From the FDA Drug Label
LOWER RESPIRATORY TRACT INFECTIONS, including pneumonia, empyema, and lung abscess, caused by Bacteroides species including the B fragilis group. Metronidazole (Flagyl) is used for treating pneumonia caused by susceptible anaerobic bacteria, specifically Bacteroides species including the B. fragilis group.
- The drug should be used to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.
- Culture and susceptibility information should be considered when available.
- In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy 1.
From the Research
Metronidazole (Flagyl) should only be used to treat pneumonia when anaerobic bacteria are suspected as the cause, particularly in cases of aspiration pneumonia or lung abscesses, as evidenced by the most recent study 2. The use of metronidazole in pneumonia treatment is limited due to its lack of effectiveness against aerobic bacteria, which are the most common cause of pneumonia. According to the study published in 2011 2, metronidazole may be appropriate in patients with aspiration pneumonia and evidence of a lung abscess, necrotising pneumonia, putrid sputum, or severe periodontal disease.
Key points to consider when deciding to use metronidazole for pneumonia treatment include:
- The patient's risk factors for aspiration, such as impaired consciousness, difficulty swallowing, or recent vomiting
- The presence of anaerobic bacteria, which can be suspected in cases of lung abscesses or necrotizing pneumonia
- The potential for metronidazole to be used in combination with other antibiotics that target different types of bacteria
- The importance of limiting the use of metronidazole to cases where it is truly necessary, in order to minimize the risk of promoting antibiotic resistance and other adverse effects, as discussed in the study 2.
It is also important to note that metronidazole is not a first-line treatment for most community-acquired or hospital-acquired pneumonias, as stated in the study 3. Instead, other antibiotics such as macrolides, doxycycline, or fluoroquinolones are typically used as first-line treatments. The decision to use metronidazole should be based on a careful assessment of the patient's individual needs and risk factors, and should be guided by the most recent and highest-quality evidence available 2.