Lithium Dosing Schedule
For acute mania, lithium should be administered at 600 mg three times daily (t.i.d.) to achieve therapeutic serum levels of 1.0-1.5 mEq/L, while maintenance therapy typically requires 300 mg three or four times daily to maintain serum levels of 0.6-1.2 mEq/L. 1
Dosing Regimens
Acute Mania Treatment
- Initial dose: 600 mg t.i.d. (1800 mg/day) 1
- Target serum level: 1.0-1.5 mEq/L 1
- Monitoring: Serum levels should be checked twice weekly during acute phase until stabilization 1
Maintenance Therapy
- Typical dose: 300 mg t.i.d. or q.i.d. (900-1200 mg/day) 1
- Target serum level: 0.6-1.2 mEq/L 1
- Some clinicians now recommend lower maintenance levels of 0.6-0.8 mmol/L 2
- Monitoring: Serum lithium levels should be checked at least every two months during remission 1
Age-Based Dosing Considerations
Dosing should be adjusted based on age:
- Patients <40 years: 25-35 mmol/day (925-1300 mg/day) 2
- Patients 40-60 years: 20-25 mmol/day (740-925 mg/day) 2
- Patients >60 years: 15-20 mmol/day (550-740 mg/day) 2
Elderly patients often require reduced dosages and may exhibit toxicity at serum levels normally tolerated by younger patients 1.
Alternative Dosing Schedules
Once-Daily Dosing
Recent evidence supports once-daily dosing as an alternative to multiple daily doses:
- Similar efficacy to twice-daily dosing 3
- Lower incidence of urinary frequency and other side effects 3
- May improve patient compliance 4
- Should be administered in the evening 5
- May require sustained-release formulations with target serum levels of 0.8-1.0 mmol/L 2
Twice-Daily Dosing
- Well-established schedule with sustained-release preparations 2
- May require higher total daily doses compared to once-daily dosing 3
- Associated with higher renal adverse effects that may be dose-related 3
Monitoring Parameters
Blood samples for serum lithium determination should be drawn 8-12 hours after the previous dose (trough level) 1. For patients on once-daily dosing, the 24-hour level should serve as the control value 2.
Monitoring should include:
- Regular clinical assessment of mood symptoms
- Medication adherence evaluation
- Side effect monitoring
- Laboratory tests: thyroid function, renal function, CBC 6
Important Considerations
- Lithium has a narrow therapeutic index, requiring careful monitoring 1
- Dosage must be individualized according to serum levels and clinical response 1
- Total reliance should not be placed on serum levels alone; accurate patient evaluation requires both clinical and laboratory analysis 1
- Renal insufficiency is a relative contraindication and requires dose adjustment 2
- During pregnancy, lithium clearance increases by 30-50% in the last trimester, requiring dose adjustments 2
Pharmacokinetic Considerations
- Standard-release lithium reaches peak plasma concentration at 1-2 hours post-dose 2
- Sustained-release formulations reach peak at 4-5 hours post-dose 2
- Elimination half-life is 18-36 hours 2
- Bioavailability is 80-100% 2
By following these dosing guidelines and monitoring protocols, clinicians can optimize lithium therapy while minimizing the risk of toxicity and adverse effects.