Application of a reservoir-type calcitriol transdermal patch in dairy cattle

Our objective was to evaluate the effects of a reservoir-type calcitriol (5 mg/animal) transdermal patch on plasma calcitriol and calcium (Ca) concentrations in dairy cattle. A group of six heifers received three different types of patches: an encapsulated reservoir solution containing calcitriol alone (CAL), calcitriol with dodecylamine (CAL+D), or vehicle (CONT). The patches were applied to the skin of the tail for duration of 2 days at intervals of at least 3 weeks. Cattle that received CAL or CAL+D showed significant increases in plasma calcitriol and Ca concentrations on day 2 and days 2 and 3, respectively. The areas under the plasma concentration-time curve (AUC) values for plasma calcitriol and Ca in the CAL and CAL+D groups increased significantly compared to the CONT group. The data of this study describe evidence of measurable transdermal absorption of exogenous calcitriol from a patch and its sufficient biological action to elevate plasma Ca concentrations.