Final answer:
Taking ciprofloxacin with antacids containing aluminum, magnesium, or calcium can decrease the effectiveness of the antibiotic.
Step-by-step explanation:
Taking ciprofloxacin with an antacid containing aluminum, magnesium, or calcium should be avoided because it can decrease the effectiveness of the antibiotic. The reason for this is that these antacids can bind to ciprofloxacin and form insoluble complexes in the stomach, which reduces the amount of the antibiotic that can be absorbed into the bloodstream. As a result, the antibiotic may not reach the target site of infection in sufficient concentrations to effectively kill the bacteria.