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Macrolides

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Macrolide

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Macrolides

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  2. 2. A Presentation On… Macrolides Presented by- Gourango Kumar Biswas & Asma Aktar, Dept. of Pharmacy, Jessore University of science & Teachnology, Bangladesh. 2
  3. 3. Macrolides- General Consideration Macrolides are a class of antibiotics which contain macrocyclic lactone ring attached to deoxy sugars.  These antibiotics are bacteriostatic in nature & act by inhibiting protein synthesis of bacteria.  These are obtained mainly from certain actinomycetes genus, such as- Streptomyces. Example- Erythromycin, clarithromycin, azithromycin, telithromycin etc. Fig- General model of macrolide. 3
  4. 4. Chemistry of Macrolides Macrolides structurally contain three characteristic parts in every molecule- I. A macrocyclic lactone ring containing 14 or 16 carbons usually. II. Multiple ketone group (O=) & hydroxyl group (-OH). III. Two deoxy sugars attached by glycosidic bond with lactone ring. Fig: General structure of macrolide. 4
  5. 5. Macrolides- Classification According to the carbon number of lactone ring, macrolides are classified into 5 types- 1) 12-membered ring macrolides 2) 13-membered 3) 14-membered (most drugs) 4) 15-membered 5) 16-membered (most drugs) Besides some special groups are available-  Azalides: 15 membered, e.g- azithromycin.  Triamilides: Combination of 13- and 15-membered, e.g- tulathromycin.  Ketolides: 14-membered with 3 ketone group, e.g- telithromycin. 5
  6. 6. Pharmacokinetics  Route of Administration: Oral & parenteral.  Absorption: Erythromycin is poorly absorbed from GIT due to acid sensitivity. Clarithromycin & azithromycin are well absorbed from GIT.  Distribution: Rapidly distributed into systemic circulation. They can cross placenta but can’t cross BBB.  Metabolism: Via liver.  Excretion: Through bile mainly, but clarithromycin is excreted through urine too.6
  7. 7. Erythromycin  1st macrolide obtained from streptomyces erytherus in 1952.  Active against G(+) bacteria.  Plasma half life: 2hrs.  Dose: adult(250-500mg 6-hourly).  Unstable in stomac acid.  Formulaed as enteric coated tablet. Most common market brand of erythromycin are-  A-mycin  Eromycin  Etrocin  Macrocin etc. 7
  8. 8. Clarithromycin  Clarithromycin is derived from erythromycin by addition of methyl group.  Active against both G(+) & G(-) bacteria.  It is more active against Mycobacterium avium complex (MAC).  It is stable in stomac acid.  Plasma Half-life: 6 hrs  Dose: 250-500mg twice daily for 7 days. Most common market brands of Clarithromycin-  Binoclar  Clarin  Claricin etc. 8
  9. 9. Azithromycin  An azalide which is derived from erythromycin by addition of methylated nitrogen into the lactone ring.  Best activity against G(-) bacteria.  Slowly released from tissue.  Plasma half life >2days.  Dose: 250-500 mg once daily for 5-7 days.  Higher efficiency & lesser side effect. Common market brands of Azithromycin-  Zimax  AZ  Zycin  Azin  Azithrocin etc. 9
  10. 10. Mechanism of Action Macrolide is a protein synthesis inhibitor. Generally it is bacteriostatic in action but acts as bacteriocidal at higher dose. Macrolides bind to 50S ribosomal sub-unit Inhibit polypeptide chain elongation & protein synthesis inhibition Result in inhibition of growth & multiplication. 10
  11. 11. Macrolide Resistance Macrolides become resistant by- 1)Target gene mutation, esp- erg gene & 2) Efflux pump. 11
  12. 12. Spectrum of Activity Gram-Positive Aerobes- Erythromycin & clarithromycin display the best activity. Clarithro>Erythro>Azithro Example-  Methicillin susceptible Staphylococcus aureus  Streptococcus pneumoniae  Bacillus pneumoniae  Corynebacterium sp. Gram-Negative Aerobes- Newer macrolides such as azithromycin has enhanced activity. Azithro>Clarithro>Erythro Example-  H. influenzae  Neisseria sp.  Bordetella pertussis. 12
  13. 13. Macrolides- Indications  Upper respiratory tract infections- pharyngitis, tonsillitis, sore throat, whooping caugh etc.  Lower respiratory tract infection- pneumonia, mycoplasma pneumonia, community derived pneumonia, anthrax etc.  COPD 13
  14. 14. Macrolides- Indications  Sinusitis  Otitis media  Peptic ulcer treatment for eradication of H. pylori in triple therapy.  Skin & soft tissue infection  MAC(Mycobacterium avium complex) infection in AIDS  Gonorrhea.  Conjunctivitis  Lyme disease.14
  15. 15. Macrolides- Contraindications  Hepatic dysfunction  Hypersensitivity to macrolides.  Pregnancy. Hypersensitivity15
  16. 16. Adverse Effect of Macrolides In case of therapeutic dose:  Gastrointestinal discomfort  Anorexia  Nausea  Vomiting  Diarrhea  Mild allergic reaction. In case of toxic dose:  Reversible hearing loss  Liver toxicity  Jaundice  Ventricular arrhythmia. Main adverse effects 16
  17. 17. Reference 1. Lippincott’s Pharmacology. 2. Essentials of MEDICINAL PHARMACOLOGY, KD Tripathy. 3. Basic & Clinical Pharmacology; Katzung, Masters & Trevor. 4. An Introduction to Medicinal Chemistry; Graham L. Patrick. 5. Apex Medical Pharmacology; Dr Javed Yousuf. 6. Foyel’s Principle of Medicinal Chemistry. 7. Qimp Index of Medical Products & Problems. 17
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