Silica coatings on clarithromycin

Pre-crystallized clarithromycin (6- O-methylerythromycin A) particles were coated with silica from the tetraethyl orthosilicate (TEOS)–ethanol–aqueous ammonia system. The coatings had a typical thickness of 100–150 nm and presented about 15 wt.% of the silica-drug composite material. The properties of the coatings depended on reactant concentration, temperature and mixing rate and, in particular, on the presence of a cationic surfactant (cetylpyridinium chloride). In the presence of cetylpyridinium chloride the silica coatings slightly decreased the rate of pure clarithromycin dissolution.