C.9. Cephalosporins

Question 1

What is the mechanism of cephalosporins?

Answer 1

Same as Penicilins and same resistance and Bacteriocidic!

Question 2

What rule applies to cephalosporins?

Answer 2

Gram positive acitivity diminishes while gram negativity increases as one progresses from first to third generation cephalosporins and so does tissue penetration.

Question 3

First generation Drugs!

Parental and oral!

Answer 3

Parental: Cephlotin and Cefazolin
Oral: cephalexin, cephradine and cephadroxil

USed for?
Gram positive cocci (not MRSA), E coli, klebsiella, pneumonia, and some proteus species

Clinical use:
Mild community aquired RTI
Uncomplicated UTI
Surgical prophylaxis
Staphyloccocal endocarditis

Question 4

Second generation cephalosporins

Answer 4

Parental: Cefoxitin, cefotaten, cefuroxime
Oral: Cefaclor, cefuroxime axetil, cefprozil, loracarbef

Used for:
Staphylocci, non-enterococcal streptoscocci Gram negative rods, some of the enterobactaeriae,
Cefoxitin: B. Fragilis
Cefuroxime: H. influenza and pneumococci

Used for: mild community acquired and nosocomial infection.
lower respiratory infections, mixed aerobic and anerbic infections of the pertinoeum and pelvis.

No drug enters the CNS except cefuroxime.

Question 5

Third generation

Answer 5

Parental: Cefotaxime, ceftriaxone, cefoperazone, ceftazidime, cetizoxime
Oral: Cefixime, ceftibuten

Spectrum:
Gram negative Bacteria: (Eneterobacteriacea).
Gram positive and gram negative cocci plus many gram negative rods (pseudomonas- ceftriaxone).

Used for biliary infections, menigitis, abdominal infections, nosocomial infections and more.

Most can enter the CNS

Question 6

4th generation

Answer 6

Cefepime (oral and parental):
Even wider spectrum
Resistant to most beta lactamase
Enter CNS

GOod against MRSA/E and broad gram negative acitivity

Indication: Severe community aquired and nosocomial infections

Question 7

Kinetics of cephalosporins:

Answer 7

renal clearane similar to penicilins with active tubular secretions blocked by probenecid
dose modification in renal dysfunction
cetraixone is largely eliminated in the bile

Question 8

side effects:

Answer 8

SOmewhat similar to penicilins
hypersensitivity reactions, 
neuropenia
anemia
bleeding problems (due to hypoprothrombinaemiae)- use vitamin K to reverse.
dysbacteriosis