About Aluminium Hydroxide Antacid,Antidote,Protectant( Topical), In hyperacidity- hyperphosphatemia. Mechanism of Action of Aluminium Hydroxide It neutralizes and reduces stomach acid relieving heartburn (acid reflux, GERD) and indigestion. This results increased pH and reduce the pepsin activity. It also binds to the phosphate in the gut and form a nonsoluble nonabsorbable aluminium phosphate complex.