What Is the Connection Between Ciprofloxacin and Metronidazole?

Women who are in the early stages of pregnancy should avoid taking metronidazole.
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  • Written By: B. Chisholm
  • Edited By: O. Wallace
  • Last Modified Date: 16 September 2014
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Ciprofloxacin and metronidazole are both antibiotics which are used to treat a variety of different bacterial infections. They act in different ways by different mechanisms of action and are used to treat different infections. In many empirical treatment regimens of sexually-transmitted diseases (STDs) both antibiotics may be given, combined with other antibiotics.

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 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.

Adverse effects, as with any medication, may occur with both ciprofloxacin and metronidazole. The use of alcohol while taking metronidazole and for a time after stopping treatment is contraindicated, as it may cause a severe adverse reaction. Central nervous system side effects, such as headache and dizziness may occur with ciprofloxacin. Both medications may cause gastrointestinal effects such as nausea, vomiting and diarrhea. Any serious adverse reactions should be discussed with a medical professional immediately.


Interactions may occur between ciprofloxacin and metronidazole and other medications and they may not be advised in some people with certain clinical conditions. 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.

Sexually-transmitted diseases may present with non-specific symptoms such as vaginal discharge or burning. Often they are treated empirically, that is a number of antibiotics are given which will treat the full range of the most commonly found STDs. 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 active against gonorrhea.

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. Stopping antibiotics before the full course has been completed may result in resistance and difficulty treating infections in the future.


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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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