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  2. 2. PENICILLINSBeta- lactam antibioticsDerivatives of 6- aminopenicillanic acid :Alteration of the side group resulted in cpds withBroader spectrum of activityResistance to penicillinaseStability in acid PHMost widely effective antibioticsLeast toxic drugs known
  3. 3. MECHANISM OF ACTIONThey act by inhibition of bacterial cell wall synthesisThus exposing the osmotically less stablemembraneThis cause lysis of bacterial cell wallThese agents are bactericidalActive against multiplying and not resting bacteriaInactive against mycobacteria, protozoa, fungi andviruses
  4. 4. Classifications of penicillins)Penicillin G ( Benzyl penicillin )(i.m ,slow i.v or infusion .1.Highest activity against Gram-positive organisms but susceptible to Beta-lactamase :Effective againstGram-positive aerobic cocci - Staph. aureus- not producing penicillinase, S.pneumoniae ( group A ) ,S.pyogenesGram-negative aerobic cocci -N.meningitidis N. gonorrhea-no longer of choiceGram- positive bacilli : Bacillus anthracisSpirochetes : T. pallidum – drug of choiceAnaerobesClostridium spp but inactive against B.fragilis)Actinomycetes israelii ( actinomycosis
  5. 5. Repository penicillinsDeveloped to prolong duration of penicillin G in the blood1. Penicillin G procaine Duration 12- 24 hr It is given i.m and not i.v( risk of procaine toxicity) Seldom used now ( increased frequency of penicillinase producing N. gonorrhea
  6. 6. Repository penicillins ( cont.)2. Penicillin G benzathin ( i.m ) Duration 3- 4 weeks Painful at the injection site ( limits its use ) Uses 1. Syphilis 2. Rheumatic fever prophylaxis( inhibits group A beta- hemolytic streptococci) 3. Streptococcal pharyngitis
  7. 7. . )Class. Of penicillins ( contDisadvantages of penicillin GA. Destroyed by gastric HCLB. Inactivated by penicillinaseC. Narrow spectrum of activity
  8. 8. . )Class. Of penicillins ( contAcid resistant penicillins. 2.Phenoxy- methyl penicillin ( penicillin v), p.o )spectrum of activity is similar to penicillin G (UsesGroup A Streptococcal pharyngitisProphylaxis against group A streptococci in patients.with history of rheumatic heart diseaseDisadvantagesReadily hydroyzed by beta-lactamase
  9. 9. . )Class. Of penicillins ( contPenicillinase-resistant penicillins. 3Methicillin OxacillinCloxacillin DicloxacillinFloxacillin NafcillinLower activity against G+ compared to Penicllin Gbut.Are the choice for infections caused by penicillinase producing S. aureus.However, MRSA & ORSA has emergedNot effective against G- aerobes( E.coli, klebsiella,N.gonorrhea or.)pseudomonas spp.Less active than penicillin on anaerobesHigh protein and food binders
  10. 10. )Class. Of penicillins ( contBroad- spectrum penicillins. 4a) Ampicillin, Ampicillin- sulbactam,Bacampicillin, Amoxicillin, Amoxicillin- ).clavulanic acid ( augmentinLess active than penicillin G against G+ cocci..Active against G- organisms
  11. 11. )Broad-spectrum penicillins ( contUsesH. Influenza infections ( otitis media, sinusitis, chronic bronchitis,).pneumonia, bacterial meningitisM.catarrhalis).E. Coli infections ( Urinary & biliary infections)Samonella infections ( typhoid fever)Shigella infections ( ampicillinGonococcal infections ( alternative for penicillin in the treatment of)gonorrheaProphlaxis of infective endocarditisDisadvantagesAmoxicillin & ampicillin alone are readily destroyed by Staph..Penicillinase
  12. 12. )Broad spectrum penicillins ( contB ) Extended- spectrum : Ticarcillin-clavulanic acid, )piperacillin,piperacillin-tazobactam ( TazocinUsesPseud. aeruginosa. For pseud.septicemia, they should be given together with an aminoglycoside ).eg. Gentamicin(DisadvantagesTicarcillin and piperacillin alone are readily destroyedby S. penicillinase. High dose may lead to.hypernatraemia due to sodium content
  13. 13. Absorption,distribution & metabolismOral absorption of most penicillins is poorException: penicillin vAmoxicillinFood interfer with absorption:To increase GI absorption: give ester formBacampicillinCarbenicillin indanyDistributionWidely distributedRelatively insoluble in lipidHence, have poor penetration into cells and BBBInflammation ( eg. Meningitis ) permits entrance into CSF
  14. 14. . )Absorp., metabolism ( cont:Protein binding differsAmpicillin and penicillin G 20% boundNafcillin, oxacillin, 90% boundcloxacillin , dicloxacillinMetabolism and excretionNot metabolized in humanExcreted mostly unchanged in urine( except. ) Nafcillin,oxacillin, cloxacillin, dicloxacillinProbenecid blocks their secretion) Half-life 30-60 min ( increased in renal failure
  15. 15. Adverse effects of penicillins1.Hypersensitivity reactions ( occur in 1-10% of pts; fatality occur in 0.002%) ( immediate, accelerated & late allergic rxns) ** Cross-reactions Urticarial rash Fever Bronchspasm Serum sickness Exfoliative dermatitis Stevens- Johnson syndrome Anaphylaxis2. Super infections3. Diarrhoea4. May cause convulsions after high doses by i.v or in renal failure
  16. 16. THANQ  