Intestinal absorption of BCS class II drugs administered as nanoparticles: A review based on in vivo data from intestinal perfusion models

An established pharmaceutical strategy to increase oral drug absorption of low solubility–high permeability drugs is to create nanoparticles of them. Reducing the size of the solid-state particles increases their dissolution and transport rate across the mucus barrier and the aqueous boundary layer. Suspensions of nanoparticles also sometimes behave differently than those of larger particles in the fed state. This review compares the absorption mechanisms of nano- and larger particles in the lumen at different prandial states, with an emphasis on data derived from in vivo models. Four BSC class II drugs—aprepitant, cyclosporine, danazol and fenofibrate—are discussed in detail based on information from preclinical intestinal perfusion models.

Direct In Vivo Human Intestinal Permeability (Peff ) Determined with Different Clinical Perfusion and Intubation Methods

Regional in vivo human intestinal effective permeability (Peff ) is calculated by measuring the disappearance rate of substances during intestinal perfusion. Peff is the most relevant parameter in the prediction of rate and extent of drug absorption from all parts of the intestine. Today, human intestinal perfusions are not performed on a routine basis in drug development. Therefore, it would be beneficial to increase the accuracy of the in vitro and in silico tools used to evaluate the intestinal Peff of novel drugs. This review compiles historical Peff data from 273 individual measurements of 80 substances from 61 studies performed in all parts of the human intestinal tract. These substances include: drugs, monosaccharaides, amino acids, dipeptides, vitamins, steroids, bile acids, ions, fatty acids, and water. The review also discusses the determination and prediction of Peff using in vitro and in silico methods such as quantitative structure-activity relationship, Caco-2, Ussing chamber, animal intestinal perfusion, and physiologically based pharmacokinetic (PBPK) modeling. Finally, we briefly outline how to acquire accurate human intestinal Peff data by deconvolution of plasma concentration-time profiles following regional intestinal bolus dosing.

Effects of verapamil on the pharmacokinetics and hepatobiliary disposition of fexofenadine in pigs

The pharmacokinetics (PK) of fexofenadine (FEX) in pigs were investigated with the focus on exploring the interplay between hepatic transport and metabolism when administered intravenously (iv) alone or with verapamil. The in vivo pig model enabled simultaneous sampling from plasma (pre-liver, post-liver and peripheral), bile and urine. Each animal was administered FEX 35mg iv alone or with verapamil 35mg. Plasma, bile and urine were analyzed with liquid chromatography-tandem mass spectrometry. Non-compartmental analysis (NCA) was used to estimate traditional PK parameters. In addition, a physiologically based pharmacokinetic (PBPK) model consisting of 11 compartments (6 tissues +5 sample sites) was applied for mechanistic elucidation and estimation of individual PK parameters. FEX had a terminal half-life of 1.7h and a liver extraction of 3%. The fraction of the administered dose of unchanged FEX excreted into the bile was 25% and the bile exposure was more than 100 times higher than the portal vein total plasma exposure, indicating carrier-mediated (CM) disposition processes in the liver. 23% of the administered dose of FEX was excreted unchanged in the urine. An increase in FEX plasma exposure (+50%) and a decrease in renal clearance (-61%) were detected by NCA as a direct effect of concomitant administration of verapamil. However, analysis of the PBPK model also revealed that biliary clearance was significantly inhibited (-53%) by verapamil. In addition, PBPK analysis established that metabolism and CM uptake were important factors in the disposition of FEX in the liver. In conclusion, this study demonstrated that CM transport of FEX in both liver and kidneys was inhibited by a single dose of verapamil.

Investigation of hepatobiliary disposition of doxorubicin following intrahepatic delivery of different dosage forms

Unresectable, intermediate stage hepatocellular carcinoma (HCC) is often treated palliatively in humans by doxorubicin (DOX). The drug is administered either as a drug-emulsified-in-Lipiodol (DLIP) or as drug loaded into drug eluting beads (DEB), and both formulations are administered intrahepatically. However, several aspects of their in vivo performance in the liver are still not well-understood. In this study, DLIP and DEB were investigated regarding the local and systemic pharmacokinetics (PK) of DOX and its primary metabolite doxorubicinol (DOXol). An advanced PK-multisampling site acute in vivo pig model was used for simultaneous sampling in the portal, hepatic, and femoral veins and the bile duct. The study had a randomized, parallel design with four treatment groups (TI-TIV). TI (n = 4) was used as control and received an intravenous (i.v.) infusion of DOX as a solution. TII and TIII were given a local injection in the hepatic artery with DLIP (n = 4) or DEB (n = 4), respectively. TIV (n = 2) received local injections of DLIP in the hepatic artery and bile duct simultaneously. All samples were analyzed for concentrations of DOX and DOXol with UPLC-MS/MS. Compared to DLIP, the systemic exposure for DOX with DEB was reduced (p < 0.05), in agreement with a slower in vivo release. The approximated intracellular bioavailability of DOX during 6 h appeared to be lower for DEB than DLIP. Following i.v. infusion (55 min), DOX had a liver extraction of 41 (28-53)%, and the fraction of the dose eliminated in bile of DOX and DOXol was 20 (15-22)% and 4.2 (3.2-5.2)%, respectively. The AUCbile/AUCVP for DOX and DOXol was 640 (580-660) and 5000 (3900-5400), respectively. In conclusion, DLIP might initially deliver a higher hepatocellular concentration of DOX than DEB as a consequence of its higher in vivo release rate. Thus, DLIP delivery results in higher intracellular peak concentrations that might correlate with better anticancer effects, but also higher systemic drug exposure and safety issues.