Anticholinergic agents with muscarinic selectivity may be effective in preventing and treating PONV. Intravenous (IV) administration of scopolamine or atropine, but not glycopyrrolate, reduces the incidence of PONV. Intuitively, as glycopyrrolate does not cross the blood-brain barrier, most postoperative anti-emetic effects of anticholinergic drugs should be mediated by central receptors.