Penicillins

• The MOA of penicillins is the inhibition of cell wall synthesis by inhibiting penicillin-binding proteins (PBPs), causing

  • transpeptidase inhibition
  • autolysin production
• Penicillin-binding proteins (PBPs) are bacterial enzymes involved in the synthesis of the cell wall.
• Penicillins are bacteriocidal.
• Natural penicillins (e.g. Penicillin G) are effective against

  • Gram-positive organisms
  • Gram-negative cocci
  • Non-beta-lactamase producing anaerobes
• • Antistaphylococcal penicillins (e.g. nafcillin) are beta-lactamase resistant and are effective against:
  • Staphylococci
  • Streptococci
• Extended spectrum penicillins (e.g. amoxicillin, piperacillin) have increased activity against Gram negative bacteria due to their ability to overcome beta lactamases.
• Penicillins according to spectrum

  • natural
  • antistaphylococcal
  • extended spectrum
  • antipseudomonal
• Fill the blanks:

  A) dicloxacillin

  B) penicillin V

  C) methicillin

  D) nafcillin

  E) oxacillin

  F) ampicillin

  G) amoxicillin

  H) piperacillin

  I) ticarcillin

  
• Resistance to penicillins occurs due to

  • Beta-Lactamase activity
  • Decreased permeability to the drug
  • Altered PBPs
• IV / IM Administration

  • ticarcillin
  • piperacillin
  • ampicillin with sulbactam
  • ticarcillin with clavulanic acid
  • piperacillin with tazobactam
• Oral administrations

  • penicillin V
  • amoxicillin
  • amoxicillin with clavulanic acid
• Procaine penicillin G and benzathine penicillin G are administered IM and serve as depot forms, which are slowly absorbed into the circulation and persist at low levels over a long time period.
• Penicillins must be administered 30 to 60 minutes before meals or 2 to 3 hours postprandial.
• All penicillins cross the placental barrier, but none are teratogenic.
• Penicillins are excreted in

  • breast milk
  • urine
• Side effects of penicillins include

  • Hypersensitivity
  • Diarrhea
  • Nephritis
  • Neurotoxicity
  • Hematologic toxicities - cytopenias, eosinophilia
  • Cation toxicity - hypokalemia, hyponatremia
• Penicillin G is effective against

  • Gram + cocci: Strep. Pneumonia, Strep. Pyogenes, Strep. Viridans
  • Gram + bacilli: B. anthracis, C. diptheria
  • Gram - cocci: N. gonorrhea, N. meningitidis
  • Anaerobic organisms: C. perferingens
  • Spirochetes: T. pallidum, T. pertenue