Controlled release of tetracycline I: In vitro studies with a trilaminate 2-hydroxyethyl methacrylate-methyl methacrylate system.

A membrane-controlled drug delivery device was developed to release tetracycline at zero-order rates. The tetracycline delivery vehicle is a trilaminate disk consisting of core and coating membranes fabricated from a series of 2-hydroxyethyl methacrylate and methyl methacrylate copolymers. Appropriate adjustment of the monomer composition ratio imparts a hydrophobic nature to the copolymer outer coating membrane (relative to the core material), which serves as the rate-limiting membrane in drug diffusion. The trilaminate disks demonstrated a zero-order tetracycline release over 4 months in vitro. The zero-order release rate was a function of the general device geometry, coating membrane thickness, disk surface, area, level of core reservoir drug loading, and membrane coating copolymer composition. Permeability parameters of tetracycline diffusion through a series of 2-hydroxyethyl methacrylate-methyl methacrylate copolymer membranes were determined by a flux-lag time method. Equilibrium hydration values of these membranes also were determined. The ability of trilaminate 2-hydroxyethyl methacrylate-methyl methacrylate devices to release tetracycline at constant rates over a prolonged period offers unique therapeutic and investigational possibilities.