RESUMO
The objective of this work was to characterize dexloxiglumide biopharmaceutical properties in vitro and relate these characteristics to its in vivo absorption performance, and to assess dexloxiglumide interaction with P-glycoprotein (P-gp) and MRP1 to anticipate its drug interaction potential. Dexloxiglumide aqueous solubility was moderate and pH dependent. Dexloxiglumide exhibited moderate Caco-2 permeability that was polarized, concentration dependent, and pH dependent. The apical-to-basolateral (AP-BL) permeability at pH 5 [14.5 (+/-1.8) x 10(-6) cm/s] was 2-fold higher than at pH 7.5 [7.24 (+/-0.27) x 10(-6) cm/s]. Neutral and ionized dexloxiglumide species displayed permeabilities of 30.8 (+/-8.4) x 10(-6) cm/s and 9.03 (+/-1.31) x 10(-6) cm/s, respectively. The transport of dexloxiglumide across MDR1-MDCK (P-gp overexpressing Madine Darby canine kidney cells) monolayers was polarized, with a BL-AP/AP-BL permeability ratio of 9.35 (+/-0.73), which was reduced to 1.03 (+/-0.03) by P-gp inhibition. Rhodamine 123 efflux was reduced by dexloxiglumide from 4.06 (+/-0.34) to 2.84 (+/-0.15) across Caco-2 monolayers, and from 17.3 (+/-0.9) to 8.26 (+/-1.38) across MDR1-MDCK monolayers, further indicating dexloxiglumide interaction with P-gp. Additionally, P-gp ATPase activity increased with dexloxiglumide concentration. Dexloxiglumide was effluxed from MRP1-NIH3T3 cells (NIH-3T3 cells expressing the multidrug resistance-associated protein 1). Dexloxiglumide increased MRP1-substrate fluorescein uptake 4-fold, and fluorescein increased dexloxiglumide uptake 1.8-fold. Overall, in vitro transport studies indicate dexloxiglumide to be moderately soluble and moderately permeable, which is in agreement with the incomplete oral absorption of dexloxiglumide. In vitro, dexloxiglumide was moderately modulated by P-gp and MRP1, which provides a rationale for the design of drug interaction studies.
Assuntos
Ácidos Pentanoicos/farmacocinética , Receptores da Colecistocinina/antagonistas & inibidores , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Adenosina Trifosfatases/metabolismo , Animais , Transporte Biológico , Linhagem Celular , Cães , Interações Medicamentosas , Genes MDR , Humanos , Técnicas In Vitro , Camundongos , Transportadores de Ácidos Monocarboxílicos/metabolismo , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Permeabilidade , SolubilidadeRESUMO
The objective of this work was to design an acyclovir prodrug that would utilize the human apical sodium-dependent bile acid transporter (hASBT) and enhance acyclovir oral bioavailability. Using each chenodeoxycholate, deoxycholate, cholate, and ursodeoxycholate, four bile acid prodrugs of acyclovir were synthesized, where acyclovir was conjugated to a bile acid via a valine linker. The affinity of the prodrug for hASBT was determined through inhibition of taurocholate uptake by COS-7 cells transfected with hASBT (hASBT-COS). The prodrug with the highest inhibitory affinity was further evaluated in vitro and in vivo. The prodrug acyclovir valylchenodeoxycholate yielded the highest affinity for hASBT (Ki = 35 microM), showing that chenodeoxycholate is the free bile acid with the greatest affinity for hASBT. Acyclovir valylchenodeoxycholate's affinity was similar to that of cholic acid (Ki = 25 microM). Further characterization showed that acyclovir was catalytically liberated from acyclovir valylchenode-oxycholate by esterase. Relative to cellular uptake studies of acyclovir alone, the cellular uptake from the prodrug resulted in a 16-fold greater acyclovir accumulation within hASBT-COS cells, indicating enhanced permeation properties of the prodrug. Enhanced permeability was due to hASBT-mediated uptake and increased passive permeability. The extent of acyclovir uptake in the presence of sodium was 1.4-fold greater than the extent of passive prodrug uptake in the absence of sodium (p = 0.02), indicating translocation of the prodrug by hASBT. The prodrug also exhibited an almost 12-fold enhanced passive permeability, relative to acyclovir's passive permeability. Oral administration of acyclovir valylchenodeoxycholate to rats resulted in a 2-fold increase in the bioavailability of acyclovir, compared to the bioavailability after administration of acyclovir alone. Results indicate that a bile acid prodrug strategy may be useful in improving the oral bioavailability of intestinal permeability-limited compounds.
Assuntos
Aciclovir/farmacocinética , Antivirais/farmacocinética , Ácidos e Sais Biliares/farmacocinética , Aciclovir/administração & dosagem , Administração Oral , Animais , Antivirais/administração & dosagem , Disponibilidade Biológica , Transporte Biológico , Células COS , Ácido Quenodesoxicólico/farmacocinética , Chlorocebus aethiops , Cinética , Pró-Fármacos/síntese química , Pró-Fármacos/farmacocinéticaRESUMO
PURPOSE: The purpose of this study was to investigate whether midazolam exhibits characteristics of a highly permeable P-glycoprotein (P-gp) substrate and to evaluate the potential influence of P-gp inhibition on 1-OH midazolam formation during midazolam transport. METHODS: P-gp interaction was investigated by P-gp ATPase assay, efflux inhibition studies, and transport studies of midazolam across MDR1-MDCK and 1-alpha,25-dihydroxy vitamin D3-induced Caco-2 monolayers with and without the P-gp inhibitor GF120918. RESULTS: Midazolam was highly permeable and transport appeared essentially unpolarized. In MDR1-MDCK, the basolateral-to-apical (B-to-A) permeability was slightly higher (16%) than apical-to-basolateral (A-to-B) permeability (p = 0.04); GF120918 increased A-to-B permeability by 27% (p = 0.01), and increased cellular midazolam accumulation during A-to-B transport by 45% (p = 0.01). Midazolam (200 microM) decreased rhodamine123 and vinblastine B/A ratios 3-fold (p < 0.006), while increasing their cellular accumulation (p < 0.003). P-gp ATPase activation by midazolam was dose-dependent and saturable [Km = 11.5(+/- 4.0) microM; Vmax = 41.1(+/- 7.4) nmol/mg/min]. P-gp inhibition increased 1-OH midazolam formation in A-to-B studies 1.3-fold when midazolam donor > or = 10 microM (p < 0.03). In B-to-A studies, P-gp inhibition did not significantly increase metabolite formation (p = 0.06). Midazolam's extraction ratio was not influenced by P-gp (p = 0.2). CONCLUSION: The results indicate that midazolam exhibited characteristics of a highly permeable P-gp substrate. 1-OH midazolam formation during A-to-B midazolam transport increased slightly when P-gp was inhibited.