Metronidazole (Noritate, Vandazole) — Compare Prices at US & Canada Pharmacies

Rarely, and usually not directly. Metronidazole only works against anaerobic bacteria — organisms that thrive without oxygen — and most UTIs simply aren't caused by that kind of bacteria. "For UTIs, the bacteria most commonly responsible are aerobic gram-negative bacteria like E. coli," explains Sazan Sylejmani, Pharm.D., owner and pharmacy manager at Westmont Pharmacy in Illinois. Between 85% and 95% of UTIs come from aerobic bacteria — mostly E. coli, with Staphylococcus saprophyticus a distant second — and metronidazole simply doesn't touch those.

There's one meaningful exception: bacterial vaginosis (BV), caused by Gardnerella vaginalis, raises UTI risk, and because metronidazole is a standard BV treatment, it ends up being 92% to 96% effective against UTIs specifically triggered by G. vaginalis. "The efficacy of metronidazole for a UTI would be limited to cases where anaerobic bacteria are involved, which is rare in uncomplicated UTI scenarios," notes Dr. Sylejmani.

For a typical UTI, standard first-line antibiotics are nitrofurantoin (Macrobid), sulfamethoxazole-trimethoprim (Bactrim), fosfomycin (Monurol), or cephalosporins like cephalexin and cefadroxil — not metronidazole. If you've been prescribed metronidazole for a urinary symptom, it's usually because a related infection like BV is the actual underlying cause.

No. Metronidazole isn't active against the bacteria that cause either infection — Neisseria gonorrhoeae (gonorrhea) or Chlamydia trachomatis (chlamydia). Standard treatment for gonorrhea is a single injection of ceftriaxone; for chlamydia, it's a course of oral doxycycline.

Where metronidazole does fit into sexual health is different: it's the standard treatment for trichomoniasis (a common STI caused by a parasite, not a bacterium in the usual sense), it's used as part of treatment for pelvic inflammatory disease (PID) when that develops as a complication of an STI, and it treats bacterial vaginosis, which isn't classified as an STI but is linked to sexual activity. If you're being treated for an STI and were prescribed metronidazole, it's most likely addressing one of these three — not the gonorrhea or chlamydia itself, which need their own antibiotics alongside it.

It doesn't treat them, and it can occasionally cause one. Metronidazole kills anaerobic bacteria and certain parasites; yeast infections come from Candida, a fungus, and need an antifungal like fluconazole (Diflucan) or a vaginal cream (miconazole, terconazole) instead.

Confusingly, the two conditions can feel similar, which is exactly why misdiagnosis happens. "A healthcare provider can help determine the cause of the infection and recommend appropriate treatment options to resolve the issue. Self-treating incorrectly can delay proper care, worsen symptoms, and increase risk of recurrence or complications," says Sweta Patel, DO, physician manager for OB-GYN Associates of Advantia.

And yes, metronidazole can itself trigger a yeast infection, the same way most antibiotics can. "One of its side effects is increased risk of yeast infections, namely candidiasis. It disrupts normal bacterial flora, which can allow the overgrowth of Candida species," explains Lipi Roy, MD, an internist and founder of SITA MED. That's not a reason to stop taking it, though — if a yeast infection shows up mid-course, keep taking the metronidazole as prescribed and get the yeast infection treated separately; stopping early over it risks leaving the original bacterial infection under-treated. Preventive antifungal use "isn't recommended" alongside metronidazole, Dr. Roy notes, since there's limited evidence it helps — cotton underwear, avoiding damp clothing, and a Lactobacillus probiotic are reasonable lower-risk steps instead.

Diverticulitis happens when small pouches that form in a weakened colon wall (diverticula) become inflamed or infected. "Metronidazole works by targeting anaerobic bacteria, types of bacteria that thrive in low-oxygen environments like parts of the gastrointestinal tract," explains Reshma Kapadia Patel, Pharm.D., founder of WiseMedRx in Dallas.

Treatment guidance has shifted in recent years, though. "Physicians are much more hesitant to prescribe antibiotics for diverticulitis because research has shown that when diverticulitis is mild, it can often resolve on its own without antibiotic therapy," says Jeffrey H. Chester, DO, medical director of the Ohana Luxury Addiction Treatment Center. Roughly 80% of cases are uncomplicated — inflammation confined to the pouches, without abscess or spread — and typically clear up in about a week with hydration, a low-fiber or liquid diet, and pain control, no antibiotics needed.

Metronidazole tends to come into play when there's a suspected bacterial component (fever, elevated inflammatory markers, notable inflammation on a CT scan), when you're at elevated risk of complications (a suppressed immune system, cardiovascular or kidney disease), or for the roughly 20% of cases that are complicated by an abscess, perforation, or spread. It's usually paired with a second antibiotic — commonly ciprofloxacin, levofloxacin, or Bactrim — since diverticulitis infections typically involve more than one type of bacteria; the combination "provides coverage against different types of bacteria, including gram-negative organisms," Dr. Patel notes.

For uncomplicated diverticulitis, the standard dose is 500 mg by mouth every 8 hours, typically for 7 to 10 days, sometimes longer. Complicated cases usually mean hospitalization, with metronidazole given intravenously. Dr. Chester advises taking it with food, since it can upset the stomach, and avoiding alcohol entirely — the combination can cause severe nausea, vomiting, headache, and heart palpitations.

Most people notice improvement within a few days. Contact your provider right away for severe abdominal pain, ongoing vomiting, numbness or tingling in the hands or feet, seizures, or signs of an allergic reaction. "As a de-prescribing pharmacist, I also encourage patients to review their full medication list when starting antibiotics to avoid unnecessary duplication or interactions," Dr. Patel adds.

Finish the entire course even once you feel better. "Stopping any antibiotics early can allow bacteria to survive. This can result in antibiotic resistance. It can cause the remaining bacteria to grow stronger, leading to a return of the infection. This can make it harder to treat future infections," Dr. Chester cautions. Metronidazole alone may not be enough for severe or complicated cases (which may need drainage or surgery alongside antibiotics), for infection that's spread into the bloodstream, or for recurrent diverticulitis — your provider will reassess if symptoms don't track as expected.

Topical metronidazole — sold as MetroGel, MetroCream, MetroLotion, and generics — is FDA-approved specifically for the inflammatory bumps and persistent redness of rosacea, a chronic condition affecting facial blood vessels. It works as an anti-inflammatory and antimicrobial applied directly to the skin, gradually reducing redness and the number and severity of breakouts. It's sometimes used alone and sometimes alongside an oral antibiotic like tetracycline or procedures like laser therapy for a stronger initial response, then continued alone for maintenance.

Cream or gel — which is better depends on your skin. "I prefer using the gel formulation for patients with oily skin, and the cream formulation for those with dry skin. The active ingredient in both (metronidazole) is the gold standard for long-term maintenance therapy," says Eleonora Fedonenko, MD, Medical Director of Your Laser Skin Care Center in Los Angeles.

Don't expect fast results — rosacea develops gradually and improves the same way. "Typically, patients will experience a 50% reduction in redness and bumps within approximately four to six weeks when utilizing either the 0.75% or 1% formulations of topical metronidazole," Dr. Fedonenko notes. It's generally used long-term as maintenance therapy rather than a short course, since stopping tends to let symptoms return.

The most common issue is local irritation — burning, stinging, extra redness, or dryness right where you apply it, which can be more noticeable on skin that's already inflamed from rosacea itself. Less commonly, topical metronidazole can cause systemic effects: metallic taste, tingling or numbness in the fingers and toes, nausea, or flu-like symptoms. Contact your dermatologist for any of these, especially tingling, numbness, or signs of an allergic reaction.

Metronidazole isn't the only option. "Rosacea-related acne is typically treated with topical antibiotics like metronidazole or azelaic acid," says Long Ly, MD, a board-certified dermatologist at MetroDerm in Atlanta. Other FDA-approved alternatives include azelaic acid, ivermectin cream (Soolantra), benzoyl peroxide, low-dose oral doxycycline (Oracea), and medications targeting the redness itself like brimonidine or oxymetazoline gel, plus laser or intense pulsed-light therapy. Since rosacea varies so much person to person, working with a dermatologist on a personalized plan — including daily gentle skincare, sun protection, and identifying your personal triggers (heat, alcohol, spicy food, sun) — matters as much as the specific medication chosen.

Generally yes, particularly in the second and third trimesters. "Metronidazole is generally considered safe for use during pregnancy, particularly during the second and third trimesters; however, it's vital to use it only when necessary and under the guidance of your doctor," says Ila Dayananda, MD, a board-certified OB-GYN and Chief Medical Officer at Oula maternity care. Most of the safety evidence comes from animal studies rather than large controlled human trials, which is why the older FDA classification system placed it in Category B — but "the risk of birth defects or miscarriage with metronidazole use during pregnancy is generally considered to be relatively low, especially when used as prescribed," Dr. Dayananda notes.

The reasoning mirrors what you'll see with other antibiotics in pregnancy: leaving an infection like bacterial vaginosis untreated carries its own real risks. Dr. Dayananda points out untreated BV can "increase the risk of complications such as preterm birth, low birth weight, and potentially serious infections in the uterus or newborn" — risks that generally outweigh the low, largely theoretical risk from the medication itself. One 2007 study did find a higher preterm birth risk in certain high-risk groups given metronidazole during the second trimester specifically, which is part of why your provider will weigh your individual situation rather than treating this as automatic.

Oral tablets appear to carry the lowest risk of the available forms — animal research found swallowed metronidazole wasn't harmful to developing mice, while injectable formulations showed more concern, according to Benjamin Gibson, Pharm.D., adjunct professor at the University of Texas at Austin. Providers generally aim for the shortest necessary course and try to avoid the first trimester when a reasonable alternative exists — options include clindamycin, erythromycin, amoxicillin-clavulanate, or tinidazole, depending on the infection. If you find out you're pregnant partway through a course, contact your provider rather than stopping or continuing on your own.

Alcohol is the big one — completely avoid it during treatment and for about 3 days after your last dose. Metronidazole blocks the enzyme that breaks down alcohol, letting a toxic byproduct (acetaldehyde) build up, which causes severe nausea, vomiting, cramping, a racing heart, headache, and flushing.

Less well known: propylene glycol, a common food additive and solvent, can trigger the same kind of reaction. It shows up in more places than you'd expect — baked goods, candy, soft drinks, salad dressings, some breads and bacon, and many liquid or syrup-based over-the-counter cold and cough medicines. "Many OTC cold and cough preparations also contain propylene glycol, so carefully examine ingredient lists before purchasing," advises Lily Grobman, PA, a certified physician assistant with Medical Offices of Manhattan. Avoid it for the same window as alcohol — during treatment and for 3 days after.

If your stomach is sensitive, mild foods like crackers can help. "Consuming the medication alongside mild foods such as crackers can help minimize gastrointestinal upset," notes Inna Melamed, Pharm.D. Extended-release tablets are the one exception to "take with or without food" — those need an empty stomach, about an hour before or two hours after eating.

Yes — a few less commonly discussed interactions are worth knowing if they apply to you:

• Disulfiram (Antabuse, for alcohol use disorder). Combined with metronidazole, this can cause acute psychosis, confusion, and hallucinations — one study found this in over 1 in 5 patients given both. Metronidazole should be avoided if you've taken disulfiram in the past two weeks.
• Busulfan (a chemotherapy drug used before stem cell transplants). Metronidazole can raise busulfan levels by roughly 80%, increasing the risk of serious busulfan toxicity — this combination needs specialist oversight and frequent monitoring if it can't be avoided.
• Mycophenolate (an immunosuppressant used after organ transplants). Metronidazole may reduce its blood levels and effectiveness, likely by killing off gut bacteria that help the body process it — long-term metronidazole use is generally avoided in people who depend on mycophenolate.
• Lithium. Metronidazole can raise lithium levels and reduce kidney function, so closer monitoring of both is typically needed.
• Cimetidine (an older heartburn medication). Can raise metronidazole levels, so watch for increased side effects.
• Phenytoin or phenobarbital (seizure medications) can also interact — mention these to your provider.
• Cockayne syndrome, a rare genetic condition, is a specific reason to avoid metronidazole altogether — case reports have linked it to acute, sometimes fatal, liver failure in people with this condition.

As always, give your provider and pharmacist your complete medication list before starting.

Usually, yes — this combination comes up often because bacterial vaginosis and a yeast infection frequently occur together (as many as 30% of women with BV also have a concurrent yeast infection), and the two drugs treat different problems: metronidazole for the bacterial side, fluconazole (Diflucan) for the fungal side.

There is one real caution: combining them may raise the risk of a serious heart rhythm abnormality called torsades de pointes. This matters more if you have long QT syndrome, existing heart disease, are 65 or older, take a diuretic, have a persistently slow heart rate, have low potassium, magnesium, or calcium, or have had severe vomiting or diarrhea. If none of that applies to you, providers often proceed with the combination without special monitoring; if it does, your provider may monitor more closely or choose a different approach.

One specific regimen sometimes used for recurrent BV combines monthly metronidazole (2,000 mg once a month) with a single 150 mg dose of fluconazole. As always, take each medication exactly as directed and mention every other medication and condition to your provider before combining them.

Metronidazole is prescribed for infections caused by anaerobic bacteria and certain parasites — bacterial vaginosis, trichomoniasis, C. diff, PID, amebiasis, giardiasis, and some dental and abdominal infections, among others. When it's not the right fit — first-trimester pregnancy, an interacting medication, poor tolerance, or a resistant organism — several alternatives exist, each suited to different situations:

• Tinidazole. A close chemical relative of metronidazole, taken with food to reduce stomach upset. Some people who tolerate metronidazole poorly do better on tinidazole — reported side effects (metallic taste, nausea, fatigue) tend to be milder.
• Solosec (secnidazole). A single-dose treatment for BV and trichomoniasis — the oral granules can be mixed into applesauce, yogurt, or pudding rather than swallowed as a pill. Vaginal yeast infection, headache, nausea, and diarrhea are the main side effects.
• Cleocin (clindamycin). Covers similar anaerobic bacteria to metronidazole and is used for skin, respiratory, bone, and joint infections as well as BV. Its own notable risk is C. difficile-associated diarrhea, which needs monitoring.
• Vancocin (vancomycin, oral). Reserved specifically for C. difficile infection and enterocolitis when taken by mouth. Common side effects are stomach pain, nausea, diarrhea, and gas.
• Alinia (nitazoxanide). An antiprotozoal rather than an antibiotic, used for giardiasis and C. difficile. Taken with food; side effects include nausea, abdominal pain, and urine discoloration.

Don't switch or stop on your own — work with your provider on a transition plan first, since stopping abruptly risks letting the infection progress unchecked. Once a plan is in place, metronidazole can be safely stopped and swapped for the alternative.

If you do continue metronidazole, complete the full course even after symptoms improve. Feeling better after a few days doesn't mean the infection is fully cleared, and stopping early lets surviving bacteria regrow — potentially returning as a harder-to-treat, resistant strain. This matters beyond your own case, too: growing antimicrobial resistance is a real public health concern, and finishing prescribed courses as directed is one of the more meaningful ways patients can help slow it.

Natural remedies and probiotics aren't a substitute for metronidazole or any prescribed antibiotic when one is genuinely needed, though a probiotic alongside your course may help offset antibiotic-associated digestive upset — ask your provider before adding one.