RiteMED Amoxicillin Drug Interactions

Allopurinol: An increased incidence of skin rashes reportedly occurs in hyperuricemic patients who are concomitantly receiving allopurinol and amoxicillin compared with those receiving amoxicillin or allopurinol alone.
Anticoagulants: Prolongation of prothrombin time has been reported rarely in patients receiving amoxicillin.
Appropriate monitoring should be undertaken when anticoagulants are prescribed concomitantly.
Bacteriostatic agents (e.g., Chloramphenicol, macrolides, sulfonamides, and tetracyclines): These antibacterial agents may interfere with the bactericidal effects of penicillin. This has been demonstrated in vitro; however, the clinical significance of this interaction is not well documented.
Beta-lactamase Inhibitors: In vitro and in vivo studies indicate that the combination of amoxicillin with clavulanic acid or sulbactam results in a synergistic bactericidal effect against many strains of β-lactamase-producing bacteria.
Digoxin: Concurrent administration with amoxicillin may result in increased absorption of digoxin.
Methotrexate: Concomitant use of penicillins (e.g., amoxicillin) may decrease the renal clearance of methotrexate, presumably by inhibiting renal tubular secretion of the drug. Increased serum concentrations of methotrexate, resulting in GI or hematologic toxicity, have been reported. Careful monitoring is recommended during concomitant therapy.
Oral Contraceptives: As with other antibiotics, amoxicillin may affect the gut flora, leading to lower estrogen reabsorption and reduced efficacy of combined oral estrogen/progesterone contraceptives.
Probenecid: Concurrent use of amoxicillin and probenecid may result in increased and prolonged blood levels of amoxicillin.
Interference with Laboratory Tests: High urine concentrations of ampicillin may result in false-positive reactions when testing for the presence of glucose in urine using Clinitest, Benedict's solution. Since the effect may also occur with amoxicillin, it is recommended that glucose tests based on enzymatic glucose oxidase reactions (e.g., Clinistix) be used.
Administration of ampicillin to pregnant women may result in a transient decrease in plasma concentrations of total conjugated estriol, estriol-glucuronide, conjugated estrone, and estradiol. This effect may also occur with amoxicillin.
Amoxicillin may interfere with protein testing when colorimetric methods are used.