Decreased absorption w/ Zn salts, tetracyclines, acetohydroxamic acid, trientine & Ca- & Mg-containing compd (including antacids & mineral supplements), bicarbonates, carbonates, oxalates or phosphates. Formation of toxic complexes w/ dimercaprol. Delayed response w/ systemic chloramphenicol. Absorption increased w/ ascorbic acid & citric acid.