May increase plasma conc w/ CYP3A4 inhibitors [eg, azole antifungals (eg, itraconazole), macrolides (eg, erythromycin, clarithromycin), amiodarone HCl, grapefruit juice]. May increase blood conc of CYP2D6 substrates [eg, TCAs (eg, amitriptyline HCl, imipramine HCl), butyrophenone antipsychotics (eg, haloperidol), flecainide acetate, vinblastine sulfate]. May decrease serum Ca level w/ calcitonin, bisphosphonates, bone absorption inhibitors (eg, pamidronate Na hydrate, alendronate Na hydrate, incadronate disodium), corticosteroids (eg, cortisol, prednisolone, dexamethasone). May affect plasma conc w/ digitoxin, diazepam.