What are the next steps for a patient on lithium (lithium carbonate) 900mg with a therapeutic lithium level of 0.7, according to the Canadian Network for Mood and Anxiety Treatments (CANMAT) guidelines?

Next Steps for Lithium Management Based on CANMAT Guidelines

With a lithium level of 0.7 mEq/L on 900mg daily, the dose should be increased to achieve the target therapeutic range of 0.8-1.2 mEq/L for acute treatment or 0.6-1.0 mEq/L for maintenance therapy, depending on the treatment phase. 1, 2

Immediate Assessment Required

Before adjusting the dose, determine the current treatment phase:

• If treating acute mania: Target serum lithium levels should be 0.8-1.2 mEq/L (some sources recommend 1.0-1.5 mEq/L for acute episodes) 1, 2, 3
• If in maintenance phase: Target levels of 0.6-1.0 mEq/L are appropriate, though some patients may require 0.8-1.2 mEq/L for optimal prophylaxis 2, 3, 4

The current level of 0.7 mEq/L is subtherapeutic for acute treatment and at the lower end for maintenance therapy 1, 2.

Recommended Dose Adjustment Algorithm

For acute mania treatment:

• Increase lithium carbonate from 900mg to 1200mg daily (typically 600mg twice daily or 400mg three times daily) 2
• Check lithium level after 5-7 days at the new stable dose 1, 2
• Continue monitoring twice weekly until both serum level and clinical condition stabilize 2
• Target range: 0.8-1.2 mEq/L 1, 2

For maintenance therapy:

• A more modest increase to 1050-1200mg daily may be sufficient 2, 3
• The current level of 0.7 mEq/L may be acceptable if the patient is clinically stable, though 0.8-1.0 mEq/L provides better prophylaxis 3, 4
• Monitor levels every 2 months during uncomplicated maintenance therapy 2

Critical Monitoring Requirements

Timing of blood draws is essential:

• Draw lithium levels 12 hours after the last dose (trough level) for accurate interpretation 2, 3
• For once-daily dosing, the 24-hour level serves as the control value 3
• Levels drawn at incorrect times will be misleadingly high or low 2, 3

Monitoring schedule:

• Check lithium levels twice weekly during acute phase and dose adjustments 2
• Once stable, monitor every 2 months during maintenance 2
• Monitor renal function (BUN, creatinine), thyroid function (TSH), and urinalysis every 3-6 months 1, 5

Important Clinical Considerations

Factors affecting lithium levels:

• Elderly patients often respond to reduced dosages and may exhibit toxicity at levels ordinarily tolerated by younger patients 2
• Renal function significantly impacts lithium clearance; reduced kidney function requires dose adjustment and more frequent monitoring 5, 3
• Concomitant medications (NSAIDs, ACE inhibitors, ARBs, thiazide diuretics) can increase lithium levels and require closer monitoring 5

Clinical response takes precedence:

• Some patients respond at lower concentrations (0.6-0.8 mEq/L), while others require higher levels 1, 2, 3
• Total reliance must not be placed on serum levels alone—accurate evaluation requires both clinical assessment and laboratory analysis 2
• If the patient is clinically stable at 0.7 mEq/L during maintenance, this may be acceptable, though most guidelines recommend 0.8-1.0 mEq/L for optimal prophylaxis 3, 4

Common Pitfalls to Avoid

• Inadequate dosing: A level of 0.7 mEq/L is clearly subtherapeutic for acute mania and may be insufficient for maintenance prophylaxis 1, 2
• Incorrect blood draw timing: Levels must be drawn 12 hours post-dose (trough) for accurate interpretation 2, 3
• Insufficient monitoring frequency: During dose adjustments, levels should be checked twice weekly, not monthly 2
• Ignoring clinical context: The target range differs between acute treatment (0.8-1.2 mEq/L) and maintenance (0.6-1.0 mEq/L) 2, 3
• Premature discontinuation: Withdrawal of lithium dramatically increases relapse risk, with over 90% of noncompliant patients relapsing versus 37.5% of compliant patients 1