Metronidazole is a synthetic antibacterial and antiprotozoal agent that belongs to the nitroimidazole class. Metronidazole is effective therapy against protozoa such as Trichomonas vaginalis, amebiasis, and giardiasis. In addition, Metronidazole is one of the most effective drugs available against anaerobic bacterial infections. Metronidazole is also useful in treating Crohn's disease, antibiotic-associated diarrhea, and rosacea. It initially was approved by the FDA in 1963 and is available in oral, parenteral, and topical formulations.Metronidazole is amebicidal, bactericidal, and trichomonicidal. Unionized Metronidazole is readily taken up by anaerobic organisms and cells. It acts selectively aganist anaerobic bacterias as only these bacteria are capabale to reduce it to its active form intracellularly. Reduced it then disrupts DNA's helical structure, thereby inhibiting bacterial nucleic acid synthesis. This eventually results in bacterial cell death.


Primary Characterstics

Molecular Structure of Metronidazole
Metronidazole also known as 5-Nitroimidazole. . It is of Synthetic origin and belongs to Nitroimidazole. It belongs to Antibiotic (Prokaryote DNA) pharmacological group on the basis of mechanism of action and also classified in Amebicides pharmacological group.The Molecular Weight of Metronidazole is 171.15.
Its pKa is 2.62.


Oral absorption of Metronidazole is found to be 97.5% ±2.5. Volume of distribution is found to be 0.76 - 1.02 l/kg and plasma protien binding is 10 %. and metabolism is reported Hepatic. Renal Excretion accounts for 80 %. also excreted in feces and plasma half life is 7.9 - 9.8 hr.



Metronidazole is contraindicated in conditions like Alcohol dependence,Blood dyscrasias,Neurosis,Seizures,Hypersensitivity,Liver damage.

Drug Interactions

Metronidazole is known to interact with other drugs, the details of drug interactions is as follows:

CarbamazepineMetronidazole enhances the serum concentration of carbamazepine.ModerateDuring coadministration carbamazepine serum kevel and clinical effects should be closely monitored.
Cimetidine (HCl)Cimetidine increases the serum concentration of metronidazole by inhibiting its hepatic metabolism.Minor
DisulfiramCoadministration results in confusion and acute psychoses.ModerateMetronidazole should not be administered when using disulfiram.
LithiumLithium toxicity occurs when lithium is used with metronidazole.
Phenytoin (Na)Metronidazole increases the serum concentration of phenytoin by inhibiting its metabolism. Also phentytoin increases elimination of metronidazole.ModerateSerum level of phenytoin should be closely monitor and dose of phenytoin should be adjusted accordingly.
PodophyllumThe risk of peripheral neuropathy may be increased during concurrent use of two or more agents that are associated with this adverse effect. In some cases, the neuropathy may progress or become irreversible despite discontinuation of the medications.ModerateCaution is advised during concomitant use of agents with neurotoxic effects. Patients should be monitored closely for symptoms of neuropathy such as burning, tingling, pain, or numbness in the hands and feet. Since the development of peripheral neuropathy may be dose-related for many drugs, the recommended dosages should generally not be exceeded.
Warfarin (Na)Metronidazole increases the plasma concentration and thus hypoprothrombinemic effect of warfarin by inhibiting is metabolism, and hence increase prothrombin time of patients taking metronidazole.MajorFrequently checked INR and dose of warfarin should be adjusted accordingly. Patient should report any sign of bleeding to physician.

These interactions are sometimes beneficial and sometimes may pose threats to life. Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.

Interference in Pathology

  • Aspartate Aminotransferase Assay

Side Effects

The severe or irreversible adverse effects of Metronidazole, which give rise to further complications include Encephalopathy, Convulsions, Ataxia, Peripheral neuropathy, Neutropenia, Seizures, Depression, Headache, Dysarthria, Aseptic meningitis.

The signs and symptoms that are produced after the acute overdosage of Metronidazole include Disorientation, Vomiting, Ataxia.

The symptomatic adverse reactions produced by Metronidazole are more or less tolerable and if they become severe, they can be treated symptomatically, these include Weakness, Dizziness, Vertigo, Headache, Anorexia, Diarrhea, Palpitation, Insomnia, Dry mouth, Maculopapular rash, Rashes, Stomatitis, Urticaria, Pruritus, Dysuria, GI upset, Flushing, Phlebitis, Nausea and vomiting, Gynecomastia, Chest pain, Metallic taste, Paresthesias, Acute pancreatitis, Darkening of urine, Dry mouth, dizziness, Thrush, Weakness.

Available Brands

Click on the appropriate strength of the dosage form to view its available brands.

Single Ingredient

Inj: 500 mg/100ml,
Inf: 500 mg/100ml,
Syrup: 75 mg/5ml,
Susp: 200 m/5ml, 75 mg/5ml, 200 mg/5ml,
Cream: 0.75 %w/w,
Gel: 0.75 %w/w,
Tabs: 200 mg, 250 mg, 400 mg, 500 mg,
Vag Tabs: 500 mg,

Multi ingredient

Syrup: 200 mg/5ml,
Susp: 200 mg, 75 mg/5ml, 100 mg/5ml, 200 mg/5ml, 250 mg/5ml, 400 mg/5ml, 321.6 mg/5ml,
Gel: 1 % w/w, 0.75 % w/w,
Tabs: 100 mg, 200 mg, 250 mg, 300 mg, 400 mg, 500 mg,


Metronidazole's dosage details are as follows:
Dose Single Dose Frequency Route Instructions

Adult Dosage

30 mg/kg30 (30)As recommended.IV
15 to 50 mg/kg32 (32.5)As recommended.OralDose very according to condition.
400 mg400 (400)As recommended.POFor 5 to 10 days , frequency could be 2 or 3 times a day.

Paedriatic Dosage ( 20 Kg. )

7.5 mg/kg7.5 (7.5)8 hourlyIntra Venous-
15 mg/kg15 (15)As recommended.IV InfusionOver 60 mins.Initial then 7.5 mg/kg every 24 hour is given starting 48 hours after initial dose.
7.5 mg/kg7.5 (7.5)8 hourlyOral-

Neonatal Dosage ( 3 Kg. )

7.5 mg/kg7.5 (7.5)8 hourlyIv Infusion
7.5 mg/kg7.5 (7.5)8 hourlyOral

High Risk Groups

Drug should not be given to Pregnant Mothers, and patients suffering from Liver Malfunction.

If prescribing authority justifies the benefits of the drug against the possible damages he/she should reevaluate them and consult the reference material and previous studies.

Warning / Precautions

Metronidazole should be used with caution in patients with any allergy. Avoid use during pregnancy or lactation. Avoid alcoholic beverages while taking this medication as severe stomach upset, nausea, vomiting, headache and flushing can occur.

Storage Conditions

Tab, Susp, Inj

Store Below 30°C. Protect from Sunlight.

comments powered by Disqus