Enhanced adsorption of tetracycline. Decreased adsorption of penicillin or chloramphenicol. May reduce effectiveness of antidiabetics (eg, acarbose, acetohexamide, chlorpropamide, glimepiride, glipizide, glyburide, metformin, miglitol, pioglitazone, repaglinide, rosiglitazone, tolazamide, tolbutamide, troglitazone); doxorubicin; etoposide; teniposide. May elevate serum INR values & potentiates anticoagulant effects of warfarin. Synergistic effects w/ steroidal agents or NSAIDs.