The quantity and distribution of radiolabeled dexamethasone delivered to tissue by iontophoresis.

A pilot study was conducted in the first of two monkeys using either radiolabeled Dm-Na-P or radiolabeled hydrocortisone sodium succinate, together with lidocaine HCl. This study indicated an approximately tenfold increase in the quantity of Dm-Na-P delivered to the test electrodes (4 mA; 20 minutes) whereas the quantity of hydrocortisone delivered from the test electrodes was only marginally (approximately 10%) increased as compared with that from the controls. In terms of an anti-inflammatory activity, the effective dose of Dm-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 minutes, 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 tritium-labeled Dm-Na-P (approximately 4.0 mg) and 2.0 ml 4% lidocaine HCl (80 mg). Local tissue concentrations of Dm-Na-P were higher than those that would be obtained by systematic therapy and lower than would be obtained by local injection.