Page 909 - Basic _ Clinical Pharmacology ( PDFDrive )

C H A P T E R

Miscellaneous 50

Antimicrobial Agents;

Disinfectants, Antiseptics,

& Sterilants

Camille E. Beauduy, PharmD, &
*
Lisa G. Winston, MD

C ASE STUD Y

A 56-year-old man is admitted to the intensive care unit of clinically stable. Clostridium difficile infection is confirmed
a hospital for treatment of community-acquired pneumonia. by stool testing. What is an acceptable treatment for the
He receives ceftriaxone and azithromycin upon admission, patient’s diarrhea? The patient is transferred to a single-bed
rapidly improves, and is transferred to a semiprivate ward room. The housekeeping staff asks what product should be
room. On day 7 of his hospitalization, he develops copi- used to clean the patient’s old room.
ous diarrhea with eight bowel movements but is otherwise

■ METRONIDAZOLE, results in products that accumulate in and are toxic to anaerobic
FIDAXOMYCIN, RIFAXIMIN, cells. The metabolites of metronidazole are taken up into bacterial
DNA, forming unstable molecules. This action occurs only when
MUPIROCIN, POLYMYXINS, & metronidazole is partially reduced, and, because this reduction
URINARY ANTISEPTICS usually happens only in anaerobic cells, it has relatively little effect
on human cells or aerobic bacteria.
Metronidazole is well absorbed after oral administration,
METRONIDAZOLE is widely distributed in tissues, and reaches serum levels of
4–6 mcg/mL after a 250-mg oral dose. It can also be given
Metronidazole is a nitroimidazole antiprotozoal drug (see intravenously. The drug penetrates well into the cerebrospinal
Chapter 52) that also has potent antibacterial activity against fluid and brain, reaching levels similar to those in serum. Met-
anaerobes, including Bacteroides and Clostridium species. Metro- ronidazole is metabolized in the liver and may accumulate in
nidazole is selectively absorbed by anaerobic bacteria and sensitive hepatic insufficiency.
protozoa. Once taken up by anaerobes, it is nonenzymatically Metronidazole is indicated for treatment of anaerobic or mixed
reduced by reacting with reduced ferredoxin. This reduction
intra-abdominal infections (in combination with other agents
with activity against aerobic organisms), vaginitis (trichomonas
* The authors thank Henry F. Chambers, MD and Daniel H. Deck, infection, bacterial vaginosis), Clostridium difficile infection, and
PharmD, for their contributions to previous editions of this chapter. brain abscess. The typical dosage is 500 mg three times daily orally
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