Preparation and evaluation in vitro of colloidal lipospheres containing pilocarpine as ion pair

Aqueous dispersions of solid lipospheres containing up to 7.5% pilocarpine as lipophilic ion pairs were submitted to a preliminary evaluation. The lipospheres (diameter 75-85 nm) consisted mainly of stearic acid and egg lecithin; pilocarpine base was incorporated as ion pair with mono-octylphosphate, monodecylphosphate and monohexadecylphosphate. The following parameters were investigated: stability constants (β) and lipophilicity of the ion pairs, size, polydispersity and drug content of the lipospheres, pilocarpine release in vitro. The preparations might constitute a promising vehicle for sustained ocular delivery of pilocarpine.