METRONIDAZOLE
Metronidazole is an antibiotic that is not directly involved in the process of anesthesia but plays an essential role in the perioperative period for preventing and managing infections related to surgical procedures. Metronidazole is particularly effective against anaerobic bacteria and certain protozoal infections. The importance of metronidazole in the context of anesthesia can be highlighted by the following factors:
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Surgical prophylaxis: Metronidazole is often used as a prophylactic antibiotic for surgeries where there is a risk of anaerobic bacterial contamination, such as in gastrointestinal, colorectal, gynecological, and dental procedures. When administered before the procedure, metronidazole helps reduce the risk of postoperative infections by targeting anaerobic bacteria. It is sometimes used in combination with other antibiotics for broader coverage of potential pathogens.
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Treatment of infections: Metronidazole may be used to treat established infections in the perioperative period, particularly those caused by anaerobic bacteria or certain protozoa. Infections such as intra-abdominal abscesses, pelvic inflammatory disease, and bacterial vaginosis can be effectively treated with metronidazole. The choice of metronidazole as a treatment option depends on the suspected or confirmed causative organisms and their susceptibility patterns.
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Anaerobic coverage: Metronidazole is especially effective against anaerobic bacteria, which can be responsible for causing infections in certain surgical procedures. Its excellent anaerobic coverage makes it a valuable option for both surgical prophylaxis and treatment in these situations..
The mechanism of action of metronidazole can be summarized as follows:
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Entry into the bacterial cell: Metronidazole diffuses passively across the cell membrane of anaerobic bacteria and certain protozoa. It is important to note that metronidazole is only activated under anaerobic or low-oxygen conditions, which is why it is effective against anaerobic bacteria and protozoa but not aerobic bacteria.
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Reduction and activation: Once inside the bacterial cell, metronidazole undergoes a chemical reduction reaction, catalyzed by specific enzymes (such as nitroreductases or pyruvate-ferredoxin oxidoreductase) present in anaerobic bacteria and certain protozoa. The reduction process converts metronidazole into its active form, which contains highly reactive nitroso free radicals.
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Damage to bacterial DNA: The reactive nitroso free radicals generated by the reduction of metronidazole interact with the bacterial DNA, causing strand breakage, inhibition of DNA synthesis, and disruption of the helical structure. This DNA damage ultimately leads to cell death, as the bacteria can no longer replicate or repair their DNA.
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Bactericidal effect: The overall effect of metronidazole's action on bacterial DNA synthesis is bactericidal, meaning it kills the bacteria rather than just inhibiting their growth. By causing DNA damage, metronidazole prevents the bacteria from replicating and leads to cell death.
Key points about Metronidazole
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Disrupts DNA and protein synthesis in susceptible organisms.
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Most notable for activity against anaerobic bacteria, including: Bacteroides, Clostridium. In addition, is active against: Trichomonas vaginalis, Entamoeba histolytica, Giardia lamblia, H. pylori, Clostridium difficile.
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Metronidazole is bactericidal against most anaerobic gram-negative bacilli and Clostridium species.
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Metronidazole is a useful part of preoperative prophylactic regimens for elective colorectal surgery.
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Side effects of metronidazole include dry mouth (metallic taste) and nausea.
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May cause Stevens-Johnson syndrome.