Antibiotics Flashcards
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.
Which generation of cephalosporins is considered the “big-gun” to use?
Fourth generation
Name three first generation cephalosporins.
- Cephalexin
- Cefazolin
- Cephapirin
What is an example of a second generation cephalosporin?
Cefoxitin
Ceftiofur, Cefpodoxime, and Cefovecin are examples of what generation of cephalosporin?
Third Generation
Name one drug that is a fourth generation cephalosporin.
Cefepime
What is the MOA of Cephalosporins?
Same as 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 are Cephalosporins used for?
- Great against Gram +
- Better than Penicillins against Gram -
- Variable against anaerobes
- Slightly more broad spectrum than Penicillins
T/F: Cephalosporins are bactericidal and time-dependent.
True
T/F: Cephalosporins have lower resistance than Penicillins.
False. They have the same amount of resistance.
Cephalosporins are less susceptible than Penicillins to B-lactamases. The B-lactamases that impact them are referred to as what?
Cephalosporinases
Are cephalosporins polar and lipid soluble?
They are polar and the are poorly lipid soluble.
T/F: Cephalosporins have great protein binding ability and are poor at metabolization and renal excretion.
False.
Cephalosporins have variable protein binding ability and variable metabolism and renal excretion.
What are the adverse effects of Cephalosporins? (5)
- Hypersensitivity reactions
- Acute anaphylaxis or local allergic reactions.
- Possible IMHA
- Alterations in intestinal microflora lead to clostridial overgrowth in guinea pigs, hamsters, and rabbits. Can also cause dysbiosis, GI stasis and endotoxemia.
- Cross hypersensitivity is variable.
This class of drugs leads to clostridial overgrowth in the GI tact of small rodents (rabbits, hamsters, and guinea pigs.)
Cephalosporins
What drug is commonly used in small animals as first-line oral antibiotics and is a first generation cephalosporin?
Cephalexin/Cefadroxil
What is Cefazolin used for?
First generation cephalosporin that is used prophylactically during surgery for small animals and horses. It should only be given parenterally.
Which cephalosporin is used to treat mastitis in cattle (intramammary infusion)?
Cephapirin
What is Cefoxitin and what is is used for?
Cephoxitin is a second generation cephalosporin that is given IV to treat serious infections.
What is the main use for Ceftiofur?
Used in large animals for foot rot, respiratory disease and mastitis.
What are some uses for Cefovecin?
Cefovecin is commonly used in small animals. It is injectable and highly protein bound - unusually long duration of activity (dosed q7-14 days.) It is labeled for pyoderma due to Staph and Strep in dogs and Pasteurella in cats.
What are some uses for Cefpodoxime?
Cefpodoxime is used in small animals for Gram - infections. It comes as a pro-drug ester that is converted to an active antibiotic after GI absorption.
Name two Carbapenem and Monobactam drugs.
Imipenem and Meropenem
What are the uses for Carbapenem and Monobactam drugs?
They are able to kill Gram - and Gram + (not MRStaph). They are resistant to most B-lactamases.
T/F: Imipenem and Meropenem are used as “Big Guns” for some extended spectrum B-lactamase (ESBL) producing E. coli.
True
T/F: Carbapenems and Monobactams are bactericidal and time-dependent.
True
What are the adverse effects of Imipenem (Carbapenem)?
- CNS effects - tremors and seizures!
- Hypersensitivity reactions
- Vomiting, anorexia, diarrhea
- Local reactions (hair loss at injection site and thrombophlebitis.)
How do Carbapenems acquire resistance?
Through chromosomal mediated or plasmid mediated secretion of B-lactamases.
What is the MOA for Glycopeptides (Vancomycin)?
Vancomycin binds to the peptidoglycan ‘ends’ thus preventing both formation of the long peptidoglycan polymers needed to form the cell wall and impairing cross-linking of the polymers that do form. Leads to structural instability and susceptibility to osmotic pressure.
Which drug class is Vancomycin in?
Glycopeptides