Co-amoxyclav is amoxicillin combined with clavulanic acid — a broader antibiotic than amoxicillin alone, used for chest, sinus, ear, urinary, dental, skin and bite infections. The numbers on the box (375, 625, 1000) are the two ingredients added together, and knowing how they break down prevents a common and avoidable mistake.
What is Co Amoxyclav?
The South African Medicine Price Registry lists co-amoxyclav under several names, including Adco Amoxyclav 375, Adco Amoxyclav 625, Adco Amoxyclav BD and Sandoz Co-Amoxyclav injection. All are Schedule 4. You will also see it spelled co-amoxiclav, and sold as Augmentin, Austell Co-Amoxiclav, Ranclav, Curam and others. Same medicine.
The numbers are totals, and the second ingredient does not scale:
| Name | Amoxicillin | Clavulanic acid |
|---|---|---|
| 375 mg | 250 mg | 125 mg |
| 625 mg | 500 mg | 125 mg |
| 1000 mg (“BD”) | 875 mg | 125 mg |
In every strength, the clavulanic acid stays at 125 mg. Only the amoxicillin rises. This is why you must never make up a strength from smaller tablets — two 625 mg tablets are not a 1000 mg dose, they are a double dose of clavulanic acid, which is the component that causes most of the diarrhoea.
“BD” means twice daily. The 1000 mg tablet delivers more amoxicillin per dose so it can be taken twice a day instead of three times — the same total, in fewer doses. It is a convenience formulation, not a stronger antibiotic in any meaningful sense.
What each ingredient does:
Amoxicillin is a penicillin. It stops bacteria building their cell walls, so they rupture as they divide.
Clavulanic acid has almost no antibiotic activity itself. Many bacteria produce an enzyme, beta-lactamase, that destroys penicillins before they can act. Clavulanic acid is a decoy that binds and disables that enzyme, letting the amoxicillin work. This is the whole reason the combination exists — it restores amoxicillin’s effect against organisms that have become resistant to it.
What is Co Amoxyclav commonly used for?
- Chest infections — bacterial bronchitis and community-acquired pneumonia.
- Sinusitis, where symptoms are severe or have persisted well beyond a viral course.
- Middle ear infection, particularly where amoxicillin alone has not worked.
- Urinary tract infections, including some kidney infections.
- Dental infections and abscesses. Common — though an abscess usually also needs drainage or dental treatment, and an antibiotic alone rarely settles it.
- Skin and soft tissue infections, including infected wounds and cellulitis.
- Animal and human bites, where it is a first-choice treatment because of the mixture of organisms involved.
- Some bone and joint infections, and as surgical prophylaxis.
It does nothing for viral infections. Colds, flu and most sore throats and coughs are viral. An antibiotic will not shorten them or prevent them becoming bacterial, and it carries real cost — side effects now, and resistance for everyone later.
Finish the course as prescribed. Feeling better on day three means it is working, not that the infection has cleared. Stopping early is a major driver of resistance and a common cause of relapse.
How Co Amoxyclav fits into this medicine category
| Group | Examples | Typical use |
|---|---|---|
| Penicillins | Amoxicillin, phenoxymethylpenicillin | Common first-line infections |
| Penicillin + inhibitor | Co-amoxyclav | Broader cover where resistance is likely |
| Macrolides | Azithromycin, erythromycin | Chest infections; penicillin allergy |
| Cephalosporins | Cefuroxime, ceftriaxone | Broad cover, often in hospital |
| Nitroimidazoles | Metronidazole | Anaerobic and dental infections |
| Tetracyclines | Doxycycline | Chest, skin, tick-bite fever |
| Quinolones | Ciprofloxacin | Reserved; significant side effects |
Co-amoxyclav is a step up, not a default. Being broader, it disturbs normal gut bacteria more and drives resistance faster than a narrow antibiotic. Careful prescribing keeps it for infections that need it.
See the antibiotics and antimicrobials hub.
What to check before using Co Amoxyclav
Tell your doctor or pharmacist about any penicillin allergy. This matters more than anything else here. Co-amoxyclav is a penicillin, and anyone allergic to penicillin, amoxicillin or ampicillin must not take it. If a past reaction involved facial swelling, breathing difficulty or collapse, say so clearly — a different class is needed.
A rash after amoxicillin is not always allergy. In glandular fever, amoxicillin causes a widespread rash in most people without allergy being involved. That still needs a doctor’s assessment, not your own.
Also mention if you:
- Have had jaundice or liver problems after co-amoxyclav or any antibiotic. This is a specific contraindication — the clavulanic acid can cause liver injury, sometimes appearing weeks after the course ends.
- Have kidney disease or liver disease.
- Take warfarin. Co-amoxyclav can raise INR and bleeding risk.
- Take allopurinol, which increases the chance of a rash, or methotrexate, whose levels can rise.
- Take the oral contraceptive pill. The interaction is weaker than once believed, but use additional contraception if you have vomiting or diarrhoea while taking it.
- Have glandular fever, or any illness with sore throat and swollen glands.
- Are pregnant or breastfeeding.
Practical points:
- Take it with food or at the start of a meal. This substantially reduces the stomach upset and diarrhoea that stop most people completing the course.
- Space doses evenly — three times daily means roughly every eight hours; BD means every twelve.
- Complete the course.
- Do not use leftover antibiotics from a previous illness or someone else’s prescription.
Possible cautions and when to ask a pharmacist or doctor
The commonest effects are diarrhoea, nausea, stomach upset and thrush — oral or vaginal. Diarrhoea is notably more common than with plain amoxicillin, because of the clavulanic acid.
Seek medical advice promptly for:
- A rash, itching or hives — stop and get advice before the next dose.
- Yellowing of the skin or eyes, dark urine, pale stools, or persistent upper abdominal pain. These suggest liver injury, and can appear during the course or up to several weeks after it finished. Mention the antibiotic even if the course is long over.
- Severe, watery or bloody diarrhoea, especially with fever or cramps, during or after treatment. This may be Clostridioides difficile and needs treatment — do not simply take an anti-diarrhoeal.
- A widespread blistering rash, peeling skin, or a rash with fever and swollen glands — get emergency help.
- Reduced urine output or blood in the urine.
- Easy bruising or bleeding, particularly on warfarin.
Get emergency help for swelling of the face, lips or tongue, difficulty breathing, throat tightness, dizziness or collapse.
Contact your doctor if you are no better after two to three days, if you feel worse, if fever climbs, or if new symptoms appear — the organism may be resistant, or the diagnosis may need revisiting. Also say if side effects are stopping you completing the course, so an alternative can be arranged rather than the course simply being abandoned.
Related medicine guides
Frequently asked questions
What is co-amoxyclav 1000 used for? The same infections as the other strengths — chest, sinus, ear, urinary, dental, skin and bite infections. It contains amoxicillin 875 mg with clavulanic acid 125 mg, and is taken twice daily rather than three times.
What do 375, 625 and 1000 mean? The two ingredients added together. The clavulanic acid is 125 mg in all of them; only the amoxicillin changes — 250, 500 and 875 mg respectively.
Can I take two 625 mg tablets instead of a 1000 mg? No. That doubles the clavulanic acid, which causes most of the diarrhoea, without giving the right amoxicillin dose. Take only what was prescribed.
Is co-amoxyclav the same as co-amoxiclav? Yes. Two spellings of the same combination, sold under many brand names.
What is the clavulanic acid for? It disables the enzyme bacteria use to destroy amoxicillin, restoring its effect against otherwise resistant organisms.
Will it help flu or a cold? No. Those are viral.
Why is it upsetting my stomach? Diarrhoea and nausea are common with this combination. Taking each dose with food helps considerably. Tell your doctor if it is severe or bloody.
Can I stop when I feel better? No. Complete the course, or the infection can return and resistance is encouraged.