In most cases, it is important to finish the entire prescribed dose of your medication. Missing doses of a prescribed course of metronidazole is not recommended and has the potential to cause therapeutic failure.

The most commonly prescribed courses of metronidazole lasts for 7 days. This duration of therapy is often recommend as it has shown very high cure rates for a variety of indications including trichomoniasis infections, bacterial vaginosis and gastrointestinal diseases. If therapy is cut short by a few days, the medication may still be effective in eradicating your infection, but there is also the possibility that it won't.

As you won't be able to finish your prescribed therapy of metronidazole, it is important to speak with your doctor regarding whether or not you need to replace the lost tablets to complete your therapy.

Shortened Antibiotic Courses

Having stated all of the above, there is some controversy as to whether or not the old mantra of "finish your entire course of antibiotics, even if you feel better" is accurate. Traditionally, it was thought that long courses of antibiotics were needed to prevent re-infection as well as to prevent bacterial resistance.

Recent evidence however, shows that longer courses of antibiotics can actually lead to higher resistance, as prolonged exposure can potentially alter our normal GI bacterial flora greatly. In addition, shorter courses of antibiotics reduces the risk of certain adverse events from the medication. It appears there may be cases in which it is OK to stop your antibiotic once you feel better.

There are many factors to consider in regard to whether or not it is OK to use shorter courses of antibiotics including:

  • Type and severity of infection
  • Antibiotic choice
  • Type of patient (e.g. pediatric, elderly etc...)

Your doctor may tell you it's okay to stop therapy at the last 2 doses, or they may recommend to replace the lost pills. In any case, it is important to reach out to them and get appropriate guidance.