Atropine methyl bromide, a muscarinic receptor (mAChR) antagonist, is a quaternary ammonium salt of atropine and a mydriatic for dilation of the pupil during ophthalmic examination. It is introduced for relieving pyloric spasm in infants for its highly polar nature. It penetrates less readily into the central nervous system than atropine[1][2].
[1]. Methylatropine. [2]. Nurminen ML, et al. Central inhibition of nitric oxide synthesis increases blood pressure and heart rate in anesthetized rats. Methods Find Exp Clin Pharmacol. 1997 Jan-Feb;19(1):35-41.