Diclofenac and Its Acyl Glucuronide: Determination of In Vivo Exposure in Human Subjects and Characterization as Human Drug Transporter Substrates In Vitro

• Published in: Drug metabolism and disposition Vol. 44; no. 3; pp. 320 - 328
• Main Authors: Zhang, Yueping, Han, Yong-Hae, Putluru, Siva Prasad, Matta, Murali Krishna, Kole, Prashant, Mandlekar, Sandhya, Furlong, Michael T, Liu, Tongtong, Iyer, Ramaswamy A, Marathe, Punit, Yang, Zheng, Lai, Yurong, Rodrigues, A. David
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.03.2016
• Subjects: Adult; ATP Binding Cassette Transporter, Subfamily B - metabolism; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters - metabolism; Biological Transport - physiology; Diclofenac - metabolism; Drug Interactions - physiology; Glucuronides - metabolism; Humans; Kidney - metabolism; Liver - metabolism; Male; Neoplasm Proteins - metabolism; Organic Anion Transporters - metabolism; Organic Anion Transporters, Sodium-Independent - metabolism; Young Adult; BCRP; DF; OAT; DDI; MRP; OATP; MK571; AUC; DF-AG; CsA; LC-MS/MS; AUCtot; FTC; HEK-293; CCK-8; ESI; HBSS
• DOI: 10.1124/dmd.115.066944
• ISSN: 0090-9556; 1521-009X

Although the metabolism and disposition of diclofenac (DF) has been studied extensively, information regarding the plasma levels of its acyl-β-D-glucuronide (DF-AG), a major metabolite, in human subjects is limited. Therefore, DF-AG concentrations were determined in plasma (acidified blood derived) of six healthy volunteers following a single oral DF dose (50 mg). Levels of DF-AG in plasma were high, as reflected by a DF-AG/DF ratio of 0.62 ± 0.21 (Cmax mean ± S.D.) and 0.84 ± 0.21 (area under the concentration-time curve mean ± S.D.). Both DF and DF-AG were also studied as substrates of different human drug transporters in vitro. DF was identified as a substrate of organic anion transporter (OAT) 2 only (Km = 46.8 µM). In contrast, DF-AG was identified as a substrate of numerous OATs (Km = 8.6, 60.2, 103.9, and 112 µM for OAT2, OAT1, OAT4, and OAT3, respectively), two organic anion–transporting polypeptides (OATP1B1, Km = 34 µM; OATP2B1, Km = 105 µM), breast cancer resistance protein (Km = 152 µM), and two multidrug resistance proteins (MRP2, Km = 145 µM; MRP3, Km = 196 µM). It is concluded that the disposition of DF-AG, once formed, can be mediated by various candidate transporters known to be expressed in the kidney (basolateral, OAT1, OAT2, and OAT3; apical, MRP2, BCRP, and OAT4) and liver (canalicular, MRP2 and BCRP; basolateral, OATP1B1, OATP2B1, OAT2, and MRP3). DF-AG is unstable in plasma and undergoes conversion to parent DF. Therefore, caution is warranted when assessing renal and hepatic transporter-mediated drug-drug interactions with DF and DF-AG.