Which antibiotic must be taken on an empty stomach?

• A. Macrolides
• B. Tetracycline
• C. Fluoroquinolone
• D. Penicillin

Answer: (B)

Tetracycline has absorption that is highly sensitive to what’s in the stomach. It binds strongly with multivalent cations, especially calcium from dairy products and minerals in antacids or iron supplements. When these substances are present at dosing, they form insoluble complexes with the drug in the gut, so very little is absorbed into the bloodstream and its effectiveness drops.

To avoid this, tetracycline is taken on an empty stomach with a full glass of water, typically one hour before meals or two hours after meals, and you should avoid dairy, calcium- or iron-containing supplements, and antacids near the dose. This timing maximizes absorption and makes it the best fit among the options for a drug that must be taken on an empty stomach. Other antibiotics in the list have different food- or interaction-related guidelines and do not require an empty stomach in all cases.