Biodegradable poly(DL-lactic-co-glycolic acid) microspheres containing tetracaine hydrochloride. In-vitro release profile

Tetracaine does not result in effective treatment of intractable pain cause d by trigeminal neuralgia because of its short duration of effect. In a sus tained release system a controlled delivery of the drug at the site of admi nistration, would avoid successive administrations. Tetracaine hydrochlorid e (HCl) has been encapsulated using a technique based on the evaporation of solvent from an 0/0 emulsion, using poly(DL-lactic-co-glycolic acid) (PLGA ) 50:50. Microspheres were separated into three fractions: 106-212, 212-300 and 300-425 mu m. The effects of two variables of the manufacturing method (volume of the inner phase of the emulsion and volume of surfactant added to the external phase) on the drug loading into microspheres, dissolution p rofiles and SEM characterization of the microspheres were evaluated. Micros pheres containing tetracaine hydrochloride (up to 94% referred to the theor etical) released the drug, iota n-nu iota tro, over 35 days. Tetracaine HCl was delivered according to zero order kinetics from day 5 until the end of the release assay. The rate of drug release depended mainly on the viscosi ty of the discontinuous phase and on the size of microparticles. Microspher e size resulted more homogeneous when using the highest volume of the surfa ctant, being almost 80% of microparticles within the range 212-300 mu m.