Can I increase my lithium (lithium carbonate) dosage from 300mg twice a day to three times a day for bipolar disorder?

Lithium Dosage Adjustment for Bipolar Disorder

Yes, you can increase lithium from 300mg twice daily to 300mg three times daily, but this should be done with careful monitoring of serum lithium levels to ensure they remain within the therapeutic range of 0.6-1.2 mEq/L. 1

Dosage Considerations

The FDA-approved lithium dosing guidelines support this change:

• Acute mania: Optimal response usually established with 600mg three times daily (t.i.d.)
• Long-term maintenance: Usually 300mg three times or four times daily (t.i.d. or q.i.d.) 1

Your current dosage of 300mg twice daily (600mg total) is below the typical maintenance dose, and increasing to 300mg three times daily (900mg total) aligns with standard maintenance dosing recommendations.

Monitoring Requirements

When increasing lithium dosage, the following monitoring is essential:

• Serum lithium levels: Must be checked within 5-7 days after dosage change

  • Target therapeutic range: 0.6-1.2 mEq/L for maintenance therapy 1
  • Blood samples should be drawn 8-12 hours after the previous dose 1

• Regular monitoring schedule:

  • Every 2 months during stable maintenance therapy
  • More frequently if symptoms change or side effects develop 2

Safety Considerations

Several factors should be evaluated before increasing the dose:

1. Current serum lithium level: If already approaching 1.2 mEq/L, increasing the dose may risk toxicity 1

2. Kidney function: Impaired renal function increases risk of lithium toxicity 3

3. Hydration status: Dehydration can increase lithium levels 3

4. Medication interactions: Some medications can increase lithium levels (NSAIDs, ACE inhibitors, diuretics) 2

5. Side effect profile: Current side effects may worsen with increased dosage 4

Potential Benefits of Three-Times-Daily Dosing

• More stable serum levels throughout the day
• Potentially fewer side effects compared to twice-daily dosing 5

A study comparing once-daily versus twice-daily dosing found that higher frequency dosing was associated with more urinary frequency side effects, suggesting that fewer daily doses may improve tolerability 5.

Potential Risks

• Increased risk of side effects including:

  • Tremor, diarrhea, polyuria, weight gain, metallic taste 4
  • Neurotoxicity at higher serum levels, especially in elderly patients 6

• Narrow therapeutic index requiring careful monitoring 3

Alternative Considerations

If the goal is better symptom control without increasing side effects:

1. Optimize current dosing: Ensure consistent timing of doses
2. Consider adjunctive treatments: Other mood stabilizers or psychotherapy 2

Follow-up Plan

After increasing to 300mg three times daily:

1. Check serum lithium level in 5-7 days
2. Assess for side effects and clinical response
3. Continue regular monitoring of thyroid function, renal function, and electrolytes every 3-6 months 2

Remember that lithium has a narrow therapeutic index, and careful attention to dosing, monitoring, and titration is required to balance efficacy and safety 3.