The Quantity and Distribution of Radiolabeled Dexamethasone Delivered to Tissue by Iontophoresis

Abstract

A pilot study was conducted in the first of two monkeys using either radiolabeled D_m-Na-P or radiolabeled hydrocortisone sodium succinate, together with lidocaine HCI. This study indicated an approximately tenfold increase in the quantity of D_m-Na-P delivered to the test electrodes (4 mA; 20 minutes) whereas the quantity of hydrocortisone delivered from the test electrodes was only marginally (≅10%) increased as compared with that from the controls. In terms of an antiinflammatory activity, the effective dose of D_m-Na-P in all tissue layers underlying the test electrodes was at least tenfold that of the hydrocortisone. Therefore, further trials with hydrocortisone were abandoned. In the Second animal, positive test electrodes (5 mA; 20 minuter, were sited over five joints on the right side of the body and matching control electrodes (0 mA: 20 minutes) were placed over corresponding joints on the left side of the body. The control and test electrodes each contained 1.0 ml tritiumlabeled D_m-Na-P (≅4.0 mg) and 2.0 ml 4% lidocaine HCI (80mg). Local tissue concentrations of D_m-Na-P were higher than those that would be obtained by systematic therapy and lower than would be obtained by injection.