How it is administered

Metronidazole is most commonly administered orally in tablet or capsule form, but it can also be given intravenously for more serious infections. There are topical and vaginal gel forms, but these are not typically used for blood cancer-related infections. Oral tablets are available in 250 mg and 500 mg strengths, and capsules are available in 375 mg strength.

How it works

Metronidazole is an antibiotic that works by entering bacterial cells and disrupting their DNA, which prevents the bacteria from multiplying and causes them to die. It is especially effective against anaerobic bacteria (bacteria that do not need oxygen to grow) and certain parasites. Once inside the bacteria, metronidazole is reduced to an active form that interacts with DNA, leading to inhibition of DNA synthesis and ultimately bacterial cell death.

This mechanism makes metronidazole particularly useful for treating infections caused by anaerobic bacteria, which can sometimes complicate the care of patients with blood cancers, especially if they develop infections in the abdomen, skin, or other tissues where anaerobic bacteria thrive.

Who Should take it

Metronidazole is used to treat serious infections caused by susceptible anaerobic bacteria. In the context of blood cancers, patients may be prescribed metronidazole if they develop infections such as intra-abdominal infections, skin and skin structure infections, gynecologic infections, bacterial septicemia, bone and joint infections, central nervous system infections, lower respiratory tract infections, or endocarditis caused by anaerobic bacteria.

It may be used as part of a combination therapy when infections are mixed (both aerobic and anaerobic bacteria are present), and is often given alongside other antibiotics that target aerobic bacteria.

Who should not take it

Metronidazole should not be taken by anyone with a known hypersensitivity to metronidazole or other nitroimidazole derivatives. It is also contraindicated in patients with Cockayne syndrome due to the risk of severe, potentially fatal liver toxicity. Patients who are pregnant should not take metronidazole for trichomoniasis during the first trimester. Additionally, metronidazole should not be used in combination with disulfiram (used for alcohol dependence) or within two weeks of taking disulfiram, as this can cause serious psychotic reactions.

Alcohol should be avoided during treatment and for at least three days after the last dose, as combining metronidazole with alcohol can cause unpleasant reactions such as nausea, vomiting, and headaches.

Commonly used with

Metronidazole is often used in combination with other antibiotics, especially when treating mixed infections that involve both aerobic and anaerobic bacteria. For example, it may be paired with antibiotics like cephalosporins, penicillins, or aminoglycosides to provide broader coverage.

In patients with blood cancers, it may be used alongside antifungal medications if there is concern for fungal superinfection, or with other supportive therapies as needed.

Commonly tested with

Metronidazole is commonly tested with other antibiotics in susceptibility testing to ensure the bacteria causing the infection are sensitive to the chosen drugs. In clinical practice, it may be used in combination with drugs such as penicillins, cephalosporins, or aminoglycosides, especially in the treatment of intra-abdominal or mixed infections.

It is important to monitor blood counts before and after therapy in patients with a history of blood dyscrasias, as metronidazole can cause mild leukopenia.