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Antibiotics - Part I Pearls
Pharmacology (NSG 124)
Herzing University
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Antibiotics – Part I Pearls Principles of Antimicrobial Therapy Antimicrobial drugs are selectively toxic – they disrupt bacterial cells without hurting host cells o They do this because bacterial cells have specific differences from mammalian cells Antimicrobial drugs target these differences Drugs can be classified by range of organisms they attack o Lehne – Table 83, p 1016 o Narrow-spectrum – targets specific organisms Always preferred when the organism in known o Broad-spectrum – targets many organisms Used initially (empirically) when we do not know the organism Must test for organism before administering these drugs Must switch to narrow-spectrum when cultures resulted (may take a few days) Not doing this leads to antibiotic resistance and superinfections o Antibiotics create imbalance by disrupting normal flora Drugs can also be classified by how they attack organisms o Lehne – Table 83, p 1016 o Seven classification groups – most common are: Inhibition of cell wall synthesis or destruction of cell wall Penicillins, cephalosporins, vancomycin, etc. Interference with protein synthesis Tetracyclines, macrolides, aminoglycosides, etc. Bactericidal vs bacteriostatic o Bactericidal drugs kill bacteria o Bacteriostatic drugs slow bacterial growth – do not kill Antibiotic stewardship o In most cases, antibiotics should not be used prophylactically Much public education still needs to be done on this o Organism should be identified, and one antibiotic should be used when indicated o Educate patients on importance of taking antibiotics for entire duration of prescription o Monitor and educate patients on adverse effects and when to alert provider o When administering IV antibiotics – never mix or run at the same time Mixing can cause precipitate (use different tubing as well) If reaction, difficult to tell which drug caused the reaction when run at the same time Penicillins Beta-lactams (have a beta-lactam ring) MOA: bactericidal – weaken cell wall, allowing water to fill cell and rupture More effective against gram-positive bacteria o Gram-positive cells – 2 layers of cell wall o Gram-negative cells – 3 layers of cell wall Not effective against bacteria that secrete beta-lactamase o Enzyme that destroys beta-lactam ring Generally classified on range of organisms they attack o Narrow, broad, and extended spectrum
Generally safe and effective o Biggest adverse effect is hypersensitivity reaction (7%) Mild to severe (anaphylaxis) Always observe for at least 30 minutes after administration – treat with epinephrine if reaction 1% of patients may have cross-sensitivity with cephalosporins Avoid use of these drugs or do a skin test if recommended treatment Lehne – Table 84, p 1036 Narrow-spectrum penicillins o Penicillin G – IM or IV Usually given IM Can cause hyperkalemia and cardiac dysrhythmia if given at high and rapid doses o Penicillin V - PO Preferred for oral therapy - more stable in stomach acid – may take with food Broad-spectrum penicillins o Can better penetrate 3rd layer of gram-negative bacteria o Does not work well on bacteria that secrete beta-lactamase Often used in combination with other drugs that inhibit beta-lactamase o Ampicillin – IV or PO IV therapy preferred Major side effect - diarrhea o Amoxicillin - PO Preferred for oral therapy – more stable in stomach acid than ampicillin Less diarrhea than ampicillin Extended-spectrum penicillin o Piperacillin - IV Works on Pseudomonas – often responsible for pneumonia Combination drugs (penicillin + beta-lactamase inhibitor) o Ampicillin/sulbactam [Unasyn] - IV o Amoxicillin/clavulanate [Augmentin] - PO o Piperacillin/tazobactam [Zosyn] – IV Cephalosporins Related to penicillins – have beta-lactam ring o 1% of patients allergic to penicillin have cross-sensitivity to these drugs as well Very popular drugs MOA: bactericidal – weaken cell wall, allowing water to fill cell and rupture Susceptible to organisms that secrete beta-lactamase o Resistant to beta-lactamase depending on generation of drug 1 st generation – minimally resistant Ex: Cephalexin [Keflex] – PO Ex: Cefazolin [Ancef] – IV o Often used prior to surgical procedures 2 nd generation – moderately resistant 3 rd-5th generations – highly resistant Ex: Ceftriaxone [Rocephin] – IM, IV (3rd generation)
Antibiotics - Part I Pearls
Course: Pharmacology (NSG 124)
University: Herzing University
