What is the step-by-step management approach for initiating and monitoring lithium (lithium carbonate) therapy in a patient with bipolar depression, including laboratory tests and dose adjustments?

Step-by-Step Management of Lithium for Bipolar Depression

Initial Visit: Laboratory Work BEFORE First Dose

You must obtain baseline laboratory tests before writing the first lithium prescription, not after. 1, 2, 3 This is a critical safety requirement that cannot be bypassed.

Required Baseline Labs (Before Any Lithium Dose):

• Complete blood count 1, 2
• Thyroid function tests (TSH, free T4) 1, 2
• Renal function: BUN, creatinine, urinalysis 1, 2
• Serum calcium 1, 2
• Pregnancy test in females of childbearing age 1, 2
• Baseline ECG if patient >40 years or has cardiac risk factors 3

First Visit Workflow:

1. Write laboratory slip for all baseline tests listed above 1, 2
2. Do NOT write lithium prescription yet 1, 2
3. Schedule follow-up visit in 3-7 days to review labs and initiate medication 1
4. Provide patient education about lithium during this visit (importance of hydration, avoiding NSAIDs, signs of toxicity) 2, 3

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Second Visit: Initiating Lithium (After Labs Return Normal)

Starting Dose:

• Write prescription for lithium carbonate 300 mg three times daily (900 mg/day total) for acute treatment of bipolar depression 3, 4
• For elderly patients or those with renal concerns, start with 300 mg twice daily (600 mg/day) 3, 4
• Target serum level for acute treatment: 0.8-1.2 mEq/L 3, 4

Monitoring Schedule During Acute Phase:

• Check lithium level twice weekly until therapeutic level achieved and patient stabilized 3
• Draw blood 8-12 hours after the previous dose (typically morning trough level before AM dose) 3
• Monitor for signs of toxicity at each visit: tremor, confusion, ataxia, nausea 2

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Dose Adjustments Based on Levels

When to Check Levels and Adjust:

• First lithium level: 5-7 days after starting (at steady state) 3, 4
• Yes, obtain new labs before each dose increase 3
• Continue checking twice weekly until level is 0.8-1.2 mEq/L and patient is clinically stable 3

Dose Adjustment Algorithm:

• If level <0.6 mEq/L: Increase by 300 mg/day 3, 4
• If level 0.6-0.8 mEq/L: Increase by 150-300 mg/day depending on clinical response 4
• If level 0.8-1.2 mEq/L: Maintain current dose (therapeutic range) 3, 4
• If level >1.2 mEq/L: Decrease dose by 150-300 mg/day and recheck in 3-5 days 3
• If level >1.5 mEq/L: Hold lithium and contact patient immediately for toxicity assessment 3

Note: Some patients respond at lower concentrations (0.4-0.7 mEq/L), but you cannot identify these patients in advance, so target 0.8-1.2 mEq/L initially 4

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Transition to Maintenance Therapy

Maintenance Dosing:

• Once acute symptoms stabilize, target maintenance level: 0.6-1.2 mEq/L 3
• Typical maintenance dose: 300 mg three to four times daily (900-1200 mg/day) 3
• Continue maintenance therapy for minimum 12-24 months after stabilization 1, 2

Maintenance Monitoring Schedule:

• Lithium levels: Every 2 months once stable 3
• Renal function (BUN, creatinine, urinalysis): Every 3-6 months 1, 2
• Thyroid function (TSH): Every 3-6 months 1, 2
• Serum calcium: Every 6-12 months 1

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Critical Clinical Considerations

Common Pitfalls to Avoid:

• Never start lithium without baseline labs - renal or thyroid dysfunction can lead to rapid toxicity 1, 2
• Never rely solely on serum levels - clinical assessment is equally important 3
• Never allow patient to take first dose before labs are reviewed - undetected renal impairment can cause immediate toxicity 2, 3
• Inadequate monitoring during acute phase leads to subtherapeutic dosing or toxicity 3
• Premature discontinuation (before 12-24 months) leads to >90% relapse rate 1

Patient Safety Instructions:

• Maintain adequate hydration (8-10 glasses water daily) 2, 3
• Avoid NSAIDs (ibuprofen, naproxen) - use acetaminophen for pain 2
• Report immediately: severe tremor, confusion, vomiting, diarrhea, slurred speech 2, 3
• Secure medication away from children and limit quantities if suicide risk present 1

When Lithium Alone Is Insufficient:

• If inadequate response after 6-8 weeks at therapeutic levels (0.8-1.2 mEq/L), consider adding olanzapine-fluoxetine combination or quetiapine 1
• Never use antidepressant monotherapy - always combine with mood stabilizer to prevent mood destabilization 1

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Special Populations

Elderly Patients:

• Start with 300 mg twice daily (600 mg/day) 3
• Target lower maintenance levels: 0.5-0.8 mEq/L 4
• More frequent monitoring due to increased sensitivity to toxicity 3

Patients Age 12-17:

• Lithium is FDA-approved for age 12 and older 1
• Use adult dosing guidelines but monitor more closely 1
• Family must secure medication to prevent overdose 1