Metronidazole
Updated onBenjamin Clanner-Engelshofen is a freelance writer in the medical department. He studied biochemistry and pharmacy in Munich and Cambridge / Boston (USA) and noticed early on that he particularly enjoyed the interface between medicine and science. That is why he went on to study human medicine.
More about the experts All content is checked by medical journalists.The active ingredient metronidazole is one of the most important antibiotics that are used in bacterial infections with anaerobic germs. Metronidazole is also used in the form of creams or gels for rosacea. It belongs to the active ingredient group of nitroimidazoles and is now contained in numerous drugs. Here you can read everything you need to know about the use and effect of metronidazole, side effects and contraindications.
This is how metronidazole works
Metronidazole is an antibiotic. Depending on the dose, it can kill anaerobic bacteria (bacteria that can or must live in an oxygen-free environment) and also some animal protozoa, which can cause diseases in humans. Applied locally to the skin, it also has an anti-inflammatory effect in the skin disease rosacea.
After ingestion, metronidazole accumulates in anaerobic bacteria and protozoa. Only special enzymes inside the germs convert the substance into the actually active compounds that damage the genetic make-up of the pathogen. This causes the germs to die.
Metronidazole has hardly any effect on oxygen-loving bacteria or human cells.
Uptake, breakdown and excretion
After oral ingestion, the antibiotic is almost completely (almost 100 percent) absorbed from the intestine into the body. It takes about eight hours for half of the active ingredient to be broken down and excreted (mainly through the kidneys).
If metronidazole is administered rectally in the form of suppositories, about 80 percent of the active ingredient gets into the blood. When used vaginally, it is only about 20 percent.
When is metronidazole used?
The antibiotic is used to treat infections with anaerobic bacteria (especially in the vaginal, gastrointestinal, ear, nose and throat and mouth areas) and to prevent them during operations.
In addition, metronidazole is used for infections caused by pathogenic protozoa such as trichomonads (trichomoniasis), amoebas (amoebiasis) or giardia (giardiasis / lambliasis).
Metronidazole cream or gel is used topically for skin diseases such as rosacea (copper rose) and inflammation around the mouth area (perioral dermatitis). The reasons: On the one hand, the antibiotic also has anti-inflammatory properties. On the other hand, such skin diseases are sometimes associated with certain types of bacteria that the antibiotic can kill. Long-term use can also be considered here.
This is how metronidazole is used
The most common dosage form of metronidazole for internal infections is tablets or capsules. There are also vaginal suppositories specially designed for vaginal infections. In the case of severe infections, the antibiotic is given as an infusion (intravenous) in the hospital.
Metronidazole cream and gel are available for the treatment of skin diseases.
When using the antibiotic, patients must strictly adhere to the doctor's instructions regarding the dosage and duration of use. Otherwise, relapses can occur.
What are the side effects of metronidazole?
During therapy with metronidazole, nausea and abdominal pain (such as stomach pressure) occur very frequently (i.e. in more than every tenth person treated).
Often (i.e. in one in ten to one hundred people treated) the side effects of metronidazole include a metallic taste in the mouth, vomiting, diarrhea and dark color of the urine (due to breakdown products of the active ingredient).
Headaches, dizziness and paresthesia (paresthesia) are also possible.
What should be considered when using metronidazole?
Alcohol should be avoided during therapy with metronidazole. Otherwise, even small amounts of alcohol can cause skin reddening, nausea, vomiting and dizziness.
Contraindications
There are no contraindications to metronidazole in life-threatening infections. In the case of known hypersensitivity to the active ingredient, severe liver damage, disorders of blood formation and diseases of the nervous system, caution is advised when using it.
Interactions
When metronidazole and various other drugs are used at the same time, interactions are to be expected. For example, the antibiotic can increase the effectiveness of oral anticoagulants (warfarin, phenprocoumon).
Conversely, epilepsy drugs with the active ingredient phenytoin can reduce the effect of metronidazole. Further interactions are possible with simultaneous use of lithium (for manic-depressive illness, etc.), barbiturates (sleeping pills and sedatives) and cimetidine (for heartburn, gastrointestinal ulcers, etc.).
Age restriction
In children under 6 years of age, oral dosage forms (e.g. tablets) should be avoided because of possible swallowing difficulties. Suppositories, for example, are available for this age group.
The effectiveness of topical application as a cream or gel has not been established in children and adolescents under 18 years of age. Its use is therefore not recommended here.
pregnancy and breast feeding period
So far there is no firm evidence that metronidazole has harmful effects on children in the womb. Nevertheless, to be on the safe side, it should not be used during pregnancy, unless it is absolutely necessary.
The use of the antibiotic is also considered very carefully when breastfeeding. If treatment with metronidazole is indicated, there is no need to stop breastfeeding.
How to get medication with metronidazole
Regardless of the dosage form, the active ingredient requires a prescription in Germany, Austria and Switzerland and is only available from pharmacies.
Since when has metronidazole been known?
Metronidazole was first developed in 1959 as an anti-protozoan agent based on a natural antibiotic produced by bacteria of the genus Streptomyces is produced (azomycin).
The antibacterial effectiveness of metronidazole was discovered by chance in 1962, when the active ingredient freed a patient from both his protozoal infection and his bacterial gingivitis.
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