Beta Lactam but not Penicillin Flashcards
(27 cards)
Relation between beta-lactamases and cephalosporins
- more stable than pencillin with dealing with beta-lactamases
- but strains of E coli and Klebsiella have beta-lactamses that hydrolyze cephalosporins - CONCERN
relation between cephalosporins and L monocytogenes?
- cephalosporins don’t work well against them
- ceftaroline has some activity against enterococci
Nucleus of cephalosporins
7-aminocephalosporanic acid
R groups of Cephalosporins
various R1 and R2 groups have allowed for a broad range of potent compounds
First generation cephalosporins
- cefazolin
- cephalexin
above are only compounds in US - cefadroxil
- cephalothin
- cephapirin
- cephradine
First-gen cephalosporins against what Gram?
positive
What bacteria are sensitive vs not as to first gen cephalosporins
- sensitive
- E coli (but the whole issue with beta-lactamases)
- K pneumonia
- Proteus mirabilis
–anaerobic cocci - peptococci
- peptostreptococci
*not as
- P aeruginosa
- indole-positive Proteus species
- Enterobacter sp
- S marcescens
- Citrobacter sp
- Acinetobacter sp
– anaerobic cocci
- Bacteroides fragilis
what is the oral first gen cephalosporin in US
Cephalexin
Doses of Cephalexin and how
- oral
- 500mg - peak serum levels: 15-20mcg/ml
- four times daily
how excretion
glomerular filtration and tubular secretion
probenecid
drug blocks tubular secretion
what is first gen parenteral (IV) cephalosporin in US
Cefazolin
doses of Cefazolin and why and excretion
- parenteral (IV)
- 1g - peak serum level: 185 mcg/mL
- 0.5 to 2g every 8 hours
- administered intramuscularly
- excretion by kidney
Oral drugs like cefazolin used to treat…
- UTI
-staph or strep infections
– including cellulitis and and soft tissue abscess - not for serious systemic infections
- used for surgical prophylaxis
- used for E coli or K pneumonia only if susceptible
- cefazolin can be used sometimes for serious staphylococcal infections like bacteremia
Cefazolin penetraes in body
most tissues like CNS but shouldn’t be used to treat meningitis
Second gen- Cephalosporins
- cefaclor
- cefamandole
- cefonicid
- cefuroxime
- cefprozil
- loracarbef
- ceforanide
*structurally similar cephamycin + activity against anaerobes
- cefoxitin
- cefmetazole
- cefotetan
second gen works against?
- all things first gen affects
- extended gram-negative coverage
like Klebsiellae
bacteria sensitive and not as with second gen
- Cefamandole, cefuroxime, cefonicid, ceforanide and cefaclor active against H influenzae but not serratia or B fragillis
- cefoxitin cefmetazole and cefotetan active against B fragilis and some serratia strains but not as much against H influenzae
- none against enterococci or P aeruginosa
- maybe in vivo effect against enterobacter species but they som times have a beta lactamase that hydrolyzes these
Dosage for second gen cephalosporins
oral
- cefaclor
- cefuroxime axetil
- cefprozil
- loracarbef
dosage
- 10-15 mg/kg/d two to four doses
* for children*”
– 20-40 mg/kg/d up to 1g/d if given multiple doses
Cefaclor and beta lactamase
Cefaclor more suspectible to beta lactamase hydrolysis compared to other agents
second gen and pneumonia
- cefuroxime axetil - works against pencillin-resistant pneumococci
- others don’t really work
Cephalosporins and allergy
- prone to same hypersensitivity reaction as penicillin
- but bc of diff nucleus some with allergy to penicillin may not have same reaction to cephalosporin
- but patients that get anaphylaxis to penicillin shouldn’t risk it with this
Methylthiiotetrazeole group in cephalosporins can cause
- hypoprothrombinemia
- bleeding disorders
- can be treated with admin of vit K1, 10mg twice weekly
- also causes severe disulfiram-like reactions
- bc of his alc/alc containing meds should be avoided
Monobactams
- activity only to aerobic gram-negative
- given to those allergic to penicillin
- only one in US - Aztreonam
- IV
