Adco-Metronidazole is metronidazole, an antibiotic that works against anaerobic bacteria and several parasites. It treats dental infections, abdominal and pelvic infections, bacterial vaginosis, trichomonas, amoebiasis and giardiasis. The 400 mg tablet is the form most people are given.
What is Adco Metronidazole?
The South African Medicine Price Registry lists Adco Metronidazole 100 ml as a Schedule 4 infusion, containing metronidazole 5 mg/ml — the intravenous form, used in hospital for serious infections and around abdominal surgery.
The 400 mg tablet that most searches are about is the standard oral strength of metronidazole, widely registered in South Africa under many brand names. The medicine is the same; only the route differs. Tablets are used for infections that can be treated at home; the infusion is used when someone is too unwell to swallow, or where high levels are needed quickly.
Metronidazole is a nitroimidazole, and it works in an unusual way. The molecule is inert as supplied. Inside organisms that survive without oxygen — anaerobic bacteria and certain parasites — it is chemically reduced into a reactive form that fragments their DNA. Human cells and ordinary oxygen-using bacteria do not perform that reduction, so they are largely unaffected.
That mechanism explains its whole clinical profile: it is highly effective against anaerobes and protozoa, and essentially useless against the aerobic bacteria that cause most chest and urinary infections. This is why it is so often prescribed alongside another antibiotic rather than instead of one — the two cover different halves of a mixed infection.
What is Adco Metronidazole commonly used for?
Bacterial infections:
- Dental infections and abscesses, often with amoxicillin, alongside dental treatment.
- Bacterial vaginosis — one of its most common uses.
- Pelvic inflammatory disease, as part of combination treatment.
- Intra-abdominal infections, appendicitis and peritonitis, usually starting intravenously.
- Infected wounds, pressure sores and diabetic foot infections, where anaerobes are involved.
- Preventing infection around bowel and gynaecological surgery.
- Clostridioides difficile infection, in some cases.
- Helicobacter pylori eradication, as part of a combination for stomach ulcers.
Parasitic infections:
- Trichomoniasis, a sexually transmitted infection. Partners must be treated too, or reinfection follows.
- Amoebiasis — amoebic dysentery and liver abscess.
- Giardiasis, a cause of persistent diarrhoea.
It does not treat most chest infections, most urinary infections, or viral illnesses such as colds and flu.
How Adco Metronidazole fits into this medicine category
| Group | Examples | Typical target |
|---|---|---|
| Nitroimidazoles | Metronidazole (Adco-Metronidazole, Metronidazole), tinidazole | Anaerobic bacteria; trichomonas, amoebae, giardia |
| Aminopenicillins | Amoxicillin | Broad cover for chest, ear, throat, urine |
| Penicillin + inhibitor | Co-amoxiclav | Mixed infections including some anaerobes |
| Macrolides | Azithromycin (Azrotrin) | Atypical chest infections; penicillin allergy |
| Antifungals | Clotrimazole, fluconazole | Thrush — a different cause of vaginal symptoms |
That last row matters for vaginal symptoms specifically: bacterial vaginosis and thrush are different conditions with different treatments. Metronidazole treats the first and does nothing for the second. Discharge that has been self-treated as thrush without improvement is a common reason people end up needing this medicine. See the antibiotics and antimicrobials hub.
What to check before using Adco Metronidazole
Do not drink alcohol while taking it, or for at least 48 hours after the last dose. This is the defining caution with metronidazole. The combination can cause a disulfiram-like reaction — flushing, throbbing headache, severe nausea and vomiting, abdominal cramps and a racing heart. It is unpleasant enough to send people to casualty.
The prohibition extends further than most people expect. Check for alcohol in cough mixtures, tonics, herbal remedies and mouthwashes, and be cautious with foods cooked in wine or containing alcohol.
Tell your doctor or pharmacist if you:
- Have liver disease. Metronidazole is processed by the liver and the dose may need reducing.
- Have a blood disorder, or have had low white cell counts.
- Have a nervous system condition, epilepsy, or existing numbness or tingling in the hands or feet.
- Take warfarin — metronidazole significantly increases its effect and raises bleeding risk. Monitoring is usually needed.
- Take lithium, phenytoin, phenobarbital, ciclosporin, busulfan or 5-fluorouracil.
- Are pregnant or breastfeeding. It is used in pregnancy where needed, but this should be a clinician’s decision.
- Are being treated for a sexually transmitted infection — partner treatment matters.
Practical points:
- Take tablets with or after food to reduce nausea, swallowed whole with water.
- Space doses evenly and complete the full course, even once symptoms settle. Stopping early is a common cause of recurrence, particularly in bacterial vaginosis.
- Expect a metallic taste. It is very common, harmless, and settles after the course.
- Your urine may darken. This is a known, harmless effect.
Possible cautions and when to ask a pharmacist or doctor
Common effects are nausea, a persistent metallic taste, loss of appetite, abdominal discomfort, headache, diarrhoea and a furred tongue.
Get emergency help for:
- The alcohol reaction — severe flushing, vomiting, chest tightness or palpitations after drinking.
- Swelling of the face, lips or tongue, difficulty breathing, or a widespread blistering rash.
- Seizures, severe confusion, or difficulty with balance and coordination.
Seek prompt advice for:
- Numbness, tingling, burning or weakness in the hands or feet. This is peripheral neuropathy, occurs mainly with long or repeated courses, and can persist — report it early rather than finishing the course and hoping.
- Unexplained fever, sore throat, mouth ulcers or unusual bruising — possible effects on blood cells.
- Severe, watery or bloody diarrhoea, especially with fever, during or after the course.
- Yellowing of the skin or eyes, or dark urine with pale stools.
- Visual disturbance.
Contact your doctor if the infection is not improving after two to three days, if symptoms return soon after finishing, if you are treating an STI and your partner has not been treated, or if you develop thrush afterwards — common after antibiotics and easily treated, but easily confused with the original problem.
Related medicine guides
Frequently asked questions
What is Adco-Metronidazole 400 mg used for? Dental infections and abscesses, bacterial vaginosis, pelvic and abdominal infections, infected wounds, and parasitic infections including trichomoniasis, amoebiasis and giardiasis.
What is the infusion used for? The same range of infections, given intravenously in hospital when someone cannot take tablets or needs treatment quickly — including around bowel and gynaecological surgery.
Can I drink alcohol on it? No — not during the course and not for at least 48 hours afterwards. The combination causes severe flushing, vomiting, headache and palpitations. Check cough mixtures and mouthwashes for alcohol too.
Why do I have a metallic taste? It is a very common effect of metronidazole. It is harmless and settles once the course ends.
Is it an antibiotic or an antiparasitic? Both. It works against anaerobic bacteria and against several parasites.
Will it treat thrush? No. Thrush is fungal and needs an antifungal. Metronidazole treats bacterial vaginosis, which is a different condition.
Will it help a chest or bladder infection? Usually not. Those are generally caused by bacteria that need oxygen, which metronidazole does not act against.
Can I stop when I feel better? Finish the course. Stopping early is a common reason infections come back.