Metformin (MTF) improves hyperglycemia primarily by suppressing glucose production by the liver. The objective
of our investigation was to evaluate nanoemulsion as a promising carrier for MTF for sustained hypoglycemic effect.
The drug was incorporated into oil phase of nanoemulsion, which finally improved biopharmaceutical properties
achieved when compared with lipid based systems. Pseudo ternary phase diagrams were prepared by aqueous titration
method. Formulations were selected at a difference of 5% v/v of oil from the o/w nanoemulsion region of phase diagrams,
and then thermodynamic stability and dispersibility tests were performed. The composition of optimized formulation was
hydrogenated castor oil (5% v/v), 30% v/v of surfactant (tween 80), co-surfactant (transcutol) and distilled water (65%
v/v) as an aqueous phase. The preparation showed maximum drug release (98.70%), optimal globule size (92.25 nm), lowest
polydispersity value (0.172), lesser viscosity (22.124 cps) and infinite dilution capability. The antidiabetic activity of optimized
MTF nanoemulsion formulation evaluated by blood glucose estimation showed significant hypoglycemic effect
which was comparable to that observed with conventional marketed formulation in experimental diabetic rats. Optimized
formulation was subjected to stability studies at different temperature and relative humidity and was found to be stable.
No significant variations were observed in the formulation over a period of 3 months at accelerated storage conditions.
Keywords: Diabetes mellitus, Hydrogenated castor oil, Metformin, Nanoemulsion, Pseudoterary Phase Diagrams, Streptozotocin.
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