Is lithium appropriate for a 19-year-old female with a history of anorexia, possible borderline personality disorder (BPD), and post-traumatic stress disorder (PTSD)?

Lithium Use in a 19-Year-Old Female with Anorexia, Possible BPD, and PTSD

Lithium can be used cautiously in this patient, but requires intensive monitoring due to the anorexia history and associated metabolic vulnerabilities. The decision hinges on whether bipolar disorder is the primary diagnosis driving treatment, as lithium is FDA-approved for bipolar disorder in patients age 12 and older 1, but carries significant risks in patients with eating disorders.

Clinical Decision Algorithm

Step 1: Clarify the Primary Diagnosis

• If bipolar disorder is confirmed: Lithium remains a first-line option per American Academy of Child and Adolescent Psychiatry guidelines, showing superior long-term efficacy for maintenance therapy and unique anti-suicide properties (reducing suicide attempts 8.6-fold and completed suicides 9-fold) 2, 3.
• If BPD is the primary diagnosis: Dialectical behavior therapy (DBT) is the evidence-based first-line treatment for borderline personality disorder, not lithium 3. Lithium has no established role in treating BPD symptoms.
• For PTSD symptoms: Lithium has no established efficacy for PTSD treatment 4. Cognitive behavioral therapy is the evidence-based intervention for PTSD 3.

Step 2: Assess Anorexia-Related Risk Factors

Critical metabolic vulnerabilities in anorexia that increase lithium toxicity risk:

• Dehydration and electrolyte imbalances (particularly sodium depletion) dramatically increase lithium levels 5, 6
• Reduced glomerular filtration from malnutrition impairs lithium clearance 7
• Purging behaviors or laxative use create unpredictable fluid shifts 8

However, limited evidence suggests lithium can be used in adolescents with anorexia when psychiatric symptoms (unstable mood, psychomotor agitation, treatment non-compliance) impair nutritional rehabilitation 8. In a case series of 7 female adolescents with anorexia treated with lithium, all showed improvement in target psychiatric symptoms with only 2 experiencing adverse effects (polyuria/polydipsia in one, elevated creatinine kinase in another) 8.

Step 3: Implement Enhanced Monitoring Protocol

If lithium is initiated, the following intensive monitoring is mandatory:

Baseline assessment:

• Complete blood count, comprehensive metabolic panel (sodium, potassium, calcium, creatinine, BUN), thyroid function tests (TSH, free T4), urinalysis, pregnancy test, and baseline ECG 2
• Body mass index, hydration status, and eating/purging behaviors 8

Ongoing monitoring (more frequent than standard due to anorexia):

• Lithium levels weekly for first month, then every 2 weeks until stable, then monthly 8
• Renal function (creatinine, BUN), electrolytes (especially sodium), and thyroid function every 3-6 months 2
• Weekly weight and hydration assessment 8
• Calcium levels should be checked before and during treatment due to consistent finding of hyperparathyroidism risk 7

Step 4: Dosing Considerations

Start at lower doses than typical due to metabolic vulnerability:

• Initial dose: 150-200 mg daily (lower than standard 300 mg) 8
• Target therapeutic level: 0.4-0.6 mEq/L (lower end of therapeutic range) rather than standard 0.6-1.2 mEq/L 8
• Administer in divided doses (three times daily) to minimize peak levels and GI side effects 8
• Maximum dose in this population typically 600 mg/day 8

Step 5: Address Specific Safety Concerns

Weight gain risk:

• Lithium causes weight gain in approximately 30% of patients (4-10 kg average) 5, 7
• This is particularly problematic in anorexia recovery, but may be therapeutically beneficial if patient is underweight 8
• Proactive nutritional counseling is essential 2

Renal effects:

• Lithium reduces urinary concentrating ability by 15% on average, causing polyuria and polydipsia 7
• In anorexia patients already at risk for dehydration, this compounds risk 5
• Ensure adequate fluid intake (2-3 liters daily) and avoid NSAIDs which increase lithium levels by 25-40% 6

Thyroid effects:

• Clinical hypothyroidism risk is increased 5.78-fold with lithium 7
• TSH increases on average by 4.0 iU/mL 7
• Monitor thyroid function every 3-6 months 2

Overdose risk:

• Lithium has significant lethality in overdose, requiring third-party medication supervision in patients with suicide history 2
• Prescribe limited quantities with frequent refills to minimize stockpiling 2
• Engage family members to restrict access to lethal quantities 2

Critical Pitfalls to Avoid

Do not use lithium if:

• Active purging behaviors are present (unpredictable fluid/electrolyte shifts) 8
• Severe malnutrition with BMI <15 or electrolyte abnormalities exist 5
• Patient cannot commit to intensive monitoring requirements 2
• Dehydration or sodium depletion is present 6

Drug interactions to avoid:

• Thiazide diuretics increase lithium levels 25-40% 6
• NSAIDs (except aspirin and sulindac) significantly impair lithium clearance 6
• ACE inhibitors may impair lithium elimination 6

Temporarily suspend lithium during:

• Intercurrent illness with vomiting/diarrhea 9
• Planned procedures requiring bowel preparation 9
• Any acute medical illness affecting hydration status 9

Alternative Considerations

If lithium is deemed too risky, consider:

• Valproate (divalproex) as alternative mood stabilizer, though it also carries weight gain risk and requires monitoring 2
• Atypical antipsychotics (aripiprazole, quetiapine) for mood stabilization, though metabolic monitoring is required 2
• Prioritize evidence-based psychotherapy (DBT for BPD, CBT for PTSD) as primary intervention 3

The decision ultimately depends on whether bipolar disorder is the confirmed primary diagnosis requiring mood stabilization. If so, lithium can be used with enhanced monitoring protocols specific to eating disorder populations 8. If BPD or PTSD are the primary concerns, psychotherapy should be prioritized over lithium 3.