What is the recommended dose of lithium (lithium carbonate)?

Recommended Dosage for Lithium Carbonate

The recommended dosage for lithium carbonate is typically 300 mg three to four times daily to maintain serum lithium levels of 0.6-0.8 mmol/L for standard formulations, with dosage adjustments based on serum levels and clinical response. 1, 2

Initial Dosing and Titration

• Starting dose:

  • 12-24 mmol (450-900 mg) per day, depending on age and weight 3
  • Typically divided into multiple doses initially

• Age-based maintenance dosing:

  • Age <40 years: 25-35 mmol (925-1300 mg) daily
  • Age 40-60 years: 20-25 mmol (740-925 mg) daily
  • Age >60 years: 15-20 mmol (550-740 mg) daily 3

Target Serum Levels

• Acute mania: 1.0-1.5 mmol/L 2
• Maintenance therapy: 0.6-1.2 mmol/L 2
  • Standard formulations: 0.6-0.8 mmol/L 1
  • Sustained-release formulations: 0.8-1.0 mmol/L (due to later peak concentration) 3

Monitoring Requirements

• Acute phase: Serum lithium levels twice weekly until stabilized 2
• Maintenance phase: Every 2-3 months 1, 2
• Blood sampling timing: 12 hours after the last dose (trough level) when concentrations are relatively stable 1, 2

Dosing Schedule Options

• Traditional: Two or three times daily dosing
• Alternative: Once-daily dosing may be viable with similar efficacy and potentially fewer side effects, particularly renal adverse effects 4
• Sustained-release formulations: May allow twice-daily or once-daily dosing 3

Special Populations

• Elderly patients:

  • Require lower doses due to reduced clearance 3
  • More sensitive to lithium toxicity, even at therapeutic levels 2
  • May need target levels of 0.5-0.8 mmol/L 5

• Patients with renal impairment:

  • Require dose reduction
  • May be contraindicated in severe cases 3

• Pregnant women:

  • Lithium clearance increases by 30-50% in late pregnancy 3
  • Requires careful monitoring and dose adjustments

Efficacy vs. Side Effect Considerations

• Higher serum levels (0.8-1.0 mmol/L) are more effective for prophylaxis but have more side effects 6
• Lower serum levels (0.4-0.6 mmol/L) have fewer side effects but 2.6 times higher risk of relapse 6
• Serum levels >1.5 mmol/L may cause mild, reversible toxic effects
• Serum levels >2.0 mmol/L may cause neurological symptoms 7

Important Monitoring Parameters

• Renal function tests
• Thyroid function tests
• Electrolytes (particularly calcium)
• Urinalysis
• Pregnancy test for females of reproductive age 1

Lithium has a narrow therapeutic index, making therapeutic monitoring essential for both efficacy and safety. The balance between achieving therapeutic effect and minimizing side effects requires careful titration and regular monitoring of serum levels.