Lithium Dosing and Monitoring Protocol
The typical starting dose of lithium carbonate is 600 mg three times daily for most adults, with lower doses of 150-300 mg daily recommended for elderly patients, and monitoring should include serum lithium levels twice weekly during the acute phase until stabilization. 1, 2
Initial Dosing
- For standard adult patients, lithium carbonate therapy typically begins with 600 mg three times daily (t.i.d.) to achieve therapeutic serum levels between 1.0-1.5 mEq/L in the acute phase 1
- For elderly patients, a lower starting dose of 150 mg/day is recommended due to increased sensitivity to lithium and reduced clearance 2
- Maintenance dosing usually requires 300 mg three or four times daily to maintain serum levels of 0.6-1.2 mEq/L 1
- Dosing must be individualized according to serum levels and clinical response 1
- Sustained-release formulations reach peak plasma concentration at 4-5 hours (versus 1-2 hours for standard-release) and may allow for once-daily dosing in some patients 3
Required Baseline Testing
- Complete blood count 2
- Thyroid function tests (TSH, free T4) 2
- Renal function (blood urea nitrogen, creatinine, GFR) 2
- Serum electrolytes including calcium 2
- Urinalysis 2
- Baseline ECG, especially in patients with cardiovascular risk factors 2
Monitoring Protocol
- During acute phase: Serum lithium levels should be measured twice per week until the serum level and clinical condition have stabilized 1
- For maintenance therapy: Serum lithium levels should be monitored at least every two months 1
- Blood samples for serum lithium determination should be drawn 8-12 hours after the previous dose (trough level) 1
- For once-daily dosing regimens, the 24-hour serum concentration should serve as the control value 3
Dosage Adjustments Based on Special Populations
- For patients with GFR < 60 ml/min/1.73 m², lower doses and more frequent monitoring are recommended 2
- For patients with GFR < 30 ml/min/1.73 m², dose should be reduced by 50% 2
- Weight affects lithium clearance - heavier patients may require higher doses, while lighter patients may need lower doses 4
- Age-based maintenance dosing recommendations 3:
- <40 years: 25-35 mmol (925-1300 mg) daily
- 40-60 years: 20-25 mmol (740-925 mg) daily
60 years: 15-20 mmol (550-740 mg) daily
Important Clinical Considerations
- Lithium has a narrow therapeutic index, making therapeutic drug monitoring essential 3
- Concomitant use of NSAIDs should be avoided as they can increase lithium levels and risk of toxicity 2
- Maintaining adequate hydration is crucial, especially during intercurrent illness 2
- Once-daily dosing may improve tolerability and reduce side effects like urinary frequency compared to twice-daily dosing 5
- Signs of lithium toxicity may appear at serum levels of 1.0-1.5 mEq/L in sensitive patients, particularly the elderly 1
- Renal insufficiency is a relative contraindication to lithium use, especially if a sodium-poor diet is required 3
- Lithium clearance increases by 30-50% during the last months of pregnancy due to increased glomerular filtration rate 3
Common Pitfalls to Avoid
- Relying solely on serum levels without clinical assessment can lead to inappropriate dosing 1
- Failure to adjust dosing in elderly patients can lead to toxicity at serum levels normally tolerated by younger patients 1
- Not accounting for drug interactions that decrease lithium clearance can lead to toxicity 2
- Inadequate monitoring during periods of illness, dehydration, or medication changes can result in dangerous lithium levels 2
- Poor patient compliance with multiple daily dosing schedules - consider once-daily dosing with sustained-release formulations when appropriate 5