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Indicated only in minor infections because of its relatively poor bioavailability, the need for dosing four times a day, and its narrow antibacterial spectrum
Amoxicillin is often preferred•Narrow-Spectrum Penicillin [Penicillinase-resistant (anti-staphylococcal PCN)]o1940s: Penicillin introducedoAll strains of S. aureuswere sensitiveo1960: 80% of S. aureusisolates in hospitals displayed penicillin resistanceoPenicillin derivative (methicillin) developed; resistant to actions of beta-lactamasesoMethicillin-resistant Staphylococcus aureus(MRSA) has a unique mechanism of resistance ‒ it produces PBPs (penicillin binding protein) with a low affinity for penicillin and all other beta-lactam antibioticsoMRSA developed this ability by acquiring genes that code for low-affinity PBPs from other bacteriaoAnti-staphylococcal penicillin: chain altered to create resistance to inactivation by enzymeNafcillin, Oxacillin, DicloxacillinVery narrow spectrum•Broad-Spectrum Penicillin(aminopenicillins) Ampicillin (po or IV), Amoxicillinand Amoxicillin-clavulunate ie: Augmentin (both are po)- From cartoonoBactericidal to susceptible organismsoUsed for: skin infection, respiratory infections, GU & GI infections, peptic ulcer, H. pylori, Otis mediaoAdverse effects: rash, diarrhea; anaphylaxis, n/v, oral/diaper/vaginal candidiasis•Extended-Spectrum Penicillin[Antipseudomonal penicillins] ticarcillin-clavulunate (Timentin), piperacillin tazobactam (Zosyn) (both IV)oBroad-spectrum, but penicillinase sensitiveoEffective against organisms susceptible to the aminopenicillins plus Pseudomonas aeruginosa, Enterobacterspecies, Proteus(indole positive), Bacteroides fragilis,and many Klebsiella species•Beta-lactamase inhibitors(combined with PCN)oExtends antimicrobial spectrum when combined with penicillinase-sensitive antibioticsoResemble beta-lactam antibiotic structureoBind to beta-lactamase and protect the antibiotic from destructionoMost successful when they bind the beta-lactamaze irreversiblyoThree important in medicineClavulanic acidSulbactamTazobactamoBeta-lactam/beta-lactamase inhibitorsAmpicillin/sulbactamAmoxicillin/clavulanateTicarcillin/clavulanatePiperacillin/tazobactamPenicillin Allergy•PCN is most common cause of drug allergy: up to 7% experience reaction•TypesoImmediate (reaction in 2 to 30 minutes)oAccelerated (reaction in 1 to 72 hours)oLate (takes days or weeks to develop)•Assess for penicillin allergy in each patient – who will be receiving penicillin•Consider skin tests for penicillin allergy, consider desensitization •Anaphylaxis-EMERGENCY!!!
oLaryngeal edemaoBronchoconstrictionoSevere hypotension•Management of patients with a history of penicillin allergy:oMild = rash/hives (raised, extremely itchy spots that come and go over a period of hours), OR tissue swelling under the skin, typically around the face (also known as angioedema)oIf history of mild reaction: consider cephalosporinoIf history of anaphylaxis