Flagyl Side Effects
Not much is known about the potential side effects of short-acting Flagyl. Side effects that have been reported with Flagyl ER (the long-acting version) include flu-like symptoms, headaches, and nausea. Certain side effects of Flagyl are potentially serious and should be reported to your healthcare provider immediately, including numbness or paralysis of a limb, seizures, or signs of an allergic reaction (such as itching or hives).
As with any medicine, side effects are possible with Flagyl® (metronidazole). However, not everyone who takes the medication will have problems. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or can easily be treated by you or your healthcare provider.
(This article covers many, but not all, of the possible side effects with Flagyl. Your healthcare provider can discuss a more complete list of Flagyl side effects with you.)
Flagyl has been studied thoroughly in clinical trials. In these studies, the side effects that occurred in a group of people taking Flagyl were documented and compared to side effects that occurred in a similar group of people taking a different antibiotic. This way, it is possible to see what side effects occurred, how often they appeared, and how they compare to the group taking a different medication. This detailed side effect information is available for long-acting Flagyl ER (a relatively new medication) but not for regular, short-acting Flagyl tablets and capsules.
In these studies, the most common Flagyl ER side effects included:
- Headaches -- in up to 18 percent of people
- Vaginal irritation or infection -- up to 15 percent
- Nausea -- up to 10 percent
- Metallic taste in the mouth -- up to 9 percent
- Bacterial infections -- up to 7 percent
- Flu-like symptoms (such as a fever and chills) -- up to 6 percent.
Other common side effects (occurring in 2 to 5 percent of people) included:
- Genital itching
- Abdominal pain (stomach pain)
- Upper respiratory tract infections, such as the common cold
- Runny or stuffy nose
- Sinus infection
- Sore throat
- Painful menstrual periods
- Vaginal yeast infections
- Dry mouth
- Urinary tract infection (UTI), such as a bladder infection