Solubilization of indomethacin using hydrotropes for aqueous injection

Indomethacin is a non-steroidal anti-inflammatory drug (NSAID) that exhibits analgesic, antipyretic and anti-inflammatory activities. It is practically insoluble in water. The effect of various hydrotropes such as urea, nicotinamide, resorcinol, sodium benzoate and sodium p-hydroxy benzoate on the solubility of indomethacin was investigated. The solubility enhancement of indomethacin by the hydrotropes was observed in decreasing order as sodium p-hydroxy benzoate > sodium benzoate > nicotinamide > resorcinol > urea. In order to elucidate the probable mechanism of solubilization, various solution properties of hydrotropes such as viscosity, specific gravity, surface tension, refractive index and specific conductance of hydrotropic solutions were studied at 25 ± 2 °C. Each solubilized product was characterized by ultraviolet, infrared, powder X-ray diffraction and differential scanning calorimetry techniques. The hydrotropic solubilization of indomethacin at lower hydrotrope concentration may be attributed to weak ionic interactions while that at higher hydrotrope concentration may be due to molecular aggregation. Aqueous injectable formulations using sodium p-hydroxy benzoate, sodium benzoate and nicotinamide as hydrotropes were developed and studied for physical and chemical stability.