Atropine methyl bromide (Methylatropine bromide) is a quaternary ammonium salt of atropine, characterized as a muscarinic receptor (mAChR) antagonist. It functions as a mydriatic to dilate the pupil during ophthalmic examination. Compared to atropine, it demonstrates reduced penetration into the central nervous system[1][2]. Its high polarity makes it particularly effective in relieving pyloric spasm in infants.