Metronidazole

What is Metronidazole?

Metronidazole is an antibiotic and antiprotozoal medication used for the treatment of certain bacterial and parasitic infections, including pelvic inflammatory disease, endocarditis (an infection of the heart) and, more specifically, bacterial vaginosis (bacterial overgrowth in the vagina), as well as various skin conditions. The medication is available via prescription in many forms, including gel and tablets. Depending on its intended use, the medication is sold in many forms and under various brand names.

What is Metronidazole used for?

Metronidazole is used for the treatment and prevention of a number of conditions, including:

• Bacterial vaginosis (BV), also known as Gardnerella vaginalis or anaerobic vaginosis
• Pelvic inflammatory disease (PID) involving infection of the female upper genital tract (womb, fallopian tubes, ovaries)
• Infections caused by bacteria of the blood, brain, bone, lung, stomach lining and pelvic area, following childbirth or in a wound following an operation
• Mouth infections including dental abscesses and infected gums
• Skin infections like rosacea
• Urinary or genital infections in women and men caused by a parasite called Trichomonas Vaginalis (TV).
• Giardiasis (infection in the small intestine)
• Dysentery or amoebic dysentery (infection of the intestines caused by parasites)
• Stomach ulcers caused by Helicobacter pylori (a type of bacteria) infection
• Prevention of infections after operations
• Infected leg ulcers and pressure sores (injuries to the skin and underlying tissue caused by prolonged pressure to the skin)

NB.: Metronidazole is not suitable to treat a vaginal yeast infection or viral infections such as the common cold.

How does Metronidazole work?

Metronidazole works by inhibiting the growth of bacteria or parasites that are responsible for the infection. By specifically targeting and disrupting the DNA of such cells, and consequently blocking their functions, Metronidazole effectively kills the viruses that cause the inflammation.

How effective is Metronidazole?

Metronidazole is one of the most effective treatments for bacterial vaginosis and is commonly prescribed. The medication is available as an intravaginal gel and in the form of oral tablets. Generally, the gel has fewer side effects when compared to the oral form.

How long does Metronidazole take to work?

It typically takes around 2 to 3 days to start seeing the effects of Metronidazole in bacterial vaginosis. However, you need to take the medication for the entire duration that it was prescribed for, even if the symptoms start to recede, in order to prevent the infection from returning. The oral treatment is generally prescribed for 7 days. 

Active ingredients

Each 500mg Metronidazole tablet contains 500mg of  the active ingredient, metronidazole.

Inactive ingredients

Metronidazole also contains the following inactive ingredients: carmellose sodium, lactose, povidone, magnesium stearate, maize starch, microcrystalline cellulose, methylhydroxypropylcellulose (E464), macrogol 400 and titanium dioxide (E171). 

Please note: Inactive ingredients may differ across different manufacturers. 

Which ingredients can cause an allergic reaction?

Metronidazole does contain lactose as one of its inactive ingredients, so if you are intolerant to lactose you might experience some uncomfortable gastrointestinal symptoms. Other than that, metronidazole is not known to cause severe allergic reactions in people unless you have a hypersensitivity to this medication.

Metronidazole dosage

The recommended dosage of Metronidazole 500mg will depend on the condition you have, your age, the severity of your condition, other medical conditions you may have, and how you react to the first dose.

The recommended dosage for women and adolescent girls to treat bacterial vaginosis is to take Metronidazole 500mg orally (by mouth) twice a day for 7 days. Alternatively, there is also the possibility to take 2g as a single dose for 1 day only.  If Metronidazole is prescribed for other conditions, the dosage may vary.

How to take Metronidazole

Do not exceed your recommended dosage. Swallow your tablets whole, during or after meals with a glass of water to prevent stomach upset. Do not chew them. Use the medicine for the full prescribed length of time, even if your symptoms improve before that.

Always take this medicine as your physician or pharmacist has prescribed you. If you are not sure, do check with your physician or pharmacist.

Metronidazole Side Effects

Get immediate medical help if you experience signs of an allergic reaction to Metronidazole:

• Skin rash (which may be itchy), swelling of your face, lips, tongue, throat; difficulty breathing.
• Symptoms of rare brain disease (encephalopathy), which can include fever, stiff neck, headache, seeing or hearing things that are not there, trouble using your arms and legs, confusion, problems speaking.
• Signs of conditions such as ‘Stevens-Johnson Syndrome’ or ‘toxic epidermal necrolysis’. You may experience skin rashes with blistering, peeling or bleeding of the skin around the lips, eyes, mouth, nose and genitals, flu-like symptoms, high temperature.

Reported side effects of Metronidazole include:

• Diarrhea
• Nausea (feeling sick) or vomiting (being sick)
• Metallic taste in your mouth
• Changes in taste
• Furry tongue
• Loss of appetite
• Dry mouth
• Hypersensitivity (including hives, rash, flushing, nasal congestion, fever)
• Headache
• Painful urination, frequent urination, darkened urine, pelvic pressure, inflammation of the bladder (Cystitis)
• Abdominal Cramps
• Constipation
• Anorexia
• Dizziness, vertigo, confusion
• Depression, weakness, irritability, insomnia (inability to sleep)
• Ataxia (disorder affecting coordination, balance, speech)
• Epigastric distress (discomfort or pain right below your ribs)
• Painful sex, reduction of sex drive
• Joint pains

Rare but serious side effects include:

• Convulsive Seizures
• Numbness/burning/pain/tingling in your hands and/or feet (peripheral neuropathy)

If you experience any serious side effects, talk to your physician.

You should avoid consuming alcohol while you are taking Metronidazole and for at least 48 hours after the last dose in order to avoid abdominal distress, nausea, vomiting, flushing, or headaches.

If you have Crohn’s disease, talk to your physician about the potential impact of Metronidazole on your health, as patients with this condition have an increased risk of gastrointestinal and other cancers due to ongoing inflammation.

Contraindications

Metronidazole is contraindicated in the following patients:

• Patients with a prior history of intolerance and hypersensitivity to Metronidazole or other nitroimidazole derivatives (other forms under which Metronidazole is supplied such as gel, cream, a liquid you drink, or suppository).
• Patients with trichomoniasis (a sexually transmitted infection) in their first term of pregnancy.

Drug interactions

Metronidazole may interfere with the following medicines:

• Disulfiram (drug to treat chronic alcoholism)
• Warfarin and other anticoagulants (blood thinners)
• Lithobid (lithium)
• Busulfan (cancer drug)
• Drugs that inhibit  CYP450 Enzymes such as Phenytoin and Phenobarbital
• Astemizole (antihistamine used to treat allergies)
• Cimetidine (used to reduce stomach acid production
• Vitamins

Always inform your doctor of the drugs, vitamins and herbal medicines you are taking before using  Metronidazole.

Metronidazole cream vs tablets

The most cost-effective treatment for bacterial vaginosis is oral metronidazole; however, the cream may be more suitable for patients who experience undesired side-effects from the oral medication, namely nausea. It should also be noted that alcohol can intensify the nauseating effects accompanied by oral Metronidazole.