May impair absorption w/ food; by the formation of insoluble complexes w/ compd containing Ca & Mg, including antacids & mineral supplements, & bicarbonates, carbonates, oxalates or phosphates. Diminished absorption w/ tetracyclines. May decrease absorption w/ Zn salts. Chelation w/ acetohydroxamic acid. Formation of toxic complexes w/ dimercaprol. May delay response w/ systemic chloramphenicol. May increase absorption w/ ascorbic acid & citric acid. Decreased absorption of cefdinir, bisphosphonates, entacapone, fluoroquinolones, levodopa, methyldopa, mycophenolate mofetil, & penicillamine. Trientine.