Impaired absorption of L-thyroxine-containing medicine. Allow 2-hr interval in concomitant use w/ H
2-antihistamines, tetracyclines, digoxin, fluoroquinolones, Fe salts, ketoconazole, neuroleptics, penicillamine, β-blockers, glucocorticoid, chloroquine, bisphosphonates, estramustine.