Which statement best explains why antacids should be avoided during fluoroquinolone therapy?

• A. They reduce absorption of the antibiotic
• B. They cause kidney failure
• C. They increase the risk of infection
• D. They have no interaction with antibiotics

Answer: (D)

Antacids interact with fluoroquinolones because their polyvalent cations (such as aluminum, magnesium, calcium, and sometimes iron) bind the antibiotic in the gut to form insoluble complexes. This chelation greatly reduces the drug’s absorption, lowering bioavailability and potentially leading to ineffective therapy or resistance. That’s why you should separate antacid use from fluoroquinolone dosing by several hours or avoid concurrent administration. Saying there’s no interaction isn’t accurate, since the presence of antacids clearly affects how well the antibiotic is absorbed.