Glycopyrrolate is a synthetic antimuscarinic medication with anticholinergic properties similar to atropine. Compared to atropine (which has a tertiary ammonium structure), glycopyrrolate has a quaternary ammonium structure and is completely ionized at physiologic pH. As a function of its structure, it does not readily cross the blood brain barrier (BBB). Clinically, it is used in conjunction with neostigmine and other anticholinesterase drugs to offset bradycardia and other cholinergic effects during the reversal of neuromuscular blockade, as an antisialagogue, and for treatment of bradycardia when atropine is not specifically indicated or available. When given intravenously, its onset of action is within 1 minute and has a duration of 2-4 hours.
Glycopyrrolate’s physiologic effects include dry mouth, tachycardia, relaxation of the lower esophageal sphincter, and inhibition of gastrointestinal motility. Because it does not cross the BBB, it notably does not cause the sedation, mydriasis, or cycloplegia that occurs from other anticholinergic drugs like atropine and scopolamine. However, its antisialagogue effects are more prominent when compared to these drugs.
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