Myclav is a prescription antibiotic containing amoxicillin and clavulanic acid. It is used for bacterial infections of the chest, sinuses, ears, urinary tract, skin and teeth — particularly where plain amoxicillin has failed or resistance is likely. It comes as Myclav 375 and Myclav 625. It does nothing for colds or flu.
What is Myclav?
Myclav contains amoxicillin with clavulanic acid and is Schedule 4 — prescription-only:
| Product | Contains |
|---|---|
| Myclav 375 | Amoxicillin 250 mg + clavulanic acid 125 mg |
| Myclav 625 | Amoxicillin 500 mg + clavulanic acid 125 mg |
The numbers are the two ingredients added together. Myclav 625 contains 500 mg of amoxicillin, not 625 mg — a common point of confusion. This combination is generally known as co-amoxiclav, and equivalents in South Africa include Augmentin, Ranclav and other generics.
Only one of the two ingredients is an antibiotic. Amoxicillin is a penicillin that kills bacteria by preventing them from building their cell walls. Clavulanic acid has almost no antibacterial activity of its own.
Its role is specific. Many bacteria produce beta-lactamase, an enzyme that destroys penicillins before they can act — the most common reason plain amoxicillin fails. Clavulanic acid binds and disables that enzyme, effectively acting as a shield so the amoxicillin survives long enough to work.
That is the entire reason the combination exists: it restores amoxicillin’s effectiveness against bacteria that would otherwise resist it. It also explains the main trade-off — clavulanic acid causes much of the diarrhoea and stomach upset associated with this medicine.
What is Myclav commonly used for?
A doctor may prescribe it for:
- Chest infections, including some pneumonia and infective exacerbations of COPD.
- Sinusitis, where symptoms are persistent, severe, or worsening after initial improvement.
- Middle ear infections, particularly where amoxicillin has not worked.
- Urinary tract infections.
- Skin and soft-tissue infections, including infected animal and human bites — a classic use, since bite wounds carry mixed bacteria this combination covers well.
- Dental infections and abscesses, alongside dental treatment.
- Bone and joint infections, in some cases.
It has no effect on viruses. Colds, flu, most sore throats, most coughs and most bronchitis are viral. An antibiotic will not shorten them or prevent complications.
Co-amoxiclav is broader-spectrum than plain amoxicillin. That is useful when resistance is likely and a disadvantage otherwise, since broader antibiotics disturb more of the body’s normal bacteria and drive more resistance. It is reserved rather than automatically first-line.
How Myclav fits into this medicine category
| Group | Examples | Typical role |
|---|---|---|
| Penicillins | Amoxicillin, flucloxacillin | Common first-line choices |
| Penicillin + inhibitor | Amoxicillin/clavulanic acid (Myclav) | Where beta-lactamase resistance is likely |
| Macrolides | Azithromycin | Chest infections, penicillin allergy |
| Fluoroquinolones | Ciprofloxacin | Urinary, gut and bone infections; reserved |
| Nitroimidazoles | Metronidazole | Anaerobic and some parasitic infections |
| Tetracyclines | Doxycycline | Chest, skin and tick-borne infections |
Which antibiotic is right depends on the likely organism, the site of infection, local resistance patterns and your history — a prescriber’s decision. See the antibiotics and antimicrobials hub.
What to check before using Myclav
Tell your doctor about any penicillin allergy before you start. This is the most important check. A previous rash, swelling or breathing difficulty on penicillin, amoxicillin or a related antibiotic must be known, because Myclav is a penicillin and the reaction can be severe.
Complete the full course, even once you feel better. Stopping early can let the infection return and encourages resistant bacteria.
Take it with food or at the start of a meal. This meaningfully reduces the stomach upset and diarrhoea caused by the clavulanic acid, and improves absorption.
Tell your doctor or pharmacist if you:
- Have had any reaction to a penicillin or cephalosporin.
- Have had jaundice or liver problems on co-amoxiclav before. This is a specific contraindication — the liver reaction can recur more severely on re-exposure.
- Have liver or kidney disease.
- Have glandular fever (infectious mononucleosis). Amoxicillin commonly causes a widespread rash in this setting, and is usually avoided.
- Take warfarin, as co-amoxiclav can increase its effect.
- Take methotrexate or allopurinol.
- Are pregnant or breastfeeding.
- Use the combined oral contraceptive pill. Antibiotics do not generally reduce its effectiveness, but severe vomiting or diarrhoea can — ask a pharmacist.
Take doses at evenly spaced intervals, and never use antibiotics left over from a previous illness or prescribed for someone else.
Possible cautions and when to ask a pharmacist or doctor
The most common 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.
Stop and seek medical attention urgently if you develop:
- Swelling of the face, lips, tongue or throat, difficulty breathing, or a widespread hives-like rash — a serious allergic reaction. Call emergency services.
- Any rash, which should be assessed rather than ignored.
- Blistering or peeling skin, or sores in the mouth or eyes.
- Severe, watery or bloody diarrhoea, during or in the weeks after the course. This may indicate a C. difficile infection, and anti-diarrhoeal medicines such as loperamide should not be used in that situation.
- Yellowing of the eyes or skin, dark urine, pale stools or itching — a possible liver reaction, which can appear up to several weeks after finishing.
- Unusual bruising or bleeding.
- Much less urine than usual.
- A seizure, which is rare and more likely with kidney impairment.
Contact your doctor if you are no better after two to three days, or if symptoms worsen at any point — the organism may not be susceptible and a different antibiotic may be needed.
Related medicine guides
- Browse Antibiotics, Antifungals & Antimicrobials guides
- Read: Azrotrin used for
- Read: Metronidazole used for
Frequently asked questions
What is Myclav 625 used for? Bacterial infections of the chest, sinuses, ears, urinary tract, skin and teeth, particularly where resistance to plain amoxicillin is likely. It contains amoxicillin 500 mg with clavulanic acid 125 mg.
What is Myclav 375 used for? The same range of infections at a lower strength — amoxicillin 250 mg with clavulanic acid 125 mg.
Why does 625 contain 500 mg of amoxicillin? The number is the two ingredients added together: 500 mg amoxicillin plus 125 mg clavulanic acid.
Is Myclav the same as Augmentin? Both contain amoxicillin and clavulanic acid. The manufacturer differs; the combination is the same.
Will it help flu or a cold? No. Those are viral, and antibiotics have no effect on them.
Why does it upset my stomach? Mostly the clavulanic acid. Taking it with food or at the start of a meal reduces this considerably.
Can I stop when I feel better? No. Finish the prescribed course unless your doctor tells you otherwise.
What if I get a rash? Contact your doctor. A rash needs assessing, and swelling or difficulty breathing is an emergency.