Rate and extent of ion-exchange process: the effect of physico-chemical characteristics of salicylate anions.

Ten salicylate anions were used as model compounds in order to investigate systematically the impact of compound lipophilicity, valence, aqueous solubility and hydrogen bonding on binding into and release from a strong anion-exchange fiber, Smopex DS-218v. The release of salicylates from the fiber was studied at 1/10, 1/1 or 10/1 molar ratios of the external chloride-ions versus the salicylate bound in the fiber. The Donnan potential between the fiber and external solution (electrostatic interaction) appeared to be the main factor affecting the release of salicylates from the strong base anion-exchange fiber--an increase in the molar amount of the external chloride-ions resulted in a more effective release of all the salicylates from the fiber.

Improved stability and release control of levodopa and metaraminol using ion-exchange fibers and transdermal iontophoresis.

Achievement of controlled drug delivery and stability of drugs during storage is a problem also in transdermal drug delivery. The objective of this study was to determine, whether an easily oxidized drug, levodopa, could be stabilized during storage using pH-adjustment and ion-exchange fibers. Controlled transdermal delivery of the zwitterionic levodopa was attempted by iontophoresis and ion-exchange fiber.