Drug Interaction Report

ADJUST DOSING INTERVAL: Theoretically, lanthanum carbonate may chelate with certain drugs in the gastrointestinal tract, resulting in reduced oral bioavailability of those drugs during coadministration. However, an in vitro study involving digoxin, enalapril, furosemide, metoprolol, phenytoin, and warfarin found no evidence that lanthanum carbonate forms insoluble complexes with these drugs in simulated gastric fluid. Studies in healthy subjects have also found no effect of lanthanum carbonate (1000 mg for 4 doses) on the absorption of a single dose of digoxin (0.5 mg), metoprolol (100 mg), or warfarin (10 mg).

MANAGEMENT: To minimize the potential for interaction, drugs that are known to interact with antacids (e.g., ACE inhibitors, beta blockers, bisphosphonates, coumarin derivatives, digitalis glycosides, fluoroquinolones, iron, phenytoin, rifampin, tetracyclines, thyroid preparations) should not be taken within 2 hours of administration of lanthanum carbonate according to the product labeling.

GENERALLY AVOID: Moderate-to-high dietary intake of potassium can cause hyperkalemia in some patients who are using angiotensin converting enzyme (ACE) inhibitors. In some cases, affected patients were using a potassium-rich salt substitute. ACE inhibitors can promote hyperkalemia through inhibition of the renin-aldosterone-angiotensin (RAA) system.

MANAGEMENT: It is recommended that patients who are taking ACE inhibitors be advised to avoid moderately high or high potassium dietary intake. Particular attention should be paid to the potassium content of salt substitutes.

GENERALLY AVOID: Lanthanum carbonate should be administered with food for therapeutic efficacy. However, it is insoluble in water (<0.01 mg/mL at pH 7.5) and therefore cannot be dissolved in liquid for administration through an enteral feeding tube, because it may result in blockage of the tube.

MANAGEMENT: Administration of lanthanum carbonate with enteral feedings is not recommended. Alternative medications such as calcium carbonate suspension should be considered.