Penicillin's & cephalosporins basics

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Penicillin's & cephalosporins basics

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Penicillin's & cephalosporins basics

  1. 1. Penicillins & Cephalosporins know the basics Dr.T.V.Rao MD Dr.T.V.Rao MD 1
  2. 2. Beginning of Antibiotics with Discovery of Penicillin • The discovery of penicillin has been attributed to Scottish scientist Alexander Fleming in 1928 and the development of penicillin for use as a medicine is attributed to the Australian Nobel Laureate Howard Walter Florey. Dr.T.V.Rao MD 2
  3. 3. Antibacterial agents • Antibacterials/antimicrobial drugs - Substances that inhibit the growth of or kill bacteria or other microorganisms (microscopic organisms = bacteria, viruses, fungi, protozoa) • Bacteriostatic = Inhibits growth of bacteria • Bactericidal = Kills bacteria • Peaks & Troughs = Serum antibacterial levels for drugs w/ a narrow therapeutic index - Too high = drug toxicity (Peak - 1 hr. after drug infused) - Too low = therapeutic range (Trough - before dose) Dr.T.V.Rao MD 3
  4. 4. Uses of Antimicrobial Agents • Antimicrobial agents are widely employed to cure bacterial diseases • Definition of Antibiotic – Antibiotics are substances that are derived from a various species of microorganisms and are capable of inhibiting the growth of other microorganism even in small concentrations. Dr.T.V.Rao MD 4
  5. 5. Antibacterials • Mechanism of Action: 1. Inhibition of cell wall synthesis - Bactericidal 2. Alteration in membrane permeability - ‘Cidal’ or ‘Static’ 3. Inhibition protein synthesis - ‘Cidal’ or ‘Static’ 4. Inhibition of bacterial RNA & DNA - Inhibits synthesis of RNA & DNA 5. Interferes with metabolism in the cell - ‘Static’ Dr.T.V.Rao MD 5
  6. 6. Antibacterial Drugs • Drugs 1. Penetrate bacterial cell wall in sufficient concentrations 2. Affinity to the binding sites on the bacterial cell: - Time drug remains at binding sites = effect - Time controlled by pharmacokinetics Dr.T.V.Rao MD 6
  7. 7. Antibacterials • Pharmacodynamics - Concentration at site or exposure time for drug plays an important role in bacteria eradication - Duration of time for use of antibacterial varies according to type of pathogen, site of infection & condition of host - With some severe infections - continuous infusion more effective than intermittent - Body defense & drugs work together to stop infectious process - Effect = drug & host’s defense mechanisms Dr.T.V.Rao MD 7
  8. 8. Effects of concentrated drug dosing Dr.T.V.Rao MD 8
  9. 9. Antibacterials • Bacterial Resistance - result naturally or may be acquired * Natural (inherent) = w/o previous exposure to antibiotic ie. pseudomonas resistant to Penicillin G * Acquired = prior exposure to antibacterial ie. staph aureus was sensitive to PCN G, now it’s not • Nosocomial infections - infections acquired while clients are in the hosp. Many are mutant strains resistant to many Antibacterials Prolonged hospital stay • Antibacterial resistance occurs when antibiotics are used frequently Dr.T.V.Rao MD 9
  10. 10. Antibacterials • Culture & Sensitivity - Blood test done to determine effect drugs have on a specific organism Culture = organisms responsible Sensitivity = what antibiotic will work best • Narrow & Broad Spectrum Narrow - primarily effective against 1 type of organism Broad - effective against both gram + & gram - organisms * Used before isolating organism through C & S * Not as effective as narrow spectrum against those single organisms Dr.T.V.Rao MD 10
  11. 11. Antibacterials Penicillins (PCN) • From mold genus Penicillium - ‘miracle drug’ from WWII • A beta-lactum structure (beta-lactum ring) interferes w/ bacterial cell wall synthesis by inhibiting the bacterial enzyme necessary for cell division & synthesis • Bacteria die of cell lysis (breakdown) • Both ‘static’ & ‘cidal’ in nature • Mainly referred to as beta-lactum antibiotics (enzymes produced by bacteria that can inactivate PCN - Penicillinase = beta-lactamases which attack Dr.T.V.Rao MD 11 PCN
  12. 12. Penicillins and Cephalosporins • Penicillin and cephalosporins act inhibiting Trans peptidases, the enzyme catalyzes the final linking step in synthesis of peptidoglycan. • Due to this reason Penicillin in bactericidal for growing bacteria since new peptidoglycan is synthesized at that stage only. • In nongrwoing cells penicillin is inactive • An intact beta – lactum is essential for antibacterial activity of penicillins Dr.T.V.Rao MD 12
  13. 13. Antibacterials Penicillins • Natural Penicillins Penicillin G, Penicillin V, Procaine, Bicillin - Good gram +, fair gram - , good anaerobic - PCN G = more effective IV or IM, but painful d/t aqueous solution - PCN V = PO; peak 2 - 4 hrs Dr.T.V.Rao MD 13
  14. 14. Classification of Penicillins • Natural Benzyl penicillin Phenoxymethyl penicillin v Semi synthetic and pencillase resistant 1 Methicillin 2 Nefcillin 3 Cloxacillin 4 Oxacillin 5 Floxacillin Dr.T.V.Rao MD 14
  15. 15. Antibacterials Penicillins • Aminopenicillins (Broad Spectrum) Amoxicillin (Amoxil), Ampicillin (Omnipen), Bacampicillin HCL (Spectrobid) - Gram + & Gram - Costlier - Inactivated by beta-lactamases = ineffective against Staphylococcus aureus (staph. A) - Amoxicillin = most prescribed PCN derivative for adults & children Dr.T.V.Rao MD 15
  16. 16. Antibacterials Penicillins • Penicillinase - Resistant Penicillins Methicillin (Staphcillin), Nafcillin (Unipen), Oxacillin (Bactocil) - Used to treat penicillinase-producing Staph A. - Gram + , not effective against Gram - IV & PO Dr.T.V.Rao MD 16
  17. 17. Antibacterials Penicillins • Extended - Spectrum Penicillins Carbenicillin (PO), Mezlocillin, Piperacillin, Ticarcillin, T icarcillin-clavulanate (Timentin) - IM & IV - Broad spectrum - good gram (-), fair gram (+) - Good against Pseudomonas aeruginosa - Not penicillinase resistant Dr.T.V.Rao MD 17
  18. 18. Antibacterials Penicillins • SE & adverse reactions of Penicillins 1. Hypersensitivity - mild or severe Mild = rash, pruritus, & hives - Rx w/ antihistamines Severe = anaphylactic shock - occurs w/ in 20 min. - Rx w/ epinephrine 2. Super infection - secondary infection when normal microbial flora of the body disturbed during antibiotic Rx Mouth, resp. tract, GI, GU or skin - usually fungus 3. Organ toxicity - esp. liver & kidneys where drugs metabolized & excreted (aminoglycosides) Dr.T.V.Rao MD 18
  19. 19. CEPHALOSPORINS Dr.T.V.Rao MD 19
  20. 20. Most commonly used Antibiotics Cephalosporins • Beta-lactam antibiotics are among the most commonly prescribed drugs, grouped together based upon a shared structural feature, the betalactam ring. Cephalosporins cover a broad range of organisms, are generally well-tolerated, and are easy to administer; thus, these agents are frequently used beta-lactam drugs Dr.T.V.Rao MD 20
  21. 21. Antibacterials Cephalosporins • From a fungus Cephalosperium acremonium - Gram (+) & gram (-) - Resistant to beta - lactamase - Bactericidal - action similar to PCN’s - 4 groups (generations) - each effective against a broader spectrum of bacteria - about 10% of people allergic to PCN also to allergic to cephalosporins - Action - inhibits bacterial cell wall synthesis - IM & IV - onset = almost immediate Dr.T.V.Rao MD 21
  22. 22. Antibacterials Cephalosporins • 1st Generation Cephalosporins - cefadroxil (Duricef) & cephalexin (Keflex) - PO; Cefazolin (Ancef) & cephalothin (Keflin) - IM - Gram (+), & gram (-) - Esp. used for skin/skin structure infections - Keflin used for resp, GI, GU, bone, & joint infections Dr.T.V.Rao MD 22
  23. 23. Antibacterial Cephalosporins • 2nd Generation Cephalosporins cefaclor (ceclor) - PO, cefoxitin (Mefoxin), cefuroxime (Zinacef), cefotetan (Cefotan) - IM & IV - Gram (+), slightly boarder gram (-) effect than 1st generation - for harder to treat infections Dr.T.V.Rao MD 23
  24. 24. Antibacterials Cephalosporins • 3rd Generation Cephalosporins cefotaxime (Claforan), ceftazidime (Fortaz), ceftriaxone (Rocephin), cefixime (Suprax) - IM or IV - More effective against gram (-), less effective against gram (+) - for harder yet to treat infections Dr.T.V.Rao MD 24
  25. 25. 4th Generation Cephalosporins • 4th Generation Cephalosporins cefepime (Maxipime) - IV or IM • - Resistant to most betalactamase bacteria • - greater gram (+) coverage than 3rd generation Dr.T.V.Rao MD 25
  26. 26. 5th Generation Cephalosporins • Ceftaroline is a novel fifth-generation cephalosporin, which exhibits broadspectrum activity against Gram-positive bacteria, including MRSA and extensively-resistant strains, such as Vancomycin-intermediate S. aureus (VISA), heteroresistant VISA (hVISA), and Vancomycin-resistant S. aureus (VRSA) Dr.T.V.Rao MD 26
  27. 27. Why 5th Generation Cephalosporins • Microbial resistance has reached alarming levels, threatening to outpace the ability to counter with more potent antimicrobial agents. In particular, methicillin-resistant Staphylococcus aureus (MRSA) has become a leading cause of skin and softtissue infections and PVL-positive strains have been associated with necrotizing pneumonia. Increasing reports of growing resistance to glycopeptide have been noted, further limiting the efficacy of standard antibiotics, such as Vancomycin. • A need for newer Antibiotics is growing need Dr.T.V.Rao MD 27
  28. 28. ceftaroline is effective in • In addition to being an exciting new agent in the anti-MRSA armamentarium, ceftaroline provides efficacy against many respiratory pathogens including Streptococcus pneumoniae, Haemophilus influenza, and Moraxella catarrhalis. Dr.T.V.Rao MD 28
  29. 29. - Antibacterials Macrolides, Lincosamide, Vancomycin • All differ in structure, but similar spectrums of antibiotic effectiveness to PCN • Used as PCN substitutes, esp. w/ people allergic to PCN • Erythromycin frequently prescribed if hypersensitive to PCN • Macrolides - Erythromycin, Azithromycin (Zithromaz), Clarithromycin (Biaxin) - PO/IV, Dirithromycin (Dynabac) - PO - Broad spectrum of activity - Low to mod dose = bacteriostatic - high doses = bactericidal SE = GI disturbances, Allergic rxns = Hepatotoxicity Dr.T.V.Rao MD 29
  30. 30. Antibacterials Lincosamide • Clindamycin (Cleosin), Lincomycin (Lincorex) - PO, IM, IV - Inhibit bacterial protein synthesis - ‘Static’ & ‘cidal’ actions depending on drug dosage - effective against most gram (+), no gram (-) - Clindamycin more effective than lincomycin Dr.T.V.Rao MD 30
  31. 31. Antibacterials Vancomycin • Glycopeptide bactericidal antibiotic - IV - Use: Drug resistant Staph A., cardiac surgery prophylaxis for clients w/ PCN allergies - SE = Ototoxicity - damage to auditory branch of 8th cranial nerve permanent hearing loss or loss of balance & Nephrotoxicity - Serum Vancomycin levels drawn to minimize toxic effects Dr.T.V.Rao MD 31
  32. 32. Antibacterials Vancomycin • Glycopeptide bactericidal antibiotic - IV - Use: Drug resistant Staph A., cardiac surgery prophylaxis for clients w/ PCN allergies - SE = Ototoxicity - damage to auditory branch of 8th cranial nerve permanent hearing loss or loss of balance & Nephrotoxicity - Serum Vancomycin levels drawn to minimize toxic effects Dr.T.V.Rao MD 32
  33. 33. • Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World • Email • doctortvrao@gmail.com Dr.T.V.Rao MD 33

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