Flagyl 400mg (Metronidazole)

Name: Flagyl 400mg
Brand: Flagyl
SKU: 678
Availability: InStock
Rating: 3.9 (12 reviews)

Flagyl 400mg is one of the world's most widely used antibiotics. Each tablet contains 400mg of Metronidazole, an antibiotic belonging to the nitroimidazole class with potent activity against anaerobic bacteria and protozoa. Flagyl has been listed on the WHO Model List of Essential Medicines for decades and is a cornerstone of treatment for infections of the gastrointestinal tract, reproductive system, skin, and other tissues.

What is Flagyl 400mg?

Flagyl 400mg is a prescription oral antibiotic tablet containing Metronidazole 400mg. It is used to treat infections caused by susceptible anaerobic bacteria and certain protozoan parasites. Unlike many antibiotics that work only against aerobic (oxygen-dependent) organisms, Metronidazole is particularly effective against anaerobic bacteria that thrive in low-oxygen environments, such as the intestines, pelvis, and deep tissues. Flagyl is not effective against viral infections, common colds, or vaginal yeast infections caused by Candida; an antifungal medication is required for the latter.

Manufacturer: Abbott Healthcare-manufactured Flagyl 400mg. Abbott Healthcare's manufacturing standards ensure consistent pharmaceutical quality.

Metronidazole, the active element and its medical action

The active ingredient is Metronidazole for bacterial infections. Once absorbed and taken up by susceptible anaerobic organisms, Metronidazole undergoes chemical reduction within the cell, generating cytotoxic intermediates that damage bacterial DNA, disrupt its helical structure, and inhibit nucleic acid synthesis. This leads to bacterial cell death rather than merely growth inhibition, making Metronidazole bactericidal. Its selectivity for anaerobic and microaerophilic organisms arises from the fact that aerobic human cells possess the antioxidant defences necessary to neutralise these reactive intermediates, while anaerobic microorganisms do not. This unique mechanism makes Flagyl the treatment of choice for a range of infections that are difficult to treat with conventional antibiotics.

Clinical uses of Metronidazole

Flagyl 400mg is used to treat bacterial vaginosis, trichomoniasis, amoebiasis (intestinal and hepatic), giardiasis, anaerobic soft tissue and skin infections, intra-abdominal infections including peritonitis, Helicobacter pylori eradication (as part of combination therapy), dental and oral anaerobic infections, and Clostridioides difficile-associated diarrhoea in mild cases. It is also used as surgical prophylaxis before colorectal procedures to reduce the risk of post-operative anaerobic infections.

Related strengths & products: Similar products include Metrogyl 200mg and other topical metronidazole-based formulations such as Roza gel 30gm.

Key benefits of Flagyle 400mg

Flagyl 400mg provides broad-spectrum coverage against both anaerobic bacteria and protozoan parasites, making it uniquely versatile among antibiotics. It achieves high tissue concentrations after oral dosing, penetrating effectively into the gut, pelvic tissues, and even the central nervous system. Its bactericidal mechanism produces rapid pathogen clearance. It is available in a highly affordable generic form, making it economically accessible for patients requiring short or extended courses.

Precautions

Usage warnings and precautionary advice for metronidazole tablets

Patients must not take Flagyl if they have a known allergy to Metronidazole or other nitroimidazoles. It is generally contraindicated in the first trimester of pregnancy and should be used with caution in the second and third trimesters only if clearly necessary. Women who are breastfeeding should discuss the risk with their doctor, as Metronidazole passes into breast milk. Patients with liver disease, blood disorders (anaemia or leukopenia), epilepsy or seizure history, or Crohn's disease must inform their doctor before starting Flagyl. The absolute prohibition on alcohol during and for 72 hours after treatment is critical — the combination causes a disulfiram-like reaction characterised by severe nausea, vomiting, flushing, palpitations, and hypotension.

Flagyl significantly potentiates the anticoagulant effect of warfarin; patients on warfarin require close INR monitoring. Interactions with lithium, phenytoin, tacrolimus, and busulfan are clinically relevant. Antibiotic-associated diarrhoea should prompt medical evaluation; C. difficile infection must be excluded before treating symptomatically.

Dosage Instructions

Side Effects

Side effects associated with metronidazole tablets

Most patients tolerate Flagyl 400mg without significant difficulty. Gastrointestinal side effects are the most frequently reported and include nausea, vomiting, stomach cramps, diarrhoea, and a persistent metallic or bitter taste in the mouth. Taking the medication with food and staying well hydrated can reduce these effects. Neurological side effects, including headache, dizziness, and peripheral neuropathy (tingling or numbness in the extremities), may occur, particularly with prolonged high-dose use; any neurological symptoms should be reported immediately. Dark or reddish-brown discolouration of urine is a well-recognised and harmless metabolic by-product of Metronidazole.

Serious adverse effects are rare but include seizures, encephalopathy, and severe skin reactions such as Stevens-Johnson syndrome. Signs of an allergic reaction, such as hives, difficulty breathing, or facial swelling, require emergency medical attention.

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How to Use

Dosage information and administration protocol related to metronidazole tablets

Flagyl 400mg should be taken strictly as directed by your doctor. Do not alter the dose or course duration without medical advice. The tablet is typically taken on an empty stomach (one hour before or two hours after meals) for maximum absorption. However, if gastric side effects are significant, taking it with food is acceptable. Swallow the tablet whole; do not crush, chew, or break it. The dosing schedule and course length depend on the infection being treated; common regimens include 400mg two to three times daily for 5 to 10 days. Always complete the full prescribed course, even if you feel better before it ends. Stopping early risks incomplete eradication and antibiotic resistance. Do not consume alcohol or alcohol-containing products during treatment and for at least 72 hours after the last dose. Missed doses should be taken as soon as possible; skip if the next dose is imminent. Never take double doses. Store at room temperature (15–30°C), away from light and moisture. Keep out of children's reach.

Infographics

FAQ

What is Flagyl 400mg used for?

Flagyl 400mg contains metronidazole, a nitroimidazole antibiotic and antiprotozoal medicine. It is effective against anaerobic bacteria (bacteria that survive without oxygen) and a range of parasitic organisms. Common uses include treating bacterial vaginosis (an imbalance of vaginal bacteria), pelvic inflammatory disease (PID), dental infections (tooth abscess, gum infections), Clostridioides difficile (C. diff) bowel infection, gastrointestinal infections caused by protozoa (Giardia — which causes giardiasis, and Entamoeba histolytica — which causes amoebiasis), and as part of H. pylori eradication therapy for stomach ulcers.

Who should not take Flagyl 400mg?

Flagyl 400mg should not be taken by anyone allergic to metronidazole, tinidazole, or other nitroimidazole medicines. It is generally avoided during the first trimester of pregnancy as a precautionary measure, though it can be used when medically necessary later in pregnancy. People with severe liver disease need a dose reduction or alternative treatment, as metronidazole is processed in the liver. People with certain neurological (nervous system) conditions should use it with caution. Always inform your doctor of all medical conditions, allergies, and current medicines.

What is the usual dose of Flagyl 400mg?

The dose and duration of Flagyl 400mg vary by condition. For bacterial vaginosis: typically 400–500mg twice daily for 5–7 days. For dental infections: usually 200–400mg three times daily for 3–7 days. For amoebiasis: 400–800mg three times daily for 5–10 days. For Giardia: 400mg three times daily for 5 days. For H. pylori eradication: part of a triple or quadruple therapy for 7–14 days. Your doctor will prescribe the dose and course appropriate to your specific infection. Complete the full course and do not stop early.

Should Flagyl 400mg be taken with food?

Flagyl 400mg is best taken with or just after food. Metronidazole can cause nausea, stomach discomfort, and an unpleasant metallic taste in the mouth — taking it with a meal significantly reduces these digestive side effects. Swallow each tablet whole with a glass of water. Avoid eating large portions of certain foods rich in tyramine (though the food interaction risk with metronidazole is much less pronounced than with linezolid). Staying well hydrated with water throughout the day is also beneficial while taking metronidazole.

Is Flagyl 400mg safe during pregnancy or breastfeeding?

Metronidazole is generally used with caution in pregnancy. During the first trimester, it is usually avoided unless absolutely necessary — an older theoretical concern about its effects on the foetus during early development has led to this precautionary approach. In the second and third trimesters, metronidazole is used when the benefit outweighs the risk, and it is sometimes used to treat bacterial vaginosis in pregnancy where untreated infection could cause complications. It passes into breast milk in significant amounts — breastfeeding during treatment should be discussed with your doctor.

Can I drink alcohol while taking Flagyl 400mg?

Absolutely not — alcohol must be completely avoided while taking Flagyl 400mg and for at least 48 hours (2 days) after the last tablet. Metronidazole blocks the breakdown of alcohol in the body, causing a toxic compound (acetaldehyde) to build up. This causes a very unpleasant and potentially dangerous reaction known as a disulfiram-like reaction — symptoms include severe flushing (a burning red face), intense headache, nausea, vomiting, rapid heartbeat, and sometimes a drop in blood pressure. Even small amounts of alcohol can trigger this reaction. Check mouthwashes and some medicines for hidden alcohol content.

How does Flagyl 400mg compare to tinidazole for treating protozoal infections?

Metronidazole (Flagyl) and tinidazole (Tiniba) belong to the same antibiotic family (nitroimidazoles) and treat the same types of infections — anaerobic bacterial infections and protozoal infections like Giardia and amoebiasis. Tinidazole generally has a longer half-life in the body, meaning fewer doses per day and a shorter overall course — for example, Giardia can sometimes be treated with a single large dose of tinidazole. Metronidazole typically requires more frequent dosing over a longer course. Both have the same alcohol interaction. Your doctor will choose based on the specific infection and your medical history.

Does Flagyl 400mg interact with other medicines?

Metronidazole has several important drug interactions. It significantly increases the blood-thinning effect of warfarin, raising the risk of dangerous bleeding — dose adjustment and close INR monitoring are needed. It interacts with alcohol to cause the disulfiram-like reaction described above. Lithium (used for bipolar disorder) levels can be raised by metronidazole. Disulfiram (used to treat alcohol dependence) combined with metronidazole can cause psychotic reactions. Phenobarbital and certain other medicines reduce metronidazole's effectiveness. Always provide your complete medication list before starting metronidazole.

Can Flagyl 400mg cause a metallic taste, and is this normal?

Yes — a metallic or bitter taste in the mouth is one of the most commonly reported side effects of metronidazole and is considered normal. It occurs because small amounts of the medicine are excreted into saliva, and metronidazole has a naturally bitter, metallic flavour. This is not a sign of anything serious — it simply means the medicine is circulating through your body as expected. The taste usually subsides once the course is finished. Drinking plenty of water, chewing sugar-free gum, or eating mild foods can help manage the taste during treatment.

Why must the full course of Flagyl 400mg be completed?

Completing the full course of metronidazole is essential for ensuring the infection is completely cleared. For infections like giardiasis, amoebiasis, or bacterial vaginosis, stopping early — even if symptoms have resolved — leaves behind surviving organisms that can cause a relapse, often with a more difficult-to-treat presentation. For C. difficile infections, incomplete treatment dramatically increases the risk of recurrence — which can be even harder to treat than the original infection. Always complete every tablet of the prescribed course regardless of how well you feel before it ends.

What are the common side effects of metronidazole?

The most commonly reported side effects of metronidazole (oral) include nausea, vomiting, stomach cramps, and diarrhoea. A metallic or bitter taste in the mouth is very characteristic of this medicine and is reported by many people. Headache, dizziness, and a dark discolouration of the urine (which is harmless) can also occur. Loss of appetite is reported by some people. As with other antibiotics, oral or vaginal thrush (yeast infection) may develop due to disruption of the body's normal bacterial balance. Most side effects resolve once the course is finished.

What side effects of metronidazole require urgent medical attention?

Seek immediate emergency care if you consume alcohol while taking metronidazole and develop the disulfiram-like reaction (severe flushing, vomiting, rapid heartbeat, chest pain, or a sense of impending doom) — this can be serious. Stop metronidazole and contact your doctor if you develop numbness or tingling in the hands or feet — this can indicate peripheral neuropathy, a nerve-related side effect that is more likely with prolonged use. Signs of an allergic reaction (rash, swelling, breathing difficulty) need immediate care. Seizures or severe confusion during treatment also require emergency assessment.

SKU	678
Generic For	Flagyl
Strength	400mg
Manufacturer	J.B. Chemichals Pvt. Ltd.
Active Ingredient	Metronidazole

Flagyl 400mg