Metronidazole vs. ketoconazole: What’s the difference?
- Metronidazole and ketoconazole are used to treat different kinds of infections.
- Metronidazole is used to treat parasitic infections including Giardia infections of the small intestine, amebic liver abscess, amebic dysentery, bacterial vaginosis, trichomonas vaginal infections, and carriers of trichomonas who do not have symptoms of infection; to treat abscesses in the liver, pelvis, abdomen, and brain; to treat infection of the colon caused C. difficile (C. diff); and Helicobacter pylori (H. pylori) that causes stomach or intestinal ulcers. Metronidazole topical gel is used for treating acne rosacea and metronidazole vaginal gel is used for treating bacterial vaginosis.
- Ketoconazole is used to treat fungal infections such thrush, ringworm, jock itch, athlete's foot, dandruff, tinea versicolor, blastomycosis, histoplasmosis, and coccidiomycosis.
- Metronidazole and ketoconazole belong to different drug classes. Metronidazole is an antibiotic and ketoconazole is an azole antifungal.
- Brand names of Metronidazole include Flagyl and Flagyl ER.
- Brand names of ketoconazole include Nizoral, Nizoral A-D, Ketodan, Extina, Xolegel, and Kuric.
- Side effects of metronidazole and ketoconazole that are similar include nausea, vomiting, headaches, abdominal cramps or pain, dizziness, and rash.
- Side effects of metronidazole that are different from ketoconazole include loss of appetite, metallic taste in mouth, diarrhea, dry mouth, dark-colored urine, weight loss, constipation, furry tongue, nasal congestion, flushing, and vaginal dryness.
- Side effects of ketoconazole that are different from metronidazole include itching, fatigue, impotence, and blood count abnormalities.
What is metronidazole? What is ketoconazole?
Metronidazole is an antibiotic used to treat parasitic infections including Giardia infections of the small intestine, amebic liver abscess, and amebic dysentery (infection of the colon causing bloody diarrhea), bacterial vaginosis, trichomonas vaginal infections, and carriers of trichomonas (both sexual partners) who do not have symptoms of infection; to treat abscesses in the liver, pelvis, abdomen, and brain; to treat infection of the colon caused C. difficile (C. diff); and Helicobacter pylori (H. pylori) that causes stomach or intestinal ulcers. Metronidazole topical gel is used for treating acne rosacea and metronidazole vaginal gel is used for treating bacterial vaginosis. Metronidazole selectively blocks some of the functions within the bacterial cells and the parasites resulting in their death.
Ketoconazole is an azole antifungal medication used to treat fungal infections such thrush, ringworm, jock itch, athlete's foot, dandruff, tinea versicolor, blastomycosis, histoplasmosis, and coccidiomycosis. Ketoconazole is in the same family of drugs as fluconazole (Diflucan), itraconazole (Sporanox), and miconazole (Micatin, Monistat). It prevents growth of several types of fungi by preventing production of the membranes that surround fungal cells.
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What are the side effects of metronidazole and ketoconazole?
Metronidazole
Common side effects are:
- Skin irritation
- Skin dryness
- Allergic contact dermatitis
- Burning and stinging
- Allergic reaction
- Candida vaginitis during or shortly after therapy
- Vaginal vulvar itching
- Gastrointestinal cramps or pain
- Nausea
- Metallic taste
Other important side effects include:
- Bloating
- Dark urine
- Depression
- Skin rash
Disulfiram reactions when used with alcohol. Disulfiram reaction is associated with signs and symptoms of severe flushing that may be accompanied by tachycardia and low blood pressure (hypotension).
Ketoconazole
Ketoconazole generally is well tolerated. Commonly reported side effects of ketoconazole are:
- rash,
- itching,
- nausea,
- vomiting,
- abdominal pain,
- headache,
- dizziness,
- fatigue,
- impotence, and
- blood count abnormalities.
Other important side effects of ketoconazole are rare; they include:
- serious allergic reactions (anaphylaxis),
- severe depression,
- hair loss, and
- tingling sensations.
Liver dysfunction also has been reported. Signs of liver problems include unusual fatigue, loss of appetite, nausea and vomiting, yellowing of the skin (jaundice), dark urine, and pale stools. Development of these symptoms while taking ketoconazole should be reported to a physician.
What is the dosage for metronidazole and ketoconazole?
Metronidazole
To treat rosacea, a thin film of metronidazole gel should be rubbed on affected areas once or twice daily.
The usual dose of vaginal metronidazole gel is one applicator full (containing 37.5mg of metronidazole) intravaginally twice daily for five days. It should be applied once in the morning and once in the evening.
Ketoconazole
Ketoconazole may be taken with or without food. The oral dose range is 200-400 mg daily. Recurrent tinea versicolor is treated with 400 mg monthly. Topical formulations are administered to affected areas once or twice daily.
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What drugs interact with metronidazole and ketoconazole?
Metronidazole
Alcoholic beverages should not be consumed while being treated with metronidazole vaginal gel since this may result in:
This is the same reaction (disulfiram reaction) that occurs in alcoholics who drink alcohol while taking disulfiram (Antabuse), a drug used to discourage alcoholics from drinking alcohol.
Oral metronidazole interacts with warfarin (Coumadin), increasing the latter's blood-thinning properties. Little metronidazole is absorbed topically or from the vagina, and it is not known if the low blood levels achieved with topical or vaginal metronidazole can result in this interaction.
Ketoconazole
If your doctor has prescribed this medication, your doctor or pharmacist may already know of any possible drug interactions and may be watching out for them. Check with your doctor, health care professional or pharmacist before starting, stoping, or changing the dosage of any medicine.
Ketoconazole has:
- severe interactions with at least 33 different drugs
- serious interactions with at least 202 different drugs
- moderate interactions with at least 241 different drugs
- mild interactions with at least 105 different drugs
This information does not contain all possible drug interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the medications and supplements you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Contact your health care professional or doctor for additional medical advice, or if you have health questions, concerns or for more information about this medicine.
Are metronidazole and ketoconazole safe to use while pregnant or breastfeeding?
Metronidazole
Animal studies have not demonstrated a risk to the fetus, but there are no adequate studies in pregnant women.
Orally administered metronidazole is secreted in human milk in concentrations that are similar to concentrations in the mother's blood. Although metronidazole concentration in blood after vaginal or topical administration is small, potential effects on the infant still should be considered.
Ketoconazole
A small amount of ketoconazole is secreted in breast milk. Nursing mothers should probably avoid breastfeeding while using ketoconazole.
