antibioticsbooks

78 PART 2 Antibacterial Drugs
association with Clostridium difficile–associated
diarrhea. Cefpodoxime has the MTT side chain
that can inhibit vitamin K production (see section
on second-generation cephalosporins for details).
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Important Facts
• Ceftazidime is the exception to the spectrum
of activity rule for third-generation agents.
Unlike the others, it is antipseudomonal and
lacks clinically useful activity against Grampositive
organisms.
• Ceftriaxone, cefotaxime, and ceftazidime cross
the blood–brain barrier effectively and are
useful for the treatment of CNS infections.
However, their differences in activity lead clinicians
to use them for different types of infections.
Ceftazidime would be a poor choice for
community-acquired meningitis, in which
Streptococcus pneumoniae predominates.
• Third-generation cephalosporins are notorious
for inducing resistance among GNRs. Though
they can be useful in nosocomial infections, too
much broad-spectrum utilization can result in
harder-to-treat organisms.
• A one-time dose of ceftriaxone 125 mg IM has
been a drug-of-choice for gonorrhea for many
years, but the dose was recently increased
to 250 mg IM due to increasing resistance.
Patients treated for gonorrhea should receive
empiric therapy for chlamydia as well, which
ceftriaxone does not work against.
• Ceftriaxone has the characteristic of having
dual modes of elimination via both renal and