Can I take calcium acetate and lanthanum carbonate (Lanthanum) together and what labs are required prior to starting this combination?

Combining Calcium Acetate with Lanthanum Carbonate

You should avoid combining calcium acetate with lanthanum carbonate, as guidelines recommend restricting calcium-based binder doses when using non-calcium binders like lanthanum to prevent positive calcium balance and vascular calcification risk. 1

Why This Combination Is Problematic

The American College of Physicians explicitly recommends restricting calcium-based binder doses when using sevelamer or lanthanum to avoid positive calcium balance, and excess calcium exposure increases vascular calcification risk across all CKD stages. 1 This guidance applies directly to your question about combining calcium acetate with lanthanum.

The evidence strongly favors using lanthanum as monotherapy rather than combining it with calcium-based binders:

• Lanthanum carbonate prevents progression of coronary and aortic calcification, while continuing calcium acetate poses significant cardiovascular risk including progression of coronary and aortic calcification. 1
• Studies show that 49.2% of patients on calcium acetate had elemental calcium intake of at least 1.5 g/day, and 25.8% had intake of at least 2.0 g/day, which may lead to complications related to calcium balance. 2
• The American Heart Association recommends that total elemental calcium intake from diet and phosphate binders should not exceed 2,000 mg/day due to risks of hypercalcemia and cardiovascular calcification. 3

Clinical Decision Algorithm

If you're considering adding lanthanum to existing calcium acetate therapy, the appropriate approach is:

1. Transition completely from calcium acetate to lanthanum monotherapy rather than combining them, as lanthanum carbonate (750-3,000 mg/day) provides similar phosphate control to calcium acetate but with significantly reduced incidence of hypercalcemia (0.4% vs 20.2% with calcium carbonate). 4

2. Consider lanthanum when pill burden is a major adherence concern, as it requires an average of 4 tablets daily compared to higher pill burdens with calcium-based binders. 1

3. Use lanthanum specifically in patients with hypercalcemia or elevated calcium-phosphorus product, as it avoids calcium load entirely. 1

Required Labs Prior to Starting

Before initiating lanthanum carbonate, you need baseline measurements of:

• Serum phosphorus - to establish starting dose and target levels of 3.5-5.5 mg/dL 1
• Serum calcium - to monitor for hypocalcemia risk, especially with concurrent calcimimetics 1
• Intact PTH levels - as baseline for monitoring every 3 months 1
• Calcium-phosphorus product - to assess cardiovascular calcification risk 4

Monitoring Schedule After Initiation

• Serum phosphorus every 2-4 weeks during titration, then monthly once stable 1
• Serum calcium monitoring for hypocalcemia, especially with concurrent calcimimetics 1
• Intact PTH levels every 3 months 1
• Dose titration every 2-3 weeks based on serum phosphorus response, starting at 500-1000 mg three times daily with meals, with typical maintenance doses ranging from 1500-3000 mg daily 1

Critical Administration Details

Lanthanum must be taken with or immediately after meals to maximize phosphate binding, and tablets should be chewed completely before swallowing for optimal absorption. 1 This is essential for efficacy and differs from calcium supplement timing.

Common Pitfalls to Avoid

• Do not add lanthanum to existing calcium acetate - transition completely to avoid excessive calcium burden 1
• Do not exceed 2,000 mg/day total elemental calcium from all sources if any calcium-based binder is used 3
• Recognize that achieving normal phosphorus may not be possible or may unacceptably decrease quality of life due to pill burden 1
• Monitor for gastrointestinal adverse events, which are the most common side effects with lanthanum carbonate 5, 6