What is the recommended dosing for lithium (lithium carbonate) in a 14-year-old patient requiring treatment?

Lithium ER Dosing for a 14-Year-Old

For a 14-year-old with bipolar disorder, lithium carbonate extended-release should be initiated at 300 mg twice daily (600 mg/day total), titrated by 300 mg weekly increments to achieve therapeutic serum levels of 0.8-1.2 mEq/L for acute mania or 0.6-1.0 mEq/L for maintenance therapy. 1, 2

Initial Dosing Strategy

• Start with 300 mg twice daily (600 mg/day) for adolescents weighing ≥30 kg, or 300 mg once daily for those <30 kg. 1
• The FDA-approved dosing for acute mania typically requires 600 mg three times daily (1800 mg/day) in adults to achieve therapeutic levels of 1.0-1.5 mEq/L, but adolescents often require lower doses due to differences in renal clearance and body composition. 2
• Increase the dose by 300 mg weekly increments based on serum lithium levels and clinical response, targeting 0.8-1.2 mEq/L for acute treatment. 1, 2

Therapeutic Monitoring Requirements

• Check serum lithium levels twice weekly during the acute phase until stable, then every 3-6 months during maintenance. 1, 2
• Draw blood samples 12 hours after the last dose for standard-release formulations, or 24 hours after the last dose for once-daily extended-release administration. 2, 3
• With sustained-release preparations, maintain serum concentrations in the upper therapeutic range (0.8-1.0 mEq/L) rather than 0.6-0.8 mEq/L used for standard formulations, due to the later peak concentration. 3

Baseline Laboratory Assessment

• Obtain complete blood count, thyroid function tests (TSH, free T4), urinalysis, blood urea nitrogen, creatinine, serum calcium, and pregnancy test in females before initiating lithium. 1, 4
• Repeat thyroid function, renal function (BUN, creatinine), and urinalysis every 3-6 months during ongoing therapy. 1, 4

Expected Maintenance Dosing

• Typical maintenance doses for adolescents range from 900-1200 mg/day in divided doses, though this varies considerably based on individual pharmacokinetics. 1, 3
• The usual maintenance daily dose for patients aged <40 years is 925-1300 mg (25-35 mmol), but adolescents may require doses at the lower end of this range. 3
• Some patients respond adequately at lower serum concentrations (0.6-0.8 mEq/L), so dosing should be individualized based on both clinical response and serum levels. 2, 3

Dosing Schedule Considerations

• Extended-release formulations allow for twice-daily dosing, which improves adherence compared to three-times-daily standard-release formulations. 3
• A single evening dose may be considered with modern sustained-release preparations, though twice-daily dosing is more commonly recommended for adolescents. 3
• Extended-release formulations reduce peak plasma concentrations by 30-50% without major changes in total drug exposure, potentially reducing acute side effects. 3

Critical Safety Considerations for Adolescents

• Lithium is the only FDA-approved mood stabilizer for bipolar disorder in patients age 12 and older, making it the first-line choice for this age group. 1
• Lithium reduces suicide attempts 8.6-fold and completed suicides 9-fold, an effect independent of its mood-stabilizing properties—particularly important in high-risk adolescents. 1
• Parents must secure lithium and remove access to lethal quantities, as lithium overdoses can be fatal; prescribe limited quantities with frequent refills. 1
• Educate patients and families on early signs of lithium toxicity: fine tremor, nausea, diarrhea, and to seek immediate medical attention if coarse tremor, confusion, or ataxia develop. 1

Common Pitfalls to Avoid

• Never discontinue lithium abruptly—taper gradually over 2-4 weeks minimum, as >90% of noncompliant adolescents relapsed versus 37.5% of compliant patients. 1
• Avoid NSAIDs (ibuprofen, naproxen) during lithium therapy, as they reduce renal lithium clearance and increase toxicity risk. 4
• Ensure adequate hydration, as dehydration increases lithium levels and toxicity risk; this is particularly important in active adolescents. 4
• Do not rely solely on serum levels—accurate evaluation requires both clinical assessment and laboratory monitoring. 2

Special Monitoring for Adolescent-Specific Concerns

• Monitor for nocturnal enuresis, polyuria, and polydipsia, which are common renal side effects that may be particularly distressing for adolescents. 5
• When nocturnal enuresis occurs in combination with polyuria and polydipsia, consider dose reduction or discontinuation if symptoms significantly impact quality of life. 5
• Monitor body mass index monthly for the first 3 months, then quarterly, as lithium is associated with weight gain. 1

Maintenance Therapy Duration

• Continue lithium for at least 12-24 months after mood stabilization; some adolescents will require lifelong treatment. 1, 4
• Withdrawal of maintenance lithium therapy dramatically increases relapse risk, especially within the first 6 months following discontinuation. 1
• The greatest risk of relapse occurs in the first 8-12 weeks after discontinuing medication, requiring close monitoring during this period. 1

When to Consider Combination Therapy

• If inadequate response after 6-8 weeks at therapeutic lithium levels (0.8-1.2 mEq/L), consider adding an atypical antipsychotic (aripiprazole, risperidone, or quetiapine) for severe mania. 1
• Combination therapy with lithium plus an atypical antipsychotic is superior to monotherapy for treatment-resistant cases and severe presentations. 1