The absorption of minocycline decreases when taken with which combination?

• A. I only
• B. I, II, III, IV
• C. I, II, IV, V
• D. I, II, III, IV, V

Answer: (C)

Minocycline absorption drops when it’s taken with substances that bring in divalent or trivalent cations, such as calcium, magnesium, aluminum, iron, or zinc. Those ions bind the drug in the gut to form insoluble chelates, which aren’t absorbed well. So, a combination that includes these interacting agents will reduce absorption. The correct option is the one that lists all the interacting items that cause this chelation effect (and excludes the item that does not affect absorption). In practice, spacing minocycline from calcium- or iron-containing products (dairy, antacids, supplements) by a few hours prevents this interaction.