamotrigine), and certain atypical antipsychotics.
• These medications have narrow therapeutic indices and significant side effect profiles requiring careful monitoring and patient education. Regular laboratory monitoring is essential to ensure safety and efficacy throughout treatment.

Commonly Confused Points

Study Tips

Knowledge Checklist

Common Pitfalls

• Failing to recognize that lithium levels should be drawn as trough levels (12 hours after the last dose)
• Confusing the therapeutic ranges of different mood stabilizers
• Overlooking the impact of dehydration, sodium changes, or medication interactions on lithium levels
• Neglecting to educate patients about the importance of consistent medication adherence
• Missing early signs of serious adverse reactions like lamotrigine-induced rash or valproic acid hepatotoxicity