Influence of storage conditions on the physical and release properties of piroxicam suppositories formulated with lipophilic bases

Abstract

This study investigated the effect of storage conditions on physical and release properties of lipophilic-based piroxicam suppositories with a view to determining the most desirable conditions for their storage. Piroxicam 20 mg suppositories were prepared by fusion method using cocoa butter, Witepsol H15® and Witepsol W35® to which 2 %w/w Tween 20® was added. Physical and dissolution properties of the suppositories were determined by established methods after preparation and at 4-month intervals for 12-month storage on the shelf (27.5 ± 0.9 °C to 32.5 ±0.8 °C) and in the refrigerator (4 ± 1 °C). The suppositories stored in the refrigerator hardened at the fourth month, with fat “blooming” observed on cocoa butter-based suppositories at 8th month. Melting points of cocoa butter-based suppositories remained below 37.5 °C on storage, while those formulated with Witepsol H15® and Witepsol W35® increased to 42.1 °C and 44.0 °C, respectively. Cocoa butter-based suppositories stored on the shelf showed decrease in melting range and mechanical strength compared with those stored in the refrigerator. There was increase in mechanical strength and disintegration time of the witepsol-based suppositories on aging. Release of piroxicam from witepsol bases decreased significantly (P < 0.05) on storage either in the refrigerator or on the shelf, while those formulated with cocoa butter base increased. In conclusion, piroxicam suppositories formulated with cocoa butter would require storage in the refrigerator, while long-term storage of those formulated with Witepsol H15® and Witepsol W35® in the refrigerator might not be desirable.Keywords: Piroxicam suppositories; Lipophilic bases; Storage conditions; Physical properties; Release properties