This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
The following is true of aluminium hydroxide gel except 
Select and explain. 
A. It causes loose motions as a side effect, B. It interferes with absorption of phosphate in the intestine, C. It is a weak and slowly reacting antacid, D. Its acid neutralizing capacity decreases on storage
A: It causes loose motions as a side effect
Answer: A: It causes loose motions as a side effect 
Explanation: Neutralization of gastric acid (Antacids) (a) Systemic:- Sodium bicarbonate, Sod. citrate (b) Nonsystemic:- Magnesium hydroxide, Mag. trisilicate, Aluminium hydroxide gel, Magaldrate, Calcium carbonate. Aluminium hydroxide gel:- It is a bland, weak and slowly reacting antacid. On keeping it slowly polymerizes to variable extents into still less reactive forms. Thus, the ANC of a preparation gradually declines on storage. The Al3+ ions relax smooth muscle. Thus, it delays gastric emptying. Alum. hydrox. frequently, causes constipation due to its smooth muscle relaxant and mucosal astringent action. Alum. hydrox. binds phosphate in the intestine and prevents its absorption--hypophosphatemia occurs on regular use. This may: (a) cause osteomalacia (b) be used therapeutically in hyperphosphatemia and phosphate stones. Ref:- kd tripathi; pg num:-649,655