From the FDA Drug Label
DOSAGE AND ADMINISTRATION ... N.B.: Blood samples for serum lithium determination should be drawn immediately prior to the next dose when lithium concentrations are relatively stable (i.e., 8-12 hours after the previous dose).
Lithium (lithium carbonate) trough levels should be measured immediately prior to the next dose, when lithium concentrations are relatively stable, which is typically 8-12 hours after the previous dose 1.
- Trough levels are measured to ensure the patient's serum lithium level is within the therapeutic range.
- Frequency of measurement:
- During the acute phase: twice per week
- For long-term control: at least every two months
- Therapeutic range:
- For acute mania: 1 to 1.5 mEq/L
- For long-term control: 0.6 to 1.2 mEq/L
From the Research
Measurement of Lithium Trough Levels
- Lithium trough levels should be measured to ensure optimal use and administration of the drug, as its efficacy is dose-dependent and reliably correlates with serum concentrations 2.
- The timing of trough level measurement is crucial, and it is generally recommended to measure trough levels 12 hours after the last dose for standard-release formulations 2.
- However, for sustained-release formulations or once-daily administration, the optimal timing for trough level measurement may be 24 hours after the last dose, as this can provide a more accurate representation of the patient's lithium levels 3.
Factors Affecting Lithium Trough Levels
- The absorption and excretion of lithium can be affected by various factors, including the type of formulation used, renal function, and patient demographics 2, 4.
- The use of sustained-release formulations can reduce peak plasma concentrations and affect the timing of trough level measurement 2, 5.
- Patient factors, such as age, weight, and renal function, can also impact lithium trough levels and should be considered when interpreting results 2, 6.
Clinical Application
- Therapeutic drug monitoring of lithium is essential to ensure optimal treatment and minimize the risk of toxicity 2, 4.
- The use of prediction models, such as the one proposed by 6, can help estimate serum lithium concentrations and guide clinical decision-making.
- Clinicians should consider the specific formulation and dosing regimen used, as well as patient factors, when interpreting lithium trough levels and adjusting treatment accordingly 2, 3, 5.