Let’s talk about cephalosporins.
Now, we divide the cephalosporins into first, second, third, and fourth generation
and in general the first generation are more gram-positive active and the fourth generation
tend to be more gram negative and there's a spectrum in between.
Now cefazolin and cefalexin are first generation agents, they're gram positive active
and they're very useful in surgical infections because a lot of surgical infections
come from staph aureus and other skin surface agents.
There's minimal effectiveness of these drugs against gram-negative bacteria.
The second generations, the prototypical agent is cefotetan.
They are much more active against gram-negative
and what's interesting is they’ll often work again -
also work against haemophilus enfluenzae
which is one of the major causes of pneumonia in many of our patients.
Other agents are in this group include cefuroxime.
Now if you notice very carefully I've underlined two of the agents,
I've underlined cefotetan and I underlined cefuroxime, these are the drugs you need to know.
Cefuroxime is commonly used in pneumonia treatment.
The third generation agents are more gram-negative active.
Once again I've underlined two of them: cefotaxime and ceftriaxone.
Cefotaxime is kind of our go to drug - it's a very, very, good gram-negative agent.
It will often work against organisms that are resistant to penicillin.
We only use these drugs in serious infections and in general they are only available in intravenous form.
Let's move on to the fourth generation cephalosporins. Cefepime is your prototypical agent
and notice that I've underlined it because it's a drug that I want you to know.
These are more resistant to the beta lactamases and they are also active against the enterobacter, haemophilus, and neisseria.
Ceftaroline has activity in infections caused by methicillin resistant staphylococci
so we sometimes use it in that case.
Now, remember that the cephalosporins are less likely to cause rashes
and allergic reactions when compared to the penicillins.
Penicillins seems to be associated quite heavily with rash and other allergic activity.
There are two new fifth generation cephalosporins called ceftaroline and ceftobiprole.
Please note that ceftaroline used to be called an unclassified cephalosporin.
I mentioned it in the fourth generation segment. These drugs are not yet available in all countries.
The definition of the fifth generation is not agreed upon by all countries, but in the USA it is commonly accepted.
These drugs are similar to the third generation cephalosporins
with respect to a broad spectrum activity against gram-negative bacteria.
They are as good as the third generation cephalosporins in this regard.
They have activity against gram-postive bacteria including MRSA as good as vancomycin or aztreonam.
Ceftaroline is approved for use in community-acquired pneumonia and skin and skin structure infections.
Ceftobiprole binds to PBP2b in MRSA.
It is approved for use in hospital-acquired pneumonia and community-acquired pneumonia.
It is an intravenous drug only.
Other betalactam drugs include aztreonam.
Now, this is not commonly used in clinical practice, and you don’t hear much about it.
It is a drug that you need to know. Why? Because it's resistant to beta lactamases which is huge.
There is no activity against gram-positive drugs with this particular agent.
It binds the penicillin binding protein type 3 or PBP3.
The half-life is prolonged in renal failure so you can adjust your medication accordingly.
Adverse events include GI upset, vertigo, headache; but the nice thing is,
is once again, it's resistant to beta lactamases and there is no cross-allergy with the penicillins.