Methylatropine (methylatroponium) is a belladonna derivative. In 1902 the Bayer Company introduced atropine methonitrate, a quaternary ammonium salt of atropine (Eumydrin), as a mydriatic for dilation of the pupil during ophthalmic examination. Due to its highly polar nature it penetrates less readily into the central nervous system than atropine and was therefore introduced for relieving pyloric spasms in infants. Atropine methyl nitrate is a muscarinic acetylcholine receptor antagonist that does not cross the blood-brain barrier. Atropine methyl nitrate has been used for its peripheral muscarinic effects (targeting the bladder, respiratory tract, and to block parasympathetic signaling to the heart, among others) and to separate central from peripheral nervous system effects, or to protect against peripheral side effects when using muscarinics that do cross the blood brain barrier.