The most common use for vancomycin is in invasive Gram positive infections
You need to consider
Vancomycin has bad oral bioavailability so it’s almost never used as a pill
Occasionally it is orally to supplement C. diff infections (because that’s going on in the GI tract)
Volume of distribution: IV serum 0.4-1 L / kg
Normally vancomycin doesn’t cross the blood brain barrier very well, but in the setting of meningitis the inflamed meninges increases permeability
Redman syndrome: A histamine-like flushing during or immediately after dose. Occurs mostly on the face and neck. This is NOT life threatening
Treatment: anti-histamine, pause infusion, then restart at a slower rate
If the reaction is severe, stop the infusion, give antihistamines, wait until symptoms resolve before restarting. When you restart, give the infusion reaaaalllllly slooooooowly (over more than 4 hours)
This is where vancomycin can get tricky, because you are aiming for a target trough (between dose) serum concentrations.
Generally the target is 10 mcg/ml, but this may need to be higher for treating MRSA or osteomyelitis
Trough concentrations should be measured 30 minutes before the 4th dose any time a course of vanco is started or the dose is changed
Monitor creatinine at least once a week (remember that whole nephrotoxicity bit)
Starting dose should be 15-20 mg/kg (based on actualnot ideal body weight) every 12 hours. This usually works out to 1-2 g IV Q12H. If the kidneys are not working well, reduce the dose.
UpToDate.com “Vancomycin: Parenteral dosing, monitoring, and adverse effects in adults”
Cephalosporins work much like penicillins, inhibiting peptidoglycan cell wall synthesis in bacteria (remember those sites of action and mechanisms?)
Of course the issue is that they just keep making new cephalosporins and each generation is a little bit different in terms of its spectrum and whether it’s better at fighting Gram positive or Gram negative bacteria. Generally the newer the generation, the more broad spectrum and less Gram positive coverage. To add another layer to the confusion, there are separate oral and IV cephalosporins for each generation and all of the cephalosporins are usually recognizable by starting with “CEF-” or “KEF-” (except for Suprax and Ancef, who ever came up with those brand names didn’t get the memo)
Antibiotics are the current bane of my existence. Most medical conditions there are a couple of different classes of drugs, but overall things are straight forward. Not so with antibiotics, not only are there a bunch of different classes, they all have different indications!
This is part 1 of my antibiotics doodles. This one outlines where the different commonly used antibiotics act on the cell, the class they belong to, and whether they are used mostly for Gram + (Staph, Strep), Gram -, or a little bit of both. Keep in mind that the bacterial cell in the drawing is a Gram + coccus.
Part 2 will go into a little more detail about the different classes.