Poloxamer 407 as a thermogelling and adhesive polymer for rectal administration of short-chain fatty acids.

OBJECTIVES: The purpose of the study was to gel a rectal solution of short-chain fatty acids to decrease the loss of active materials in the colonic lumen and thereby optimize their absorption.
METHODS: Five thermogels were prepared with poloxamer 407 at concentrations ranging from 17% to 20%. Their viscosities were measured at room temperature and 37 degrees C, and their gelling temperatures were determined. The adhesive properties of each gel were assessed in vitro at 37 degrees C. Short-chain fatty acid release was studied using Guyot cells.
RESULTS: From the threshold concentration of 17.5%, the solutions, Newtonian at room temperature (50-80 mPa x s), gelled at 37 degrees C. The higher the concentration, the higher the viscosity (1750 to 49,000 mPa x s), the lower the gelling temperature (27.6 degrees C to 23.4 degrees C), and the stronger the work of adhesion (2.2 to 4.5 mJ). Short-chain fatty acid release from the 18% polymer gel was decreased by 60% compared to the rectal solution.
CONCLUSION: The 18% poloxamer 407 concentration provided a solution that was liquid at room temperature, that gelled at 37 degrees C, possessed adhesive properties, and controlled short-chain fatty acid release.