Poly (DL-lactide) nanocapsules containing diclofenac: I. Formulation and stability study

Abstract

The aim of this work was to formulate nanocapsules prepared from poly(DL-lactide) containing a non-steroidal anti-infammatory drug, diclofenac, and to study their stability during storage at room temperature. The influence of some factors wich could affect stability, namely, the type of oily phase used or/and its concentration, the concentrations of drug and of surfactants, was investigated. The pH of the preparation, the particle size, the quantity of drug remaining (encapsulated and total) and polymer molecular weight were determined at intervals for up to 8 months after nanocapsule preparation. Although colloidal systems which were physically stable over this period could be obtained with either of the two oils tested, polymer degradation was more rapid in the presence of benzyl benzoate than with Miglyol 810®. The optimal concentration of the latter was found to be 3.33%. The highest loading of diclofenac consistent with a stable preparation was 1.00 mg/ml. Stable nanocapsules could be obtained with as little as 0.75% lipophilic surfactant together with a similar concentration of hydrophilic surfactant. These concentrations are considerably lower than those described in the literature for the formulation of this type of colloid.