Why should the antacid be stopped in a patient who is taking levofloxacin?

• A. Antacids reduce absorption of fluoroquinolones.
• B. Antacids cause kidney damage.
• C. Antacids increase the risk of antibiotic resistance.
• D. Antacids enhance the effectiveness of the antibiotic.

Answer: (C)

The key idea is that certain drugs interact in the gut and affect how much medicine gets absorbed. Antacids contain polyvalent cations (like calcium, magnesium, and aluminum) that bind to levofloxacin in the intestine, forming insoluble complexes. This dramatically reduces the drug’s absorption, lowering its blood levels and potentially making the infection harder to treat.

Because of this, avoid taking an antacid at the same time as levofloxacin. If you need both, separate their doses by several hours (for example, take the antibiotic a couple of hours before or several hours after the antacid). This preserves the antibiotic’s effectiveness.

The other ideas aren’t the main issue here: antacids don’t directly cause kidney damage or increase resistance through a different mechanism, and they certainly don’t enhance the antibiotic’s effect.