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Cell wall inhibitors
| Term | Definition |
|---|---|
| bacterial cell wall inhibitors 1-Narrow spectrum | Penicillin G&V , Anti-staphylococcal Penicillins (Oxacillin, Nafcillin), 1st generation Cephalosporins & Aztreonam |
| 2-Moderately broad | Amin-openicillin(Ampicillin), Anti-pseudomonal Penicillins (Pipracillin , Ticarcillin) , 2nd generation Cephalosporins |
| 3-Broad spectrum: | Amin-openicillin + ß-lactamase inhibitors (Ampicillin + sulbactam), 3rd & 4th generation Cephalosporins |
| 4-Very broad spectrum: | Anti-pseudomonal +ß-lactamase inhibitors (Pipracillin+ tazobactam > Ticarcillin+ clavulanate), Carbapenems (Imipenem+ Cilastatin & Meropenem) |
| Penicillins | contain ß-lactam ring are derivatives of 6-aminopenicillanic acid |
| Modifications of R-group side-chain attached to ß-lactam ring.. | → differences in the pharmacokinetic properties &antimicrobial spectrum of activity → Resistance to hydrolysis by enzymatic ß-lactamase →Susceptibility or stability against gastric acid |
| Pharmacokinetics of Penicillins: | → Oral administration depending on their gastric acid stability (acid-resistance) Acid-resistant Penicillins →given orally→ PenicillinV Acid-sensitive Penicillins →given IV → PenicillinG 30 minutes before or 2-3 hours after meal |
| Distribution of penicillin | well distributed in body fluids , lipid-insoluble → don’t enter tissue cells & poor/no penetration into CSF, unless inflammation is present (meningitis) |
| Elimination | excreted unchanged in urine→ mainly by active tubular excretion (> 90% ) except anti-staphylococcal class (Nafcillin) → metabolized in the liver → can be given in renal failure (RF) |
| How does Probencid ↑ T1/2 of penicillinG!!! | It blocks the active renal secretion of penicillin ...↓ the frequency of penicillin administration & prolong it’s action |
| Mechanism of action of Penicillins: | ..Binding of the drug → “PBPs” located on the bacterial inner membrane ..inactivation of the bacterial transpeptidation reaction prevent cross-linked of “peptidoglycan chain 3- Activation of autolytic enzymes |
| Resistance to Penicillins: | Inactivation of antibiotic with β-lactamase Modification of target PBPs Impaired penetration of drug to target PBPs Presence of efflux pump Peptidoglycan Porins |
| P.aeruginosa is intrinsically resistant to many antibiotics……Why | -highly selective porins -produces multiple efflux pumps -ß-lactamase → amino- penicillins & most Cephalosporins are ineffective against this bacterium |
| [Penicillinase-enzyme | is the most common & most important mechanism of resistance of ß-lactam antibiotics] |
| ß-lactamses-inhibitors : | Structurally related to penicillin Amoxicillin/clavulanic acid, Ampicillin/sulbactam,piperacillin/tazobactam no antimicrobial properties irreversibly inhibits ß-lactamse- producing organisms ↑the activity of ß-lactams & extend their usefulness |
Created by:
ahmad445
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