Women's Health

Metronidazole Side Effects

Metronidazole Side Effects

Key Takeaways

  • The various forms of this medication have their different side effects.
  • Patients on metronidazole drugs are highly discouraged from drinking because alcohol consumption leads to a chemical reaction that inhibits the body from breaking down the alcohol.
  • Serious side effects can also occur when taking the medications, although such cases are rare. 

Metronidazole is a medication specifically prescribed to treat illnesses caused by parasites or bacteria affecting many parts of the body. The medication operates by eliminating the germs that usually cause the infection and is accessible in a variety of forms.

They include:

• Oral tablets and immediate-release capsules,
• Vaginal gels,
• Topical creams,
• Lotions,
• Gels, etc.

These various forms of the medication have their different side effects.

Side effects of capsules and tablets

The extended-release and immediate-release metronidazole tablets as well as capsules are ingested by mouth and absorbed via the stomach. The extended-release medication stays active for longer periods than does the immediate-release type. Furthermore, extended-release medication is mainly used in treating vaginal-related infections, while immediate-release metronidazole is used to get rid of bacterial infections that affect other various parts of the body, and also infections caused by parasites.

More common side effects

While taking metronidazole tablets or capsules, some common side effects typically occur. They include:

• Vomiting,
Diarrhea,
• Heartburn,
Constipation,
• Yeast infections,
• Headaches,
• Vaginal discharge,
• Appetite loss, etc.

Serious side effects

Serious side effects can also occur when taking the medications. However, such cases of severe side effects are rare. They include:

• Cancer: The tablets and capsules have a black box warning, the most severe warning from the FDA (Food and Drug Administration). In studies conducted on animals, it was found that prolonged high doses of metronidazole can lead to the development of cancer in animals, and such can be the case in humans too.

• Encephalopathy: This is an abnormal brain reaction resulting from taking metronidazole medication and can be identified by the following signals: dizziness, inability to control volunatarily-controlled muscles, and slurred speech that becomes difficult to comprehend. When experiencing such symptoms, the patient should make sure to contact their physician immediately, although upon stopping the use of metronidazole, the symptoms commonly disappear after some days or weeks.

• Seizures: Before taking metronidazole, the person should inform the doctor whether he or she, the patient, has a history of recurrent seizures. The patient should immediately contact the doctor if they experience seizures after taking the medication. The physician can prescribe alternative medication.

• Meningitis: Symptoms associated with meningitis usually occur after hours of taking the metronidazole medication. Meningitis is the inflammation of the membrane covering the spinal cord or the brain. Such inflammations typically result in fever, stiff neck, and severe headache. Whenever the patient experiences such symptoms, he or she should immediately contact the doctor because untreated meningitis can be life-threatening. Nevertheless, the risks associated with meningitis disappear once the metronidazole medication is stopped.

Peripheral neuropathy: When the nerves become damaged, peripheral neuropathy arises. Symptoms indicating the presence of the condition will be experienced in the hands and feet and commonly include a burning sensation, numbness, shooting pains, and “pins and needles.” The patient should always contact the doctor upon experiencing such symptoms because if left unattended, severe conditions like muscle weakness, loss of balance, and a reduction in reflexes usually occur. Even though the person may stop taking metronidazole, it is not a guarantee that peripheral neuropathy will disappear.

• Severe allergic reaction: When a person is allergic to metronidazole, he or she may experience the following symptoms: breathing problems, tongue and throat swelling, hives, and a rash on the body. Upon experiencing such symptoms, the person should quickly contact the physician, since some allergic reactions can be life-threatening.

• Steven-Johnson syndrome: A rare skin disorder that can manifest itself in the following order of symptoms: flu-like symptoms (tiresomeness and fever), a painful red rash, and the top layer of the skin starts to shed.

The syndrome is usually a medical emergency, meaning that the doctor’s attention should be quickly sought when a person begins to experience the above symptoms.

• Neutropenia: When the levels of particular white blood cells (neutrophils) responsible for fighting off infections become low, the resulting condition is neutropenia. Having the condition puts the body at greater risk of acquiring an infection because the defense mechanisms are weak. Therefore, a person should always contact the physician when she or he develops an infection while taking metronidazole medication.

Side effects of Metronidazole topical cream, gel, and lotion

The above products are responsible for treating rosacea inflammation, a condition that leads to the reddening of the skin and the formation of small bumps on the skin.

More common side effects

Side effects resulting from metronidazole lotions, topical creams, and gels are mild and disappear after some days. Common side effects include irritation, itching, dryness, redness, burning and stinging sensation, and lastly, worsened rosacea. Other additional side effects resulting from the topical gel include the common cold, headaches, and respiratory infections.

Side effects of metronidazole vaginal gel

The gel plays a significant role in treating bacterial vaginosis. The side effects are mild and include itchy vagina, nausea, vomiting, menstrual cramps, and vaginal yeast infection. The product's severe side effects are usually rare but can occur in some cases, and they include cancer, seizure, and peripheral neuropathy.

Watch out for alcohol

Patients on metronidazole drugs are highly discouraged from drinking because alcohol consumption leads to a chemical reaction that inhibits the body from breaking down the alcohol. Symptoms usually include nausea, flushing, headaches, vomiting severely, and abdominal cramps.

Patients should always contact the doctor upon such symptoms. Furthermore, they ought to check their other medications, if any, to see whether they contain alcohol, which can interfere with the metronidazole medication. Such medications include mouthwashes, aftershaves, perfumes, hair sprays, bug sprays, breath strips, and cough syrups. Generally, patients should be very cautious with drugs containing alcohol, even those that have only small amounts.

Important information

The patient should make sure that he or she takes the metronidazole as prescribed and for the full length of time. Adhering to medication improves the symptoms before infection completely disappears. Meanwhile, skipping medication can lead to adverse effects such as the condition antibiotics resistant.

Before taking this medicine

Patients who are allergic to metronidazole should not take the drug, and instead use an alternative medication prescribed by the doctor. Furthermore, women must avoid the medication if they are pregnant, or communicate with particular doctor if they are planning to get pregnant during the medication process. Lastly, women who are breastfeeding should talk with the doctor before taking the medication as it can pass via breast milk, in turn harming the baby. Therefore, corrective measures must be in place.

Other important issues that the patient can communicate to his or her doctor before taking metronidazole include whether the patient has liver disease, intestinal disease, a blood cell disorder, nerve disorder, or epilepsy or seizures.

In the event that the patient has any of the above health issues, he or she should adjust the dose or go for alternative medication.

How should I take metronidazole?

The medicine comes as an immediate-release or extended-release tablet of capsule. The dose, however, will depend on the condition and how the body reacts to the treatment. The medication should be taken every day at a consistent time. Furthermore, whatever the doctor has prescribed or the instructions she or he has laid out should be followed to the letter.

To make sure that the medication does not lead to adverse effects, the patient should regularly have his or her blood and liver functions tested. Furthermore, whenever the patient is treated by a different doctor, the new physician should be told if one is using metronidazole.

What happens if a patient misses a dose?

If the patient misses a dose but the next scheduled dose is close, he or she can skip the missed dose. Otherwise it is imperative that the missed dose be taken immediately once the patient remembers or realizes that he or she has missed a dose.

Metronidazole Overdose

An overdose of the medication will be indicated by the following signals: nausea, vomiting, seizures, dizziness, loss of body balance, and numbness. A patient should always seek the services of the poison control center whenever they suspect an overdose.

Other drugs that may affect metronidazole

The patient should notify the physician on other types of medication that they are using. The common ones that typically affect the functioning of the metronidazole include cimetidine, seizure medications (e.g., luminal), blood thinners (e.g., jantoven), lithium, and disulfiram.

It is important to always be on the lookout for such drugs because drug interactions usually increase the risks of the various medications' side effects. The patient should not change in any way the prescribed dose unless the doctor approves it.Also, the patient should keep a list of all the medications he or she is using, both prescription and nonprescription drugs. The patient should then share the list with his or her physician to facilitate the dosage adjustment process when needed.

Apart from medications that may interact with the metronidazole, there exist other products that also interact with the medicine. Such kinds of products include alcohol-containing products such as cold syrups, aftershaves, or products containing propylene glycol, lithium, or lopinavir solution.

Furthermore, if the patient is taking disulfiram, he or she should avoid the use of metronidazole but rather take other alternative drugs that the physician may prescribe. Additionally, the patient must always communicate to lab personnel before any test is carried out, because metronidazole medication may in some instances interfere with certain lab tests, which may lead to the occurrence of false lab results. When the lab personnel know about the drug you use, they will be able to prepare lab tests with which metronidazole will not interfere.

It is known that most antibiotics usually do not have severe effects on hormonal birth control pills, rings, or patches. However, some antibiotics like rifabutin and rifampin can reduce the effectiveness of these contraceptives. Such instances might result in pregnancy due to the weakening of the efficacy of the birth control pills, ring, or patch. Therefore, women who are using hormonal birth control must always talk with their doctors if they are taking the metronidazole.

Pregnancy and Metronidazole

Women who are pregnant must not take metronidazole in the first trimester. The patient must communicate to his or her physician when she is pregnant or plan to get pregnant if she is or will still be using metronidazole by that time.

Furthermore, the medication can get into a woman's breast milk, and this can harm the breastfeeding baby in the process. Therefore, it is imperative for the person not to breastfeed while taking metronidazole medication, without the doctor's approval.

Nevertheless, recent studies have not shown the risk of defective fetal outcomes or congenital anomalies after the consumption of the metronidazole medication during the pregnancy period. In fact, the risk of the infant getting cancer due to metronidazole exposure was not identified in three consecutive studies that were carried out to assess the possibility. Nevertheless, there was limited ability to detect the signals that would indicate the presence.

Due to the imminent risks of vaginal trichomoniasis if it occurs during pregnancy, the CDC recommends the use of metronidazole at any stage during pregnancy to prevent vaginal trichomoniasis.

Metronidazole for dogs and cats

Dogs and cats are given metronidazole to cure diseases such inflammatory bowel disease, periodontal disease, diarrhea, and numerous other infections. However, the person will be in need of a veterinarian's prescription to obtain the medication for the pet.

Communicate with the doctor

In the event where the patient is unsure about metronidazole's side effects, it would be best if they were to talk with their respective doctors and share their concerns. The doctor, in turn, would be instrumental in helping the patient understand the effects of metronidazole.

To be on the right track, the patient can start with the following questions:

• What are the potential risks of the numerous side effects of metronidazole?
• Is there an alternative to metronidazole that might have slightly fewer side effects?
• What are some of the ways whereby an individual can reduce the side effects associated with metronidazole?

Having well-laid out questions can ensure that the doctor and the patient share information with each other, so that the physician can come up with a treatment plan that is efficient and safe.