C/8. Penicillins

Question 1

Penicillins

MOA

Answer 1

Inhibit cell wall synthesis
Beta-lactam antibiotics bind specific PBP’s in the bacterial wall and inhibit assembly of the peptidoglycan chains, resulting bacterial cell death (bactericidal effect)

Question 2

Penicillin

Pharmacokinetic/dynamic properties

Answer 2

Orally active(resistant to gastric acid inactivation)
Parenteral formulation (penicillin G, ampicillin, piperacillin, tigarcillin)
Excreted unchanged in the urine
Biliary clearance (nafcillin, oxacillin), enterohepatic cycling (ampicillin)
Short half life, requires multiple dosing 3-4 times daily, or continuous IV infusion
Cross BBB only when meninges are inflamed
Synergistic effect with aminoglycosides
Enhanced if used in combination with beta-lactamase inhibitors (Clavularic acid, sulbactam, tazobactam)

Question 3

Penicillin

Answer 3

Penicillin G(IV)
Penicilling V(Oral)

Narrow-spectrum
Beta-lactamase sensitive

Streptococcal infections(pharyngitis, rheumatic fever, endocarditis)
Gram positive rods (Actinomyces israelii)
Clostridium perfringens
Entercocci
Prophylaxis against group B strp. (S. Agalactiae)
Neisseria meningitis

Hypersensitivity/allergic reaction; fever, urticaria, pruritus, joint swelling, anaphylaxis
Drug induced hemolytic anemia
Intestitial nephritis
Jarisch-Herxheimer reaction

Benzathine penicillin G
Syphilis - IM depot injection (slow release)

Question 4

Oxacillin

Answer 4

Very narrow spectrum
Beta-lactamase resistant

Staphylococcal infections (skin and soft tissue infections, endocarditis, osteomyelitis)

Interstitial nephritis
Neutropenia

Question 5

Ampicillin

Ammoxicillin

Answer 5

Broad-spectrum
Beta-lactamase sensitive
Amino-peniciilin

Ampicillin (IV)

against gram - rods
E.coli, enterococci
L. Monocytogen
Anaerobic infection
Otitis media and sinusitis caused by H. Influenza, S. Pneumoniae, M. Catarrhalis
Pneumonia caused by S. Pneumoniae and H. Influenza
Streptococcal pharyngitis
H. Pylori eradication
Borellia burgdoferi
Prophylaxis

Maculopapular skin rash
GI disturbances
Steven-Johnson syndrome

Question 6

Piperacillin

Answer 6

Extended-spectrum
Beta-lactamase sensitive
Ureido-penicillin

Pseuomonas infection
Sepsis

Question 7

Commonly used combination preparations

Answer 7

Amoxicillin/Clavularic acid (Augmentin)
Ampicillin/Sulbactam
Piperacillin/Tazobactam