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Rifamycins

RIFAMYCIN PHARMACOLOGY

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Rifamycins

  1. 1. RIFAMYCINS A PRESENTAION ON PRESENTING BY BIBEK GC (O5)
  2. 2. INTRODUCTION Complex macrocyclic antibiotics. Naturally produce by Streptomyces mediterranei. Bactericidal drug (intracellular and extracellular). Particulary effective against Mycobacteria. Used to treat TB, Leprosy and mycobacterium avium complex.
  3. 3. CLASSSIFICATION Based on production a) Natural rifamycins e.g. rifamycins B,O,SV and x. b) Semi-synthetic rifamycins derivatives e.g. rifampicin, rifabutin, rifaximin and rifapentine
  4. 4. MECHANISM OF ACTION • Inhibits bacterial DNA-dependent RNA synthesis by inhibiting bacterial DNA- dependent RNA polymerase. • Halts initiation of mRNA transcription • Prevention of translation of polypeptides
  5. 5. SELECTIVITY • Inhibits only prokaryotic DNA-primed RNA polymerase • In normal concentration-does not inhibit mammalian enzyme.
  6. 6. ANTIMICROBIAL SPECTRUM • High activity against gram +ve and mycobacteria. • Suceptible organisms: Stayphylococcus, Nesseria, Chlamydia, Mycobacterium sps etc. • Some activity against a few gram –ve; Brucella and vaccinia virus
  7. 7. BACTERIAL RESISTANCE • Natural resistance in gram –ve(due to failure to penetrate organism) • Resistance quickly when use sole. • Alteration in DNA dependent RNA polymerase.
  8. 8. PHARMACOKINETICS ABSORBTION • Well absorbed (40-70%) from GI tract in oral administration • I/m injection site – rapid absorption.
  9. 9. PHARMACOKINETICS DISTRIBUTION • Rapidly distributed to body tissues & fluids. • Enters into the cell. • Effective concentration reaches to many organs and body fluid including CSF. • Also penetrate abscess and caseous material.
  10. 10. PHARMACOKINETICS METABOLISM • In liver by deacetylated. EXCRETION • Mainly in bile(60-65%) and to a lesser extent to urine(30%)
  11. 11. ADVERSE EFFECT • Hepatitis • GI disturbances- nausea, vomiting, abdominal cramps with or without diarrhoea • CNS effects- headache, drowsiness, ataxia, and confusion
  12. 12. ADVERSE EFFECT • Myelosuppression • Respiratory – breathlessness • Cutaneous - flushing, pruritus, rash, redness and watering of eyes • Hypersensitivity reactions
  13. 13. CONTRAINDIACATION/PRECAUTION • Patient with Hypersensitivity to rifamycins. • Cautiously use in patient with pre-existing hepatic dysfunction. • Use carefully in pregnant animal, although significant teratogenicity has not been reported
  14. 14. Drug interaction Help in the metabolism/elimination of DRUGS • digitalis, coticosteriods, • quinidine, barbiturates, • ketoconazole, propranolol, • verapamil and oral anticoagulant (Effective liver enzyme inducer-hepatic cytochrome P450)
  15. 15. Drug interaction • Synergism with amphotericin B • Drugs Increasing toxicity of rifamycins azoles protease inhibitors The macrolide Clarithromycin Nonnucleoside reverse transcriptase inhibitors (increase levels of rifamycins by inhibiting CYP450 enzymes )
  16. 16. CLINICAL USES • TB • LEPROSY • MYCOBACTERIUM AVIUM COMPLEX
  17. 17. THANK YOU

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