A 28-year-old woman is diagnosed with early latent syphilis. She is treated with a single intramuscular injection of benzathine penicillin G. What is the primary pharmacokinetic advantage of this formulation over aqueous penicillin G?
- A Higher peak serum concentration
- B Longer duration of action ✓
- C Better oral bioavailability
- D Enhanced penetration into the cerebrospinal fluid
Correct answer: B. Longer duration of action
Explanation
Benzathine penicillin G is an intramuscular depot formulation that provides a prolonged duration of action, maintaining treponemicidal levels for 2 to 4 weeks. Aqueous penicillin G has a short half-life and requires frequent dosing. Procaine penicillin G has an intermediate duration. Neither benzathine nor procaine penicillin achieves reliable CSF penetration compared to aqueous penicillin. This allows for single-dose therapy in syphilis, ensuring patient compliance and cure.
Reference: Katzung and Trevor's Pharmacology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.