Ciprofloxacin (Cipro) and Metronidazole are commonly prescribed antibiotics with distinct characteristics. They both fight bacterial infections, but they do so in different ways, making them valuable tools in the medical field.
This article examines the differences between Cipro and Metronidazole, mainly how they work, their uses, side effects, dosages, drug interactions, and safety considerations. This article also discusses how to take metronidazole and ciprofloxacin together.
Ciprofloxacin and Metronidazole Differences
Cipro and Metronidazole are both used to fight bacterial infections. For instance, doctors prescribe ciprofloxacin and metronidazole for colitis treatment. Simply put, they kill off disease-causing bacteria in the body to prevent damage to the surrounding cells. However, they use two distinct methods to kill the invading microorganisms.
What is Ciprofloxacin?
Known by the brand name Cipro, Ciprofloxacin belongs to a class of antibiotics called fluoroquinolones. Ciprofloxacin is usually used to treat bacterial infections like pneumonia, gonorrhea, and skin infections.
It is often a first-line treatment for rare bacterial infections like typhoid fever, severe internal infections of the bones, joints, prostate, or abdomen, and pathogens used in bioterrorism attacks like anthrax or plague.
It may be used against urinary tract infections, bronchitis, or sinus infections that have not responded to other medications. Ciprofloxacin kills bacteria by disrupting their replication process.
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What is Metronidazole?
Metronidazole also goes by the name Flagyl. It belongs to a category of antibiotics known as nitroimidazoles. Metronidazole is typically effective against anaerobic bacteria (bacteria that can thrive in environments without oxygen) and certain parasites like giardia and amoebas.
Metronidazole is an oral medication used to treat a severe intestinal infection called C. difficile; ulcers; abscesses of the liver, brain, pelvis, and abdomen; and vaginal trichomonas infections.
It is also a topical gel for acne rosacea and bacterial vaginosis. Metronidazole works by damaging a disease-causing organism’s DNA so it can’t reproduce.
How Do They Work?
Both Cipro and Metronidazole prevent bacteria from replicating. Bacteria reproduce asexually through binary fission—first, a single bacterium will make a copy of its DNA, then split into two identical organisms. Sometimes, doctors prescribe ciprofloxacin and metronidazole together for UTIs.
Enzymes are a type of protein that help facilitate the chemical reactions underlying this process. Ciprofloxacin prevents one of these enzymes, DNA gyrase, from being able to do its job. Without DNA gyrase, the bacteria can’t complete binary fission. When a population of bacteria can’t reproduce, they die off.
On the other hand, Metronidazole works directly on the bacterium’s DNA. You’ve probably seen a replica of the double-stranded helix of DNA. When exposed to Metronidazole, the double helix breaks down like rungs rotting off a ladder. Eventually, the DNA becomes so unstable that the cell dies.
What are the uses of Cipro vs. Metronidazole?
Cipro and Metronidazole are most effective against different types of bacteria and are usually used against various infections.
Uses of Cipro
Cipro is a broad-spectrum antibiotic that effectively kills several species of bacteria that cause various infections throughout the body.
Ciprofloxacin is also a powerful antibiotic. Some bacteria have evolved to become resistant to certain types of antibiotics. However, very few bacteria are resistant to Cipro. This is why doctors often prescribe Cipro after other antibiotics have failed to relieve an infection.
Metronidazole is effective against bacteria adapted to low-oxygen environments (anaerobic or microaerophilic bacteria) and several species of protozoa, parasitic single-celled animals. Common parasitic infections that respond well to Metronidazole include intestinal parasites like Giardia lamblia, blastocystis, Entamoeba histolytica, and Balantidium coli.
It is also used against a sexually transmitted parasite called Trichomoniasis vaginalis.
Bacteria susceptible to Metronidazole cause infections throughout the body, including the intestine, liver, bones, joints, blood, central nervous system, heart, reproductive tract, abdominal cavity, and skin.
In addition to acute infections, Metronidazole is used to manage chronic conditions like ulcers caused by Helicobacter pylori and—in a topical preparation—acne rosacea.
Metronidazole and Ciprofloxacin Together Side Effects
Most medications have the potential to cause adverse effects. Since antibiotics can kill the beneficial bacteria in your body as well as the harmful bacteria, you may experience digestive issues or secondary yeast infections.
If your doctor has prescribed you antibiotics, they have determined that the benefits outweigh the potential side effects.
However, there are still some more severe side effects and adverse reactions you should watch out for while taking these medications.
Cipro Side Effects
Many of the most common side effects of ciprofloxacin are similar to common side effects of other antibiotic medications and include:
- Nausea and vomiting
- Yeast infection, usually indicated by vaginal itching and discharge
- Dizziness or drowsiness
Cipro Serious Side Effects
Cipro can sometimes cause more severe side effects, especially in children under 18. If you experience any of the following, call your doctor or get immediate medical attention, and stop taking ciprofloxacin:
Joint pain. Cipro increases your risk of tendonitis or a tendon rupture in more severe cases. Tendons are the fibrous tissues that connect your muscles to your bones.
Symptoms of tendonitis include pain, swelling, tenderness, stiffness, or limited mobility at a joint or muscle. If your tendon ruptures, you may feel or hear a snap or pop at the tendon area, notice bruising, and lose the ability to move or bear weight on the joint or muscle.
The risk of tendon problems remains elevated months after you discontinue treatment.
- Seizures and other problems with your nervous system.
- Nerve damage. It may include numbness, tingling, or a burning sensation.
- Changes in mood, thought, or behavior
- Blood vessel damage. If this occurs, you will feel sudden, severe pain in your torso, abdomen, and extremities and may experience shortness of breath.
- Abnormal heartbeat
- Liver or kidney problems
- C. difficile or other infectious diarrhea, usually with a fever and severe stomach cramps.
- Allergic reaction. Signs include rash or hives; swelling of the face, lips, tongue, or throat; difficulty breathing.
Metronidazole Side Effects
Metronidazole’s most common side effects affect the digestive system and include abdominal cramps, nausea, vomiting, and diarrhea. Patients may also experience:
- Loss of appetite
- A rash (rarely)
- Metallic taste in the mouth
- Weight loss
- Furry tongue
- Nasal congestion
- Dry mouth
- Dark-colored urine
- Irritability or depressed mood
- Trouble sleeping
- Vaginal dryness or itching
- Metronidazole Serious Side Effects
Rare but serious side effects may occur while taking Metronidazole, including:
- Nerve damage
- Sudden changes in vision
- Confusion or altered mental state
- Meningitis. Symptoms will include a sudden, severe headache that doesn’t go away and a stiff neck.
- Allergic reaction
Read also: Using Metronidazole for STD
Ciprofloxacin and Metronidazole Dosage
Both Cipro and Metronidazole are more potent against pathogens at higher doses, but the risk of side effects, severe ones, also increases with dose. Your dosage will depend on the type and severity of your infection.
For adults, the typical dose of Cipro ranges from 500 milligrams to 1000 milligrams per day. This may be taken once daily with an extended-release tablet or through two daily doses of 250 to 500 milligrams as an oral suspension or tablet.
If exposed to plague, you may have to take up to 1500 milligrams daily. For gonorrhea, you may only have to take one 250-milligram dose per day.
Usually, your course of Cipro will last anywhere from 3 to 14 days. However, if you have been exposed to anthrax, you must take Cipro every 12 hours for 60 days.
Children are rarely prescribed ciprofloxacin, but if they have to be, the dose will depend on their weight, usually 10-20 milligrams per kilogram, not exceeding 500 milligrams per day.
Metronidazole can be administered as an intravenous, oral tablet, oral solution, oral capsule, oral extended-release tablet, or topical gel or cream. Capsules usually contain
Most Metronidazole treatment regimens call for 500 milligrams to be taken orally twice daily for 7 to 10 days. Standard capsules contain 375 milligrams, while tablets contain 250 or 500 milligrams. Extended-release tablets can contain up to 750 milligrams of Metronidazole.
Oral liquid suspensions come in strengths of 100 milligrams per liter and 50 milligrams per liter, making the average dose 5 to 10 milliliters twice daily. Some infections may call for 500 to 750 milligrams of Metronidazole up to three times daily.
Intravenous Metronidazole solutions usually contain 500 milligrams per 100 milliliters. 500-milligram doses can be administered up to 4 times daily, depending on the patient’s body weight.
Gel, cream, and lotion preparations contain between .75% and 1.3% Metronidazole and are applied once or twice daily to cover the affected area.
Need a prescription for Metronidazole?
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Metronidazole and Ciprofloxacin Interactions
You may already be taking other medications to manage acute or chronic conditions. Some of these drugs can interact with Cipro and Metronidazole. Interactions may worsen the side effects of one or both medicines, prevent one medicine from working as well as it should, or lead to an overdose.
Both Cipro and Metronidazole can affect your heart rhythm. If you have a heart arrhythmia or are taking another medication that can affect your heart rhythm, speak with your doctor about the potential risks and benefits of taking either drug.
Cipro Drug Interactions
Ciprofloxacin can cause other medications to work too well, creating potentially hazardous effects. Examples include diabetes medications like metformin or sulfonylureas and blood thinners like warfarin. This may cause your blood sugar to drop too low or cause you to bleed more easily, both of which can be dangerous.
Cipro can also increase the levels of other drugs in your system or inhibit them from being metabolized, meaning they stay in your body at higher concentrations for longer.
Cipro may worsen side effects or increase your risk of toxicity from theophylline (an asthma and COPD medication), zolpidem (known as the sleep aid Ambien), tizanidine (a muscle relaxer sold under the name Zanaflex), and an anti-depressant called duloxetine or Cymbalta.
You should also avoid food or supplements that contain magnesium, aluminum, calcium, iron, or zinc, as they may stop your body from adequately absorbing Cipro.
Metronidazole Drug Interactions
Like Cipro, Metronidazole can also interact with warfarin and cause you to bleed more easily. You should not drink alcohol when taking Metronidazole as it may cause vomiting, nausea, and flushing.
Metronidazole also interacts poorly with disulfiram, a medication used to treat alcohol use disorder. When taken together, they may cause psychosis.
If you take the mood stabilizer lithium, Metronidazole may cause a toxic increase of lithium in your blood. Lithium toxicity can cause seizures, confusion, and other neurological symptoms.
On the other hand, some medications can increase the levels of Metronidazole in your system and cause more intense side effects. These include the heartburn medicine cimetidine, amiodarone, clarithromycin, diltiazem, and medications containing cobicistat.
Some medicines may also cause your liver to break down Metronidazole too quickly and prevent it from treating your infection correctly. Some examples are phenytoin, phenobarbital, rifampin, and carbamazepine.
Always check with your doctor and pharmacist before taking Metronidazole to ensure it won’t interact with any other medications you may take.
When to See a Doctor
Bacterial infections rarely go away without treatment. Certain rare or severe infections may require treatment with Cipro or Metronidazole. Talk to a doctor immediately if you have signs of a bacterial infection.
If you don’t have a primary care physician or time to visit a doctor’s office, consider making a telehealth appointment to get the care you need on your schedule.
Read also: Doxycycline vs Amoxicillin
Frequently Asked Questions
Cipro and Metronidazole can be taken together safely. Doctors may sometimes prescribe this combination to treat Crohn’s disease, or they suspect an infection with multiple bacteria, including an anaerobic pathogen. In addition, doctors prescribe ciprofloxacin and metronidazole for diverticulitis.
Some medications may increase a woman’s risk of miscarriage, stillbirth, preterm birth, low birth weight, and congenital disabilities if taken during pregnancy.
While animal studies have shown some increase in adverse effects, especially related to fetal bone formation, when pregnant mothers are given Cipro, research has shown that women who took Cipro did not exhibit higher rates of miscarriage, preterm birth, low birth weight, stillbirth, or congenital malformations than would be expected.
Still, many doctors prefer to prescribe alternative antibiotics to pregnant mothers whenever possible. Cipro can also be excreted through breast milk and may disrupt an infant’s sensitive gut microbiome.
Waiting 3 to 4 hours after taking the medication before feeding or pumping can decrease exposure, but some woman and their doctors may choose to discontinue breastfeeding or the drug.
There is some evidence that Metronidazole may increase the risk of miscarriage if taken during early pregnancy. Still, it is hard to tell if this is because of the medication itself or triggered by the underlying infection.
Otherwise, Metronidazole is not known to cause congenital disabilities, stillbirth, preterm delivery, or low birthrate.
Since Metronidazole targets particular bacteria, its benefits outweigh the risks of not treating an infection while pregnant. It is generally considered safe to take Metronidazole when breastfeeding.
Both Cipro and Metronidazole can cause digestive issues, including diarrhea. However, if your bowel movements seem severely loose and watery, contain blood, are an unusual color, occur frequently, or have a foul smell, you should contact your doctor. You should also consult your doctor on what to eat when taking cipro and flagyl.
There is no evidence that Cipro can cause a miscarriage. Some women have experienced a higher incidence of pregnancy loss after taking Metronidazole, but whether the medication or the underlying infection caused this is unclear. Each woman should work with her doctor to discuss the risks and benefits and find the best option for her and her baby.