3C. B-Lactams: Cephalosporins

Front 1

How does the distribution of Cephalosporins in the body compare to that of penicillins?

Back 1

Similar - well distribute to most places, but only a few penetrate the CSF.

Front 2

How does the administration of the Cephalosporins compare to that of penicillins?

Back 2

Most cephalosporins require IV administration as opposed to oral.

Front 3

How do the half-lives of the Cephalosporins compare to those of penicillins?

Back 3

Similarly short

Front 4

What is the mechanism of action of the Cephalosporins?

Back 4

Similar to the Penicillins - they both have the B-lactam ring.

Front 5

What is the implication of the fact that the Cephalosporins mechanism is via B-lactam inhibition of transaminases?

Back 5

The same resistance mechanisms apply as for Penicillins.

Front 6

And what are the 3 resistance mechanisms against B-lactam drugs?

Back 6

1. Changes in the PBPs
2. Limitation of access to the PBPs (gram negs)
3. Enzymatic destruction (b-lactamase)

Front 7

What are the 3 generations of cephalosporins?

Back 7

1st: Cefazolin, Cephalexin
2nd: Cefuroxime, Cefaclor, Cefoxitin
3rd: Ceftriaxone, Ceftazidime

Front 8

How can you remember the 2 1st generation cephalosporins?

Back 8

-Cefazolin has a Z which is complete opposite of #1
-Cephalexin is the only one with a ph

Front 9

What is the major difference between the generations in the cephalosporins?

Back 9

Their spectrum of action - generally they become increasingly effective against Gram neg organisms.

Front 10

What is the main method of excretion/metabolism of the cephalosporins?

Back 10

Renal - GFR and tubular secretion (OAT)

Front 11

What are 4 adverse reactions of cephalosporins?

Back 11

HAND
-Hepatocellular damage
-Allergic reactions
-Nausea/vomiting
-Diarrhea/enterocolitis

Front 12

With what other drug allergy do cephalosporins show cross reactivity?

Back 12

Penicillin in 1-20%

Front 13

And how are most of the cephalosporins administered?

Back 13

IV

Front 14

What are 2 cephalosporins that can be given orally?

Back 14

-Cephalexin (1st gen)
-Cefaclor (2nd gen)

Front 15

Listen for specifics of these drugs

Back 15

ok

Front 16

In general what are the early generation cephalosporins most effective against?

Back 16

Gram pos organisms - Staphs and streps even if they're b-lactamase positive.

Front 17

What are the later generation cephalosporins more effective against?

Back 17

Gram negative bugs

Front 18

What cephalosporins are effective in killing Streps?

Back 18

All of them!

Front 19

What are the 2 1st generation cephalosporins to know?

Back 19

Cefazolin
Cephalexin

Front 20

What are 1st generation cephalosporins often used for?

Back 20

Surgical prophylaxis to prevent gram pos skin flora from contaminating the wound site.

Front 21

What is the most commonly used injectable 1st gen cephalosporin by hospitals?

Back 21

Cefazolin

Front 22

Why is Cefazolin the best agent for surgical prophylaxis?

Back 22

Because it has the lowest MIC values against Staph/strep and it has a longer half life than other 1st gen cephalosporins.

Front 23

What are 4 things the 1st generations are NOT effective against?

Back 23

-Listeria
-Enterococcus
-Methicillin resistant Staph
-Meningitis

Front 24

How Cephalexin administered?

Back 24

Orally

Front 25

What type of MIC does Cephalexin have for gram neg bugs like E. coli?

Back 25

Very low

Front 26

Then how can Cephalexin be used for treating UTI's caused by GNB like E. coli?

Back 26

It is dumped very quickly into the urine and very quickly reaches high levels there, effective enough to kill E. coli.

Front 27

What are the 3 2nd generation cephalosporins to know?

Back 27

-Cefaclor
-Cefuroxime
-Cefoxitin

Front 28

Which 2nd generation has the best gram pos activity of them all?

Back 28

Cefaclor

Front 29

Why is cefaclor an attractive drug for treating gram pos infections?

Back 29

It is one of the few cephalosporins given orally (like Cephalexin)

Front 30

What are 2 things that make Cefuroxime famous?

Back 30

-Only 2nd gen drug to penetrate CSF
-Best 2nd generation for Haemophilus

Front 31

What makes Cefuroxime less attractive?

Back 31

It is not the best against enterics

Front 32

If Cefuroxime is so good at penetrating the CSF, why isn't it used for treating meningitis?

Back 32

The 3rd generation agents are superior for this.

Front 33

Which 2nd generation cephalosporin is good for Anaerobes? Which anaerobe specifically?

Back 33

Cefoxitin - B. fragilis!

Front 34

What is the most widely used 3rd generation Cephalosporin?

Back 34

Ceftriaxone

Front 35

4 treatment indications for Ceftriaxone?

Back 35

-Meningitis
-Tx of choice for Gonorrhea
-Lymes disease
-Typhoid fever

Front 36

What are 3 agents that could be meningitis and that Ceftriaxone is effective in treating empirically?

Back 36

-Neisseria meningitidis
-Strep pneumo
-Haemophilus

Front 37

What is the half life of Ceftriaxone?

Back 37

6-9 hours!! almost unheard of for cephalosporins.

Front 38

What 3rd generation is the most active against Pseudomonas aeruginosa?

Back 38

Ceftazidime

Front 39

What is Ceftazidime NOT good for?

Back 39

Gram pos organisms - it is the poorest 3rd generation for them.

Front 40

What is the first side effect of Cephalosporins to remember?

Back 40

Allergic reactions

Front 41

Though there are cross reactions between Penicillins and cephalosporins, will all patients that are allergic to penicillin react to cephs too?

Back 41

no

Front 42

Does the Pre-pen test work for cephalosporins?

Back 42

no; there is no effective skin test to detect allergy to cephalosporins.