ENHANCEMENT OF ORAL BIOAVAILABILITY OF REPAGLINIDE BY SELF-NANOEMULSIFYING DRUG DELIVERY SYSTEM

Abstract

Repaglinide is considered the drug of choice for diabetic patients with impaired kidney function as it is excreted mainly in the bile. Unfortunately, it possesses low oral bioavailability of approximately 56 %. Therefore, nano-sized globules containing the drug are expected to enhance its bioavailability and sustain its glucose lowering action. Self nano-emulsifying drug delivery systems (SNEDDS) of repaglinide have been prepared for improving the water solubility and oral bioavailability of the drug. Various compositions of SNEDDS were prepared using four types of oils (oleic acid, isopropyl myristate IPM. Labrafil 1944 and 2125), surfactants (chromophore El35, chromophore RH 40, Labrasol and Span 20) and a variety of co-surfacatnts. Low energy emulsification was adopted as the method of preparation for its feasibility and low cost. The prepared nano-emulsions showed small average droplet size (13.5-20 nm) and low polydispersity index (0.10 - 0.30). In-vitro dissolution studies indicated that the drug release from some of the prepared nanoemulsion droplets reached 75 % within the first 30 minutes. The in-vivo data demonstrated that repaglinide in the nano-emulsion formulations F8 (IPM, Cremophor EL35 and Propylene glycol) and F16 (Oleic acid, Cremophor RH40 and Lauroglycol FCC) lowered the plasma glucose level (< 110 mg/dL) of experimental rabbits in a similar trend to that of the commercial product (Novonorm^®), moreover, it caused an excess reduction in blood glucose level at the end of the 24 hrs period by virtue of its long circulation time compared to the marketed formula.