Antibiotics
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Antibiotics

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Antibiotics Antibiotics Presentation Transcript

  • ANTIBIOTICS Antibiotics are obtained from Fungi penicillins,cephalosporin,griseofulvin Bacteria polymyxin B,Tyrothricin colistin,aztreonam,bacitracin Actinomycetes aminoglycosides,macrolides,tetracyclines polyenes,chloramphenicol
  • CLASSIFICATION- A) Chemical structure Β -lactam antibiotics- penicillins,cephalosporins,monobactams,carbapenems Tetracyclins Oxytetracycline,doxytetracycline Nitrobenzene derivative- chloramphenicol Aminoglycosides Streptomycin,gentamycin,amikacin,neomycin
  • Macrolide antibiotics Erythromycin,clarithromycin,azithromycin Glycopeptide antibiotics Vancomycin,teicoplanin Lincosamide antibiotics Lincomycin,clindamycin Oxazolidinone- linezolid
  • Polypeptide antibiotics Polymyxin-B, colistin,bacitracin Polyene antibiotics Nystatin,amphotericin-B B. Mechanism of action 1. Inhibit cell wall synthesis penicillins,cephalosporins,cycloserines vancomycin,bacitracin
  • 2 . Causes leakage from cell wall membrane Polypeptide-polymyxins,colistin,bacitracin Polyenes- amphotericin B,nystatin 3. Inhibit protein syntheis tetracyclins,chloramphenicol,erythromycin, clindamycin 4. Cause misreading of m-RNA code and affect permeability Aminoglycosides-streptomycin,gentamycin
  • SPECTRUM OF ACTIVITY Narrow spectrum penicillin G streptomycin erythromycin Broad spectrum tetracyclines chloramphenicol
  • PENICILLINS First antibiotic to be used clinically in 1941 Originally obtained from fungus Penicillium notatum Present source is a high yeilding mutant of P. chrysogenum
  • CHEMISTRY AND PROPERTIES 1- Thiazolidine ring 2- β -lactam ring CH C CH 3 CH 3 CH S C NH COOH C N O O R 1 2 Benzyl side chain PENICILLINS Amide linkage
    • MECHANISM OF ACTION
    • - Inhibit transpeptidase so that cross linking
    • does not take place
    • When bacteria divide in presence of β -lactam
    • antibiotics –cell wall deficient(CWD) forms are
    • produced
    • -because the interior of the bacterium is
    • hyperosmotic ,the CWD forms swell & burst
    • bacterial lysis
  • Lytic effect of these antibiotics may also be due to derepression of some bacterial autolysins which normally function during cell division Penicillin G Spectrum - narrow active only against gram +ve bacteria Cocci: Streptococci,Pneumococci gram –ve cocci- Neisseria gonorrhoeae N.meningitidis
    • Bacilli: gram +ve - Corynebacterium. Dephtheriae
    • clostridia tetani
    • garm –ve- Actinomyces israelii
    • BACTERIAL RESISTANCE
    • Many bacteria are inherently insensitive to PnG
    • Because in them the target enzyme & PBPs are located
    • deeper under lipoprotein barrier wher PnG is unable to penetrate
    • Production of penicillinase
    • it is a narrow spectrum β -lactamase which opens the
    • β -lactam ring and inactivates PnG.
    • Some bacteria become Penicillin tolerant –their target
    • Enzymes are altered to have low affinity for penicillin
    • Gram –ve bacteria have porin channels located in their
    • outer membrane.some gram –ve bacteria become resistant
    • By loss or alteration of porin channels.
  • PHARMACOKINETICS A - PnG is acid labile-destroyed by gastric acid absorption from i.m route is rapid & complete D – Reaches most of the body fluids Penetration in CSF is poor M- Little metabolised because of rapid excretion E - Very rapid renal excretion
    • ADVERSE EFFECTS
    • Local irritancy and direct toxicity
    • pain at i.m injection site
    • nausea on oral ingestion
    • Larger dose injected i.v –
    • Mental confusion
    • Muscular twitching
    • convulsions,coma.
    • Hypersensitivity
    • rash,itching & fever
  • USES 1.Streptococcal infections 2. Pneumococcal infections 3.Meningococcal infections 4.Gonorrhoea 5.Syphilis 6. Diphtheria 7.Tetanus
    • 8.Drug of choice for rare infections like
    • anthrax,rat bite fever,trench mouth
    • SEMISYNTHETIC PENICILLINS
    • Shortcomings of PnG
    • -Poor oral efficacy
    • Suseptibility to penicillinase
    • Narrow spectrum of activity
    • Hypersensitivity reactions
  • CLASSIFICATION 1.Acid resistant alternative to PnG phenoxymethyl penicillin(Penicillin V) 2.Penicillinase-resistant penicillins methicillin,cloxacillin 3.Extended spectrum penicillins a) aminopenicillins: ampicillin.bacampicillin,amoxicillin b) carboxypenicillins: carbenicillin,ticarcillin c) ureidopenicillins: piperacillin,mezlocillin β -lactamase inhibitors Clavulanic acid,sulbactum,tazobactum
  • 1.Acid resistant alternative to PnG - acid stable -oral absorption better -antibacterial spectrum identical to PnG -but it is1/5 as active against Neisseria 2.Penicillinase-resistant penicillins - these have side chains that protect the β -lactam ring from attack by staphylococcal penicillinase Methecillin - penicillinase resistant but not acid resistant
  • Cloxacillin- Highly penicillinase resistant as well as acid resistant 3. Extended spectrum penicillins Effective against gram-ve bacilli 1. Aminopenicillins -These have amino group in side chain -prodrugs -none is resistant to penicillinase
  • AMPICILLIN Uses -UTI -RTI -Meningitis -Gonorrhoea BACAMPICILLIN Ester prodrug of ampicillin Completely absorbed from g.i.t AMOXICILLIN Close congener of ampicillin Not a prodrug Oral absorption is better
  • 2. CARBOXYPENICILLINS - active against pseudomonas aeruginosa & proteus - Carbenicillin is neither penicillinase resistant nor acid resistant -inactive orally 3. UREDOPENICILLINS Piperacillin - 8 times more active than carbenicillin -used mainly in immunocompromised patients having serious gram-ve infections
  • BETA-LACTAMASE INHIBITORS Clavulanic acid Obtained from streptomyces clavuligerus Has β lactam ring but no antibacterial activity