Metronidazole is a type of medicine that belongs to the class of antibiotics and antiprotozoals. It is used to treat various infections caused by bacteria and parasites, such as pelvic inflammatory disease, endocarditis, bacterial vaginosis, trichomoniasis, amoebiasis, giardiasis and others. It is also used in combination with other antibiotics to treat stomach ulcers caused by Helicobacter pylori bacteria. Metronidazole is also known by its brand name Flagyl and other names.
But how much do you know about metronidazole? How does it work, how should you use it, what are the possible side effects and interactions, and who should avoid it? In this blog post, we will answer some of the most frequently asked questions about metronidazole and provide you with useful information to help you use this medication safely and effectively.
What is metronidazole and how does it work?
Metronidazole is a synthetic drug that was developed in the 1950s by a pharmaceutical company called Rhône-Poulenc. It was first approved by the Food and Drug Administration (FDA) in 1963 for the treatment of trichomoniasis, a sexually transmitted disease caused by a parasite. Later, it was also approved for the treatment of other bacterial and parasitic infections. It is available in various forms, such as tablets, capsules, creams, gels, lotions, suppositories and injections. It can be bought with a prescription from a doctor or over-the-counter (OTC) without a prescription.
Metronidazole works by entering the cells of bacteria and parasites and interfering with their DNA synthesis. This prevents them from growing and multiplying and eventually kills them. Metronidazole is effective against anaerobic bacteria (bacteria that do not need oxygen to survive) and certain protozoa (single-celled organisms that can cause infections). Metronidazole is not effective against aerobic bacteria (bacteria that need oxygen to survive) or fungi (such as yeast).
How should you use metronidazole?
The dose and frequency of metronidazole depend on your age, weight, medical condition and response to treatment. You should always follow the instructions on the label or the prescription from your doctor. Do not take more than the recommended dose or for longer than advised.
The usual adult dose of metronidazole for bacterial vaginosis is 500 mg twice a day for 7 days or 2 g once as a single dose. The usual adult dose of metronidazole for trichomoniasis is 2 g once as a single dose or 500 mg twice a day for 7 days. The usual adult dose of metronidazole for amoebiasis is 750 mg three times a day for 5 to 10 days. The usual adult dose of metronidazole for giardiasis is 250 mg three times a day for 5 days. The usual adult dose of metronidazole for H. pylori infection is 500 mg twice a day in combination with other antibiotics for 7 to 14 days.
The usual pediatric dose of metronidazole for bacterial vaginosis is 35 to 50 mg per kg of body weight per day divided into three doses for 7 days. The usual pediatric dose of metronidazole for trichomoniasis is 15 to 30 mg per kg of body weight per day divided into three doses for 7 days. The usual pediatric dose of metronidazole for amoebiasis is 35 to 50 mg per kg of body weight per day divided into three doses for 10 days. The usual pediatric dose of metronidazole for giardiasis is 15 mg per kg of body weight per day divided into three doses for 5 days.
The usual OTC dose of metronidazole for vaginal infections is one applicatorful (5 g) of gel or cream inserted into the vagina once or twice a day for 5 days.
You can take metronidazole with or without food, but taking it with food may help prevent stomach upset. Do not crush, chew or break the tablets or capsules; swallow them whole with a glass of water. If you are using a cream, gel, lotion or suppository of metronidazole, follow the directions on the package or the prescription from your doctor. Do not use more or less than prescribed.
If you miss a dose of metronidazole, take it as soon as you remember, unless it is almost time for your next dose. In that case, skip the missed dose and continue with your regular schedule. Do not double the dose to make up for the missed one.
If you take too much metronidazole, seek medical attention immediately. Symptoms of overdose may include nausea, vomiting, diarrhea, stomach pain, dizziness, headache, loss of coordination, seizures, numbness or tingling in the limbs, and metallic taste in the mouth.
What are the possible side effects and interactions of metronidazole?
Metronidazole is generally well tolerated by most people, but it can cause some side effects in some cases. The most common side effects are:
- Nausea, vomiting, diarrhea, stomach pain or indigestion
- Headache, dizziness or fatigue
- Loss of appetite or weight loss
- Metallic taste in the mouth or dry mouth
- Dark urine or changes in urine color
- Vaginal itching, burning or discharge
Most of these side effects are mild and temporary and can be reduced by taking metronidazole with food or milk. However, some side effects can be serious and require medical attention. These include:
- Allergic reactions, such as rash, itching, hives, swelling, difficulty breathing or anaphylaxis (a severe and potentially life-threatening reaction that requires immediate medical attention)
- Severe skin reactions, such as Stevens-Johnson syndrome or toxic epidermal necrolysis (a rare but serious condition that causes blistering and peeling of the skin and mucous membranes)
- Nervous system problems, such as seizures, confusion, hallucinations, depression, anxiety, insomnia, irritability or peripheral neuropathy (damage to the nerves that causes numbness or tingling in the limbs)
- Blood problems, such as anemia (low red blood cell count), leukopenia (low white blood cell count), thrombocytopenia (low platelet count) or agranulocytosis (severe drop in white blood cells)
- Liver problems, such as hepatitis (inflammation of the liver) or liver failure
- Pancreas problems, such as pancreatitis (inflammation of the pancreas)
If you experience any of these side effects while taking metronidazole, stop taking it and contact your doctor right away.
Metronidazole can also interact with other drugs and affect their effectiveness or increase their side effects. Some of the drugs that can interact with metronidazole are:
- Alcohol and other products that contain alcohol or propylene glycol (such as mouthwash, cough syrup or cosmetics), which can cause a disulfiram-like reaction when taken with metronidazole. This reaction can cause flushing, nausea, vomiting, headache, chest pain, palpitations and low blood pressure. You should avoid alcohol and products that contain alcohol or propylene glycol while taking metronidazole and for at least 3 days after you stop taking it.
- Anticoagulants (blood thinners), such as warfarin or heparin, which can increase the risk of bleeding when taken with metronidazole. You may need to monitor your blood clotting time and adjust your dose of anticoagulants while taking metronidazole.
- Anticonvulsants (seizure medications), such as phenytoin, phenobarbital or carbamazepine, which can decrease the levels and effects of metronidazole. You may need to monitor your blood levels of these drugs and adjust your dose of anticonvulsants while taking metronidazole.
- Antidepressants, such as citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine or sertraline, which can increase the levels and effects of these drugs when taken with metronidazole. This can increase the risk of serotonin syndrome, a rare but serious condition that causes agitation, confusion, hallucinations, fever, sweating, tremors, muscle rigidity and seizures. You should consult your doctor before taking metronidazole with any antidepressant.
- Antifungals, such as ketoconazole, itraconazole or voriconazole, which can increase the levels and effects of metronidazole. You may need to monitor your blood levels of these drugs and adjust your dose of antifungals while taking metronidazole.
- Antimycobacterials (tuberculosis medications), such as rifampin or rifabutin, which can decrease the levels and effects of metronidazole. You may need to monitor your blood levels of these drugs and adjust your dose of antimycobacterials while taking metronidazole.
- Antiretrovirals (HIV medications), such as efavirenz, etravirine or nevirapine, which can decrease the levels and effects of metronidazole. You may need to monitor your blood levels of these drugs and adjust your dose of antiretrovirals while taking metronidazole.
- Busulfan (a drug used to treat leukemia), which can increase its levels and toxicity when taken with metronidazole. You may need to monitor your blood levels of busulfan and adjust your dose of busulfan while taking metronidazole.
- Cyclosporine (a drug used to prevent organ rejection after transplantation), which can increase its levels and effects when taken with metronidazole. You may need to monitor your blood levels of cyclosporine and adjust your dose of cyclosporine while taking metronidazole.
- Disulfiram (a drug used to treat alcoholism), which can cause a severe reaction when taken with metronidazole. This reaction can cause flushing, nausea, vomiting, headache, chest pain, palpitations and low blood pressure. You should not take disulfiram within 14 days before or after taking metronidazole.
- Lithium (a drug used to treat bipolar disorder), which can increase its levels and effects when taken with metronidazole. This can increase the risk of lithium toxicity, which can cause nausea, vomiting, diarrhea, tremors, confusion, seizures and coma. You should consult your doctor before taking metronidazole with lithium.
- Metoclopramide (a drug used to treat nausea and vomiting), which can increase the levels and effects of metronidazole. You may need to monitor your blood levels of metoclopramide and adjust your dose of metoclopramide while taking metronidazole.
- Phenylbutazone (a drug used to treat pain and inflammation), which can increase the levels and effects of metronidazole. You may need to monitor your blood levels of phenylbutazone and adjust your dose of phenylbutazone while taking metronidazole.
This is not a complete list of all the possible interactions of metronidazole. Before taking metronidazole, tell your doctor about all the medications, supplements and herbal products you are using or planning to use. Do not start, stop or change the dose of any drug without your doctor’s approval.
Who should avoid metronidazole?
Metronidazole is not suitable for everyone. Some people may have an allergy or intolerance to metronidazole or any of its ingredients. Symptoms of an allergic reaction may include rash, itching, hives, swelling, difficulty breathing or anaphylaxis. If you have ever had an allergic reaction to metronidazole or any other nitroimidazole drug, such as tinidazole or secnidazole, do not take metronidazole.
Some medical conditions may also make metronidazole unsafe or ineffective for you. You should not take metronidazole if you have:
- A history of blood disorders, such as anemia, leukopenia, thrombocytopenia or agranulocytosis
- A history of nervous system disorders, such as seizures, peripheral neuropathy or encephalopathy
- A history of liver disorders, such as hepatitis or liver failure
- A history of pancreas disorders, such as pancreatitis
- A history of alcoholism or alcohol abuse
You should also avoid metronidazole if you are pregnant, planning to become pregnant or breastfeeding. Metronidazole can harm the unborn baby or cause birth defects. It can also pass into breast milk and affect the nursing baby. Talk to your doctor before taking metronidazole if you are pregnant, planning to become pregnant or breastfeeding.
Metronidazole is not recommended for children under 6 months of age. The safety and effectiveness of metronidazole in this age group have not been established. Metronidazole can cause serious side effects in children, such as growth problems, bone problems, infections and vitamin deficiencies.
How to use metronidazole safely and effectively?
Metronidazole can be a useful medication for treating various infections caused by bacteria and parasites, such as pelvic inflammatory disease, endocarditis, bacterial vaginosis, trichomoniasis, amoebiasis and giardiasis, but it should be used with caution and care. Here are some tips to help you use metronidazole safely and effectively:
- Use the lowest effective dose for the shortest possible time.
- Do not exceed the recommended dose or duration of treatment.
- Take metronidazole with food or milk to help prevent stomach upset.
- Avoid alcohol and products that contain alcohol or propylene glycol while taking metronidazole and for at least 3 days after you stop taking it.
- Monitor your symptoms and response while taking metronidazole, as it can cure the infection and prevent complications.
- Watch for signs of side effects or interactions and report them to your doctor promptly.
- Keep metronidazole out of reach of children and pets.
- Store metronidazole in a cool, dry place away from heat and light.
Conclusion
Metronidazole is a common antibiotic and antiprotozoal medication that can help treat various infections caused by bacteria and parasites, such as pelvic inflammatory disease, endocarditis, bacterial vaginosis, trichomoniasis, amoebiasis and giardiasis. However, it can also cause side effects and interactions that can be serious or even life-threatening. Therefore, it is important to use metronidazole wisely and responsibly. Always follow the instructions on the label or the prescription from your doctor. Do not take more than the recommended dose or for longer than advised. Tell your doctor about all the medications, supplements and herbal products you are using or planning to use. Do not take metronidazole if you have an allergy or intolerance to it or any of its ingredients. Do not take metronidazole if you have certain medical conditions that make it unsafe or ineffective for you. Do not take metronidazole if you are pregnant, planning to become pregnant or breastfeeding. Do not give metronidazole to children under 6 months of age. Use the lowest effective dose for the shortest possible time. Take metronidazole with food or milk to help prevent stomach upset. Avoid alcohol and products that contain alcohol or propylene glycol while taking metronidazole and for at least 3 days after you stop taking it. Monitor your symptoms and response while taking metronidazole, as it can cure the infection and prevent complications. Watch for signs of side effects or interactions and report them to your doctor promptly. Keep metronidazole out of reach of children and pets. Store metronidazole in a cool, dry place away from heat and light.
I hope this blog post has been helpful and informative for you. If you have any questions or comments, please feel free to leave them below. Thank you for reading and have a nice day! 😊