Decreased therapeutic effect of chlorpropamide, lithium, salicylates, tetracyclines. Increased therapeutic effect of amphetamines, ephedrine/pseudoephedrine. Risk of systemic alkalosis & development of Ca stones (in patients w/ uric stones) & hypernatremia w/ antacids; increased Al absorption w/ Al-containing antacids. Reduced solubility of quinolones. Additive effect w/ laxatives.