Antibiotics Flashcards
(134 cards)
What are the four categories of antibiotics?
- Inhibitors of cell wall synthesis
- Inhibitors of cell membranes
- Inhibitors of protein synthesis
- Inhibitors of nucleic acid synthesis
Name three classes of drugs that are cell wall inhibitors.
- B-lactams
- Glycopeptides
- Bacitracin
What are the four categories of drugs under B-lactams?
- Penicillins
- Cephalosporins
- Carbapenems and monobactams
- B-lactamase inhibitors
What is the MOA of Penicillins?
B-lactam ring binds to an enzyme (DD-transpeptidase) that would normally catalyze the cross links between peptidoglycan layers. DD-transpeptidase is also known as Penicillin binding protein.
What is another name for DD-transpeptidase?
Penicillin binding protein
What do Penicillins do?
They can kill Gram +, some Gram - and anaerobes.
They are bactericidal and time-dependant.
What is the resistance of Penicillins?
Bacteria that do not have cell walls lack Penicillin binding protein, therefore they have poor permeability (Gram -) and are not actively dividing. All of these have intrinsic resistance. Acquired resistance is through chromosomal or plasmid mediated secretion of B-lactamases.
T/F: Formulation of Penicillin affects its absorption rate.
True
T/F: Penicillins are weak acids that tend to ionize and stay in the ECF.
True.
High concentration in kidneys, synovial fluid, lungs, skin, and soft tissue. Poor penetration into the eye, prostate, and CNS.
How are Penicillins excreted from the kidney?
Unchanged!
Some have biliary excretion (amoxicillin and ampicillin.)
Renal excretion of Penicillins can be blocked by ______ and other _____ _____ (same for all B-lactams.)
Renal excretion can be blocked by probenecid and other weak acids.
What are some types of Penicillin?
Penicillin G, Amoxicillin, Ampicillin, Cloxacillin, Ticarcillin, Amoxicillin-Clavulanic Acid.
What are some adverse effects of Penicillins? (5)
- Generally a wide safety margin
- Can have hypersensitivity reactions, especially in horses, and cross-hypersensitivity is possible.
- Can have alterations in GI microflora, leading to dysbiosis, GI stasis, and endotoxemia.
- Hyperkalemia/arrhythmia
- CNS excitement/convulsions.
Name three features of Penicillin G.
- Kill Gram + and anaerobic bacteria (narrow spectrum.)
- Susceptible to B-lactamases
- Used more often in large animals.
Name three features of Ampicillin and Amoxicillin.
- Kill more Gram - bacteria but do kill slightly less Gram +.
- Susceptible to B-lactamases
- Used in small animals, equines and cattle mastitis.
Name two features of Cloxacillin.
- B-lactamase resistant!
2. Used to treat bovine mastitis.
Name three features of Ticarcillin.
- “Anti-pseudomonas” drug
- Not frequently used
- Used as a topical for ear infections.
What are B-lactamase Inhibitors?
They are a type of drug that can be combined with B-lactams because they combat B-lactamase.
These drugs are not antibiotics themselves but are combined with a B-lactam (usually Penicillin) and allow them to do their job more effectively.
Name three B-lactamase Inhibitors.
- ** Clavulanic acid **
- Sulbactam
- Tazobactam
How many generations of drugs are Cephalosporins?
Four
What does a first generation cephalosporin do?
- Effective against Gram + bacteria.
- It is less susceptible to B-lactamases than Penicillins.
- It is not effective against Gram - bacteria.
What do second generation cephalosporins do?
They are similar to first generation but have greater efficacy against Gram - bacteria (more broad spectrum.)
What are third generation cephalosporins used for?
- They are more effective against Gram - and anaerobic bacteria.
- They have less Gram + activity (except for Ceftiofur.)
What are fourth generation cephalosporins used for?
- Broad spectrum drug with activity against Gram + cocci, Gram - bacilli, and pseudomonas.
- They are resistant to B-lactamases from Gram -.
- They are the “big-gun” cephalosporin.