Reserpine and calcium: interaction at the injection site.

The subcutaneous administration of calcium prior to reserpine prevented the development of the well-known reserpine effects. Pretreatment with other bivalent cations induced a similar effect. The inhibitory effect of reserpine on the in vitro uptake of labelled catecholamines in brain homogenates was also prevented in rats pretreated with bivalent cations. On the other hand when calcium was injected at a site other than that of reserpine, there was no antagonistic effect. The latter results suggest an interaction between bivalent cations and reserpine at the injection site that prevents the systemic absorption of reserpine.