Flagyl

What Flagyl is used for

Flagyl is a brand of metronidazole, an antibiotic that treats infections caused by anaerobic bacteria — germs that live where there is little or no oxygen — and by certain single-celled parasites. That covers dental and gum infections, infected wounds, and some gut and pelvic infections. It is also used for protozoal illnesses such as giardiasis (a gut infection picked up from contaminated water) and trichomoniasis (a sexually transmitted infection). Bacterial vaginosis, a common vaginal infection, is another. The tablets come as 200mg and 400mg.

How it works, and how the course runs

Metronidazole does nothing until it gets inside the organisms it targets. They convert it into a short-lived, reactive form that damages their DNA, so they can no longer multiply and the infection clears. Human cells don't make that conversion, which is why healthy tissue is largely left alone.

Course length follows the infection rather than a fixed rule — a single dose, two doses in one day, or a tablet two or three times daily for several days. Swallow the tablets whole with water, and finish the whole course even after you feel better; stopping early leaves the infection partly treated and gives the bacteria a chance to become resistant. Keep the pack dry and out of sunlight.

Side effects to expect

A metallic taste is the one people notice first — food and drink taste odd for as long as the course lasts. Nausea, an upset stomach, diarrhoea, headache, a dry mouth and a furry tongue are also common, and most of these settle. Numbness or tingling in the hands or feet is uncommon and turns up mainly with longer courses. Swelling of the face, lips or throat, a rash that keeps spreading, or trouble breathing counts as an emergency.

Alcohol, disulfiram and other medicines

Drinking while metronidazole is in your system brings on flushing, nausea, vomiting, stomach cramps, headache and sweating, often within minutes. Alcohol-containing cough syrups and mouthwashes can do the same, so it is easier to leave alcohol out altogether until the course is over. Disulfiram, used for alcohol dependence, is never taken alongside metronidazole, and at least two weeks need to pass after the last disulfiram dose before metronidazole starts. Metronidazole also strengthens warfarin and similar blood thinners, which raises the chance of bleeding.

Flagyl or plain metronidazole tablets?

Both contain metronidazole at 200mg and 400mg, so the choice comes down to the name on the pack and the pack size you want — 30 tablets or several hundred. Metronidazole is the plain-labelled version sold here, and metronidazole explains the ingredient itself, from what it treats to how it behaves in the body.