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  • Imipenem and cilastatin shows color change usually pink after its reconstitution in 2-3 days whereas Meropenem does not show any color change for 5-6 days after its reconstitution. That is why Imipenem could not be due to its much wastage as the Total cost of therapy will be more for the patient receiving Imipenem than Meropeam. Could you please share me how the Imipenem gets colored in 2-3 days. My email id:
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  1. 1.  -Lactam Antibiotics Carbapenems Dr. Salman Khan Department of Pharmacology LM&DC
  2. 2. Carbapenems <ul><li>Carbapenems are  - Lactams that contain fused  - Lactam ring system – different from penicillins. It is unsaturated and contains a carbon atom instead of the sulfur atom. </li></ul>
  3. 4. Classification <ul><li>Imipenem </li></ul><ul><li>Meropenem </li></ul><ul><li>Etrapenem </li></ul><ul><li>Aztreonam (monobactam – monocyclic  - Lactam compound) </li></ul>
  4. 5. Imipenem <ul><li>Mechanism of Action: </li></ul><ul><ul><li>ß- lactam antibiotics inhibit the key enzyme in bacterial wall synthesis. (tanspeptidase) </li></ul></ul><ul><ul><li>They also appear to activate one or more cell-wall autolytic enzymes, causing lysis of the bacterium. </li></ul></ul>
  5. 6. Imipenem <ul><li>Spectrum: </li></ul><ul><ul><li>Aerobic & anaerobic micro-organisms </li></ul></ul><ul><ul><ul><li>Streptococci (including penicillin resistant S. pneumoniae ) </li></ul></ul></ul>
  6. 7. Spectrum continued… <ul><ul><li>Enterococci (except E-Faecium non-  - Lactamase producing penicillin resistant strains) </li></ul></ul><ul><ul><li>Staphylococci </li></ul></ul><ul><ul><li>Listeria </li></ul></ul><ul><ul><li>Some MRSA </li></ul></ul>
  7. 8. Continued .. <ul><ul><li>Pseudomonas </li></ul></ul><ul><ul><li>Acinetobacter </li></ul></ul><ul><ul><li>Bacteroides ( B. fragilis ) </li></ul></ul>
  8. 9. Pharmacokinetics <ul><li>Not absorbed orally </li></ul><ul><li>The drug is hydrolyzed rapidly by Dipeptidase found in the brush border of the proximal renal tubule – because active drug concentration in urine were very low, cilastatin (dehydropeptidase inhibitor) was synthesized and combined in equal amount with imipenem </li></ul>
  9. 10. Pharmacokinetics continued… <ul><li>After I/V administration of 500mg imipenem + cilastatin peak plasma concentration is 33  g/ml. both have a half life of 1 hour. </li></ul><ul><li>70 % of imipenem, if given in combination with cilastatin, is recovered as active drug in urine </li></ul><ul><li>Dosage should be modified in renal insufficiency </li></ul>
  10. 11. Adverse effects <ul><li>Nausea and vomiting are most common (1% - 20%) </li></ul><ul><li>Seizures – 1.5% (esp. if high doses are given in to patients with CNS lesions and in those with renal insufficiency) </li></ul><ul><li>Hypersensitivity – seen in patients allergic to other  - Lactam antibiotics. </li></ul>
  11. 12. Therapeutic uses <ul><li>Urinary tract infections </li></ul><ul><li>Lower respiratory tract infections </li></ul><ul><li>Intra-abdominal infections </li></ul><ul><li>Gynecological infections </li></ul><ul><li>Skin and soft tissue, bones and joint infections </li></ul><ul><li>Cephalosporin-resistant nosocomial bacteria (Citrobacter Freundii, Enterobacter spp.) </li></ul>
  12. 13. Meropenem <ul><li>Newer drug </li></ul><ul><li>Not sensitive to dipeptidase – cilastatin is not required </li></ul><ul><li>Toxicity </li></ul><ul><li>Similar to imipenem </li></ul><ul><ul><li>But less likely to cause seizures </li></ul></ul>
  13. 14. Meropenem <ul><li>Spectrum </li></ul><ul><ul><li>Similar to imipenem but it is good in vitro against some imipenem resistant P. aeruginosa, while less against gram +ve cocci </li></ul></ul><ul><ul><li>In clinical experience both the drugs are therapeutically equivalent </li></ul></ul>
  14. 15. Ertapenem <ul><li>Larger serum half life – allows single daily dose </li></ul><ul><li>Spectrum: </li></ul><ul><ul><li>Inferior activity against P. aeruginosa and Acinetobacter spp. </li></ul></ul><ul><ul><li>Good against gram +ve enterobacteriaceae & anaerobes – makes it attractive for use in intra-abdominal and pelvic infections </li></ul></ul>
  15. 16. Aztreonam <ul><li>It is a monocyclic  - Lactam compound (monobactam) </li></ul><ul><li>Mechanism: </li></ul><ul><ul><li>Interacts with penicillin-binding proteins of susceptible micro-organisms and induces the formation of long filamentous bacterial structures </li></ul></ul><ul><ul><li>It is resistant to many of the  - Lactamases that are elaborated by most gram-negative bacteria </li></ul></ul>
  16. 17. Aztreonam <ul><li>Spectrum </li></ul><ul><ul><li>Differs from other  - Lactam antibiotics and closely resembles to aminoglycosides </li></ul></ul><ul><ul><li>Active only against gram –ve bacteria </li></ul></ul><ul><ul><li>No activity against gram +ve bacteria and anaerobic organism </li></ul></ul><ul><ul><li>However excellent against enterobacteriaceae and P. aeruginosa </li></ul></ul><ul><ul><li>H. influenza and gonococci ( in vitro ) </li></ul></ul>
  17. 18. Pharmacokinetics <ul><li>Administered I/M or I/V </li></ul><ul><li>Peak conc. = 50  g/ml after 1g I/M dose </li></ul><ul><li>T ½ = 1.7 hrs prolonged to 6 hrs in anephric patients </li></ul><ul><li>Most of the drug is recovered unchanged in urine </li></ul><ul><li>Dose = 2g every 6 -8 hrs (reduced in renal patients) </li></ul>
  18. 19. Adverse effects <ul><li>Usually well tolerated </li></ul><ul><li>Patients with penicillins or cephalosporin allergy appear not to react to aztreonam (except ceftazidine) </li></ul>
  19. 20. Uses <ul><li>Quite useful for treatment of gram negative infections that normally would be treated with a  - Lactam were it not for the history of prior allergic reaction </li></ul>