What is the recommended dose of lithium (lithium carbonate) for treating unipolar depression?

Lithium Dosing for Unipolar Depression

For unipolar depression, lithium should be dosed at 150-300 mg per day to achieve blood levels of 0.2-0.6 mEq/L, which is generally adequate for therapeutic effect. 1

Therapeutic Dosing and Monitoring

Initial Dosing

• Start with 150 mg per day of lithium carbonate 1
• Titrate gradually based on clinical response and serum levels
• Lower starting doses (150 mg daily) are particularly appropriate for:
  • Elderly patients
  • Patients with renal impairment
  • Patients with lower body weight

Target Blood Levels

• For unipolar depression: 0.2-0.6 mEq/L 1
• This is lower than the traditional bipolar disorder range (0.6-1.2 mEq/L) 2
• Lower doses minimize side effects while maintaining efficacy for depression

Monitoring Parameters

• Serum lithium levels should be checked:
  • 5-7 days after initiation
  • 5-7 days after each dose change
  • Every 3-6 months during stable therapy
• Additional monitoring:
  • Baseline and periodic renal function
  • Thyroid function tests
  • Electrolytes, particularly sodium
  • Complete blood count

Clinical Applications

Indications for Lithium in Unipolar Depression

• Augmentation of antidepressant therapy in treatment-resistant depression 2
• Prophylaxis after 2 episodes of depression within 5 years, particularly for:
  • Depression with melancholic features 3
  • Depression with psychotic features 3
  • Patients with high suicide risk 3, 4
  • Patients with clearly episodic course 3
• Maintenance treatment following ECT 3

Efficacy Evidence

• Lithium has demonstrated effectiveness in preventing relapse in unipolar depression 3, 4
• Low-dose lithium (300-450 mg/day) has shown efficacy as augmentation therapy with response rates of 51% 5
• Lithium significantly reduces suicide risk in both unipolar and bipolar depression 3, 4

Important Considerations

Side Effects at Therapeutic Doses

• Common side effects at recommended doses are minimal but may include:
  • Mild tremor
  • Increased thirst
  • Increased urination
  • Nausea
  • Weight gain

Cautions

• Renal function must be monitored as lithium is excreted by the kidneys
• Sodium depletion (dehydration, low-salt diet) can increase lithium levels
• Drug interactions with NSAIDs, ACE inhibitors, and diuretics can increase lithium levels
• Elderly patients require lower doses and more careful monitoring

Duration of Treatment

• For prophylaxis: continue treatment for at least 2 years after symptom stabilization 2
• In cases of severe depression with high suicide risk, lifelong treatment may be considered 3

Comparison with Bipolar Dosing

• Unipolar depression typically requires lower lithium levels (0.2-0.6 mEq/L) compared to bipolar disorder (0.6-1.2 mEq/L) 1, 2
• This lower dosing range reduces side effect burden while maintaining efficacy for depression

While higher lithium levels (0.8-1.0 mmol/L) have shown greater efficacy in preventing relapse in bipolar disorder 6, the lower range of 0.2-0.6 mEq/L is generally adequate for unipolar depression, offering a better side effect profile while maintaining therapeutic benefit.