The simultaneous administration of ciprofloxacin (oral) and multivalent cation-containing drugs and mineral supplements (e. g. calcium, magnesium, aluminium, iron), polymeric phosphate binders (e. g. sevelamer), sucralfate or antacids, and highly buffered drugs (e. g. didanosine tablets) containing magnesium, aluminium, or calcium reduces the absorption of ciprofloxacin.