title: Enhanced bioavailability of piroxicam via salt formation with ethanolamines.
abstract: Piroxicam can be ionized as a zwitterion that has two pKa values (pKa1=1.86 and pKa2=5.46). Consequently, piroxicam has a low solubility in both polar and nonpolar media, and a low lipophilicity, which results in a low permeability. Three piroxicam-ethanolamine salts were prepared, which had a higher area under the curve (AUC) than piroxicam. There were minimal differences in the AUC among the salt forms. It was reported that the piroxicam triethanolamine salt had a lower permeability across the skin than piroxicam but it had a higher oral bioavailability. Piroxicam monoethanolamine showed the highest Cmax followed by piroxicam diethanolamine and piroxicam triethanolamine. The dissolution rates of piroxicam and its salts were similar at pH 1.2. Piroxicam monoethanolamine showed the highest dissolution rate at pH 6.8, which was followed by the piroxicam diethanolamine and piroxicam triethanolamine salts. The order of dissolution rate at pH 6.8 matched the order of Cmax or the AUC after oral administration.
authors.affiliation: College of Pharmacy, Ewha Women's University, Seoul 120-750, Republic of Korea.
authors.forename: Hye-Sun
authors.initials: HS
authors.lastname: Gwak
authors.forename: Jun-Shik
authors.initials: JS
authors.lastname: Choi
authors.forename: Hoo-Kyun
authors.initials: HK
authors.lastname: Choi
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001682:Biological Availability; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004983:Ethanolamines / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008297:Male; D010894:Piroxicam / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000737:chemistry / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D012995:Solubility
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004983:Ethanolamines; D010894:Piroxicam; C032801:tenoxicam