# Mood Stabilizers and Anticonvulsants in Youth

## Introduction

Mood stabilizers and anticonvulsants play an important role in the management of pediatric bipolar disorder, aggression, and certain seizure-related psychiatric conditions. Lithium remains the prototypical mood stabilizer with the longest track record, while valproate, lamotrigine, and carbamazepine are used for their mood-stabilizing properties. Understanding their pharmacology, evidence base, and safety profiles in developing children is essential for informed prescribing.

## Lithium

### Pharmacology

The precise mechanism of lithium remains incompletely understood but involves modulation of inositol phosphate signaling, inhibition of glycogen synthase kinase-3 beta, and neuroprotective effects. Lithium enhances serotonergic neurotransmission and modulates glutamate activity. It is unique among psychotropic medications for its demonstrated anti-suicidal properties, a characteristic not shared by other mood stabilizers. Its narrow therapeutic index necessitates regular serum level monitoring.

### Pediatric Indications

Lithium is FDA-approved for bipolar disorder in adolescents aged twelve and older. It is effective for both acute mania and maintenance treatment. Evidence for its anti-suicidal effects extends to adolescent populations, making it particularly valuable in this age group. It may also be used for augmentation in treatment-resistant depression, although pediatric data for this indication are limited.

### Dosing and Monitoring

Target serum levels are 0.6-1.2 mEq/L for acute treatment and 0.6-1.0 mEq/L for maintenance. A typical starting dose is 300 mg twice daily, titrated based on serum levels and clinical response. Levels should be drawn twelve hours after the last dose, at steady state, which is reached approximately five days after any dose change. Baseline laboratory work should include a basic metabolic panel for renal function, TSH, CBC, calcium, urinalysis, a pregnancy test, and an ECG. Ongoing monitoring requires lithium levels, renal function tests, and thyroid function tests every three to six months.

### Adverse Effects

Renal effects include polyuria, polydipsia, nephrogenic diabetes insipidus, and chronic interstitial nephritis with long-term use. Thyroid effects include hypothyroidism in up to 25% of treated patients and goiter. Neurological side effects include tremor, cognitive dulling, and ataxia at toxic levels. Gastrointestinal symptoms include nausea, diarrhea, and weight gain. Dermatological effects include acne and psoriasis exacerbation. Teratogenicity is a critical consideration for adolescent females, as lithium exposure during the first trimester increases the risk of Ebstein's anomaly, a cardiac malformation. Lithium toxicity is a medical emergency presenting with confusion, seizures, renal failure, and cardiac arrhythmias.

## Valproate (Valproic Acid / Divalproex Sodium)

### Pharmacology

Valproate enhances GABAergic inhibition through multiple mechanisms, blocks voltage-gated sodium channels, modulates calcium channels, and inhibits histone deacetylase with potential epigenetic effects.

### Pediatric Use

Valproate is not FDA-approved for bipolar disorder in youth but is widely used off-label. Evidence supports its efficacy in acute mania in adolescents. It is used for aggression and mood instability in youth both with and without bipolar disorder. It does hold FDA approval for epilepsy and migraine prevention in pediatric populations.

### Dosing and Monitoring

Target serum levels are 50-125 mcg/mL. The starting dose is typically 10-15 mg/kg/day, divided into twice-daily dosing. Baseline laboratories should include a CBC with differential, hepatic function panel, coagulation studies, and a pregnancy test. Monitoring of CBC and liver function should occur at one, three, and six months, then every six months. An ammonia level should be checked if lethargy or cognitive changes develop.

### Adverse Effects

Hepatotoxicity presents the greatest risk in children under two years of age on polytherapy and can be fatal. Pancreatitis is rare but life-threatening. Thrombocytopenia and platelet dysfunction can occur. Common side effects include weight gain, alopecia, tremor, and gastrointestinal distress. Polycystic ovarian syndrome, characterized by hyperandrogenism, menstrual irregularities, and weight gain, is a significant concern for female patients. Teratogenicity is severe, with a 1-2% risk of neural tube defects and documented cognitive impairment in exposed children, making it effectively contraindicated in pregnancy when alternatives exist. Hyperammonemic encephalopathy can occur even with normal valproate levels, presenting as lethargy and confusion.

## Lamotrigine

### Pharmacology

Lamotrigine inhibits voltage-gated sodium channels and modulates glutamate release. It has a unique mood stabilizer profile with primary efficacy in bipolar depression rather than mania, distinguishing it from most other mood stabilizers.

### Pediatric Use

Lamotrigine is FDA-approved for epilepsy in children aged two and older and for bipolar maintenance in adults aged eighteen and older. Off-label use in adolescent bipolar depression and maintenance is increasingly common. Evidence for efficacy in adolescent populations is growing, though large pediatric randomized controlled trials remain limited. It may be particularly well suited for patients in whom the depressive polarity predominates.

### Dosing

Lamotrigine requires very slow titration to minimize the risk of Stevens-Johnson syndrome and toxic epidermal necrolysis. The starting dose is 25 mg daily for two weeks, reduced to 12.5 mg if the patient is also taking valproate. The dose is then increased by 25 mg every two weeks, with a target dose of 100-200 mg daily. Lower target doses are used when lamotrigine is combined with valproate, because valproate doubles lamotrigine levels by inhibiting glucuronidation.

### Adverse Effects

Stevens-Johnson syndrome and toxic epidermal necrolysis occur at a rate of approximately 0.8% in children, which is higher than the rate in adults, and the risk is highest during the first eight weeks of treatment. Risk factors include rapid titration, concurrent valproate use, and young age. Any rash appearing during titration should prompt immediate clinical evaluation and possible discontinuation. Other side effects include headache, dizziness, insomnia, and nausea. Lamotrigine is generally well tolerated, with low rates of weight gain, sedation, and cognitive effects compared to other mood stabilizers.

## Carbamazepine and Oxcarbazepine

### Carbamazepine

Carbamazepine blocks voltage-gated sodium channels and stabilizes neuronal membranes. It is effective for acute mania in adults but has limited pediatric bipolar data. It is a potent CYP3A4 inducer with numerous drug-drug interactions, including significant reduction in the efficacy of oral contraceptives. Auto-induction of its own metabolism requires dose adjustments over the first two to four weeks. Serious adverse effects include agranulocytosis, aplastic anemia, hyponatremia, and Stevens-Johnson syndrome, with the latter being particularly associated with the HLA-B*1502 allele. HLA-B*1502 testing is mandatory before prescribing carbamazepine to patients of Southeast Asian ancestry.

### Oxcarbazepine

Oxcarbazepine is a structural analog of carbamazepine with fewer drug interactions and no auto-induction. It is FDA-approved for partial seizures in children aged two and older. Off-label use for mood stabilization exists but is supported by limited pediatric evidence for bipolar disorder. Hyponatremia is the most clinically significant risk and requires sodium level monitoring. It is generally better tolerated than carbamazepine.

## Comparative Considerations

Lithium has the strongest evidence for pediatric bipolar disorder and is the only agent with demonstrated anti-suicidal properties. Valproate may be preferred for mixed episodes and rapid cycling but carries significant risks for females of reproductive age. Lamotrigine is favored for bipolar depression prevention but requires slow titration that limits its usefulness in acute situations. Atypical antipsychotics are often used preferentially in practice due to more robust acute efficacy data and faster onset, though they carry their own metabolic risks. Combination therapy is frequently necessary and should be guided by the specific symptom domains being targeted.

| Feature | Lithium | Valproate | Lamotrigine | Carbamazepine |
|---|---|---|---|---|
| FDA Pediatric Approval | Bipolar (12+) | Epilepsy/migraine only | Epilepsy (2+); bipolar maintenance (18+) | Epilepsy only |
| Primary Mood Target | Acute mania, maintenance | Acute mania, mixed episodes | Bipolar depression prevention | Acute mania (limited data) |
| Target Level | 0.6-1.2 mEq/L | 50-125 mcg/mL | Dose-based (100-200 mg) | 4-12 mcg/mL |
| Anti-Suicidal Properties | Yes (unique) | No | No | No |
| Key Monitoring | Renal, thyroid, lithium levels | CBC, LFTs, ammonia | Rash surveillance | CBC, sodium, LFTs, HLA-B*1502 |
| Major Risks | Renal toxicity, hypothyroidism, Ebstein's anomaly | Hepatotoxicity, pancreatitis, PCOS, teratogenicity (NTDs) | Stevens-Johnson syndrome (0.8% in children) | Agranulocytosis, SJS, drug interactions |
| Weight Gain | Moderate | Moderate-high | Low | Low |
| Teratogenicity Concern | Ebstein's anomaly | Neural tube defects (1-2%), cognitive effects | Low risk | Moderate risk |

## Clinical Pearls

Lithium remains the gold-standard mood stabilizer for pediatric bipolar disorder, with unique anti-suicidal properties not shared by other mood stabilizers. Valproate should be used with extreme caution in females of reproductive age due to its teratogenicity and association with polycystic ovarian syndrome; robust contraception counseling is essential. Any rash during lamotrigine titration warrants immediate clinical evaluation; the risk of Stevens-Johnson syndrome is highest with rapid dose escalation and concurrent valproate use. Mood stabilizers generally require weeks to achieve full therapeutic effect, and premature discontinuation is a common cause of relapse.

## References

1. Findling, R. L., Robb, A., McNamara, N. K., et al. (2015). Lithium in the acute treatment of bipolar I disorder: a double-blind, placebo-controlled study. *Pediatrics*, 136(5), 885-894.
2. Wagner, K. D., Redden, L., Kowatch, R. A., et al. (2009). A double-blind, randomized, placebo-controlled trial of divalproex extended-release in the treatment of bipolar disorder in children and adolescents. *Journal of the American Academy of Child & Adolescent Psychiatry*, 48(5), 519-532.
3. Cipriani, A., Hawton, K., Stockton, S., & Geddes, J. R. (2013). Lithium in the prevention of suicide in mood disorders: updated systematic review and meta-analysis. *BMJ*, 346, f3646.
4. Harden, C. L., Meador, K. J., Pennell, P. B., et al. (2009). Management issues for women with epilepsy: focus on pregnancy. *Epilepsia*, 50(5), 1247-1255.