Amoxicillin/clavulanate: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on May 16, 2024.

1. How it works

• Amoxicillin/clavulanate is a penicillin-type combination antibiotic made up of amoxicillin (the active, antibiotic part) and clavulanate potassium (which boosts the effectiveness of amoxicillin). It may be used to treat infections caused by certain susceptible bacteria.
• Amoxicillin works by inhibiting the synthesis of bacterial cell wall mucopeptides (these are crystal lattice-like structures composed of amino acids that make up the cell wall). This weakens and destroys the bacterial cell wall and kills the bacteria. Clavulanate potassium protects amoxicillin from inactivation by beta-lactamases by binding strongly to beta-lactamases near their active site. By itself, clavulanate potassium only has weak antibacterial activity, but when used together with amoxicillin, it extends its spectrum so that it may be used to treat infections caused by beta-lactamase-producing organisms.
• Amoxicillin/clavulanate belongs to the group of medicines known as penicillins. It may also be called a beta-lactam penicillin or antimicrobial.

2. Upsides

• Effective against more organisms than amoxicillin by itself.
• Used to treat infections of the airways, ears, sinuses, skin, and urinary tract caused by susceptible bacteria including beta‑lactamase-producing isolates of Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, Escherichia coli, Klebsiella species, and Enterobacter species.
• Available in tablet, chewable tablet, extended-release, and liquid formulations.
• Generic amoxicillin/clavulanate potassium is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• Diarrhea or loose stools, nausea, skin rashes or itching, or vomiting.
• May cause the overgrowth of the yeast, Candida, causing thrush (a yeast infection in the mouth) or vaginal yeast infections.
• Amoxicillin/clavulanate should not be used if susceptibility results show susceptibility to amoxicillin, indicating that the infectious bacteria are not producing beta-lactamase. Amoxicillin should be used instead.
• May cause an allergic reaction in those allergic to penicillin or cephalosporins.
• Different formulations and strengths of amoxicillin/clavulanate may not be interchangeable. For example, the 250mg and 500mg tablets of the brand of amoxicillin/clavulanate called Augmentin both contain 125mg of clavulanate potassium; therefore two 250mg tablets should not be substituted for one 500mg tablet. In addition, the 250mg tablet of Augmentin contains 125mg of clavulanate potassium and the 250mg chewable tablet contains 62.5mg of clavulanate potassium; therefore the tablet should not be substituted for the chewable tablet and vice-versa.
• The dosage of amoxicillin/clavulanate may need to be reduced in very severe renal impairment.
• Severe diarrhea associated with Clostridium difficile is a potential side effect of almost all antibacterial agents, including amoxicillin/clavulanate.
• May not be suitable for some people including those with a previous history of hepatic dysfunction associated with amoxicillin/clavulanate, allergic to penicillin or cephalosporins, with mononucleosis, or with an infection caused by bacteria that are not susceptible to amoxicillin/clavulanate.
• May interact with some other medications including probenecid, allopurinol, oral contraceptives, oral anticoagulants, and some urine glucose tests.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

• Amoxicillin/clavulanate is a combination penicillin-type antibiotic that should be reserved for the treatment of infections caused by susceptible beta-lactamase-producing bacteria. Its use may be limited by resistance and side effects such as diarrhea and yeast overgrowth.

5. Tips

• Take amoxicillin/clavulanate at the start of a light meal to improve the absorption of clavulanate potassium and minimize the potential for gastrointestinal intolerance.
• Some bacteria are inherently resistant to amoxicillin/clavulanate whereas others can acquire resistance. To help prevent resistance and treatment failure, be sure to complete the full course of an antibiotic, even if you feel better.
• Do not take it if you are allergic to penicillin or any other penicillin-like antibiotic such as ampicillin, dicloxacillin, oxacillin, or others.
• Call for emergency help if you experience any allergic-type reactions including a rash; swelling of the face, lips, or throat; difficulty breathing; or tightness in the chest.
• Amoxicillin/clavulanate may encourage the overgrowth of yeasts, such as Candida. This may be seen as oral or vaginal thrush. See your doctor if you suspect you have developed thrush as a result of amoxicillin/clavulanate use.
• See your doctor if you develop prolonged or significant diarrhea while taking amoxicillin/clavulanate or within several months of finishing the course.
• May cause tooth discoloration (brown, yellow, or gray staining); the risk is higher in pediatric patients. Brushing or professional dental cleaning reduces or eliminates discoloration.
• Phenylketonurics should avoid Augmentin chewable tablets and Augmentin powder for oral solution (Augmentin is a brand of amoxicillin/clavulanate) because these products contain aspartame (which contains phenylalanine).

6. Response and effectiveness

• Peak concentrations are usually seen within 1.5 hours of a dose of amoxicillin/clavulanate; however, it may take up to 48 hours of dosing for a clinical improvement to be seen.
• Effective against more organisms than amoxicillin by itself.
• Some bacteria are inherently resistant to amoxicillin/clavulanate whereas others can acquire resistance. To help prevent resistance and treatment failure, be sure to complete the full course of an antibiotic, even if you feel better.

7. Interactions

Medicines that interact with amoxicillin/clavulanate may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with amoxicillin/clavulanate. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with amoxicillin/clavulanate include:

• allopurinol (may increase the incidence of rash)
• anticoagulants (blood thinners), such as warfarin (may prolong bleeding time)
• oral contraceptives (may decrease absorption leading to reduced efficacy)
• probenecid (may increase blood concentrations of amoxicillin).

Amoxicillin/clavulanate may cause a false-positive reaction for glucose in the urine with copper reduction tests (eg, Benedict's or Fehling's solution), but not with enzyme-based tests.

Note that this list is not all-inclusive and includes only common medications that may interact with amoxicillin/clavulanate. You should refer to the prescribing information for amoxicillin/clavulanate for a complete list of interactions.

References

• Amoxicillin and clavulanate potassium. Revised 01/2024. ASHP. https://www.drugs.com/monograph/amoxicillin-clavulanate.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use amoxicillin/clavulanate only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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