Drug Interaction Report

MONITOR: Coadministration of bisphosphonates and loop diuretics may potentiate the risk of hypocalcemia. Bisphosphonates alone often cause mild, asymptomatic hypocalcemia via inhibitive effects on bone resorption and possibly chelation of blood calcium. These effects may be additive with those of loop diuretics, which tend to increase the urinary excretion of calcium.

MANAGEMENT: Caution is advised if bisphosphonates are coadministered with loop diuretics. Renal function as well as serum calcium levels should be monitored during and after treatment, since the effects of bisphosphonates can continue for many weeks after discontinuation. Patients and clinicians should be alert to signs and symptoms of clinical hypocalcemia such as muscle spasm, carpopedal spasm, laryngeal spasm, tetany, convulsions, mental changes (irritability, depression, psychosis), increased intracranial pressure, papilledema, QT interval prolongation, and cardiac arrhythmias.

ADJUST DOSING INTERVAL: Food significantly decreases the bioavailability of oral ibandronate. The manufacturer reports up to a 75% decrease in bioavailability when administered 2 hours after a standard meal.

MANAGEMENT: Oral ibandronate should be administered on an empty stomach (after an overnight fast of at least 6 hours) with a 180 to 240 mL glass of plain water and no other food or drink should be taken for at least 30 minutes after administration.