Flagyl 400 ​

Giardiasis infection

Last Updated December 20th, 2021

Therapeutic Indications for Flagyl 400

Flagyl 400 is a nitroimidazole antimicrobial effective against infections caused by bacteria. Flagyl 400 contains metronidazole and is a broad-spectrum antibiotic. Flagyl 400 is manufactured by Abbott Healthcare Pvt Ltd. This antiprotozoal effectively treats sexually transmitted infections as well as genitourinary infections.

Broadly, Flagyl 400 caters to control and management of the infections involving the central nervous system, skin and skin structure, lower respiratory tract, gynecologic infections as well as bone and joint infections.

Importantly, Flagyl 400 effectively prevents infection prior, during and post operation of the intestine. Doctors also prescribe this medicine to treat chronic dental and gum infections. To treat leg ulcers, doctors prescribe Flagyl 400 as an effective treatment.

Healthcare providers prescribe Flagyl 400 to treat

  • Inflammatory bowel disease
  • Symptomatic trichomoniasis: A sexually transmitted infection
  • Asymptomatic trichomoniasis: A genitourinary infection
  • Amebiasis: parasitic infection of the colon
  • Giardiasis: parasitic intestinal infection
  • Endocarditis: serious heart infection
  • Bacterial septicemia: blood poisoning
  • Acute ulcerative gingivitis: painful bleeding gums
  • Chronic apical infections: pus inside the teeth

Flagyl 400 is available as a tablet, capsule, gel, cream, injection, liquid and in solution form. It is also available as extended-release tablets.


Cream: 7.5 mg and 10 mg

Tablet and capsule: 250 mg, 400 mg, 500mg, 375 mg ,  & 750 mg

Injection, solution: 500 mg/100ml

Gel: 7.5 mg, 10 mg and 13 mg

Liquid: 5 mg

Do I need a Prescription?

Flagyl 400 is available at any pharmacy or drug store only with a prescription from a qualified medical practitioner.


Giardiasis infectionAlways follow the dosage instructions and guidelines provided by your doctor on the label of the medicine.

Take Flagyl 400 orally along with food or after a meal. It should be ideally swallowed with water. Do not chew the tablet. Also, do not crush or break the tablet.

The adult dosage of Flagyl 400 is 750 mg oral intake 03 times daily for a period of five to ten days. Patients must not exceed the maximum dose of 2000 mg per day. In some cases, healthcare providers prescribe a single dose of 2000 mg per day for a stipulated period, especially to treat sexually transmitted infections.

Doctors use the weight-based dose calculator to arrive at the precise dosage for children. So, the pediatric dosage of  Flagyl 400 could be set at 35 to 50 mg/kg or 15.9 to 22.7 mg/lb/kg for the oral intake to be taken 03 times daily for a period of 10 days. The general dosage period of Flagyl 400 is as follows for the following diseases.

Severe Dental infection: 3-7 days

Pressure sores:  7 days

Anaerobic bacterial infections: 7-10 days

Amebiasis:5-10 days

Acute ulcerative gingivitis: 3 days

Trichomoniasis: 07 days

Giardiasis:3-10 days

Bacterial Vaginosis: 5-7 days

Leg ulcers: 07 days

  • Doctors may prescribe Flagyl 400 mg for a longer duration to treat bone and joint infections as well as lower respiratory tract problems.
  • Do not stop Flagyl 400 mg abruptly even if you find immediate relief from your symptoms.
  • Doctors usually prescribe a lower dose of Flagyl 400 for senior adults to reduce the incidence of side effects
  • It is important to store Flagyl 400 me away from direct heat and sunlight at temperatures below 25°C (77°F). Make sure it is stored away from children and pets.

Facts on Flagyl 400

  • Flagyl 400 Tablet is ineffective against viral infections, for instance, the common cold.
  • Reduce dosage of Flagyl 400 by 50% for patients with severe liver damage (Child-Pugh C).
  • Alteration in alkaline phosphatase occurs with the use of Flagyl 400 tablet. The liver enzyme, AST, increases when Flagyl 400 is given to the patient
  • There is a risk of mutations (mutagenicity) in humans if Flagyl 400 is used for a prolonged period
  • Patients on treatment with Flagyl 400 are at an increased risk to develop peripheral neuropathy.

Chemical Composition

Flagyl 400 contains Metronidazole as a key ingredient.

Mechanism of Action

Sleeping sickness parasiteMetronidazole, the active ingredient in Flagyl 400 acts as an impediment to DNA synthesis in the organism, which hampers its growth. Flagyl 400 functions well in ejecting out parasitic worms or other parasites from the body by killing them. This is with no adverse effect on the host.

Users experience the effect of Flagyl 400 one or two hours after administration. This is the time the medicine achieves peak efficiency. The drug and its effects remain in the system for about 24 hours until it is discharged from the system.



If you are allergic to any of the ingredients of Flagyl400 or to any other substance or medicine, for instance to the nitroimidazole-antimicrobial, make it known to your healthcare provider. Alternative medicine is a good option, in this case.

Medical Conditions

The existence of the following medical conditions may trigger drug interactions in the presence of Flagyl 400 in the body

  • Blood Dyscrasia: A blood disorder can cause slight problems such as lowered blood count
  • Liver Disease: Dose adjustment may be required for such patients
  • Crohn’s Disease: Digestive tract inflammation
  • Kidney disease: Generally, specialists adjust the dose of Flagyl 400 for such patients
  • Cockayne syndrome: Characterised by varying degrees of delays in learning
  • Liver encephalopathy: Build-up of toxins in the bloodstream due to inadequate/impaired liver function

Pregnancy and Breastfeeding

Keep your doctor informed if you are planning to start a family or are already pregnant.  Take the medicine only if the benefits of taking Flagyl400 far exceed the risks.

Flagyl 400 does pass through breast milk to the baby. Therefore, doctors do not recommend its use for lactating mothers.


If you are on the Flagyl 400 treatment course, it is better to keep away from alcohol. Alcohol may increase drug reaction and cause nausea, vomiting, and headache. Stomach cramps is also a high probability of alcohol in the presence of Flagyl.

Driving/Using Heavy Machinery

Drowsiness while on Flagyl 400 treatment course is a reality, therefore it is good to avoid driving. Any activity that demands absolute alertness, for instance, the use of heavy machinery may enhance safety risks. The risk of seizures in some Flagyl users makes it even more imperative to stay away from any activity that risk safety.

Senior Adults

Drug interaction with Flagyl amongst this population can increase side effects. Doctors may want to adjust the dose accordingly.

Side Effects

While taking Flagyl 400, patients must be aware of the following side effects. The moderate side effects settle down after a few days of the treatment. If the side effects last longer than usual, seek medical assistance. The severe ones need immediate medical care.

Moderate side effects

  • Headache
  • Bumps on the tongue
  • Diarrhea
  • Stomach cramps
  • Lowered sexual desire
  • Abnormal urination pattern/output
  • Discolored urine
  • Difficulty in urination
  • Constipation
  • Nausea
  • Vomiting

Rare side -effects

  • Dizziness
  • Mouth dryness
  • Irritability
  • Muscle and Joint pain
  • Hives
  • Insomnia
  • Low white blood cell count
  • Nasal congestion
  • Reversible neutropenia
  • Loss of body movements
  • Reduced levels of thrombocytes
  • Metallic taste
  • Fainting
  • Vertigo
  • Vaginal dryness
  • Nasal congestion
  • Allergy
  • Rashes
  • Fatigue

Severe Side effects

Intake of Flagyl 400 can result in the following acute side effects

  • Allergic reactions
  • Kidney disorders
  • Gastrointestinal disorders
  • Pancreatic disorders
  • Liver disorders
  • Eye disorders
  • Acute loss of liver function
  • Infections of the female reproductive organ
  • Seizures
  • Discoloration of urine
  • Aseptic meningitis
  • Liver damage
  • Fluid-filled blisters serious disorder of the skin and mucous membranes

Drug Interactions with Flagyl 400

Intake of a certain class of drugs can cause serious drug interactions along with Flagyl 400.

  • Warfarin: oral anticoagulants
  • Disulfiram: used to treat alcoholism
  • Busulfan, Fluorouracil: Anti-cancer medications
  • Lithium: to treat depressive disorders
  • Ciclosporin: is an immunosuppressant. Flagyl 400 in combination with ciclosporin may enhance levels of ciclosporin in the blood.

What do to if I skip a dose?

If you forgot to take the scheduled dose of Flagyl 400, you can take it as soon as you remember. However, if the next dose schedule is just around the corner, simply avoid taking the missed dose. Do not repeat the dose in quick succession as you could be putting yourself at risk of overdose.


An overdose of Flagyl 400 leads to abnormal levels of medicine in the body. Some of the symptoms of overdose show up as seizures, nausea, damage to nerves, the problem with body movements, vomiting. Although there is no particular antidote for Flagyl overdose, seek medical assistance for receiving therapy and support.

Generic brand names of Flagyl 400

Generic: Metronidazole

Brand name: Flagyl

Manufacturer: JB Chemicals and Pharmaceuticals Pvt Ltd

Different brand names of Flagyl 400

Substitutes of Flagyl 400

The list of medicines below share the same composition, strength, and form as Flagyl 400 Tablet, and hence is a good substitute.

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