Download presentation
Presentation is loading. Please wait.
1
Antibiotics Introduction
4th Year 2016
27
Chemical structure of penicillin
Beta lactam
30
Stereochemistry of Penicillins
It contains three chiral carbon atoms at C3, C4 & C6. L- configuration , C3 & C6 chiral centers are trans to each other.
31
Synthesis of Penicillin
32
Chemical degradation of penicillin a- Acidic hydrolysis
34
Mechanism of action Like all β-lactam antibiotics , inhibit the synthesis of bacterial cell wall . Through inhibition transpeptidase enzyme They are bactericidal on the actively growing bacteria.
38
Combination therapy Penicillin + Beat lactamase
Many baterial β-lactamases are inhibited by clavulaic acid ± amoxicillin (co-amoxiclav) antibiotic is effective against penicillinase-producing organisms. Co-amoxiclav indicated in resp and UT infections, which are confirmed to be resistant to amoxicillin
39
SAR Conclusions Amide and carboxylic acid are involved in binding
Carboxylic acid binds as the carboxylate ion Mechanism of action involves the b-lactam ring Activity related to b-lactam ring strain (subject to stability factors) Bicyclic system increases b-lactam ring strain Not much variation in structure is possible Variations are limited to the side chain (R)
40
Another strategy for complete protection of the β-lactam ring is introduction of 6 α-OCH 3, which is bulky enough to prevent β - lactamase attack from the back side. y Important example is temocillin, which is 6 α-methoxyticarcillin.
41
Metabolism & Excretion
Not metabolised Excreted unchanged in urine Probenecid blocks their secretion Nafcillin is mainly cleared by biliary route Oxacillin by both kidney & biliary route.
42
Aminopenicillins(Ampicillin &Amoxicillin)
Therapeutic uses 1)H.influenza 2)E.coli 3)Salmonella&Shigella infections only ampicillin 4)Prophylaxis of infective endocarditis 5) Urinary tract infections 6) Effective against penicillin –resistant pneumococci
43
Adverse effects Hypersensitivity reactions
High dose in renal failure ---seizure Naficillin (neutropenia) Oxacillin (hepatitis) Methicillin(nephritis) B.S.P.(pseudomembraneous colitis ) Secondary infections
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.