Cephalosporins

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Cephalosporins

  1. 1. CEPHALOSPORINS <ul><li>Semisynthetic antibiotics </li></ul><ul><li>Derived from cephalosporin-C obtained from a fungus </li></ul><ul><li>Cephalosporium </li></ul><ul><li>Chemically related to penicillins </li></ul><ul><li>Nucleus consists of a β -lactum ring fused to </li></ul><ul><li>dihydrothiazine ring (7-aminocephalosporanic acid) </li></ul><ul><li>- Bactericidal </li></ul>
  2. 2. CH CH 2 CH S NH C C N O R 1 1 2 Cephalosporin Amide linkage COOH C C R 2
  3. 3. CLASSIFICATION First generation Parenteral oral Cephalothin cefazolin Cephalexin Cephradine Cefadroxil Second generation Parenteral oral Cefuroxime Cefoxitin Cefaclor Cefuroxime axetil
  4. 4. Third generation Parenteral oral Fourth generation Parenteral Cefotaxime Ceftizoxime Ceftriaxone Ceftazidime Cefoperazone Cefixime Cefpodoxime proxitil Cefdinir Ceftibutin Cefepime Cefpirome
  5. 5. Individual cephalosporins differ in their: a) Antibacterial spectrum and relative potency against specific organism b) Susceptibility to β -lactamases from different organisms c) Pharmacokinetic properties d) Local irritancy on i.m. injection MOA Inhibition of cell wall synthesis
  6. 6. <ul><li>RESISTANCE </li></ul><ul><li>Alteration in target proteins (PBPs) reducing affinity for </li></ul><ul><li>the antibiotics </li></ul><ul><li>Impermeability to the antibiotic so that iy does not </li></ul><ul><li>reach its site of action </li></ul><ul><li>Elaboration of β -lactamases which destroy specific </li></ul><ul><li>cephalosporins </li></ul>
  7. 7. FIRST GENERATION Developed in 1960s Have high activity against Gram +ve but weaker against Gram –ve bacteria Cephalothin -1 st cephalosporin used clinically Active against- streptococci, staphylococci, gonococci meningococci etc.
  8. 8. SECOND GENERATION More active against Gram –ve organisms Some members active against anaerobes Cafoxitin - highly resistant to β -lactamases produced by gram –ve bacteria. Used in- surgical infections lung abscess
  9. 9. THIRD GENERATION Introduced in 1980s Highly active against gram-ve bacteria All are highly resistant to β -lactamases from gram –ve bacteria Cefotaxime Potent action on aerobic gram-ve as well as gram+ve bacteria Not so active on anaerobes
  10. 10. USE Hospital acquired infections Septicaemias Infections in immunocompromised patients FOURTH GENERATION CEPHALOSPORINS Developed in 1990s Highly resistant to β -lactamases Active - P.Aeruginosa and S.aureus
  11. 11. <ul><li>ADVERSE EFFECTS </li></ul><ul><li>Pain </li></ul><ul><li>Diarrhoea </li></ul><ul><li>Hypersensitivity reactions </li></ul><ul><li>Nephrotoxicity </li></ul><ul><li>Bleeding –hypoprothrombinemia </li></ul><ul><li>USES </li></ul><ul><li>As alternative to PnG in patients developing rashes </li></ul><ul><li>Respiratory,urinary & soft tissue infections-gram-ve </li></ul><ul><li>bacteria </li></ul>
  12. 12. <ul><li>Septicaemias caused by gram-ve organisms </li></ul><ul><li>Surgical prophylaxis </li></ul><ul><li>Meningitis caused by H.influenzae </li></ul><ul><li>Gonorrhoea </li></ul><ul><li>Thyphoid </li></ul><ul><li>Mixed aerobic-anaerobic infections seen in cancer patients </li></ul>
  13. 13. <ul><li>MONOBACTAMS </li></ul><ul><li>Aztreonam </li></ul><ul><li>Novel β -lactam antibiotic </li></ul><ul><li>Inhibit gram-ve enteric bacilli , H.influnzae & </li></ul><ul><li>pseudomonas </li></ul><ul><li>Do not inhibit gram+ve cocci </li></ul><ul><li>Dose 0.5-2g i.m or i.v. 6-12 hourly </li></ul><ul><li>Uses </li></ul><ul><li>Hospital acquired infections </li></ul><ul><li>In patients allergic to penicillins or cephalosporins </li></ul>
  14. 14. CARBAPENEMS Imipenem Extremely potent & very broad spectrum β -lactam antibiotic Effective against- gram+ve cocci P.aeruginosa anaerobes like- B.fragilis C.difficile Disadvantage - rapid hydrolysis by enzyme dehydropeptidase I Overcome by- giving in combination with cilastatin
  15. 15. Dose- imipenem-cilastatin 0.5g i.v. 6 hourly USES: Hospital acquired infections including cancer & AIDS patients

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