Purpose:
To prepare and evaluate floating microspheres of
silymarin for prolonged gastric residence time and
increased drug bioavailability.
Methods:
Cellulose microspheres – formulated with hydroxylpropyl
methylcellulose (HPMC) and ethyl cellulose (EC) – and
Eudragit microspheres – formulated with Eudragit®
S 100 (ES) and Eudragit® RL (ERL) - were
prepared by an emulsion-solvent evaporation method. The
floating microspheres were evaluated for flow properties
based on parameters such as angle of repose and
compressibility index, as well as for various other
physicochemical properties including particle size,
incorporation efficiency, in vitro floatability, and in
vitro drug release. The shape and surface morphology of
the microspheres were characterised by optical and
scanning electron microscopy.
Results:
Mean particle size increased while drug release rate
decreased with increasing EC and ES contents of
cellulose and Eudragit microspheres, respectively.
Scanning electron microscopy showed pores on the surface
and interior of the microspheres. The microspheres
exhibited prolonged drug release for 12 h while still
remained buoyant. Drug release kinetics, evaluated using
the linear regression method, followed Higuchi kinetics
and drug release mechanism was of the non-Fickian type.
Conclusion:
The developed floating microspheres of silymarin
exhibited prolonged drug release in simulated gastric
fluid for at least 12 h, and, therefore, could
potentially improve the bioavailability of the drug as
well as patient compliance.
Keywords:
Gastroretentive; Prolonged release; Silymarin; Floating
microspheres; Ethyl cellulose; Hydroxypropyl methyl
cellulose; Eudragit
