Flagyl ER (Metronidazole)

This medicine is called Flagyl (metronidazole). It belongs to a group of medications called antibiotics/antiprotozoals. It helps treat certain bacterial and protozoal infections when prescribed by a Canadian clinician.

What Is Metronidazole?

It can be used to:

• treat serious infections caused by susceptible anaerobic bacteria (for example, intra-abdominal infections, skin and skin structure infections, gynecologic infections, bacteremia/septicemia, central nervous system infections, lower respiratory tract infections, and endocarditis);
• treat trichomoniasis and amebiasis

Clinicians in Canada may sometimes prescribe it for other uses as well, depending on local guidelines and individual factors (off-label use).

Pharmacokinetics

After oral use, metronidazole is well absorbed, with peak plasma concentrations reached 1 to 2 hours after a dose. The average elimination half-life in healthy people is about 8 hours. About 20% of the dose is excreted unchanged in the urine. Metronidazole is found in cerebrospinal fluid and other tissues at concentrations similar to those in plasma.

How to Take Metronidazole

Always take this medicine exactly as your doctor tells you. It is important to finish the full course of treatment. How long treatment lasts will depend on your needs and the infection being treated.

Check with your doctor or pharmacist if you are not sure.

• Swallow the tablets whole with a drink of water
• Do not crush or chew the tablets
• Take them exactly as prescribed

Typical adult oral regimens based on product information (examples; your prescriber may individualize dosing):

Pediatric use: safety and effectiveness in pediatric patients have not been established, except for the treatment of amebiasis (pediatric dosing is weight-based and should be prescribed by a clinician).

Your doctor will decide how much to take and how often, based on the type and severity of the infection.

People with Kidney Dialysis

Hemodialysis can remove a substantial amount of metronidazole from the bloodstream. If dosing cannot be scheduled separately from the dialysis session, your prescriber may consider an extra dose after hemodialysis depending on your clinical situation.

People with Liver Problems

Your doctor may tell you to use a lower dose or take the medicine less often. A dose reduction is recommended in severe hepatic impairment.

If You Take More Metronidazole Than You Should

If you take more than you should, contact your doctor or go to the nearest emergency department right away. If possible, take the box, this leaflet, and any tablets left over with you so the doctor knows what you have taken.

If You Forget to Take the Dose

If you miss a dose, take it as soon as you remember and continue as usual. If it is almost time for your next dose, skip the missed dose and continue as usual. Do not take a double dose to make up for a missed dose.

If you have any further questions about using this product, ask your doctor or pharmacist.

Important Safety Information

Do not take Metronidazole Tablets if you are allergic (hypersensitive) to metronidazole or other nitroimidazole derivatives. Signs of an allergic reaction include a rash, trouble swallowing or breathing, and swelling of your lips, face, throat, or tongue.

Alcohol warning: Do not drink alcohol (and avoid products containing propylene glycol) while you are taking metronidazole and for at least 3 days after finishing your course. Drinking alcohol while taking metronidazole may cause unpleasant side effects such as nausea, vomiting, stomach pain, flushing, headache, and cramping.

Pregnancy and Breastfeeding

Tell your doctor before using this medicine if you are pregnant, might become pregnant, or think you may be pregnant.

• Trichomoniasis: metronidazole tablets are contraindicated during the first trimester. If treatment is needed later in pregnancy and alternative treatment has been inadequate, the one-day (2 g) regimen should generally be avoided because it results in higher serum levels.
• Other indications: published studies include first-trimester exposures; discuss the risks and benefits with your clinician.
• Breastfeeding: metronidazole is present in human milk. Because of the potential for tumorigenicity seen in animal studies, a decision should be made whether to stop breastfeeding or stop the drug. Alternatively, a nursing mother may pump and discard milk during therapy and for 24 hours after therapy ends and feed stored human milk or formula.

Ask your doctor or pharmacist for advice before taking any medicine.

Driving and Using Machines

While taking metronidazole, you may feel sleepy, dizzy, or confused, see or hear things that are not there (hallucinations), have fits (convulsions), or have temporary eyesight problems (such as blurred or double vision). If this happens, do not drive or use any machinery or tools.

Your doctor may want to carry out some tests if you have been using this medicine for more than 10 days.

Possible Side Effects

Metronidazole is generally well tolerated. Common side effects can include nausea, a metallic taste, and stomach upset. Serious nervous system effects (including seizures, encephalopathy, optic or peripheral neuropathy) have been reported, particularly with prolonged use; stop taking the medicine and seek medical advice if you develop neurologic symptoms such as numbness, tingling, weakness, vision changes, or severe dizziness.

Stop taking metronidazole and see a doctor or go to a hospital right away if you get swelling of the hands, feet, ankles, face, lips, or throat that may cause difficulty swallowing or breathing. You may also notice an itchy, raised rash (hives) or nettle rash (urticaria). This may mean you are having an allergic reaction.

Talk to your doctor right away if you notice yellowing of the skin or eyes (jaundice), unusual bruising or bleeding or severe tiredness (possible blood effects), or severe stomach pain that may spread through to your back (pancreatitis).

Long-Term Use

Metronidazole has shown tumorigenicity in mice and rats; unnecessary use should be avoided and treatment should be reserved for appropriate indications.

Interactions

Please tell your doctor or pharmacist if you are taking or have recently taken any other medications. This includes medications obtained without a prescription, including herbal medicines.

• Disulfiram: do not use metronidazole if you have taken disulfiram within the last 2 weeks.
• Alcohol / propylene glycol: avoid during treatment and for at least 3 days after the last dose.
• Warfarin and other coumarin anticoagulants: metronidazole may increase bleeding risk; monitoring/adjustment may be needed.
• Lithium (may increase lithium toxicity; monitoring may be needed).
• Busulfan (may increase busulfan exposure/toxicity).
• Phenytoin, phenobarbital (may alter metronidazole levels and effects).
• Ciclosporin / tacrolimus (levels may increase; monitoring may be needed).

Storage and Stability: Store below 25°C (77°F) and protect from light.