Maximum Daily Dose of Lithium
The maximum daily dose of lithium is typically 1800 mg (60 mEq) for standard formulations, with serum levels not to exceed 1.2 mmol/L due to increased risk of toxicity at higher levels. 1
Dosing Guidelines and Therapeutic Range
Lithium dosing must be carefully managed due to its narrow therapeutic index:
- Standard therapeutic range: 0.6-0.8 mmol/L for maintenance therapy 1
- Higher range: 0.8-1.2 mmol/L may be used in some cases 2
- Toxic levels:
Typical Dosing by Age
Maintenance dosing varies by age due to differences in lithium clearance:
- <40 years: 25-35 mmol/day (925-1300 mg lithium carbonate) 2
- 40-60 years: 20-25 mmol/day (740-925 mg) 2
- >60 years: 15-20 mmol/day (550-740 mg) 2
Administration Schedule Options
Lithium can be administered in different schedules:
- Traditional schedule: Two or three times daily dosing 2
- Modern approach: Once-daily dosing (preferably in the evening) using sustained-release formulations 4, 5
Once-daily dosing has shown similar efficacy with potentially fewer side effects, particularly reduced urinary frequency, which may improve patient compliance 4.
Monitoring Requirements
Due to lithium's narrow therapeutic window, regular monitoring is essential:
- Initial phase: Serum levels twice weekly until stabilized 1
- Maintenance phase: Every 2-3 months 1
- Blood samples: Draw 12 hours after the last dose for accurate measurement 1
- Additional monitoring: Renal function, thyroid function, and urinalysis every 3-6 months 1
Important Considerations
- Formulation differences: Sustained-release preparations may require maintaining serum levels in the upper range (0.8-1.0 mmol/L) 2
- Special populations: Lower doses are required for elderly patients and those with renal impairment 1
- Contraindications: Renal insufficiency is a contraindication, especially with sodium-poor diets 2
- Pregnancy: Lithium clearance increases by 30-50% during the last months of pregnancy 2
Cautions
- Always check serum lithium levels before increasing dose
- Never exceed 1.2 mmol/L serum concentration without extremely careful monitoring
- Be aware that lithium toxicity can occur at lower serum levels in elderly patients or those with comorbidities
- Drug interactions can decrease lithium clearance, potentially increasing toxicity risk 2