Which penicillin is more sensitive to acid degradation?

Which penicillin is more sensitive to acid degradation?

• A. Penicillin V
• B. Amoxicillin
• C. Dicloxacillin
• D. Penicillin G

Answer: (D)

Acid stability of penicillins hinges on how well the beta-lactam ring resists hydrolysis in gastric acid. Penicillin G is more susceptible to acid degradation because its structure lacks the side-chain features that help protect the beta-lactam in acidic environments. That makes the ring break down more quickly in the stomach, so Penicillin G is typically not given orally and must be administered by injection. In contrast, Penicillin V has a phenoxymethyl side chain that stabilizes the molecule in acid, allowing it to survive stomach pH and be taken orally. Amoxicillin and dicloxacillin also have substitutions that improve acid stability relative to Penicillin G, so they’re generally less acid-labile than Penicillin G. Therefore, Penicillin G is the penicillin most sensitive to acid degradation.

Acid stability of penicillins hinges on how well the beta-lactam ring resists hydrolysis in gastric acid. Penicillin G is more susceptible to acid degradation because its structure lacks the side-chain features that help protect the beta-lactam in acidic environments. That makes the ring break down more quickly in the stomach, so Penicillin G is typically not given orally and must be administered by injection. In contrast, Penicillin V has a phenoxymethyl side chain that stabilizes the molecule in acid, allowing it to survive stomach pH and be taken orally. Amoxicillin and dicloxacillin also have substitutions that improve acid stability relative to Penicillin G, so they’re generally less acid-labile than Penicillin G. Therefore, Penicillin G is the penicillin most sensitive to acid degradation.