Medication

Amoxicillin / clavulanate

Antibiotic (aminopenicillin + beta-lactamase inhibitor)

Brand names: Augmentin

Oral health effects

Oral candidiasis (thrush)
Broad-spectrum antibiotics suppress commensal bacteria, allowing Candida overgrowth in the mouth.
Mechanism: Loss of competitive inhibition from normal flora.
Clinical management: Watch for thrush, especially with repeated courses; treat with an antifungal; reinforce hygiene.
Antibiotic-associated diarrhea / gut dysbiosis
Higher rate of GI upset/diarrhea than amoxicillin alone due to the clavulanate component.
Clinical management: A probiotic (e.g., Saccharomyces boulardii) during the course may modestly lower the risk of antibiotic-associated diarrhea; the evidence is low certainty. Avoid probiotics in immunocompromised or severely ill patients. See the Gut Health page.
Black hairy tongue, glossitis and stomatitis
Darkly stained, elongated papillae on the tongue, or a sore, inflamed tongue and oral mucosa. Listed in postmarketing reports; frequency not established.
Clinical management: Teach daily tongue brushing/scraping and good oral hygiene. Bland rinses (saline or sodium bicarbonate) for soreness. Check for candidiasis, which can look similar. Persistent or severe ulceration warrants contacting the prescriber.