Introduction Resultant increases in gastric pH and empyting time may affect the action of other drugs via changes in absorption ↑ absorption of weak bases ↓ absorption of weak acids bioavailability urinary excretion Class can cause hypokalemia via alkalinzation of the blood Aluminum Hydroxide Toxicity constipation and hypophosphatemia proximal muscle weakness osteodystrophy seizures Magnesium Hydroxide Toxicity diarrhea note: milk of magnesia is a laxative hyporeflexia hypotension cardiac arrest magnesium is a key ion in cardiac arrhythmias Calcium Carbonate Toxicity belching hypercalcemia can be used as a source of supplmental calcium rebound acid ↑ chelatation of other drugs e.g. tetracycline