The aim of this study was to obtain a prolonged release of
Vitamin A palmitate (RAP) and
aciclovir from biodegradable
microspheres for intraocular administration with an
antiviral action and to be capable of preventing the inherent risks of intravitreal administration. The RAP effect on the
microsphere characteristics was also studied.
Poly(D,L-lactic-co-glycolic) acid microspheres were prepared by the
solvent evaporation method. Different quantities of
aciclovir (40-80 mg) and RAP (10-80 mg) were added to the internal phase of the
emulsion.
Microspheres were analysed by scanning electron microscopy, which revealed a spherical surface and a porous structure, and granulometric analysis that showed an adequate particle size for intraocular administration. The
aciclovir loading efficiency increased when
Vitamin A palmitate was added. Differential scanning calorimetry detected no differences in the
polymer glass transition temperature and the
aciclovir melting endotherm in all formulations. The release of
aciclovir during the first days of the in vitro assay was improved with respect to
microspheres without RAP. The
microspheres showed a constant release of
aciclovir and RAP for 49 days. Best results were obtained for
microspheres prepared with 40 mg
aciclovir, 80 mg RAP and 400mg
polymer. A dose of 4.74 mg of
microspheres would be therapeutic for the
herpes simplex and Epstein-Barr viruses' treatment in an animal model and would reduce the intravitreal adverse effects. The injectability of a
suspension of
microspheres in isotonic
saline solution resulted appropriate for its injection through a 27 G needle.