Atropine and glycopyrrolate effects on lung mechanics in normal man

To assess the comparative bronchomotor effects of large systemic doses of glycopyrrolate and atropine intravenous glycopyrrolate (10 micrograms/kg), atropine (20 micrograms/kg), or a placebo was administered to six healthy male volunteers in double-blind fashion. Both drugs produced bronchodilation reflected by significant decreases in airway resistance and increases in specific airway conductance (sGAW) compared to placebo. Glycopyrrolate increased sGAW to a maximal level of 100% +/- 7% above control; bronchodilation persisted at this level for more than 4 hours after drug administration. Atropine increased sGAW to a maximum of 88% +/- 5% above control 30 minutes after administration, but sGAW returned to control levels between 3 and 4 hours after the drug was given. Both drugs increased maximum expiratory flow rates over the same time course as sGAW, but the percent increases in flow were significantly less than changes in sGAW. Lung elastic recoil was decreased by both drugs over the full range of lung volume. The 32% maximum increase in heart rate after glycopyrrolate was significantly less (p< 0.01) than the 60% increase after atropine. It was concluded that vagal blockade with glycopyrrolate dilates large and small airways to the same extent as atropine, but that the effect is more sustained and associated with less cardiac vagal blockade. Lower doses of glycopyrrolate were also studied and the findings showed that maximal bronchodilation is achieved with lower doses (3.2 micrograms/kg), which are commonly used in routine premedication.