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Cephalosporins and Carbapenems
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- 1Give eg's of & indications for cephalosporins and carbapenems.egs: cefalexin, cefotaxime, meropenem, ertapenem
Indications:
• UTI's, RTI's - 2nd & 3rd line Rx (oral cephalosporins)
• Very severe, complicated or ABx resistant infxn - IV cephalosporins & carbapenems - 2MOA of cephalosporins & carbapenems.Cephalosporins & carbapenems are derived from naturally occurring antimicrobials produced by fungi & bacteria. Like penicillins, their antimicrobial effect is due to their β-lactam ring. During bacterial cell growth, cephalosporins & carbapenems inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls. This weakens cell walls, preventing them from maintaining an osmotic gradient, resulting in bacterial cell swelling, lysis & death. Both types of ABx have a broad spectrum of action. For cephalosporins, progressive structural modification has led to successive ‘generations’ (first to fifth), with ^activity against Gram -ve bacteria & less oral activity. Cephalosporins & carbapenems are naturally more resistant to β-lactamases than penicillins due to fusion of the β-lactam ring with a dihydrothiazine ring (cephalosporins) or a unique hydroxyethyl side chain (carbapenems).
- 3SE's of cephalosporins & carbapenems.• GI upset
• ABx associated colitis - ABx's kill normal gut flora & allow overgrowth of C. difficile
• Hypersensitivity reactions
• CNS toxicity inc seizures - in high doses or in renal impairment - 4CI's, cautions, & important interactions of cephalosporins & carbapenems.CI's:
• Hx of allergy - inc to penicillin (due to similar structure) especially if there was an anaphylactic reaction
Cautions:
• People at risk of C. difficile infxn - elderly & hospitalised
• Epilepsy (reduce dose)
Important interactions:
As broad-spectrum ABx's, cephalosporins & carbapenems can enhance the anticoagulant effect of warfarin by killing normal gut flora that synthesise vitamin K. Cephalosporins may ^nephrotoxicity of aminoglycosides. Carbapenems reduce plasma concentration & efficacy of valproate.