Classes of Penicillins

Natural penicillins include Pen G (injectable, not used for dentistry) and Pen V. The generic “Pen VK” is Pen V plus Potassium (“K”).

Anti-pseudomonas penicillins (Aziocillin, carbenicillin, ticarcillin, piperacillin) are specific for pseudomonas and used mostly in the hospital setting.

Penicillinase-Resistant Penicillins include Methicillin, nafcillin, cloxacillin, dicloxacillin, flucloxacillin, and oxacillin. For these agents, you don’t need to include a beta lactamase inhibitor.

Aminopenicillins include ampicillin, bacampicillin, cyclacillin, and amoxicillin (a synthetic amino penicillin, vulnerable to penicillinase; usually prescribed with a penicillinase inhibitor as “Augmentin” [amoxicillin + penicillinase inhibitor]).

Penicillin VK has a relatively short half-life (1h!) so its given qid to maintain the blood levels, as seen in the following sample prescription.

Rx: Pen VK 500 mg

Disp: 28 tablets

Sig: take 1 tab 4 times a day

If a pt says they have an AB allergy, find out the history, the nature of reaction, the agent (Fluoroquinolones are less likely, penicillins are more likely) and distinguish a true allergy from side effects.

Category: Pharmacology Notes