Comparison of Intravenous and Topical Effectiveness of Various Vasoconstrictors on the Terminal Vascular Bed of the Rat Mesoappendix

Abstract

In a comparative study using 107 rats, constrictors, given intravenously produced a narrowing of the metarterioles of the mesoappendix which was indistinguishable from the action of the same constrictor applied topically. The threshold constrictor concentration applied topically is 5-10 times as great as that which would be achieved by mixing the threshold intravenous dose of the constrictor with the entire blood volume of the rat. Rat-to-rat variability in constrictor thresholds was significantly greater when the drug was applied topically than when it was given intravenously. The following intravenous doses in micrograms or units were calculated to be equivalent to 1 [mu]g of epinephrine: norepinephrine, 2.7; neosynephrine, 6.3; Pitressin, 0.009, and angiotonin, greater than 1.5.