Most Common Side Effects of Augmentin (Amoxicillin/Clavulanate)
The most common adverse effects of Augmentin are gastrointestinal disturbances—specifically diarrhea (occurring in approximately 3-13% of patients), nausea, vomiting, and abdominal discomfort—along with skin reactions including rash and contact dermatitis (diaper rash in children). 1
Gastrointestinal Effects
The gastrointestinal side effects are primarily attributable to the clavulanate component rather than amoxicillin alone. Penicillins and cephalosporins as a class are most commonly associated with gastrointestinal disturbances including nausea, diarrhea, and abdominal distention and discomfort 2.
Recent comparative data demonstrates that:
- Protocol-defined diarrhea occurred in 12.9% of pediatric patients treated with high-dose Augmentin ES-600 1
- In comparative trials, 44% of patients treated with high-dose amoxicillin-clavulanate experienced adverse events (rash, diarrhea, vomiting, abdominal pain) compared to 14% with placebo 3
- A 2023 large cohort study found amoxicillin-clavulanate carried a 15% higher risk of gastrointestinal symptoms compared to amoxicillin alone (RR 1.15) 4
The clavulanic acid component is more strongly associated with gastrointestinal side effects, including Clostridioides difficile infection, and limits the maximum daily dose of amoxicillin that can be given in combination formulations 5, 6.
Dermatologic Reactions
Skin reactions are the second most common category of adverse effects:
- Contact dermatitis (diaper rash) occurs in 3.5-6.1% of pediatric patients 1
- General rash occurs in approximately 1.1% of patients 1
- Hypersensitivity reactions ranging from mild drug eruptions to anaphylaxis can occur, though severe reactions are uncommon (0.07-0.3%) 2
Other Common Effects
Additional frequently reported adverse effects include:
- Moniliasis/yeast infections (1.4% in children; 33% higher risk than amoxicillin alone per recent data) 1, 4
- Upper respiratory tract infections (3-4%) 1
- Vomiting (2.2-6.9%) 1
- Fever (5.5-6.1%) 1
Important Clinical Considerations
Severity and Duration
These common side effects are generally mild to moderate and transient in nature. Only 4.4% of patients discontinued therapy due to drug-related side effects in pediatric trials, with diarrhea (2.5%) and vomiting (1.4%) being the most common reasons for withdrawal 1.
Age-Related Patterns
The risk of adverse events varies by age. In the 2023 cohort study, the relative risk of adverse events after amoxicillin-clavulanate was:
- RR 1.23 for ages 0-5 years
- RR 1.19 for ages 6-11 years
- RR 1.04 for ages 12-17 years 4
This demonstrates that younger children experience higher rates of adverse effects.
Rare but Serious Effects
While not among the "most common," clinicians should remain vigilant for rare serious reactions:
- Hepatotoxicity: Moderate rises in liver enzymes can occur; severe hepatic dysfunction is rare but has been reported 1
- Severe hypersensitivity reactions: Including Stevens-Johnson syndrome, toxic epidermal necrolysis, and anaphylaxis (very rare) 1
- Hematologic effects: Thrombocytopenia, anemia, leukopenia (rare and usually reversible) 1
The statement in your question accurately reflects the evidence: diarrhea, nausea/vomiting, and skin rashes are indeed the most common Augmentin side effects, they are generally mild and resolve after completing the antibiotic course, while rare serious effects like liver problems and severe skin reactions require immediate medical attention.