Metronidazole is a type of antibiotic medication that is used to treat several different infections and it is commonly used to treat bacterial vaginosis (BV). It usually comes in the form of 400mg tablets, but can also come as a gel, cream, liquid, or suppository. Metronidazole is a very effective and fast-acting treatment, which is why it is one of the most popular medicines used to treat BV and other infections.
Metronidazole is used to treat a range of different bacterial and parasitic infections (as well as some other conditions). These conditions include bacterial vaginosis (BV), pelvic inflammatory disease, skin infections, rosacea and mouth infections (such as infected gums and dental abscesses).
Bacterial vaginosis is a common condition which is thought to be caused by a change in the natural balance of bacteria that live in the vagina. The vagina is naturally a slightly acidic environment, due to a bacteria called lactobacilli which produces lactic acid. The resulting acidity prevents other bacteria from growing inside the vagina and maintains a healthy environment.
When the natural balance of this bacteria is disrupted (which could be due to all sorts of different factors), the number of lactobacilli decreases, which means the vagina isn’t acidic enough to prevent other bacteria from growing; this imbalance of bacteria is what causes BV. Metronidazole helps to kill some of the excess bacteria that occur in BV and returns the balance of bacteria to normal.
A full course of metronidazole tablets is the common treatment. Metronidazole is an antibiotic. This clears BV in most cases. The usual dose is 400-500 mg twice a day for 5-7 days. A single dose of 2 grams of metronidazole is an alternative, although this may be less effective and may cause more side-effects. It is important to finish the course you have been prescribed, and not to miss any tablets.
Some people feel sick or may be sick (vomit) when they take metronidazole. This is less likely to occur if you take the tablets straight after food. A metallic taste is also a common side-effect.
Do not drink any alcohol while taking metronidazole, nor for 48 hours after stopping treatment. The interaction of metronidazole with alcohol can cause severe sickness and vomiting, and may also cause flushing and an increased pulse rate.
Always use this medication exactly as your clinician has told you. Check with our clinical team or your GP or pharmacist if you are not sure.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
Gastrointestinal Issues:
- Nausea and Vomiting: Commonly reported, metronidazole can cause nausea and vomiting, which may range from mild to severe.
- Diarrhea: Some individuals may experience diarrhea or loose stools.
- Abdominal Pain: Cramping or discomfort in the abdominal area can occur.
- Metallic Taste: A distinctive metallic or bitter taste in the mouth is a frequent side effect.
Central Nervous System Effects:
- Dizziness: Feeling lightheaded or unsteady may occur.
- Headache: Headaches are a common side effect, ranging from mild to severe.
- Confusion or Disorientation: Rarely, metronidazole can cause confusion, disorientation, or mood changes.
Allergic Reactions:
- Rash: Some individuals may develop skin rashes, which can vary from mild to severe.
- Itching (Pruritus): Itching of the skin may accompany a rash.
Hematological Effects:
- Leukopenia: A decrease in white blood cells, which may increase the risk of infections. Regular blood tests might be needed to monitor this.
- Thrombocytopenia: A reduction in platelets, which can affect blood clotting.
Liver Effects:
- Hepatitis: Rarely, metronidazole can cause liver inflammation, which may be indicated by symptoms such as jaundice (yellowing of the skin and eyes) and dark urine.
- Elevated Liver Enzymes: Liver enzyme levels may increase, necessitating monitoring during treatment.
Urinary System Effects:
- Dark Urine: Metronidazole can cause urine to become dark or reddish-brown, which is generally harmless but may be concerning to some patients.
Other Reactions:
- Dry Mouth: Some people may experience a dry mouth during treatment.
- Increased Sensitivity to Alcohol: Consumption of alcohol during treatment and for at least 48 hours after completing metronidazole can cause a disulfiram-like reaction, including nausea, flushing, and palpitations.
Rare Side Effects:
- Peripheral Neuropathy: Rarely, long-term use can lead to peripheral neuropathy, characterized by tingling, numbness, or pain in the extremities.
- Seizures: Very rarely, metronidazole can induce seizures, particularly in individuals with predisposing conditions.
For full information on side effects and correct use, see the patient information leaflet. If any side effects concern you, or you are experiencing any of the side effects mentioned in the patient information leaflet whilst taking this medication, please contact our clinical team or speak to your GP.
You should not take Metronidazole tablets if any of the following apply to you:
- You have (or have ever had) a liver problem
- You are having kidney dialysis
- You have a disease of the nervous system
- You are pregnant or breastfeeding
You should not drink alcohol during your course of Metronidazole tablets or for 48 hours afterwards. The combination of Metronidazole and alcohol can cause unwanted side effects such as nausea, vomiting, flushing, stomach pain, palpitations and headaches.
Get emergency medical help if you have signs of an allergic reaction to this medication. These include:
- Hives
- Dizziness
- Fast or pounding heartbeats
- Wheezing
- Difficult breathing
- Swelling of your face, lips, tongue, or throat.
It is important that you let us know which prescription, over-the-counter medicines and recreational drugs you are currently taking. You must also tell us about any other medical conditions that you currently have (or had in the past). This will help us ensure the prescribed medication is safe and appropriate for you to take.
For full information on warnings, medication interactions and contraindications, refer to the Patient Information Leaflet. Please read all packaging and the Patient Information Leaflet before taking any new medicine and inform our clinical team or your GP of medicines you are taking or intend to take.
