[Glycopyrrolate (Robinul), a new anticholinergic substance]

Glycopyrrolate is a quaternary ammonium compound with indications for use similar to those for atropine. Because of the quaternary nature, it is poorly absorbed when taken orally and penetrates neither placental nor blood-brain barriers. When given by the parenteral route, the cardio-vagal blocking action of glycopyrrolate is twice that of atropine while inhibition of salivation is 5-6 times greater. The use of glycopyrrolate for premedication provides a therapeutic margin 2-3 times wider than that of atropine. Glycopyrrolate administered with neostigmine to antagonise the residual neuromuscular blockade of non-depolarising relaxants has advantages over atropine because the pharmacodynamic profile is more suited to that of neostigmine. The abrupt changes in cardiac rate, therefore, become minimal. If glycopyrrolate, 5 micrograms/kg-1, is injected intravenously just before the induction of anaesthesia, severe bradycardia is inhibited when repeated doses of succinylcholine are used. Although the alkalinising effect on gastric secretions has not been substantially verified, glycopyrrolate does provide long lasting bronchodilatation from its blocking action on smooth muscle. Only a few studies with glycopyrrolate in children have yet been published. However, it appears that this drug provides no real advantages over atropine when used in paediatric anaesthesia.