Flagyl (Generic Metronidazole)


Metronidazole is a nitroimidazole antimicrobial with both antiprotozoal and antibacterial activity against the anaerobic bacterial example Giardia lamblia, Entamoeba histolytica. It is commonly known as Flagyl.

Mechanism of action

Metronidazole exhibits selective toxicity. Metronidazole selectively diffuses in protozoa and anaerobic bacteria and little or no diffusion in anaerobic bacteria and human cells. After uptake into the cells, the nitro group in metronidazole is reduced which in turn leads to active cytotoxic compounds that bind covalently to the helical structure of the DNA thus inhibiting nucleic acid synthesis. This leads to cell death of the protozoans and anaerobes. The cytotoxic compounds produced during reduction are usually intermediate acting thus give rise to inert products.

Dosage and formulation

Metronidazole tablets are usually formulated in two forms which include;- immediate release tablets which are absorbed readily into the bloodstream immediately after administration and Extended-release tablets which are absorbed slowly into the bloodstream. Metronidazole Immediate release tablets are taken with food this helps reduce stomach upset while extended-release tablets should be taken an hour before meals or two hours after meals. It is used to treat PIDs (pelvic inflammatory diseases), Bacterial Endocarditis and vaginosis among with other antibiotics or alone.

As with antibiotics, you should take this medication only as directed by your pharmacist or doctor. It is advisable to take this medicine with a lot of water or with food to prevent stomach upsets. Every person/ patient is given a different dosage depending on the condition they have or how they are responding to treatment hence take the drug as advised by your health professional.

Antibiotics are very specific and thus for better results it is good when you space this drug as prescribed. If you are to take it 8 hourly, ensure you take it at the same time of the days. i.e. if you take the drug today at 6 am, 2 pm and 10pm, let the schedule follow for the remaining days until the dosage is over.

If your doctor has told you to take this drug for a week or 5 days at most, ensure to adhere to the number of days and the dosage strictly. It does not matter whether the symptoms start disappearing on the third day of the medication, all you are supposed to do is continue taking the drug. This prevents drug-resistant bacteria from emerging. This tactic should be followed for all antibiotics and not necessarily metronidazole alone. If the condition persists, consult with your doctor about the situation.


Metronidazole is absorbed in the small intestines. It is widely distributed in the body with increased therapeutic concentrations in body fluids example semen, vaginal secretions, cerebrospinal fluid, and saliva.Metronidazole is metabolized in the liver hence not prescribed in patients with liver diseases or elderly patients due to decreased liver function with age. Excretion is mainly in urine and small amounts in feces.

Side effects

Metronidazole has certain effects when used. Most of them are normal and not life threatening: 

  • Metallic taste in the oral cavity especially after taking the drug
  • Nausea and vomiting
  • Constipation
  • Diarrhea
  • Decrease in appetite
  • Stomach discomforts due to abdominal cramping
  • Heartburn
  • A headache
  • Neutropenia
  • Increased risk for yeast infections and vaginal irritation.

The Metronidazole side effects are usually less severe and often go away during the medication period or after you stop the medication. However, if the symptoms persist you should contact your doctor or pharmacist.

Serious side effects.

Usually present as nervous system side effects which include:

  • A headache.
  • Convulsions
  • Seizures
  • Dizziness.
  • Ataxia which is degeneration of the cerebellum which leads to loss of balance and equilibrioception, loss of muscle coordination, problems with speech and eye movements
  • Encephalopathy
  • Peripheral neuropathy which presents as numbness or a feeling of pins and needles.

Allergy warning

Metronidazole has been associated with hypersensitivity reactions which present as wheezing, red rash, fever, chills or peeling skin. It is important to contact your doctor or pharmacist immediately you start experiencing any of the above effects.

Drug interactions

Metronidazole interacts with other drugs which might lead to a subsequent increase or decrease in concentrations of the drug. Increase in concentration leads to increased risk of side effects while a decrease may worsen the pre-existing disease. Some of the drugs include:

Alcohol - This leads to disulfiram reactions which presents as abdominal cramps, nausea, vomiting or a headache.

Cimetidine - This results in increased metronidazole concentration.

Anti-coagulants example warfarin which may increase bleeding.

Phenobarbital and Phenytoin - co-administration of the two drugs led to the fast metabolism of metronidazole hence decreased concentration in blood.

It is important to inform your doctor or pharmacist of any medications, supplements or herbs you are taking. This will avoid any adverse reactions.

Metronidazole contraindications

Pregnant women- Metronidazole is classified under Pregnancy Category B thus may only be used when the benefits of use exceed the potential risks. However, metronidazole is avoided in the first trimester of pregnancy.

Patients with liver disease- Metronidazole is metabolized in the liver. A liver disease may increase metronidazole concentration in blood this may increase the risk of side effects.

Patients with kidney disease- This is because the drug is eliminated in urine.

Lactating mothers- Metronidazole is secreted in breast milk which might affect the fetus.

Use of alcohol is contraindicated during the course of treatment or three days after discontinuing the medication.


Metronidazole should be kept under lock and key out. This is a drug that you do not want to get into the hands of babies hence put them out of reach of children. Some of the conditions treated with Metronidazole such as trichomonas vaginalis requires the two couples or the two sexual partners to come together for proper treatment since, despite treatment, one can still pass it to another person. Go with your partner to your health professional.

Metronidazole Price

Metronidazole cost is very affordable. You can buy Metronidazole tablets online on various sites which are accredited to sell drugs through their websites such as FairPriceRX.com

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