Combination of amoxicillin with clavulanic acid results in synergistic effect against β-lactamase producing bacteria, because clavulanic acid have a high affinity binding to β-lactamase that can inactivate amoxicillin.
Combination of amoxicillin with methotrexate may decrease renal secretion of methotrexate. Increase serum methotrexate results in GI or hematologic toxicity. Patients should be monitored carefully.
Oral probenecid administered shortly before amoxicillin slow the rate of renal secretion of amoxicillin; produced higher an prolonged concentration of the drugs. This effect is used in treatment of gonorrhea or acute pelvic inflammatory disease.
Allopurinol may potentiate aminopenicillin allergy. Concomitant use of the drugs should be avoid of possible.