What is the recommended dosing pattern for Lithium (lithium carbonate) in adults?

Lithium Dosing Pattern in Adults

For acute mania, start with lithium carbonate 600 mg three times daily (1800 mg/day total) targeting serum levels of 1.0-1.5 mEq/L, then transition to maintenance dosing of 300 mg three to four times daily (900-1200 mg/day) targeting levels of 0.6-1.2 mEq/L. 1

Acute Phase Dosing

• Initial dose: 600 mg three times daily for acute mania, which typically produces effective serum lithium levels between 1.0-1.5 mEq/L 1
• Alternative starting approach: Begin with 12-24 mmol (450-900 mg) per day depending on age and body weight 2
• Monitor serum levels twice per week during the acute phase until levels and clinical condition stabilize 1, 3
• Draw blood samples 8-12 hours after the previous dose (immediately before the next dose) when concentrations are relatively stable 1

Maintenance Phase Dosing

• Target serum levels: 0.6-1.2 mEq/L for long-term control 1
• Standard maintenance dose: 300 mg three to four times daily (900-1200 mg/day total) 1
• More conservative target range of 0.6-0.8 mmol/L is now generally accepted, though some clinicians favor 0.8-1.2 mmol/L 2
• Monitor serum levels at least every two months during uncomplicated maintenance therapy 1

Age-Specific Dosing Adjustments

Elderly patients require substantially lower doses due to decreased renal clearance and increased sensitivity to lithium 1, 3:

• Age <40 years: 25-35 mmol daily (925-1300 mg lithium carbonate) 2
• Age 40-60 years: 20-25 mmol daily (740-925 mg) 2
• Age >60 years: 15-20 mmol daily (550-740 mg) 2
• Elderly patients: Start with 150 mg/day 3
• The dose required decreases threefold from middle age to old age (500 mg vs 1500 mg to achieve 1.0 mmol/L) 4

Renal Function Considerations

Renal impairment necessitates significant dose reductions 3:

• GFR <60 ml/min/1.73 m²: Use lower doses with more frequent monitoring 3
• GFR <30 ml/min/1.73 m²: Reduce dose by 50% 3
• Significant renal impairment is a contraindication to lithium use 3

Special Clinical Situations

Lithium augmentation of antidepressants requires lower target levels 3, 5:

• Target blood levels: 0.2-0.6 mEq/L 3
• Starting dose: 600-900 mg/day 5
• May increase to achieve therapeutic range of 0.8-1.2 mEq/L if needed 5
• Continue treatment for at least 3-6 weeks, as some patients respond quickly while others require longer combined treatment 5

Dosing Schedule Options

Multiple administration schedules are acceptable 2:

• Traditional: Two to three times daily (no strong evidence favoring three-times-daily, and midday compliance is questionable) 2
• Sustained-release preparations: Twice daily is well established 2
• Single evening dose: Recommended by some expert panels with modern sustained-release preparations 2
• Sustained-release formulations: Target upper therapeutic range (0.8-1.0 mmol/L) rather than 0.6-0.8 mmol/L due to later peak concentrations 2

Critical Safety Monitoring

Lithium toxicity is closely related to serum concentrations and can occur at doses near therapeutic levels 3, 6:

• Toxicity risk begins at 1.5 mEq/L 3
• Serious toxicity occurs at >2.0 mEq/L 3
• Patients abnormally sensitive to lithium may exhibit toxic signs at 1.0-1.5 mEq/L 1

Baseline and Ongoing Laboratory Tests

Required baseline assessments 3:

• Complete blood count 3
• Thyroid function tests (TSH, free T4) 3
• Renal function (BUN, creatinine, GFR) 3
• Serum electrolytes including calcium 3
• Urinalysis 3

Important Drug Interactions and Precautions

Avoid NSAIDs as they increase lithium levels and toxicity risk 3

Maintain adequate hydration, especially during intercurrent illness 3

Contraindications include 3:

• Significant renal impairment
• Cardiovascular disease
• Severe dehydration
• Sodium depletion