Summary bar plots of the mean times to respiratory arrest under control and test conditions for several pharmacological agents applied topically at the concentrations noted following injection of brown snake venom at the equivalent of 1/kg.

<p>All agents caused significant increase in time to respiratory arrest compared to control. Asterisks indicate significant differences with respect to control obtained by Mann Whitney test (* p<0.05, ** P<0.01, *** p<0.001; n = 11, 8, 5, 5 & 7 for control, nifedipine, lignocaine, 100 mM sodium nitroprusside and 0.2% wt/wt glyceryl trinitrate ointment respectively).