Amotrex 200 mg Tablet (Metronidazole) – ACI Limited

1. About Amotrex 200 mg Tablet (Metronidazole)

Amotrex 200 mg Tablet contains Metronidazole 200 mg, a first-line nitroimidazole antibiotic and antiprotozoal agent, manufactured by ACI Limited, Bangladesh. Metronidazole is one of the most essential and widely prescribed antimicrobials in Bangladesh, with activity against a broad spectrum of anaerobic bacteria and pathogenic protozoa including Entamoeba histolytica, Giardia lamblia, and Trichomonas vaginalis.

First introduced in 1959, metronidazole remains on the WHO Essential Medicines List. In Bangladesh's clinical landscape, it is a cornerstone agent for treating amoebiasis, giardiasis, bacterial vaginosis, anaerobic infections, Helicobacter pylori eradication, and as prophylaxis in colorectal surgery. The 200 mg tablet is the lower-dose formulation, used particularly for paediatric dosing, H. pylori triple therapy, and conditions where lower doses are appropriate.

2. Mechanism of Action

Metronidazole is a prodrug activated selectively within anaerobic and microaerophilic organisms:

• Selective activation: Once inside susceptible organisms (anaerobic bacteria and protozoa), the nitro group of metronidazole is reduced by low-redox-potential electron transport proteins (ferredoxin, pyruvate:ferredoxin oxidoreductase). This reduction produces cytotoxic nitro radical anions and nitroso metabolites.
• DNA damage: These reactive intermediates interact with DNA, causing strand breaks and disruption of the helical structure — leading to rapid cell death. The damage is irreversible.
• Selective toxicity: Aerobic human cells lack the low-redox protein systems needed to activate metronidazole — this is the basis of its selective toxicity against pathogens while sparing host cells.
• Broad anaerobic spectrum: Active against gram-negative and gram-positive anaerobic bacteria including Bacteroides fragilis (the most common pathogen in intra-abdominal infections), Fusobacterium, Prevotella, Clostridium perfringens, and C. difficile.

3. Indications

Amotrex 200 mg Tablet (Metronidazole) is indicated for:

• Amoebiasis: Intestinal amoebiasis (amoebic dysentery), amoebic liver abscess, and asymptomatic intestinal carriage of Entamoeba histolytica — one of the most common indications in Bangladesh
• Giardiasis: Infection with Giardia lamblia (Giardia intestinalis) causing chronic diarrhoea, malabsorption, and bloating — highly prevalent in Bangladesh
• Bacterial Vaginosis (BV): Treatment of BV caused by Gardnerella vaginalis and associated anaerobes — the most common vaginal infection in women of reproductive age
• Trichomoniasis: Urogenital infection with Trichomonas vaginalis in both female and male partners
• Helicobacter pylori Eradication: Triple therapy combination (metronidazole + amoxicillin/clarithromycin + proton pump inhibitor) for peptic ulcer disease and H. pylori gastritis
• Anaerobic Bacterial Infections: Intra-abdominal infections (peritonitis, appendicitis), pelvic inflammatory disease, septicaemia, lung abscess, and brain abscess caused by anaerobic organisms
• Pseudomembranous Colitis: Caused by Clostridium difficile — oral metronidazole is a first-line treatment option for mild-moderate disease
• Dental/Periodontal Infections: Acute necrotising ulcerative gingivitis (ANUG), pericoronitis, and dental abscesses with anaerobic component
• Surgical Prophylaxis: Pre-operative bowel preparation and prophylaxis for colorectal and gynaecological procedures
• Diabetic Foot Infections: Part of combination antibiotic therapy for diabetic foot infections with anaerobic component

4. Dosage and Administration

Amoebiasis (intestinal):

• Adults: 400–800 mg 3 times daily for 5–10 days
• Children: 35–50 mg/kg/day in 3 divided doses for 5–10 days

Amoebiasis (amoebic liver abscess):

• Adults: 400 mg 3 times daily for 5–10 days (often 800 mg 3 times daily)

Giardiasis:

• Adults: 400 mg 3 times daily for 5–7 days (or 2g single dose)
• Children: 15 mg/kg/day in 3 divided doses for 5 days

Bacterial Vaginosis:

• Adults: 400 mg twice daily for 7 days

Trichomoniasis:

• 2 g single dose (treat partner simultaneously), or 400 mg twice daily for 7 days

H. pylori Eradication (triple therapy):

• Adults: 400 mg twice daily for 7–14 days (with amoxicillin 1g BD + omeprazole 20mg BD)

Anaerobic Infections:

• Adults: 400 mg every 8 hours (3 times daily) for 7–14 days depending on severity

Surgical Prophylaxis:

• Adults: 400 mg 2 hours before surgery, then 400 mg 8-hourly for 24 hours post-operatively

Administration note: Take with or after food to reduce nausea. Swallow whole with water. Do NOT drink alcohol during treatment and for at least 48 hours after the last dose.

5. Contraindications

• Known hypersensitivity to metronidazole or other nitroimidazoles (tinidazole, ornidazole)
• First trimester of pregnancy — use with caution; avoid in first trimester unless clearly needed
• Disulfiram use within 2 weeks — combined use can cause psychotic reactions
• Concomitant alcohol consumption — absolute contraindication; causes severe disulfiram-like reaction

6. Warnings and Precautions

ALCOHOL — ABSOLUTE CONTRAINDICATION: Do not consume any alcohol during metronidazole treatment and for at least 48 hours after the last dose. Even small amounts cause a severe disulfiram-like reaction: intense nausea, vomiting, flushing, sweating, headache, palpitations, and hypotension. This includes alcohol-containing mouthwashes, tonics, and some medications.

Peripheral Neuropathy: Prolonged or high-dose use can cause peripheral neuropathy (numbness, tingling, pain in hands/feet). Particularly important in diabetic patients who already have diabetic neuropathy — the symptoms may be confusingly additive. Report any new numbness or tingling to your doctor promptly.

CNS Effects: High doses can cause encephalopathy, cerebellar toxicity (ataxia, dysarthria), and seizures. Use caution in patients with pre-existing CNS disorders or epilepsy.

Hepatic impairment: Metronidazole is extensively metabolised by the liver. Severe hepatic impairment requires dose reduction (by one-third to one-half).

Diabetic patients: No direct effect on blood glucose. However: (1) Diabetic patients are highly susceptible to infections including anaerobic foot infections requiring metronidazole. (2) Pre-existing diabetic peripheral neuropathy may be worsened by metronidazole's neurotoxicity — use cautiously in diabetic patients with established neuropathy; avoid prolonged courses. (3) Monitor renal function as metronidazole metabolites accumulate in renal failure.

Pregnancy: Use with caution — avoid in first trimester if possible. May be used in 2nd and 3rd trimesters when clearly indicated for serious infection.

Carcinogenicity: Metronidazole is mutagenic in bacteria and carcinogenic in rodents at high doses; evidence in humans is not established. Avoid unnecessary prolonged use.

7. Side Effects

Very common (≥10%):

• Nausea — most common side effect; take with food to reduce
• Metallic or bitter taste in mouth (very characteristic of metronidazole)

Common (1–10%):

• Vomiting, diarrhoea, abdominal cramps
• Headache, dizziness
• Dry mouth, glossitis (tongue inflammation), furring of tongue
• Darkening of urine (brown-red discolouration — harmless metabolite excretion)

Uncommon:

• Peripheral neuropathy (especially with prolonged use)
• Transient leukopenia (reduced white cell count)
• Skin rash, urticaria

Rare/Serious:

• Seizures, encephalopathy (high dose or prolonged use)
• Cerebellar toxicity — ataxia, nystagmus
• Severe hypersensitivity reactions (anaphylaxis)
• Stevens-Johnson syndrome (very rare)

8. Drug Interactions

• Alcohol: Severe disulfiram-like reaction — absolute contraindication (see Warnings)
• Warfarin/anticoagulants: Metronidazole significantly inhibits CYP2C9 — markedly increases warfarin effect and INR, risking serious bleeding. Monitor INR closely and reduce warfarin dose if needed.
• Disulfiram: Combined use causes acute psychosis and confusion — allow 2 weeks after stopping disulfiram before starting metronidazole
• Phenytoin: Metronidazole inhibits phenytoin metabolism — increased phenytoin levels and toxicity. Monitor phenytoin levels.
• Phenobarbitone/rifampicin: CYP inducers — accelerate metronidazole metabolism, reducing its efficacy
• Lithium: Reduced lithium clearance — increased lithium toxicity risk. Monitor lithium levels.
• Fluorouracil (5-FU): Metronidazole inhibits 5-FU metabolism — increased 5-FU toxicity
• Ciclosporin: May increase ciclosporin blood levels

9. Pharmacokinetics

Absorption: Well absorbed orally with bioavailability ~80–100%. Tmax ~1–2 hours. Food slightly delays but does not reduce absorption.

Distribution: Widely distributed — penetrates body fluids, tissues, cerebrospinal fluid, brain, bones, liver, and bile at therapeutic concentrations. Plasma protein binding ~20% (low). Vd ~0.6–0.7 L/kg.

Metabolism: Extensively metabolised in the liver (CYP3A4 and other pathways) to an active hydroxy metabolite (approximately 30% activity of parent drug) and inactive metabolites (glucuronide conjugates).

Elimination: Excreted in urine (~60–80% as metabolites, ~20% unchanged) and faeces (~6–15%). Terminal half-life ~6–9 hours (parent drug), allowing twice or three-times daily dosing. Half-life prolonged in severe hepatic impairment.

10. Metronidazole in Diabetic Foot Infection Management

Diabetic foot infections are a major complication of diabetes mellitus, responsible for the majority of diabetes-related hospitalizations in Bangladesh. Anaerobic bacteria play a significant role in moderate-to-severe diabetic foot infections, particularly in:

• Deep tissue infections (fasciitis, myonecrosis)
• Gangrenous (wet/gas gangrene) infections
• Infections following ischaemia or necrosis
• Malodorous wounds with sloughy necrotic tissue

Standard combination antibiotic therapy for moderate-to-severe diabetic foot infections in Bangladesh includes metronidazole to cover the anaerobic component, typically combined with a cephalosporin or fluoroquinolone for aerobic gram-negative coverage. Amotrex 200 mg tablets are commonly used orally in the community management phase of diabetic foot infections.

11. Amoebiasis and Giardiasis — Bangladesh Context

Amoebiasis (Entamoeba histolytica) and giardiasis (Giardia lamblia) remain highly prevalent in Bangladesh due to contaminated water sources and sanitation challenges. Metronidazole is the treatment of choice for both:

• Amoebic dysentery: Bloody diarrhoea, tenesmus, abdominal cramps — metronidazole plus luminal agent (diloxanide furoate) for complete eradication
• Amoebic liver abscess: Right upper quadrant pain, fever — metronidazole is curative in majority without drainage
• Giardiasis: Chronic watery diarrhoea, bloating, malabsorption — common cause of growth failure in children in Bangladesh

12. ACI Limited — Pharmaceutical Excellence

Amotrex is manufactured by ACI Limited, Bangladesh's leading pharmaceutical company founded in 1968. ACI Limited operates under WHO-GMP guidelines and supplies a comprehensive range of essential medicines to Bangladesh's healthcare system. ACI's Amotrex metronidazole range — 200 mg tablets, 400 mg tablets, 200 mg/5 ml oral suspension, and 500 mg/100 ml IV infusion — provides complete coverage for all clinical settings from primary care to hospitalised patients requiring IV therapy.

13. Storage

• Store below 30°C in a cool, dry place
• Protect from direct sunlight and moisture
• Keep in original packaging until use
• Keep out of reach of children
• Do not use after expiry date on the strip/box

Frequently Asked Questions (FAQ)

Q1: What infections does Amotrex (Metronidazole) treat?

Amotrex 200 mg (Metronidazole) treats a wide range of infections caused by anaerobic bacteria and protozoa. In Bangladesh it is most commonly used for: amoebiasis (amoebic dysentery and amoebic liver abscess caused by Entamoeba histolytica), giardiasis (Giardia lamblia), bacterial vaginosis, trichomoniasis, H. pylori eradication (triple therapy for peptic ulcer), anaerobic bacterial infections (intra-abdominal, pelvic, dental), and as part of combination therapy for diabetic foot infections. It has no activity against aerobic bacteria (like E. coli), viruses, or fungi.

Q2: Can I drink alcohol while taking Amotrex (Metronidazole)?

No — absolutely not. Metronidazole causes a severe disulfiram-like reaction with any alcohol. Even small amounts of alcohol during treatment — or within 48 hours of the last dose — cause intense nausea, vomiting, flushing, sweating, rapid heartbeat, and severe headache. Avoid all alcohol, including alcohol-containing mouthwashes, cough syrups, and tonics, during the full course of Amotrex and for at least 48 hours after completing treatment.

Q3: Why does Amotrex give a metallic taste in the mouth?

The metallic or bitter taste is a very common and well-known side effect of metronidazole, affecting most patients. It occurs because metronidazole and its metabolites are secreted in saliva. It is harmless and temporary — it disappears completely within a few hours to days after finishing the course. To help: eat after taking the tablet, chew sugar-free gum, and rinse your mouth with water after each dose. Dark brown discolouration of urine is also normal and harmless during metronidazole treatment.

Q4: Is Metronidazole safe for diabetic patients?

Metronidazole can be used in diabetic patients but requires some extra caution: (1) It does not directly affect blood glucose. (2) Diabetic patients with pre-existing peripheral neuropathy should use it carefully — metronidazole can cause or worsen neuropathy symptoms with prolonged use. Report any new numbness or tingling in hands or feet immediately. (3) In diabetic kidney disease, metabolites may accumulate — shorter courses are preferable. (4) The alcohol interaction is critically important — even patients who consume alcohol socially must abstain completely. Consult your physician about the appropriate dose and duration.