May lead to pathological increase of the serum Ca level or intensification w/ Ca-containing drugs (eg, acetolye). Reduce administration w/ Al hydroxide. Reduction of serum phosphate. May interfere absorption w/ drugs forming sparingly soluble compd w/ Ca [eg, tetracyclines, quinolones (eg, ciprofloxacin & norfloxacin), Fe, fluoride or estramustine containing drugs]. Increased risk of arrhythmia w/ heart/cardiac-active glycosides.