title: A novel concentration dependent amino acid ion pair strategy to mediate drug permeation using indomethacin as a model insoluble drug.
abstract: Assessment of oral drug bioavailability is an important parameter for new chemical entities (NCEs) in drug development cycle. After evaluating the pharmacological response of these new molecules, the following critical stage is to investigate their in vitro permeability. Despite the great success achieved by prodrugs, covalent linking the drug molecule with a hydrophobic moiety might result in a new entity that might be toxic or ineffective. Therefore, an alternative that would improve the drug uptake without affecting the efficacy of the drug molecule would be advantageous. The aim of the current study is to investigate the effect of ion-pairing on the permeability profile of a model drug: indomethacin (IND) to understand the mechanism behind the permeability improvement across Caco-2 monolayers. Arginine and lysine formed ion-pairs with IND at various molar ratios 1:1, 1:2, 1:4 and 1:8 as reflected by the double reciprocal graphs. The partitioning capacities of the IND were evaluated using octanol/water partitioning studies and the apparent permeabilities (Papp) were measured across Caco-2 monolayers for the different formulations. Partitioning studies reflected the high hydrophobicity of IND (LogP=3) which dropped upon increasing the concentrations of arginine/lysine in the ion pairs. Nevertheless, the prepared ion pairs improved IND permeability especially after 60 min of the start of the experiment. Coupling partitioning and permeability results suggest a decrease in the passive transcellular uptake due to the drop in IND portioning capacities and a possible involvement of active carriers. Future work will investigate which transport gene might be involved in the absorption of the ion paired formulations using molecular biology technologies.
authors.affiliation: Drug Discovery, Delivery and Patient Care (DDDPC), School of Pharmacy and Chemistry, Kingston University London, Penrhyn Road, Kingston Upon Thames, Surrey KT1 2EE, UK; Aston Pharmacy School, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
authors.forename: Amr
authors.initials: A
authors.lastname: ElShaer
authors.affiliation: Aston Pharmacy School, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Hanson
authors.affiliation: Aston Pharmacy School, Aston University, Aston Triangle, Birmingham B4 7ET, UK. Electronic address: a.u.r.mohammed@aston.ac.uk.
authors.forename: Afzal R
authors.initials: AR
authors.lastname: Mohammed
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D001120:Arginine / Q000737:chemistry*; D018938:Caco-2 Cells; D006801:Humans; D007213:Indomethacin / Q000737:chemistry* / Q000494:pharmacology*; D008239:Lysine / Q000737:chemistry*; D010539:Permeability / Q000187:drug effects; D012995:Solubility; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D001120:Arginine; D008239:Lysine; D020003:1-Octanol; D007213:Indomethacin
keywords: Active carriers; Amino acids; Caco-2 monolayers; Ion-pairs; Permeability