Metronidazole: Effects, Uses & Risks

Metronidazole belongs to the group of antibiotics. It is used in medicine to treat and prevent various inflammations caused by certain bacteria, such as clostridia. Diarrhea, nausea and vomiting, and allergic skin reactions such as redness or pustules are particularly common side effects. Metronidazole should not be taken in the first trimester of pregnancy.

What is metronidazole?

Metronidazole is one of the antibiotics. It is used in medicine to treat and prevent various inflammations. Metronidazole is a drug that belongs to antibiotics. It kills anaerobic bacteria (bacteria that live in an oxygen-free environment) and parasites, so it is often used in the treatment of diseases caused by such bacteria and parasites. If the diseases are caused by other bacteria or, for example, by viruses, it is not effective. Due to its special spectrum of action, the use of metronidazole is only indicated for certain diseases. This is always decided by the attending physician. Metronidazole is available from different manufacturers under various trade names (including Clont, Arilin, Flagyl).

Pharmacologic action

Metronidazole is converted to an active form by certain bacteria and parasites. This occurs when electrons (charged particles) in metronidazole are rearranged by enzymes in the bacteria. This changes the properties of the antibiotic. The active form inserts itself into the genetic material of the bacteria, the DNA, and destroys it. In this way, the bacteria’s metabolism comes to a standstill and they die. Metronidazole and its degradation products are excreted by the kidneys. In the case of reduced kidney function, therefore, special care should be taken and attention paid to the concentration of metronidazole in the blood in order to avoid unnecessary side effects. The mechanism of DNA damage is also the basis for the assumption that metronidazole in pregnant women could harm the unborn child. Although this has never been demonstrated in humans, metronidazole should not be taken within the first three months of pregnancy.

Medicinal use and application

Metronidazole is used primarily to treat diseases caused by so-called anaerobic bacteria, which occur in an environment without oxygen. These include bacterial gastritis (then in combination with other drugs) and infections of the colon caused by bacteria, and also abscesses, i.e., encapsulated boils, in the bone, teeth, mouth, jaw, skin, abdominal cavity, or brain. Another area of application for metronidazole is diseases caused by parasites. These include trichomoniasis, a sexually transmitted inflammation of the genitals, lambliasis, a diarrheal disease, and amoebic dysentery, a diarrheal disease with cramping abdominal pain. Additionally, metronidazole is used during surgery on the colon, rectum, and female reproductive organs to prevent wound infections. For all these purposes, metronidazole is available in various forms, for example, as a tablet to be taken orally, as an ointment, as a vaginal tablet, as a suppository, or as an infusion solution (to be administered via the vein). Like all antibiotics, metronidazole must always be prescribed by a doctor and taken according to the doctor’s instructions. The duration of use is particularly important. It does not exceed 10 days as a rule, but if taken for too short a time, there is a risk of persistent inflammation and complications.

Risks and side effects

Common side effects of taking metronidazole include gastrointestinal disorders such as diarrhea, nausea, and vomiting. When taking metronidazole in tablet form, a metallic taste is often experienced. Since the active ingredient also tastes bitter, the tablets should not be crushed. In addition, the urine may turn red, which is caused by the degradation products of metronidazole and has no clinical value. More frequently, allergic reactions of the skin such as itching, redness or pustule formation also occur. Occasionally, headaches and dizziness, sometimes also seizures, coordination disorders and tingling in the hands and feet may occur.Consumption of alcohol should be avoided while taking metronidazole, otherwise particularly severe side effects are to be expected.