6b - Cephalosporins Flashcards
1
Q
Cephalosporins
A
- Part of beta-lactam family and still have side chains
- Spelling: old ones “ph”, new ones “f”
- Various generations
o Early=older ones are more NARROW SPECTRUM or can’t administer by certain routes of administration
2
Q
What are the need to know cephalosporins in Vet med?
A
- Cephalexin
- Ceftiofur
- Cefovecin (Convenia injectable solution)
- Cefpodoxime (Simplicef tablets)
- Cephapirin (dry and lacting cows)
- *Cefazolin (NOT A VET PRODUCT)
3
Q
Cephalexin
A
- Only ORAL products
- Indicated for canine superficial pyoderma caused by susceptible strains of S. pseudointermedius
4
Q
Ceftiofur
A
- 3 salt forms
o Sodium (Excenel): cattle, horses, pigs, sheep and dogs (not labeled for IV, but can go IV), SHORT TERM
o HCl: milky, long acting, once a day, cattle and pigs
o Excede: crystalline free acid, very LONG acting, slow release, cattle, horses, pigs
5
Q
Convenia for dogs
A
- *injectable, long acting
o Not first choice for routine infections
o Works well when poor owner compliance - Skin infections
- Urinary tract infections
6
Q
Convenia for cats
A
- *injectable, long acting
- infections
7
Q
Cefazolin
A
- Human sterile injectable formulation
- Once mixed: refrigerate, but still don’t last long (use within 24hrs)
- *used perioperatively and IV in clinic
o Need to give it at the RIGHT time=use it immediately before you cut
o Want effective plasma concentrations when you are actually doing the surgery (NOT long acting ones)
o Only use for as long as you need (short=1 dose is likely fine)
8
Q
Antimicrobials (potassium Pen G and cefazolin) and orthopedic surgery
A
- Saline: slightly higher risk of infection
- Slightly lower in antimicrobial group
o Didn’t make a difference between potassium Pen G vs. cefazolin
9
Q
Compounded Ceftiofur sodium biobullets
A
- Big deal in US and Canada (BANED BY FDA in US)
- *BULLSHIT
o Shooting animals (NOT good animal welfare): if sick enough you could probably get them
o Dosing: 500mg for a cow=shooting it 5 times (100mg)
o PK? No one knows, depends where they got shot and the power of the gun, injection site lesions and drug residues?
10
Q
Cephalosporins: mechanism of action (same as penicillin)
A
- Act by disrupting synthesis of bacterial cell wall
- Inhibit the penicillin-binding proteins (‘beta-lactam binding proteins’)
- Interferes with cell wall peptidoglycan synthesis
11
Q
What are the general advantages of cephalosporins over some penicillins?
A
- Stable against SOME beta-lactamase enzymes
- Good affinity for target proteins
- Good ability to penetrate bacterial cell wall: including Gram +
12
Q
Emergence of resistance to cephalosporins
A
- Different beta-lactamase enzymes
o Extended-spectrum beta-lactamase enzymes (ESBL)
o AmpC cephalosporinases
o Metallo-beta-lactamase enzymes - EXAM:Modify by PBPs (mecA gene, others): methicillin resistant
- Reduce cellular concentrations
o Decrease bacterial cell wall permeability
o Induction of efflux pumps
13
Q
What are the bacteria typically susceptible to cephalosporins?
A
- Gram +
o Strep
o Stap. Aureus and pseudintermedius
o Many gram + (does NOT mean it is more susceptible than penicillins) - Gram –
o Many enterbacteriaciae (Histophilius, Mannheimia, Pasteurella) - Most anaerobes
14
Q
What are the bacteria typically RESISTANT to cephalosporins?
A
- Gram +
o Methicillin resistant
o **enterococcus: INTRINSICALLY resistant to cephalosporins - Gram –
o Many enteric pathogens with ESBL activity
o R. equi
o Pseudomonas
o Mycobacteria - Anaerobes (except cefoxitin)
15
Q
Cephalosporins: PK oral absorption
A
- generally good
- Ex. Simplicef: Cefpodoxime proxetil=prodrug
o De-esterified in GI tract
o Cefpodoxime absorbed - give cephalexin with food: minimize adverse events and slightly better bioavailability
