Bacterial vaginosis is a relatively common condition affecting women of reproductive age. It occurs when the vaginal flora becomes disrupted. This can happen when one or more types of bacteria, which are usually naturally present within the vagina, but in smaller numbers, becomes too prominent, reaching much greater numbers than it does in healthy women. As such, this condition usually isn’t caused by an introduction of a new type of microorganisms, but an imbalance in the population of the bacteria that were already living within the vagina, prior to the onset of this condition. Usually, this condition is marked by strong-smelling vaginal discharge of an off-white colour.

While sexually active women are at a significantly higher risk, bacterial vaginosis cannot be considered to be a “conventional” STI since it is, in a significant number of cases, caused by various other factors. These include douching with certain types of shampoo or use of intrauterine devices such as contraceptive diaphragms.

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How is bacterial vaginosis (BV) treated?

This condition can remain symptomless for long periods of time, when it is extremely difficult to identify the condition. However, as the condition is not particularly harmful, treatment might not be required at all if the symptoms aren’t present. However, if the symptoms do manifest, then proper treatment is strongly recommended.

This condition is usually combated by the use of prescription antibiotics, with most commonly used being Flagyl and its generic version Metronidazole that carries the same name as the active ingredient of this medicine – Metronidazole. These medicines work by preventing further bacteria growth within the body, thus helping the immune system to combat the infection and return the balance of microorganisms to normal.

How does Flagyl (metronidazole) work?

The active ingredient of both branded Flagyl and generic Metronidazole works by preventing the bacteria from synthesising and releasing certain self-sustaining chemicals which the bacteria cells use in order to stabilize their cellular functions and reproduce. Without his crucial compound, bacteria won’t be able to further increase their number, thus becoming easy targets for the body’s own immune system.

Which treatment should I use?

The differences between these two medicines are limited to the name, box and, of course, the price, with Metronidazole being significantly cheaper as a generic treatment, as opposed to branded Flagyl. However, as is the case with all generic medicines, before becoming available on the market, the manufacturers of the drug needed to provide the evidence of bioequivalence with the original drug. This means that the generic version comes with the same concentration of the same active ingredient and it is used for the treatment of same conditions in the same manner, even with the same side effects.

It is important to note that prior to obtaining any of these medicines, you will need to get a prescription, which means that your condition first needs to be confirmed. You can do this either through sexual health clinic, your general practitioner or even via a home testing kid.

How are Flagyl and Metronidazole used?

Since both of the medicines are antibiotics, it is important to follow the instructions provided by your prescriber while adhering to all the safety procedures that are provided in the official patient information leaflet (issued within every box of the medicine).

  • Always take tablets as directed
  • For the treatment of BV, the typical dose is one 400mg tablet taken twice per day
  • Try to separate the doses as much as you can – for example, by taking one in the morning and the other in the evening
  • Complete the course as prescribed even if the symptoms disappear earlier
  • Take the tablet whole with water
  • Take the tablet with food or after eating
  • Be careful not to exceed the prescribed daily among
  • Avoid alcohol while on this medicine
  • If you miss a dose, don’t take the next one double to make up for it – instead just continue the treatment as usual

What are the side effects?

In terms of potential adverse effects, antibiotics are usually considered to be rather safe, with only a small percentage of patients reporting any side effects. The only exception to this is a relatively common metallic taste in the mouth during the course of the treatment which is a nuisance, but not a danger in any way.

It is still important to be familiar with the potential side effects, so you can contact your doctor in case you experience them. If this is the case, you might need a change of treatment.

Reported side effects of Flagyl and Metronidazole include:

  • Allergic reaction
  • Diarrhoea
  • Nausea, vomiting or stomach pain
  • Confusion and coordination problems
  • Liver problems
  • Ulcers
  • Bruising
  • Bleeding gums
  • Drowsiness
  • Headache
  • Change in urinary consistency
  • Muscular weakness, numbness, tingling or pain

Flagyl and Metronidazole interactions with other medicines

There are certain medicines that are known to compromise the effectiveness of metronidazole treatment which is why it’s important to inform your doctor about any drugs or supplements you might be taking at the moment. Those you should be especially aware of include:

  • Epilepsy drugs (phenytoin, primidone, phenobrabitone)
  • Anticoagulants
  • 5 fluorouracil
  • Busulfan
  • Ciclosporin
  • Lithium


There are some situations when the use of metronidazole-based medicines would not be advised. One of those situations includes a presence of a known medical condition that might make antibiotic treatment dangerous to the point where risks would outweigh the benefits. You should always disclose your full medical history to your doctor. Conditions to be especially aware of include:

  • Liver problems
  • Kidney problems (treated by dialysis)
  • Diseases of the nervous system

Another scenario when this treatment would not be recommended is if you are pregnant or are currently breastfeeding. Exceptions to this can be made, but only if the treatment is absolutely necessary.

Metronidazole precautions

While using this medicine you should avoid consuming alcohol as it can significantly increase the risk of side effects. Even after the treatment is completed, you should wait at least 48 hours since the last tablet before drinking.

While you capacity to drive or operate heavy machinery should not be compromised by the use of metronidazole-based medicines, it is recommended that you still avoid it during the early days of the treatment, so you can notice if you experience potentially impairing side effects.