PENICILLIN

MOA:
  • Penicillins are bactericidal antibiotics as they kill the microorganisms when used at therapeutic dose
  • The synthesis of cell wall of bacteria is completely depended upon an enzyme named as transpeptidase. 
  • Primarily, Penicillin inhibits the cell wall of bacteria by blocking transpeptidase after binding to penicillin-binding protein (PBP) and prevents its synthesis.
PENICILLIN RESISTANCE Mechanism of resistance are -
  • Penetration into the cell
  1. Gram negative bacteria have an outer membrane just outside the cell wall.
  2. Outer membrane is not present in gram positive bacteria, so this mechanism of resistance is not for gram positive organisms.
  • Beta-lactamase (Penicillinase) Production
  1. This is the most common mechanism
  2. Both gram positive and gram negative organism produce beta-lactamase which open the beta-lactam ring and inactivate the antibiotic.
  • Altered penicillin bindinE protein (PBP)
  1. Bacteria can alter the structure of penicillin binding protein, which is not other than transpeptidase.
  2. So, penicillin can not bind to the site where it acts.
  3. MRSA defends itself in this way.
  4. Organism resistant to methicillin, MRSA is resistant to all other beta-lactam antibiotics.
CLASSIFICATION:
  • SOURCE
  1. NATURAL( Endrin plant Penicillin)
  2. Penicillin-G 
  3. Penicillin-V
  • SEMI- SYNTHETIC 
  1. Oxacillin 
  2. Cloxacillin 
  3. Dicloxacillin 
  4. Methicillin 
  5. Nafcillin 
  6. Ampicillin 
  7. Amoxycillin 
  8. Carbencillin 
  9. Piperacillin 
  • ROUTE OF ADMINISTRATION:
  1. ORAL 
  2. Ampicillin 
  3. Amoxycillin 
  4. Penicillin-V 
  5. Oxacillin 
  6. Cloxacillin 
  7. Dicloxacillin 
  8. PARENTERAL 
  9. Penicillin-G 
  • Methicillin (Methicillin is Acid Labile penicillin)
  1. Nafcillin 
  2. Carbencillin 
  3. Piperacillin(anti-pseudomonal drug) 
  4. Ticarcillin 
  • SPECTRUM OF ACTIVITY:
  • NARROW SPECTRUM 
  1. Methicillin 
  2. Oxacillin 
  3. Nafcillin 
  4. Dicloxacillin 
  • BROAD SPECTRUM 
  1. Ampicillin 
  2. Amoxycillin 
  • INTERMEDIATE SPECTRUM 
  1. Penicillin-G 
  2. Penicillin-V
  • EXTENDED SPECTRUM 
  1. Carbencillin 
  2. Ticarcillin 
  3. Piperacillin
  4. Mezlocillin 
  • RESISTANCE TO ENZYME:
  • RESISTANCE TO β-LACTAMASE 
  1. Methicillin 
  2. Nafcillin 
  3. Oxacillin 
  4. Cloxacillin 
  5. Dicloxacillin 
  • NON- RESISTANCE TO β-LACTAMASE 
  1. Penicillin-G 
  2. Penicillin-V 
  3. Ampicillin 
  4. Amoxycillin 
  5. Carbencillin 
  • RESISTANCE TO ACIDS:
  1. ACID STABLE 
  2. Penicillin-V 
  3. Ampicillin 
  4. Amoxycillin 
  5. Oxacillin 
  6. Cloxacillin 
  7. Dicloxacillin 
  • ACID UNSTABLE 
  1. Penicillin-G 
  2. Methicillin 
  3. Nafcillin 
  4. Carbencillin 
  5. Piperacillin 
  6. Ticarcillin
USES:
  • Streptococcal Infections: 
  1. Pharyngitis, 
  2. Otitis Media, 
  3. Scarlet Fever 
  4. Rheumatic Fever (1.2 MU every 4 weeks of benzathine penicillin)
  5. Subacute Bacterial Endocarditis 
  6. Treatment of spreading streptococcal cellulitis
Pneumococcal Infections: 
  • Lobar Pneumonia
Meningococcal Infections: 
  • Meningitis 
  1. Gonococcal Infections: Syphilis(2.4 MU single i.m. of benzyl penicillin )
  2. Ophthalmia Neonatorum 
  • Treatment for clostridial myonecrosis 
  1. Leptospirosis:
  2. Presence of fever, jaundice and renal failure in a sewage worker (contact with rat urine) suggests a diagnosis of Wen syndrome or Icterohemorrhageic fever caused by leptospirae. Penicillin G (intravenously) is the recommended agent.
  • Diphtheria
  • Tetanus 
  • Anthrax 
  • Quinsy 
  • Treatment of contaminated wound in Gas Gangrene 
  • Drug of choice for Treponema Pallidum
  • Actinomycosis:for thoracic actinomycosis
  • Antipseudomonal penicillins include the carboxypenicillin and the ureidopenicillins.
  • Enterococcus faecalis: when isolated in the blood, requires the synergistic activity of penicillin plus an aminoglycoside for appropriate therapy
  • Rat bite fever 
  • Prophylaxis 
  1. Rheumatic Fever 
  2. Bacterial Endocarditis
  3. Agranulocytosis
ADVERSE EFFECT:
  • Hypersensitivity- 
  1. rash, itching, urticaria, fever 
  2. wheezing, angioneurotic edema, serum sickness, exfoliative dermatitis (less common)
  3. Anaphylaxis (rare, but fatal)
  • Superinfections 
  1. Bowel, respiratory and cutaneous microflora can undergo changes
  2. Jarisch- Herxheimer Reaction
  • Local irritation 
  1. Pain at injection site 
  2. Thrombophlebitis 
  • Neurotoxicity
  1. Mental confusion, muscular twitching, convulsions, coma
  2. Bleeding 
  3. Due to interference of platelet function 
  • Intrathecal PnG injections (not recommended)
  1. Arachnoiditis, degenerative changes in spinal cord 
  2. Accidental IV procaine penicillin injection 
  3. CNS stimulation, hallucinations, convulsions
Exam Question
  • Treatment of S. aureus infection with penicillin is often complicated by theProduction of penicillinase by S. aureus
  • Carbencillin is NON- RESISTANCE TO β-LACTAMASE
  • Syphilis, Anthrax and Bacterial meningitis are therapeutic uses of penicillin G
  • Antipseudomonal penicillins include the carboxypenicillin and the ureidopenicillins.
  • Penicillin Binding Proteins (PBPs) are essential for cell wall synthesis
  • Penicillin Binding Proteins (PBPs) act as carboxypeptidases and traspeptidases
  • Alteration in PBP's is the primary bases of resistance in MRSA
  • β- Lactamase production is the most common mechanism of resistance to Penicillin 
  • Alteration in permeability / penetration of antibiotic causes resistance only in Gram negative bacteria
  • β-Lactamase production causes resistance in both Gram positive and Gram negative bacteria
  • Penicillin would be LEAST effective in treating Mycoplasma pneumonia
  • Enterococcus faecalis when isolated in the blood, requires the synergistic activity of penicillin plus an aminoglycoside for appropriate therapy
  • Plant penicillin is Endrin
  • Penicillins inhibits cell wall synthesis 
  • Methicillin is Acid Labile penicillin
  • Penicillinase resistant penicillin Methicillin 
  • Dosage of benzyl penicillin in treatment of primary syphlis is 2.4 MU single i.m.
  • Treatment for clostridial myonecrosis is Penicillins 
  • Penicillin is Drug of choice for Treponema Pallidum
  • Penicillin is Drug of choicefor thoracic actinomycosis
  • Penicillin in high doses can cause convulsions
  • The clinical presentation of fever, altered sensorium and purpuric rashes, is highly suggestive of meningiococcal meningitis is treated with Penicillin 
  • TOC for penicillin resistant gonorrhoea Ceftriaxone
  • Presence of fever, jaundice and renal failure in a sewage worker (contact with rat urine) suggests a diagnosis of Wen syndrome or Icterohemorrhageic fever caused by 
  • leptospirae.Penicillin G (intravenously) is the recommended agent.
  • Treatment of spreading streptococcal cellulitis is Penicillin 
  • Treatment of contaminated wound in Gas Gangrene is Penicillin 
  • Rapidly spreading infection of the external auditory canal with involvement of the bone and presence of granulation tissue point towards malignant otitis externa treated with Penicillin 
  • Penicillin is used in treatment of quinsy 
  • Piperacillin is an anti-pseudomonal drug of penicillin class
  • Dose and duration of benzathine penicillin for prophylaxis of rheumatic fever is 1.2 MU every 4 weeks
Don't Forget to Solve all the previous Year Question asked on PENICILLIN