Type
Bacteriocidal
Mechanism of Action
inhibit bacterial growth by interfering with the transpeptidation reaction of bacterial cell wall synthesis. As structural analogs of the natural D-Ala-D-Ala substrate, β-lactams covalently bind to the active site of PBPs. This inhibits the transpeptidation reaction halting peptidoglycan synthesis, and the cell die.
Mechanism of Resistance
(1) inactivation of antibiotic by β-lactamase [mc ]
(2) modification of target PBPs
(3) impaired penetration of drug to target PBPs
(4) efflux
Contraindications
History of severe allergic reactions; anaphylaxis
Unique Side Effect
Jarish Herxheimer Reaction: Febrile reaction after first injection of penicillin in spirochetal infection
| Penicillins | Targets | Nota Bene |
|---|---|---|
| Natural PCN (Pen G, Pen V) | Gram-positive organisms, gram-negative cocci, and non–-lactamase producing anaerobes | |
| PCNase resistant PCN (Oxacillin, Nafcillin) | Staphylococci and streptococci | Nafcillin = Excreted by liver |
| Extended-Spectrum Penicillins (Ampicillin, Amoxicillin) | Retain antibacterial spectrum of penicillin PLUS improved activity against gram-negative organisms and enterococcus | Ineffective against PCN resistant staph |
| Antipseudomonal Penicillins (Ticarcillin) | See above cell | Hypernatremia, hypokalemia, platelet dysfx |
| Antipseudomonal Penicillins (Mezlocillin, Pipercillin) | See above cell | 1. More biliary secretion 2. Susceptible to innoculum effect and slow kill rate |