Solubilization of etodolac for patenteral administration

Etodolac (ETO) is a nonsteroidal antiinflammatory drug (NSAID) that exhibits analgesic, antipyretic and antiinflammatory activities and is practically insoluble in water.The solubility of ETO in four different cosolvents; ethanol, propylene glycol, polyethylene glycol 400, and glycerol, three sugars; sucrose, sorbitol, and mannitol, two hydrotropic salts; sodium benzoate and sodium sallcylate, and two enhancers;Tween 80 and Brij 58 was investigated.The solubility of ETO by the used co-solvents can be arranged in the following order: ethanol>PEG 400>PG>glycerol. Similar increase in solubility was observed with Tween 80 and Brij 58. The increase in temperature from 25 to 37° was accompanied by an increase in drug solubility at higher concentrations of co-solvents and hydrotropic solutions but the effect was insignificant with Tween 80 and Brij 58. The thermodynamic parameters calculated for some of these systems showed positive entropy and enthalpy in addition to negative free energy values suggesting high degree of randomness, endothermic dissolution and spontaneity of the solubility process.The used sugars and sodium salicylate showed no effect on ETO solubility. Based on the solubility data, a trial has been done to propose a formulation (100 mg/3 ml) for parenteral use in an aqueous solvent blend. The proposed formulation was tested physically for color, turbidity and precipitation upon storage for two months. In addition, the formulation didn't show any evidence of visible precipitation upon dilution with normal saline or 5% dextrose intravenous fluid except in low dilutions. Finally, in addition to parenteral formulation, the solubilized systems of ETO could be appreciable in the design of other liquid formulations intended for topical and oral administration of the drug.