Chapter 30

The agents discussed in this chapter include miscellaneous antimicrobials, including those specific for urinary infections, and disinfectants and antiseptics (Figure 30–1). Because physical therapists often treat patients with infections and use equipment that can potentially transfer pathogens, the use of antiseptics and disinfectants discussed in the latter half of the chapter is particularly relevant to rehabilitation practice.

###### Figure 30–1.

These agents are divided into miscellaneous antimicrobials, those specific for urinary infections and disinfectants and antiseptics. Subsequent divisions are based on chemical class or clinical use.

### Metronidazole

#### Chemistry and Pharmacokinetics

Metronidazole is a nitroimidazole drug used primarily in treating infections caused by anaerobic bacteria and protozoa. Metronidazole can be administered orally, intravenously, or by rectal suppository. The drug penetrates readily into almost all tissues, including the cerebrospinal fluid, achieving levels similar to plasma.

#### Mechanism of Action and Clinical Uses

Metronidazole kills amoebae, bacteria, and sensitive protozoans. The drug is readily taken up by anaerobic organisms and cells, where it acts by disrupting DNA and inhibiting nucleic acid synthesis. Metronidazole is the treatment of choice for anaerobic or mixed intra-abdominal infections, pseudomembranous colitis, and brain abscess involving susceptible organisms. Metronidazole may be used in treating anaerobic infections such as might be present in empyema, lung abscess, bone and joint infections, and diabetic foot ulcers. In the treatment of diabetic lower extremity infections in older males, once-daily use of metronidazole combined with another antibiotic has been shown to be as effective as the traditional antibiotic regimen given every 6 hours with significantly less associated cost. Metronidazole is also used to treat infections caused by Clostridium difficile, a gram-positive bacillus that can precipitate pseudomembranous colitis, which is clinically manifested as severe diarrhea (C difficile–associated diarrhea, CDAD). C difficile is one of the most rapidly increasing communicable infections, possibly exceeding methicillin-resistant Staphylococcusaureus (MRSA) and other drug-resistant microorganisms.

Metronidazole has many other uses. As an oral tablet or topical vaginal gel, it effectively treats bacterial vaginosis. As part of a multidrug regimen, metronidazole is commonly used in the eradication of Helicobacter pylori in peptic ulcer disease. As an antiprotozoaldrug, metronidazole is the drug of choice for treating giardiasis (traveler’s diarrhea) and the common sexually transmitted disease trichomoniasis. Metronidazole is also used as a topical antibiotic for the chronic dermatologic condition rosacea.

#### Toxicity

The most common adverse effects include nausea or vomiting, gastrointestinal discomfort, diarrhea, headache, dizziness, dry mouth, and altered taste sensation (especially the perception of a sharp metallic taste). Because metronidazole has a disulfiram-like effect, drinking alcoholic beverages while taking metronidazole can cause stomach pain, nausea, vomiting, headache, and flushing of the face. Patients should be instructed to avoid alcohol (including alcohol-containing cough syrups) while taking this drug and for ...

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