Penicillins And Cephalosporins Flashcards
How is penicillin synthesized❓
1. Produced by: Fungi Ascomycetes Actinomycetes bacteria
OR
Synthesized from:
Valine
Cysteine
Penicillins are bactericidal but can only act on dividing cells
True or false
True
What is the mechanism by which penicillins work❓
Their beta-lactam ring inhibits the formation of peptidoglycan crosslinks in bacterial cell walls (esp gram +ve)
How well are penicillins distributed in the body❓
Poorly lipid soluble
🚫Cross BBB, except inflamed (meningitis)
How is penicillin excreted❓
Actively, through the kidney
*Dose should be reduced in renal failure
What happens in penicillin resistance❓
Give examples of bacteria that are penicillin resistance
1.
Production of beta-lactamase
⬇️
Destruction of beta-lactam ring
- Staphylococcus aureus
Haemophilus influenzae
Neisseria gonorrhoea
What are the properties of Benzylpenicillin (Penicillin G)❓
How is it administered❓
Which bacterial organisms would it get rid of❓
- Acid labile
Beta-lactamase sensitive - Only parenterally
3. Streptococcus pyogenes S. pneumonia Neisseria meningitis Neisseria gonorrhoeae Treponemes Listeria Actinomycetes Clostridia
What are the properties of Phenoxymethylpenicillin (Penicillin V)❓
How is it administered❓
Which bacterial organisms would it get rid of❓
1.
Acid stable
Used to treat minor infections
2.
Given orally
3. Streptococcus pyogenes S. pneumonia Neisseria meningitis Neisseria gonorrhoeae Treponemes Listeria Actinomycetes Clostridia
What are the properties of Ampicillin❓
How is it administered❓
Which bacterial organisms would it get rid of❓
1. Acid stable Beta-lactamase sensitive ⬇️active than Penicillin G Wider spectrum than Penicillin G
2.
Orally
Parenterally
3. S. faecalis Haemophilus influenzae E. coli Klebsiella Proteus
Streptococcus pyogenes S. pneumonia Neisseria meningitis Neisseria gonorrhoeae Treponemes Listeria Actinomycetes Clostridia
Amoxycillin is better absorbed orally than the rest of the penicillins
True or false
True
What would you combine with amoxycillin for a better antibacterial effect❓
Why❓
Clavulanic acid + amoxycillin
The beta-lactam in clavulanic acid binds strongly to beta-lactamase and blocks off it’s action
It extends the spectrum of amoxycillin
What are the differences between ampicillin and benzylpenicillin❓
Ampicillin is less active against gram +ve bacteria
Ampicillin has a wider spectrum
Ampicillin is acid stable
Benzylpenicillin is acid labile
Ampicillin can be given orally or parenterally
Benzylpenicillin can only be given parenterally
What are the differences between phenoxymethylpenicillin and benzylpenicillin❓
Phenoxymethylpenicillin is acid stable
Benzylpenicillin is acid labile
Phenoxymethylpenicillin is given orally
Benzylpenicillin is given parentally
Phenoxymethylpenicillin is used in treating minor infections
What are the properties of Flucloxacillin❓
How is it administered❓
Which bacterial organisms would it get rid of❓
- Acid stable
Beta-lactamase resistant - Orally
Parenterally
3. Staphylococcus aureus (narrow spectrum)
What are the properties of Azlocillin❓
How is it administered❓
Which bacterial organisms would it get rid of❓
- Acid labile
Beta-lactamase sensitive
Broad spectrum - Parenterally
IV in life-threatening infections w an aminoglycoside - Pseudomonas aeruginosa
Proteus
What are the acid labile penicillins you know❓
Benzylpenicillin
Azlocillin
What are some side effects you might observe in patients being treated with penicillins❓
Allergy (0.7-1.0% pts)
Nephritis
Acute renal failure
Super infections
GI upsets when given orally
What percentage of patients with penicillin allergies will also be allergic to cephalosporins❓
10-20%
What drug interactions are typical of ampicillins/broad spectrum antibiotics❓
⬇️effectiveness of oral contraceptives by ⬇️enterohepatic circulation
List some penicillinase-resistant penicillins
Oxacillin
Cloxacillin
Dicloxacillin
Methicillin
*resistant against staphylococcus penicillinase
What are the properties of cephalosporins❓
Bacteriocidal (🚫beta-lactam ring)
Broad spectrum
Used on sensitive microorganisms
First generation cephalosporins are used in treating ❓
- Most active against gram +ve cocci bacterial infections
- Alternative for staph and strep infections
- Used in treating UTIs
Second generation cephalosporins…
- Is used in treating ❓
- Active against gram -ve enterobacteriaceae ie E. coli, Klebsiella and Proteus sps
- May also be active against H. influenza and N. meningitis
- Cefaclor
Cefuroxime
Cefprozil
Cefmetazole
Third generation cephalosporins…
- Is used in treating ❓
- Give some examples
- Most active against gram -ve rods
Less active against gram +ve bacteria - Cefixime
IV:
Cefotaxime
Ceftriaxone
Ceftazidine
