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Why it's used

Metronidazole is used to treat a sexually transmitted infection (called symptomatic trichomoniasis). It is a prescription medicine. This medicine works by interacting with DNA that interferes with the DNA synthesis that leads to the end of bacteria. Metronidazole is also used to treat a genitourinary infection (called asymptomatic trichomoniasis). It is also used to treat asymptomatic sexual partners. Metronidazole is also used to treat a parasitic infection of the colon (amebiasis) and a parasitic infection of the small intestine (giardiasis). Metronidazole is also used to treat certain anaerobic bacterial infections that include intra-abdominal infections, skin and skin structure infections, female reproductive organ (gynecologic) infections, blood poisoning (bacterial septicemia), lower respiratory tract infection, serious heart infection (endocarditis), central nervous system infections, and bone and joint infections. Metronidazole is also used to prevent the infections that may occur before, during or after the operation of the intestine (elective colorectal surgery). This medicine helps by decreasing the incidence of infection received after a surgical procedure in patients experiencing elective disorders of the rectum, anus, and colon (colorectal surgery). Metronidazole is also used to treat acute dental infections e.g. painful infection of the gums (acute ulcerative gingivitis or acute pericoronitis) and pus inside the teeth (acute apical infections). Metronidazole is also used to treat anaerobically-infected leg ulcers and pressure sores.
When not to use
Metronidazole will not work against viral infections such as the common cold.
Nitroimidazole Antimicrobial
Metronidazole belongs to a class of medicines called Nitroimidazole Antimicrobial. Nitroimidazole Antimicrobial.

How to use

Follow directions on the product label, information guide, and provided by your doctor before using Metronidazole. Use this medicine as per your doctor's instructions.
Metronidazole is used with or after food. Metronidazole should be swallowed with water. It should not be chewed.
The typical adult dose of Metronidazole is 750 mg three times daily orally for 5 to 10 days. The typical dose for children is 35 to 50 mg/kg/24 hours or 15.9 to 22.7 mg/lb/kg/24 hours, orally for 10 days divided into three doses. The maximum dose for adults of Metronidazole is 2000 mg per day. This medicine is commonly used for a period of 7 days for trichomoniasis, 5-10 days for amebiasis, 7-10 days for anaerobic bacterial infections, 5-7 days for bacterial vaginosis, 3-10 days for giardiasis, 3 days for acute ulcerative gingivitis, 3-7 days for acute dental infections, 7 days for leg ulcers and pressure sores, and 7-14 days for eradication of Helicobacter pylori.
This medicine should be used on an as-needed basis. Infections of the bone and joint, endocardium, and lower respiratory tract may require longer treatment. You should continue to use this medicine as directed by the doctor even if you feel well.
Tell your doctor if your condition does not improve or worsens. Talk to your doctor if stomach pain, abnormally low weight, nausea, vomiting, fever, feeling of discomfort, fatigue, yellowing of the skin, dark urine, and discolored stools or itching. If you have issues with the health of your liver, For patients with severe liver damage (Child-Pugh C), the dose of Metronidazole should be reduced by 50%.
To see the impact of Metronidazole on the body, your doctor may recommend a lower initial dose. Please follow your doctor's instructions carefully. Older patients may see an increase in the risk of side-effects. Hence, a lower dose may be recommended.
If you are giving Metronidazole to a child, be sure to use a product that is meant for use in children. Before giving this medicine, use the child's weight or age to find the right dose from the leaflet or product package. You can also read the dosage section of this page to know the correct dose for your child. Else, consult with your doctor and follow their recommendation.
To decrease the possibility of side-effects, you might be recommended to use the extended-release form of this medicine by your doctor. The extended-release medicine helps in maintaining a steady level of the medicine in your body for a longer period of time. Do not crush or chew the medicine, unless indicated on the package or by your doctor.
Metronidazole is intended for intravenous (into the veins) use only. Metronidazole is to be given slowly by intravenous drip infusion only, either as a constant or periodic infusion. Intravenous admixtures comprising Metronidazole and other drugs should be avoided. Metronidazole Injection, USP is a ready-to-use isotonic solution. There is no requirement of dilution or buffering and do not refrigerate the injection.
Avoid drinking alcohol with Metronidazole.
Your doctor may require that certain tests be performed before using Metronidazole. The doctor may ask you to have Antibiotic Susceptibility test. This test helps the doctor in selecting an appropriate antibacterial drug for starting the therapy. Your doctor may request liver function test test. Liver function tests must be done just before to the start of treatment, throughout and after the end of treatment until liver function is within average ranges, or till the baseline values are achieved. Metronidazole should be discontinued if the liver function tests become markedly raised during treatment.
Medicines may be given for uses other than those listed in the medicine guide. Do not use Metronidazole for symptoms for which it was not prescribed. Do not give Metronidazole to others who may have similar symptoms as you. Self-medication can cause harm.
Store Metronidazole below 25°C (77°F), away from excess heat and moisture, and protect from light. Keep this medicine away from children and pets.

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How to take Metronidazole

Your dose and how often you take Metronidazole will depend on the following factors:
  • age
  • weight
  • patient's health
  • the health of the patient's kidneys
  • response to the medicine

Metronidazole Dosage

Dosage for sexually transmitted infection caused by a parasite (trichomoniasis)

Adult
  • Recommended: 2000 mg as a single dose or 1000 mg in two divided doses on the same day or 250 mg three times a day for seven days.
Children (Children 1 to 10 years)
  • Recommended: 40 mg/kg (18.18 mg/lb) in a single dose or 15-30 mg/kg (6.8- 13.6 mg/lb) in a day divided in 2-3 doses
  • Maximum: 2000 mg per dose

Dosage for parasitic infection of the colon (amebiasis)

Adult
  • Recommended: 500 mg or 750 mg three times daily for 5 to 10 days
Children
  • Recommended: 35 to 50 mg/kg/day (15.9-22.7 mg/lb/day) divided into three doses daily for 10 days

Dosage for anaerobic bacterial infections

Adult
  • Recommended: 7.5 mg/kg (3.3 mg/lb) (approximately 500 mg for a 70 kg/154 lb adults) every six hours for 7 to 10 days
  • Maximum: 4000 mg in a day for 7 to 10 days

Dosage for bacterial overgrowth in the vagina (bacterial vaginosis)

Adult (adults and children over 10 years)
  • Recommended: 2000 mg as a single dose on the same day or 400 mg twice a day for 5 to 7 days

Dosage for a parasitic infection of the small intestine (giardiasis)

Adult (adults and children over 10 years)
  • Recommended: 2000 mg once a day for 3 days or 400 mg three times a day for 5 days or 500 mg twice a day for 7-10 days
Children (children 7 to 10 years)
  • Recommended: 1000 mg once a day for 3 days
Children (children 3 to 7 years)
  • Recommended: 600-800 mg once daily for 3 days
Children (children 1 to 3 years)
  • Recommended: 500 mg once daily for 3 days

Dosage for infection of the gums (acute ulcerative gingivitis)

Adult (adults and children over 10 years)
  • Recommended: 200 mg three times a day for 3 days
Children (children 7 to 10 years)
  • Recommended: 100 mg three times daily for 3 days
Children (children 3 to 7 years)
  • Recommended: 100 mg twice daily for 3 days
Children (children 1 to 3 years)
  • Recommended: 50 mg three times daily for 3 days

Dosage for acute dental infections

Adult
  • Recommended: 200 mg three times a day for 3 to 7 days

Dosage for leg ulcers and pressure ulcers

Adult
  • Recommended: 400 mg three times daily for 7 days

Dosage for eradication of Helicobacter pylori bacteria

Children
  • Recommended: 20 mg/kg/day (9.09 mg/lb/day) for 7-14 days
  • Maximum: 500 mg for 7-14 days

Minimum Age

infants less than 8 weeks

Dosage calculation for children

To calculate the dosage for children please use the weight based dose calculator to calculate the appropriate dosage as per the weight of your child.

Forms

Tablet
Strength: 500 mg and 250 mg
Capsule
Strength: 375 mg and 500 mg
Cream
Strength: 7.5 mg/1g, 0.75%, 1%, 10 mg/1g, 10 mg/60g, and 10%
Gel
Strength: 7.5 mg/1g, 0.75%, 1%, 10 mg/1g, 65 mg/5g, and 13 mg/1g
Tablet, extended release, film coated
Strength: 750 mg
Injection, solution
Strength: 500 mg/100ml
Liquid
Strength: 5 mg

Missed Dose

A missed dose should be taken as early as you remember it. However, if the time for the next dose is almost there, then the missed dose should be skipped, and the regular dosing schedule should be continued. Avoid taking a repeated dose to make up for a missed one.

Overdose

What to do if you overdose on Metronidazole?
There is no specific antidote for an overdose of Metronidazole. In cases of massive overdose, supportive and symptomatic therapy should be started.
Symptoms of an overdose of Metronidazole
If you use too much of this medicine, it could lead to dangerous levels of the medicine in your body. In such cases, symptoms of an overdose may include:
If you think you have overdosed on Metronidazole, call a poison control center immediately. You can look up the poison control center information from the Poison Center Finder at TabletWise.com.

Precautions while using Metronidazole

Before you use Metronidazole, tell your doctor if you are allergic to it or its ingredients. Your doctor may prescribe an alternative medicine and update your medical records to record this information. Discuss with your doctor if you are allergic to nitroimidazole-antimicrobial.
Before you use Metronidazole, tell your doctor of your medical history including blood disorder (blood dyscrasia), inflammation of the digestive tract (Crohn’s disease), liver disease, kidney disease, or rare disease causing short stature, premature aging, severe sensitivity to sun, and moderate to severe delay in learning (Cockayne syndrome). Patients with blood disorders such as dyscrasia are at a risk to develop mild abnormalities like decreased blood cell count. In patients with liver damage, adjustment of dose is required and patients who have Crohn's disease are at an increased risk to develop stomach and intestinal cancers. Patients with Cockayne syndrome should be advised by the doctor for regular monitoring of liver function both during and after the treatment with Metronidazole.
The use of Metronidazole may change alkaline phosphatase. The liver enzyme, AST is found to increase when Metronidazole is given to the patient.
The use of this medicine may change alanine transaminase, ALT. The liver enzyme, AST is found to increase when Metronidazole is given to the patient.
The use of Metronidazole may change aspartate transaminase, AST. The liver enzyme, AST is found to increase when Metronidazole is given to the patient.
Consult with your doctor on the use of Metronidazole during pregnancy or if you are planning to become pregnant. Metronidazole is known to cross the placenta but its effects on the formation of organs in the human fetus are not known. It should only be given to pregnant women if the doctor finds it essential and not otherwise. Consult with your doctor on the use of Metronidazole during breastfeeding. Metronidazole is found to be present in human milk. The decision to use this medicine should depend on the importance of Metronidazole to the mother and only if the doctor finds it essential to be given to the mother.
Avoid drinking alcohol with Metronidazole. Consumption of alcohol may cause a reaction to a medicine (disulfiram-like reaction), cramps in stomach, nausea, vomiting, headache, and flushing.
Metronidazole can make you feel sleepy. Be careful, especially while driving, while using heavy machinery, or when doing any activity that needs you to be completely alert. The consumption of alcohol with Metronidazole can worsen the sleepiness. Metronidazole may cause seizures in some people. Hence, you should discuss with your doctor before performing any activities where a loss of consciousness may cause harm to you or others.
Older patients may have a higher incidence of side-effects when using Metronidazole.
There is a risk of mutations (mutagenicity) in humans if Metronidazole is used for longer treatment than it is usually required.

Metronidazole Side-effects

The following side-effects may commonly occur when using Metronidazole. If any of these side-effects worsen or last for a long time, you should consult with your doctor:
  • ECG changes in T-wave amplitude
  • a decrease in sexual desire (decrease of libido)
  • change in the color of urine (darkened urine)
  • constipation
  • cramps in the stomach
  • diarrhea
  • excessive production of urine
  • headache
  • inflammation of a vein caused by a blood clot (thrombophlebitis)
  • nausea
  • pain in upper part of the stomach
  • painful and difficult urination
  • serious eating disorder (anorexia)
  • tiny bumps on the surface of the tongue (furry tongue)
  • vomiting
Rarely, the use of Metronidazole may cause the following side-effects:
  • a sense of pelvic pressure
  • abnormally low levels of neutrophils (reversible neutropenia)
  • abnormally low levels of thrombocytes
  • decreased white blood cell count
  • dizziness
  • dryness of the mouth
  • dryness of vagina or vulva
  • fainting
  • flushing
  • hives
  • inability to control urine (urinary incontinence)
  • incoordination
  • inflammation of the tongue (glossitis)
  • insomnia
  • irritability
  • loss of body movements
  • nasal congestion
  • pain in joints (arthralgia)
  • pain in muscle
  • painful or difficult sexual intercourse (dyspareunia)
  • rashes due to diseases, allergic reactions, and infections (erythematous rash)
  • severe itching
  • speech disorder
  • swelling in the lower layer of skin
  • unpleasant metallic taste
  • vertigo
  • weakness
The following severe side-effects may also occur when using Metronidazole:
  • stomach and intestinal (gastrointestinal) disorders
    Symptoms: painful swelling and sores inside the mouth, inflammation of rectum (proctitis), inflammation of the digestive tract (Crohn’s disease) colon cancer
  • liver and pancreatic disorders
    Symptoms: increase in liver enzymes (AST, ALT, alkaline phosphatase), inflammation of the liver (hepatitis), liver damage (hepatocellular liver injury and liver failure), yellow discoloration of the skin (jaundice) inflammation of the pancreas (pancreatitis)
    The symptoms of pancreatitis are reversible if the drug is discontinued.
  • kidney disorders
    Symptoms: infection of the urinary system (cystitis)
  • female reproductive organ infections
    Symptoms: fungal infection of the vagina
  • central nervous system including brain diseases (encephalopathy)
    Symptoms: convulsive seizures, inflammation of the membranes of the brain and spinal cord (aseptic meningitis), damage to the optic nerve (optic neuropathy), weakness, numbness, tingling sensation and pain due to nerve damage in the hands and feet (peripheral neuropathy), confusion depression
    The symptoms of nervous system due to the use of Metronidazole may resolve if the drug is discontinued.
  • allergic reactions
    Symptoms: a serious and life-threatening disorder of the skin (Stevens-johnson syndrome) fleeting joint pain that resembles an allergic reaction
  • Symptoms: an abnormal decrease in white blood cells, agranulocytes, deficiency of red blood cells, white blood cells and platelets (pancytopenia)
  • eye disorders
    Symptoms: double vision (diplopia) short-sightedness (myopia)
Your doctor has prescribed Metronidazole because they judge that the benefit is greater than the risk posed by side-effects. Many people using this medicine do not have serious side-effects. This page does not list all possible side-effects of Metronidazole.
If you experience side-effects or notice other side-effects not listed above, contact your doctor for medical advice. You may also report side-effects to your local food and drug administration authority. You can look up the drug authority contact information from the Drug Authority Finder at TabletWise.com.

Warnings

Discoloration of urine

Patients who on treatment with Metronidazole are at an increased risk to develop darken urine.

Use of Metronidazole for longer treatment

Patients on longer treatment than usual with Metronidazole are at an increased risk. Such patients may develop changes in the amount or structure of the genetic material of cells (mutagenicity).

Convulsive seizures

Patients who on treatment with Metronidazole are at an increased risk to develop seizures.

Loss of liver function

As the breakdown of Metronidazole is done by liver enzymes, hence in the patients with damaged liver functions, the removal of Metronidazole has interfered. Accumulation of Metronidazole may occur in patients in whom the functions of the brain are lost when a damaged liver does not remove harmful substances from the blood (liver encephalopathy), and the high levels of Metronidazole in the blood may contribute to the symptoms of the encephalopathy. Such patients should take Metronidazole with caution, and the daily dose should be reduced to one third and should be given once a day.

Patients undergoing the procedure of blood purification (hemodialysis)

In patients who are undergoing hemodialysis treatment, Metronidazole and its metabolites are removed following a period of eight hours of dialysis. Metronidazole should be given immediately after performing hemodialysis.

Adverse drug reactions which result in fluid-filled blisters (severe bullous skin reactions)

Patients who are undergoing treatment with Metronidazole are at increased risk to develop severe bullous skin reactions such as serious disorder of the skin and mucous membranes (Stevens-Johnson syndrome) and rare skin reaction (acute generalized exanthematous pustulosis). If these symptoms occur, discontinue the use of Metronidazole.

Severe liver damage

Patients who are on treatment with Metronidazole are at an increased risk of severe liver damage, it may result in a life-threatening outcome. In such patients, Metronidazole should be used after careful monitoring and only if there is no other treatment available. Tests for the liver function must be performed before starting the therapy, during and after the therapy until the liver function is within normal values. The drug should be discontinued in case the values of liver function tests become considerably increased during treatment. Patients who have Cockayne syndrome should be advised to report the symptoms of liver injury to their doctor and should be informed to stop taking Metronidazole.

Inflammation of membranes of the brain and spinal cord (aseptic meningitis)

Patients undergoing treatment with Metronidazole are at an increased risk to develop inflammation of the brain and spinal cord (meningitis).

Weakness, numbness, and pain due to nerve damage (peripheral neuropathy)

Patients who are on treatment with Metronidazole are at an increased risk to develop peripheral neuropathy. Such patients are at an increased risk to experience peripheral neuropathy, numbness or tingling sensation of an extremity.

Brain disease that alters brain function or structure (encephalopathy)

Encephalopathy and peripheral neuropathy (including optic neuropathy) patients are at an increased risk when using Metronidazole. Such patients are at an increased risk to experience encephalopathy and weakness, numbness, and pain due to nerve damage in the hands and feet (peripheral neuropathy). Metronidazole should be utilized with caution in patients with liver encephalopathy and the dose should lower to one third or may use once a day.

Interactions with Metronidazole

When two or more medicines are taken together, it can change how the medicines work and increase the risk of side-effects. In medical terms, this is called as a Drug Interaction.
Metronidazole interacts with warfarin and other oral anticoagulants, which are used to prevent blood clots. The patients who use Metronidazole in combination with anticoagulants such as warfarin may experience an increased anticoagulant effect of warfarin and other oral anticoagulants, which may further prolong the blood clotting time. In such patients, the time that blood takes to clot (prothrombin time and international normalized ratio) should be carefully monitored.
There may be an interaction of Metronidazole with alcoholic beverages, which is an alcoholic drink containing ethanol, known as alcohol. The patients undergoing treatment with Metronidazole may experience cramps in stomach, nausea, vomiting, headache, and flushing if they consume alcohol or substances containing propylene glycol during or after treatment. Patients who are on treatment with Metronidazole should stop consumption of alcohol or products that contain propylene glycol during and after three days of therapy with Metronidazole.
Metronidazole may interact with disulfiram, which is used for the treatment of alcoholism. The patients who use Metronidazole in combination with disulfiram may develop mental problems (psychotic reactions). The patients who have taken disulfiram within the last two weeks should not take Metronidazole.
Your doctor's guidelines may need to be followed while taking this medicine along with Busulfan, which is used in the treatment of certain types of cancers. The patients who use Metronidazole in combination with busulfan may experience an increase in the levels of busulfan in the blood, which may result in an increased risk of harmful effects of busulfan due to its accumulation. Patients who are on treatment with Metronidazole should not be given busulfan if the benefit by busulfan is less than the risk. If there is no other treatment available, the levels of busulfan in the blood should be monitored routinely and its dose should be adjusted properly.
Special instructions need to be followed while taking this medicine along with lithium, which is used to treat a major depressive disorder. The patients who are on high dose levels of lithium and who undergo short-term treatment with Metronidazole have been associated with increased levels of lithium in the blood. In some cases, lithium poisoning may occur due to high levels of lithium. The levels of lithium and creatinine in the blood should be monitored after certain days of beginning treatment with Metronidazole to recognize any increase that may lead to clinical symptoms of damage due to lithium accumulation.
Your doctor's guidelines may need to be followed while taking this medicine along with 5 fluorouracil, which is used in the treatment of cancer. When Metronidazole is given along with 5 fluorouracil, the clearance of 5 fluorouracil is decreased and the accumulation of 5 fluorouracil can result in harmful effects.
Special instructions need to be followed while taking this medicine along with ciclosporin, which is used as an immunosuppressant. The patients who use Metronidazole in combination with ciclosporin may experience an increase in ciclosporin levels in the blood. Patients who are on treatment with both Metronidazole and ciclosporin should closely monitor the levels of ciclosporin and creatinine in the blood.
Metronidazole interacts with drug or laboratory tests. The patients who use Metronidazole may interfere with certain types of tests of blood chemistry values such as aspartate aminotransferase, lactate dehydrogenase, alanine aminotransferase, triglycerides, and glucose hexokinase and the values of zero have been observed.
There may be an interaction of Metronidazole with drugs that induce CYP450 enzymes such as phenytoin or phenobarbital, which is used for the prevention of tonic-clonic seizures. The patients who use Metronidazole in combination with the drugs that induce microsomal liver enzymes such as phenytoin or phenobarbital may enhance the elimination of Metronidazole. It results in reduced levels of Metronidazole in the blood and disrupted clearance of phenytoin has also been reported.
Metronidazole may interact with drugs that prevent CYP450 enzymes such as cimetidine, which is used to treat certain types of ulcers. The patients who use Metronidazole in combination with the drugs that prevent CYP450 enzymes such as cimetidine may increase the level and decrease the clearance of Metronidazole from the blood.
This page does not contain all the possible interactions of Metronidazole. Share a list of all medicines that you use with your doctor and pharmacist. Do not start, stop, or change the dose of any medicines without the approval of your doctor.

Traveling With Medication

  • Ensure that you carry enough doses of each of your prescription medicines to last the entire trip. The best place to store your medicines is in the carry on baggage. However, while flying, if carrying liquid medicines, make sure you do not go over the limits imposed for carry-on liquids.
  • While traveling overseas, make sure that you can carry each of your prescription medicines legally to your destination country. One way to ensure this is by checking with your destination country's embassy or website.
  • Make sure that you carry each of your medicines in their original packaging, which should typically include your name and address, and the details of the prescribing doctor.
  • If your travel involves crossing time zones, and you are required to take your medicine as per a fixed schedule, make sure that you adjust for the change in time.

Expired Medication

Taking a single dose of expired Metronidazole is unlikely to cause a side-effect. However, please discuss with your doctor or pharmacist, if you feel unwell or sick. An expired medicine may become ineffective in treating your prescribed conditions. To be on the safe side, it is important not to use an expired drug. You are much safer by always keeping a fresh supply of unexpired medicines.

Safe Disposal of Medication

  • If there are disposal instructions on the package, please follow the instructions.
  • If there are medicine take-back programs in your country, you should contact the respective authority to arrange for the disposal of the medicine. For example, in the USA, the Drug Enforcement Administration regularly hosts National Prescription Drug Take-Back events.
  • If there are no take-back programs, mix the medicine with dirt and place them in a sealed plastic bag. Throw the plastic bag in your household trash. Separately, remove all personal information including the prescription label from the medicine packaging and then dispose off the container.
  • If specifically indicated on the medicine package that it needs to be flushed down the toilet when no longer needed, perform the required step.
This page provides information for Metronidazole .
Bacterial Infections
Parasitic Diseases
Skin Infections
Sexually Transmitted Diseases

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