Serum Lithium Monitoring After Initiation
Serum lithium levels should be measured twice per week during the acute phase of treatment, starting from initiation, until the serum level and clinical condition of the patient have stabilized. 1
Initial Monitoring Schedule
- Blood samples for serum lithium determination should be drawn immediately prior to the next dose when lithium concentrations are relatively stable (8-12 hours after the previous dose) 1
- For patients receiving once-daily administration, the serum concentration should be measured at 24 hours after the dose 2
- The first lithium level check should occur within the first week of starting therapy to ensure appropriate dosing 1, 3
- Regular monitoring is essential during the initial phase as lithium has a narrow therapeutic window with potential for toxicity 1, 4
Target Therapeutic Ranges
- The therapeutic range for acute mania is typically 1.0-1.5 mEq/L 1
- For long-term maintenance therapy, the target range is 0.6-1.2 mEq/L 1
- Elderly patients may require lower serum levels due to increased sensitivity to lithium 1
- Some experts now recommend maintaining concentrations between 0.6-0.8 mmol/L for maintenance, though some still favor 0.8-1.2 mmol/L 3
Factors Affecting Lithium Levels
- Renal function significantly impacts lithium clearance 3
- Medications that affect renal function can alter lithium levels 5
- Intercurrent illness may require more frequent monitoring due to potential changes in lithium clearance 6
- Lithium should be temporarily discontinued during serious intercurrent illness that increases risk of acute kidney injury 7
Signs of Toxicity Requiring Immediate Testing
- Early signs of lithium toxicity include tremor, nausea, diarrhea, and polyuria-polydipsia 6, 5
- If toxicity is suspected, immediate serum lithium testing is warranted regardless of the regular monitoring schedule 5
- Lithium toxicity can occur at serum levels of 1.5 mEq/L or higher, though some patients may exhibit toxicity at lower levels 1, 8
Baseline and Ongoing Monitoring
- Before starting lithium, baseline tests should include complete blood count, thyroid function tests, renal function tests, serum calcium, urinalysis, and pregnancy test in females of reproductive age 6
- After stabilization, ongoing monitoring should include renal function tests, thyroid function tests, and urinalysis every 3-6 months, and serum calcium at least annually 6
Remember that while serum level monitoring is crucial, clinical evaluation remains equally important for proper lithium management. Total reliance must not be placed on serum levels alone, as accurate patient evaluation requires both clinical and laboratory analysis 1.