What Is the Connection between Ciprofloxacin and Metronidazole?

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  • Originally Written By: B. Chisholm
  • Revised By: C. Mitchell
  • Edited By: O. Wallace
  • Last Modified Date: 21 January 2019
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Ciprofloxacin and metronidazole are both antibiotic drugs that can be used to treat similar bacterial infections, though they also have a number of important differences. Whether a healthcare provider will prescribe both or one over the other depends a lot on the specifics of the condition and the patient involved. They’re often used together to treat aggressive cases of sexually transmitted diseases like gonorrhea, but each has its own separate list of strengths and weaknesses. They are in different antibiotic “families,” which means that they work in different ways; the processes through which they’re made varies, too, and the chemical composition of each is quite distinct. Each carries its own list of side effects and interaction precautions as well. In most cases, the biggest connection is why they’re used, not how they work.

Understanding Antibiotics Generally

Antibiotics are special types of drugs that are designed to specifically target bacterial strains. In most cases they both kill the bacteria and prevent it from reproducing, which makes them more effective for actually treating infections than drugs that seek to relieve pain or boost the body’s natural immune response. There are many different types or families of antibiotics, and how they’re classified depends in large part on how they work and the sorts of bacterial strains they’re best suited to attack. Both ciprofloxacin and metronidazole are effective for a range of conditions, but they’re often different in terms of the conditions for which they’re best suited.


How Each Drug Works

Metronidazole is an antibacterial and antiprotozoal drug. It works on anaerobic bacteria and kills them by damaging their DNA and preventing them from producing more DNA. The drug is usually prescribed to treat infections such as dysentery, giardiasis, amoebic abscesses, and trichomoniasis.

Ciprofloxacin, on the other hand, belongs to the antibiotic class of fluoroquinolones. It works by inhibiting an enzyme needed for the bacteria to produce DNA. Unlike metronidazole, it is not effective against anaerobes. It is, however, effective against a broad spectrum of bacteria and is used to treat a wide range of infections. These include urinary tract infections, typhoid fever, bone infections, and gonorrhea.

Common Overlaps

One of the most common instances in which both antibiotics are prescribed together is in the case of sexually transmitted diseases, or STDs. Sexually transmitted diseases come in many forms, but they’re almost always bacterial. They may present with non-specific symptoms such as vaginal discharge or burning during urination. Often they are treated empirically, which is to say that a number of antibiotics are given at once treat the full range of the most commonly found STDs, even if a patient is only showing symptoms of one or two. These include chlamydia, gonorrhea and trichomoniasis. Often ciprofloxacin and metronidazole form part of the treatment regimen, although resistance to ciprofloxacin has been reported in some countries and has been replaced with a different drug that has found to be more active against gonorrhea specifically.

Adverse Effects and Interactions

Both antibiotics carry a range of side effects and possible reactions. People should usually avoid consuming alcohol while on either medication, as it can impair the antibiotic’s efficacy; this is particularly true of metronidazole. Central nervous system side effects, such as headache and dizziness, are very common with ciprofloxacin, and both medications may cause gastrointestinal problems like nausea, vomiting and diarrhea. Any serious adverse reactions should be discussed with a medical professional immediately.

Interactions might occur between ciprofloxacin, metronidazole, and a range of other medications. Any underlying medical disorders should be discussed with the prescribing doctor. Pregnancy, desired pregnancy, and lactation should also be discussed before starting treatment with either antibiotic, as the drugs can carry risks for unborn children and breastfeeding babies.


While ciprofloxacin and metronidazole are both antibiotics, they are prescribed for different indications and at different doses. The prescribed dose of either should never be exceeded and the full course must be completed in order for the drugs to be effective. Stopping antibiotics before the full course has been completed may result in resistance and difficulty treating infections in the future.


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Discuss this Article

Post 7

Why would my doctor give me ciprofloxacin hcl 500mg and metronidazole 250mg for a stomach infection?

Post 6

I have been on these both for over two years now. I had my colon removed to prevent cancer and I fear that the Doc screwed up. Life is worse now than before the surgery.

Post 5

The two are given together to treat two different bacterial infections. The metronidazole treats bacterial vaginosis, and the cipro treats urinary tract infections. Women can get both of these at the same time during sexual intercourse.

Post 4

I think I know why in my case I acquired NGU after having unprotected oral sex without ejaculation. Symptoms started about a week later with urtheritis and dysuria, intermittent itchy urethra. Eventually, I had pain upon first urination, after ejaculation, low grade fevers, night sweats, fatigue, abdominal pains, chills, again all coming and going. By the time I finally went to the doctor, it had reached my prostate. My doctor gave me cipro but my blood test and urine culture all came back negative. They were taken four weeks post exposure. I am not being treated for trich., yet I am still having symptoms after two weeks of cipro treatment.

I think the docs prescribe these together for cases like

mine when multiple organisms may have been passed. I will contact my doctor to ask him about changing my regimen. I am just praying when I go in for my retests that everything else will still be negative. Lesson learned.
Post 3

@ysmina-- So did you actually have a bacterial infection?

I think the only reason why these antibiotics should be given together is when two different types of bacteria are involved because they kill different types of bacteria. And I guess, to know that, the doctor would have to do a urine test to check for which bacteria are present.

I know that in thyroid fever, ciprofloxacin is the first line of treatment. I'm not sure why ciprofloxacin and metronidazole would be given together in this situation. But it must be because there is more than one type of bacteria right?

Does anyone know?

Post 2
@fify-- I've been on these two antibiotics in the past as well, but I was on them because of colitis. I have Crohn's disease and when I'm having a flare, I get very bad inflammation in my colon. I've gotten good results on antibiotics but the bad part is, the more you use an antibiotic, the less effective it becomes.

That's why I had to take both of these antibiotics together to actually see results the last couple of flares. I just hope these drugs don't stop working because I don't know what I'm going to do then.

Post 1
I worked at a hospital in India for a while and ciprofloxacin and metronidazole were sometimes given together for really hard to treat infections.

I specifically remember one patient who was suffering from a very serious parasitic infection called amoebiasis. The patient wasn't responding to the antibiotics that were given to him so the doctor prescribed ciprofloxacin and metronidazole together.

I think that it depends on the type of infection and how serious it is, but these antibiotics aren't used together often because of the possible contradictions. But when the infection is really serious and doesn't respond to other antibiotics, ciprofloxacin and metronidazole can be used together.

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