antibioticsbooks

50 PART 2 Antibacterial Drugs
to be lower between different types of betalactams
than previously thought.
• Seizures can result from very high doses of any
beta-lactam. Some are more notorious for this
adverse effect than others. Accumulation to
toxic levels can occur when the dose of a betalactam
is not properly adjusted for a patient’s
renal function. Did you check your patient’s
renal function?
• All beta-lactams share a mechanism of
action—inhibition of transpeptidases (that is,
penicillin-binding proteins) in the bacterial cell
wall. Thus, giving two beta-lactams in combination
for the same infection is generally not
useful. There are a few exceptions to this rule,
but not many.
• All beta-lactams lack activity against atypical
organisms such as Mycoplasma pneumoniae
and Chlamydophila pneumoniae. Add another
drug to your regimen if you are concerned about
these bugs, as in cases of community-acquired
pneumonia.
• Nearly all currently available beta-lactams
lack activity against MRSA. Add vancomycin
or another agent if this bug is suspected.
Among the available beta-lactams, only the
fifth generation cephalosporin ceftaroline has
anti-MRSA activity.
Once you know the similarities among beta- lactams,
it is easier to learn the differences among them.