First Aid USMLE Step 1: Pharmacology (Complete)

First Aid USMLE Step 1: Pharmacology (Complete) Penicillin G (IV and IM) Penicillin M (oral) Correct Answer: *MOA:* *β-lactam*: a structural analog of D-ala-D-ala (a normal component of cell walls) which binds and inactivates bacterial transpeptidases (penicillin-binding protein, PBPs) to block peptidoglycan cross linking *Clinical use:* Bactericidal for Gram-⊕ cocci/rods, Gram-⊖ cocci (Neisseria), and spirochetes Mostly used for Gram-⊕ organisms (S. pneumoniae, S. pyogenes, Actinomyces). Also used for Gram-⊖ cocci (mainly N. meningitidis) and spirochetes (namely T. pallidum). Bactericidal for Gram-⊕ cocci, Gram-⊕ rods, Gram-⊖ cocci, and spirochetes. Penicillinase sensitive. *Toxicity:* Hypersensitivity reactions (type II), hemolytic anemia *MOR:* Penicilinase (a type of β-lactamase) in bacteria cleaves Oxacillin Nafcillin Dicloxacillin Correct Answer: Penicillinase-resistant penicillins *MOA:*