Development and characterization of a novel mucoadhesive sol-gel suppository of sumatriptan: design, optimization, in vitro  and ex vivo evaluation for rectal drug delivery.

Aim: Sumatriptan (ST) is used for the treatment of migraine and cluster headaches. However, it exhibits low oral bioavailability (15%) due to the high first-pass metabolism. The aim of this work was to formulate an ST rectal hydrogel. Methods: Hydrogels were formulated according to a Box-Behnken design using pluronic F-127 (PF-127) and chitosan as thermogelling and mucoadhesive agents, respectively. The rectal permeability was examined using a sheep rectal mucosa. Results: Among all the formulations, the hydrogel S2 showed satisfactory drug content (4.50%), gelling temperature (32°C), pH (6.41), viscosity (105 cP) and strength (15.90 sec). Mucoadhesive strength was adequate to provide a prolonged residence time. The flux of hydrogel S2 was calculated to be 0.0003 μg/cm 2 .min. Conclusion: The ST hydrogel can provide a potential opportunity to overcome the first pass metabolism and reduce drug dose.