FLAGYL: A Complete Guide to Metronidazole Uses, Dosage, Side Effects and More

Flagyl (generic name: metronidazole) is a prescription antibiotic and antiprotozoal medication used to treat certain bacterial infections, as well as some parasitic infections. It works by stopping the growth of bacteria and parasites.

Uses of Flagyl/Metronidazole

Some of the most common uses and indications for Flagyl tablets and other forms of metronidazole include:

  • Bacterial vaginosis
  • Pelvic inflammatory disease
  • Endocarditis prophylaxis
  • Rosacea
  • Dental infections
  • GI infections e.g. diverticulitis
  • Intra-abdominal infections
  • Lung abscess
  • Bone and joint infections
  • Central nervous system infections
  • Flagyl tablets are also sometimes prescribed off-label for diarrhea or inflammatory bowel disease.

Flagyl is a very versatile medication with a range of FDA-approved indications as well as some off-label uses. It is most commonly prescribed for bacterial vaginosis, pelvic infections, dental infections, GI infections, and rosacea.

Flagyl Dosage

The standard dosage of Flagyl tablets is usually between 250mg to 500mg, taken two to four times daily. The duration of treatment can range from one dose to 14 days depending on the type of infection being treated.

Age GroupGenderCondition Being TreatedDosageFrequency
AdultsMale/FemaleBacterial vaginosis500 mgOrally, twice a day for 7 days
AdultsMale/FemaleDental infections250-500 mgOrally, 3 times a day for 3-7 days
AdultsMale/FemaleGIardiasis250 mgOrally, 3 times a day for 5-7 days
AdultsMale/FemaleUlcers caused by H. pylori500 mgOrally, 3 times a day with other antibiotics for 10-14 days
AdultsMale/FemaleAnaerobic bacterial infections500 mgIV every 6-8 hours usually for 7-10 days
Children ages 7-10 yearsMale/FemaleBacterial infections15-30 mg/kg/dayOrally, divided in 3 doses for 7 days
Children under 7 yearsMale/FemaleBacterial infections15-30 mg/kg/dayOrally, divided in 3 doses for 7 days
Infants < 3 monthsMale/FemaleBacterial infections15 mg/kg/dayIV/Orally in 3 divided doses for 7 days
Flagyl Dosage chart

Some common Flagyl dosage guidelines include:

  • Bacterial vaginosis: 500mg twice daily for 7 days
  • Dental infections: 250mg 3 times daily for 3-7 days
  • Diverticulitis: 500mg 3 times daily for 7-10 days
  • Pelvic inflammatory disease: 500mg twice daily for 14 days
  • Rosacea: 250mg daily for 6-8 weeks

For more serious CNS or bone infections, Flagyl can be given intravenously at higher doses for a longer treatment duration.

The maximum dosage is normally 500-750mg three times per day orally or 1,500mg/day intravenously. Higher doses may be used for severe infections.

Always take Flagyl tablets exactly as prescribed by your healthcare provider. The dosage is optimized based on the type and severity of the infection being treated. Using too little could lead to recurrent infection while using too much can increase side effects.

Signs Flagyl is Working

It can take a few days of treatment with oral Flagyl tablets before you notice a significant improvement in infection symptoms. However, some signs indicating the Flagyl is working include:

  • Decreased pain, redness, and swelling of the infected area
  • Resolution of fever
  • Improved energy and well-being
  • Return of normal vaginal discharge (for bacterial vaginosis)
  • Reduced abdominal discomfort (in GI infections)

You should notice a gradual improvement in symptoms over the first 3-5 days. Contact your doctor if symptoms worsen or do not start improving within several days of starting Flagyl. Additional medication or tests may be needed.

Flagyl Side Effects

Type of Side EffectSide EffectSymptomsRisk FactorsManagement
CommonNauseaTaking Flagyl on an empty stomachOTC antispasmodics; call doctor if severeTake with food; small, frequent meals
CommonMetallic/bitter tasteAltered sense of tasteRoutine side effectTemporary; resolves after stopping
CommonAbdominal crampsStomach pain, tendernessConcurrent GI issues e.g. Crohn’sCall the doctor immediately. May require stopping drug.
SeriousNeuropathyTingling and numbness in hands & feetHigh doses, liver/kidney issues, malnutrition, alcohol useCall the doctor immediately. May require stopping drugs.
SeriousSevere diarrheaFrequent watery stools, stomach cramps, feverAntibiotic disruption of gut microbiotaCall the doctor immediately. Requires stopping drug.
SeriousLiver toxicityDark urine, yellow skin/eyes, stomach pain, nauseaUnderlying liver disease, high dosesCall the doctor immediately. Requires stopping the drug.
SeriousAllergic reactionRash, itching, swelling, dizziness, trouble breathingDrug hypersensitivityCall the doctor immediately. Requires stopping the drug.
Flagyl Side Effects chart

Flagyl tablets are usually well-tolerated when used correctly for appropriate indications. However, as with most medications, it can cause some mild to moderate side effects including:

  • Nausea, vomiting, metallic taste
  • Abdominal discomfort
  • Headache
  • Yeast infections
  • Diarrhea or loose stools
  • Darkening of urine

Alcohol consumption should be completely avoided during Flagyl treatment and for at least 3 days afterward as this can cause a disulfiram reaction characterized by:

  • Flushing of skin
  • Pounding heartbeat
  • Difficulty breathing
  • Vomiting
  • Hypotension

Rare but serious side effects warranting emergency care include:

  • Fever
  • Extreme fatigue
  • Numbness/tingling of extremities
  • Seizures
  • Hallucinations
  • Dark urine
  • Yellow skin/eyes

Tolerance of Flagyl is improved by taking it with food and plenty of fluids unless otherwise directed. Side effects generally resolve within a few days after stopping treatment. Contact your doctor if any side effects are severe or do not go away on their own.

Flagyl and Pregnancy/Breastfeeding

CategorySafety & RisksRecommendations
Pregnancy– Considered generally safe for use in all trimestersOnly use if needed- Weigh risks vs benefits- Monitor fetal growth if 1st-trimester use
1st Trimester– Limited absorption may prevent fetal exposure – Early studies showed some birth defects but later studies did not confirm this– Generally considered safe – Use the shortest effective course
2nd & 3rd Trimesters– Use for the shortest effective course – Monitor infant stool patterns– Deemed low-risk for birth defects or complications- Can cross the placenta but not teratogenic
Breastfeeding– Metronidazole transfers into breast milk- Routine use not recommended– Use only if the clear benefit outweighs risks- Monitor the infant for diarrhea or thrush
Infants– Long-term exposure via breastmilk may alter gut bacteria and cause diarrhea– Use for shortest effective course – Monitor infant stool patterns

Oral Flagyl tablets have been assigned Pregnancy Category B by the FDA. This means animal studies have not shown evidence of fetal harm, but robust clinical studies in pregnant women are lacking.

Flagyl does cross the placenta and also enters breast milk in low concentrations. It should only be used in pregnancy or lactation when indicated and the benefits outweigh potential risks. Always consult your OB-GYN before using Flagyl while pregnant or breastfeeding.

Flagyl Interactions

  • Alcohol – Severe reactions as described above
  • Blood thinners e.g. warfarin – Flagyl can increase bleeding risk
  • Lithium – Increased lithium blood levels
  • Certain seizure medications – flagyl can worsen side effects
  • Cimetidine – Increased metronidazole concentrations

Inform your doctor of any other medications, herbal products, or supplements you take. Dosage adjustments may be warranted, and combining Flagyl with alcohol should always be avoided.

Is Flagyl Safe For Long-Term Use?

The safety and effectiveness of long-term Flagyl therapy have not been well-established. Most infections can be treated with short 7-14 day courses consistent with FDA labeling.

However, some doctors do prescribe Flagyl tablets off-label for extended periods to treat conditions like inflammatory bowel disease or rosacea. Potential risks of long-term use include nerve damage resulting in numbness or tingling of extremities – this is usually reversible when stopping Flagyl.

Do not take Flagyl tablets or other metronidazole formulations for more than 14 days unless specifically directed by your physician. And report any neurologic side effects that develop so the dosage can be adjusted.

Buying Flagyl Safely Online

You should always purchase Flagyl and generic metronidazole only after being examined by a doctor who has written you a prescription. Taking this medication without medical oversight or using someone else’s prescription can be unsafe.

Beware of shady online pharmacies claiming to offer Flagyl without a prescription. These products could be fake, contain the wrong dosage, or have contaminants that endanger your health. Legitimate telehealth platforms can connect you with a licensed physician for treatment if accessing care in person is difficult. But review site credentials carefully first.

Get medical help right away if you take Flagyl purchased online and experience any unusual side effects or potentially dangerous reactions. Stop taking it until speaking to your doctor.

The Takeaway

When used properly as prescribed by a physician, Flagyl tablets and other forms of metronidazole can safely and effectively treat a wide variety of bacterial infections as well as certain parasitic infections. Typical treatment duration is 7-14 days. Take exactly as prescribed and avoid alcohol during treatment.

Common mild side effects like nausea and headaches usually resolve after finishing the course of Flagyl. Seek immediate medical care if you experience severe reactions like seizures, fever, or hallucinations. Alert your physician to any persisting numbness or nerve pain as well.

Only take Flagyl tablets from legitimate pharmacies after being examined and getting a prescription from your doctor. This ensures appropriate treatment monitoring and reduces the risks associated with misuse. Follow all dosage guidelines to maximize benefit and safety when taking Flagyl/metronidazole.

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