1.
Bergman, Ebba, 1977-, et al.
(författare)
The Enterohepatic Disposition of Rosuvastatin in Pigs and The Impact of Concomitant Dosing with Cyclosporine and Gemfibrozil
2009
Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 37:12, s. 2349-2358
Tidskriftsartikel (refereegranskat) abstract
The hepatobiliary transport and local disposition of rosuvastatin in pig was investigated, along with the impact of concomitant dosing with two known multiple transport inhibitors; cyclosporine and gemfibrozil. 80 mg rosuvastatin was administered as an intrajejunal bolus dose in Treatments I, II and III (TI, TII, and TIII, respectively; n=6 per treatment). Cyclosporine (300 mg) and gemfibrozil (600 mg) were administered in addition to the rosuvastatin dose in TII and TIII, respectively. Cyclosporine was administered as a two hour intravenous infusion and gemfibrozil as an intrajejunal bolus dose. In Treatment IV (TIV, n=4) was 5.9 mg rosuvastatin administered as an intravenous bolus dose. The study was conducted using a pig model, which enabled plasma sampling from the portal (VP), hepatic (VH) and femoral veins and bile from the common hepatic duct. The biliary recovery of the administered rosuvastatin dose was 9.0±3.5% and 35.7±15.6% in TI and TIV, respectively. Rosuvastatin was highly transported into bile as the median AUCbile/AUCVH ratio was 1770 (1640-11300) in TI. Gemfibrozil did not have an effect on the plasma pharmacokinetics of rosuvastatin, most likely because the unbound inhibitor concentrations did not exceed the reported IC50-values. However, cyclosporine significantly reduced the hepatic extraction of rosuvastatin (TI; 0.89±0.06, TII; 0.46±0.13) and increased the AUCVP and AUCVH by 1.6 and 9.1-fold, respectively. In addition, the biliary exposure and fe, bile were reduced by ≈50%. The strong effect of cyclosporine was in accordance with inhibition of sinusoidal uptake transporters, such as members of the OATP-family, rather than canalicular transporters.
2.
Bergman, Ebba, 1977-
(författare)
The Hepatobiliary Transport of Rosuvastatin In Vivo
2009
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In vivo studies of hepatobiliary disposition are challenging. The hepatobiliary system is complex, as its physiological localization, complex cellular structure with numerous transporters and enzymes, and the interindividual variability in protein expression and biliary flow will all affect the in vivo disposition of a drug under investigation. The research included in this thesis has focused on the involvement of hepatic transport proteins in the hepatobiliary disposition of rosuvastatin. The impact that several transport inhibitors had on the pharmacokinetics of rosuvastatin was investigated in healthy volunteers and in pigs. The effects were considerable, following inhibition of sinusoidal transport proteins by cyclosporine and rifampicin. These inhibitors significantly reduced the hepatic extraction of rosuvastatin by 50 and 35%, respectively, and the plasma exposure increased by factors of 9.1 and 6.3, respectively. Drug-drug interactions (DDI) resulting in markedly higher plasma exposures are important from a drug safety perspective as increased extrahepatic exposure of statins is associated with an increased risk of severe side-effects, such as myopathy which in rare cases could develop into rhabdomyolysis. The DDI caused by cyclosporine and rifampicin can probably be attributed to inhibition of hepatic uptake transporters. In contrast, inhibition of canalicular transporters by imatinib did not significantly affect the pharmacokinetics of rosuvastatin, which suggests that the intracellular concentration of the inhibitor in the hepatocyte was insufficient to affect the transport of rosuvastatin, or that imatinib is not a sufficiently potent inhibitor in vivo. Furthermore, gemfibrozil administered as a single dose into the jejunum in healthy volunteers and pigs did not affect the plasma or biliary pharmacokinetics of rosuvastatin. The previously reported DDI in humans upon repeated dosing with gemfibrozil might be explained by the accumulation of metabolites able to affect the disposition of rosuvastatin. The investigations presented in this thesis conclude that transport proteins are of considerable importance for the hepatobiliary disposition of rosuvastatin in vivo. The Loc-I-Gut catheter can be applied for the investigation of biliary accumulation and to determine bile specific metabolites, however it has limitations when conducting quantitative measurements. In the porcine model, hepatic bile can be collected for up to six hours and enables the determination of the hepatic extraction in vivo.
3.
Gram, Luise K, et al.
(författare)
Impact of carriers in oral absorption : Permeation across Caco-2 cells for the organic anions estrone-3-sulfate and glipizide
2009
Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 37:3-4, s. 378-386
Tidskriftsartikel (refereegranskat) abstract
Carriers may mediate the permeation across enterocytes for drug substances being organic anions. Carrier mediated permeation for the organic anions estrone-3-sulfate (ES) and glipizide across Caco-2 cells were investigated kinetically, and interactions on involved carriers evaluated. Initial uptakes (P(UP)) at apical and basolateral membranes, apparent permeabilities (P(APP)) and corresponding intracellular end-point accumulations (P(EPA)) of radioactive labeled compounds were studied. Possible effects of other anionic compounds were investigated. Apical P(UP) and absorptive P(APP) for ES were inhibited and its absorptive P(EPA) prevented in presence of the investigated organic anions and apical P(UP) was saturable with K(m) 23microM. Basolateral P(UP) and exsorptive P(APP) were inhibited, its exsorptive P(EPA) was prevented, and basolateral P(UP) and exsorptive P(APP) were saturable with K(m) 44microM and 38microM, respectively. BCRP inhibition affected both absorptive an exsorptive P(EPA) and P(APP) for ES. Glipizide apical P(UP) and absorptive P(APP) were not inhibitable. Basolateral P(UP) for glipizide was inhibitable, its P(EPA) prevented, and P(UP) was saturable with K(m) 56microM, but exsorptive P(APP) was not affected. Carrier mediated exsorption kinetics for ES are seen at both apical and basolateral membranes, resulting in predominant exsorption despite presence of absorptive carrier(s). Carrier mediated basolateral P(UP) for glipizide was observed, but glipizide P(APP) was not described by carrier kinetics. However, glipizide is affecting exsorption for ES, due to interactions on basolateral carrier. The study confirms that estrone-3-sulfate can be used to characterize anionic carrier kinetics. Furthermore it is suggested that estrone-3-sulfate may be used to identify compounds which may interact on anionic carriers.
4.
Johannsson, Gudmundur, 1960, et al.
(författare)
Improving glucocorticoid replacement therapy using a novel modified-release hydrocortisone tablet: a pharmacokinetic study.
2009
Ingår i: European journal of endocrinology / European Federation of Endocrine Societies. - 1479-683X .- 0804-4643. ; 161:1, s. 119-30
Tidskriftsartikel (refereegranskat) abstract
BACKGROUND: Endogenous plasma cortisol levels have a well-defined circadian rhythm. The aim of this project is to develop a once daily oral dual-release formulation for cortisol replacement therapy that mimics the diurnal variation in the plasma cortisol profile. OBJECTIVE: To determine single-dose plasma pharmacokinetics and dose-proportionality of oral 5 and 20 mg dual-release hydrocortisone tablets in healthy volunteers. In addition, the effect of food intake was investigated for the 20 mg dose. DESIGN: A randomised, controlled, two-way cross-over, double-blind, phase I study of oral hydrocortisone (modified (dual) release; 5 and 20 mg) with an open food-interaction arm. METHODS: The single dose pharmacokinetic studies were performed with betamethasone suppression. The two first study days were blinded and randomised between morning administration of 5 and 20 mg tablet in a fasting state. The third day was open with a 20 mg tablet taken 30 min after a high-calorie, high-fat meal. The plasma samples were assayed using both a validated LC-MS/MS and an immunoassay. The plasma pharmacokinetic variables were calculated using non-compartmental data analysis. RESULTS: The time to reach a clinically significant plasma concentration of cortisol (>200 nmol/l) was within 20 min and a mean peak of 431 (s.d. 126) nmol/l was obtained within 50 min after administration of the 20 mg tablet. Plasma cortisol levels remained above 200 nmol/l for around 6 h thereafter and all plasma concentrations 18-24 h after intake were below 50 nmol/l. In the fed state the time to reach 200 nmol/l was delayed by 28 and 9 min based on LC-MS/MS and immunoassay, respectively. The 5 and 20 mg tablets produced an increase in plasma exposure of cortisol that was not fully dose proportional. CONCLUSION: The dual release hydrocortisone tablet with once-daily administration produced a diurnal plasma cortisol profile mimicking the physiological serum cortisol profile.
5.
Knutson, Tina, et al.
(författare)
Increased understanding of intestinal drug permeability determined by the LOC-I-GUT approach using multislice computed tomography
2009
Ingår i: Molecular pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 6:1, s. 2-10
Tidskriftsartikel (refereegranskat) abstract
This study further evaluated the in vivo single-pass perfusion technique (LOC-I-GUT) in three different ways. First, the intestinal radius of the human small intestinal segment was measured on plain X-ray films; second, evaluation was performed by applying multislice computed tomography investigations; and third, furosemide was used as model drug in a transport study. In total 17 (6 + 4 +7) intubation/perfusion studies were performed in healthy volunteers. Mixobar was used as a positive radiographic contrast agent in the first six volunteers when plain film examination was made, followed by four studies using multislice computed tomography. Mantel area calculations of the perfused segment after X-ray investigations using barium as contrast were determined to be 101.0 +/- 2.9 cm2. Maximal dilatation of the closed segment with room air as contrast and using MSCT revealed a mantel area of 121.30 +/- 7.0 cm2 (P < 0.01). Thus, the mantle area increased a further 20% when the bowel was fully distended, reflecting different physiologic distention patterns for air and fluid. A jejunal single-pass perfusion study was performed in a further seven volunteers. In each experiment furosemide was perfused during 200 min, and in the treatment period (100-200 min), fexofenadine was added to the perfusion solution. The mean (+/-SD) P (eff) for furosemide was 0.17 +/- 0.07 and 0.12 +/- 0.09 x 10-4 cm/s in the control and treatment period, respectively. This study showed that the calculation of human in vivo permeability is based on physiological values, which are important for the wide application of these in vivo permeability data in physiologically based pharmacokinetic modeling.
6.
Lennernäs, Hans
(författare)
Ethanol-drug absorption interaction : potential for a significant effect on the plasma pharmacokinetics of ethanol vulnerable formulations
2009
Ingår i: Molecular pharmaceutics. - : American Chemical Society (ACS). - 1543-8384 .- 1543-8392. ; 6:5, s. 1429-1440
Tidskriftsartikel (refereegranskat) abstract
Generally, gastric emptying of a drug to the small intestine is controlled by gastric motor activity and is the main factor affecting the onset of absorption. Accordingly, the emptying rate from the stomach is mainly affected by the digestive state, the properties of the pharmaceutical formulation and the effect of drugs, posture and circadian rhythm. Variability in the gastric emptying of drugs is reflected in variability in the absorption rate and the shape of the plasma pharmacokinetic profile. When ethanol interacts with an oral controlled release product, such that the mechanism controlling drug release is impaired, the delivery of the dissolved dose into the small intestine and the consequent absorption may result in dangerously high plasma concentrations. For example, the maximal plasma concentration of hydromorphone has individually been shown to be increased as much as 16 times through in vivo testing as a result of this specific pharmacokinetic ethanol-drug formulation interaction. Thus, a pharmacokinetic ethanol-drug interaction is a very serious safety concern when substantially the entire dose from a controlled release product is rapidly emptied into the small intestine (dose dumping), having been largely dissolved in a strong alcoholic beverage in the stomach during a sufficient lag-time in gastric emptying. Based on the literature, a two hour time frame for screening the in vitro dissolution profile of a controlled release product in ethanol concentrations of up to 40% is strongly supported and may be considered as the absolute minimum standard. It is also evident that the dilution, absorption and metabolism of ethanol in the stomach are processes with a minor effect on the local ethanol concentration and that ethanol exposure will be highly dependent on the volume and ethanol concentration of the fluid ingested, together with the rate of intake and gastric emptying. When and in which patients a clinically significant dose dumping will happen is almost impossible to predict and will depend on drinking behavior and the highly variable gastrointestinal factors of importance for dissolution, transit and absorption. Therefore, controlled release products which show a vulnerability to ethanol during two hours in vitro should be required to demonstrate clinical safety by going through in vivo testing with an alcoholic beverage of up to 40% ethanol and of a sufficient volume (probably 120 mL or more), consumed in a relatively short period of time. Alternatively, such preparations should be reformulated in accordance with quality-by-design principles.
7.
Lundahl, Anna, et al.
(författare)
Identification of Finasteride Metabolites in Human Bile and Urine by High-Performance Liquid Chromatography/Tandem Mass Spectrometry
2009
Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 37:10, s. 2008-2017
Tidskriftsartikel (refereegranskat) abstract
The objective of this study was to further investigate the metabolism of the 5α-reductase inhibitor, finasteride, and to identify previously unknown phase I and phase II metabolites in vitro and in vivo in human bile and urine. Healthy volunteers were given 5 mg of finasteride, directly to the intestine, and bile and urine were collected for 3 and 24 h, respectively. A single-pass perfusion technique, Loc-I-Gut, was used for drug administration and bile collection from the proximal jejunum, distal to papilla of Vater. Incubations with human liver microsomes/S9 fractions and different cofactors were performed with finasteride and the previously known metabolites, ω-hydroxy finasteride (M1) and finasteride-ω-oic acid (M3). Liquid chromatography coupled to triple quadrupole mass spectrometry (MS) with positive/negative electrospray ionization and ion trap with MSn measurements were used for structural investigations and identification of metabolites. Two hydroxy metabolites of finasteride, other than M1, and one intact hydroxy finasteride glucuronide were identified in vitro and in bile and urine. The glucuronide and at least one of the hydroxy metabolites were previously unidentified. M1 and M3 were glucuronidated in vitro by specific human UDP-glucuronosyltransferases, UGT1A4 and UGT1A3, respectively. M1 glucuronide was not identified in vivo, and M3 glucuronide, an acyl glucuronide, was present in low amounts in bile from a few individuals. In conclusion, previously undescribed metabolites were identified, in vitro and in human urine and bile. Bile collection using the Loc-I-Gut technique followed by sensitive mass spectrometry analysis led to the discovery of novel, both phase I and phase II, finasteride metabolites in human bile.
8.
Lundahl, Anna, et al.
(författare)
The effect of St. John's wort on the pharmacokinetics, metabolism and biliary excretion of finasteride and its metabolites in healthy men
2009
Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 36:4-5, s. 433-443
Tidskriftsartikel (refereegranskat) abstract
The aim of this study was to investigate what the consequences of induced drug metabolism, caused by St. John's wort (SJW, Hypericum perforatum) treatment, would have on the plasma, biliary and urinary pharmacokinetics of finasteride and its two previously identified phase I metabolites (hydroxy-finasteride and carboxy-finasteride). Twelve healthy men were administered 5mg finasteride directly to the intestine via a catheter with a multi-channel tubing system, Loc-I-Gut, before and after 14 days SJW (300mg b.i.d, hyperforin 4%) treatment. Bile samples were withdrawn via the Loc-I-Gut device from the proximal jejunum. LC-ESI-MS/MS was used to analyze finasteride and its metabolites in plasma, bile and urine. HPLC-UV was used to analyze hyperforin in plasma. The herbal treatment significantly reduced the peak plasma concentration (C(max)), the area under the plasma concentration-time curve (AUC(0-24h)) and the elimination half-life (t(1/2)) of finasteride. The geometric mean ratios (90% CI) were 0.42 (0.36-0.49), 0.66 (0.56-0.79) and 0.54 (0.48-0.61), respectively. Finasteride was excreted unchanged to a minor extent into bile and urine. Hydroxy-finasteride was not detected in plasma, bile or urine. Carboxy-finasteride was quantified in all three compartments and its plasma pharmacokinetics was significantly affected by SJW treatment. Hyperforin concentration in plasma was 21+/-7ng/ml approximately 12h after the last dose of the 14 days SJW treatment. In conclusion, SJW treatment for 2 weeks induced the metabolism of finasteride and caused a reduced plasma exposure of the drug. New knowledge was gained about the biliary and urinary excretion or the drug and its metabolites.
9.
Sjögren, Erik, et al.
(författare)
The multiple depletion curves method provides accurate estimates of intrinsic clearance (CLint), maximum velocity of the metabolic reaction (Vmax), and Michaelis constant (Km) : accuracy and robustness evaluated through experimental data and Monte Carlo simulations
2009
Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 37:1, s. 47-58
Tidskriftsartikel (refereegranskat) abstract
The use of multiple depletion curves for the estimation of maximum velocity of the metabolic reaction (V(max)), the Michaelis constant (K(m)), and intrinsic clearance (CL(int)) was thoroughly evaluated by means of experimental data and through a series of Monte Carlo simulations. The enzyme kinetics of seven compounds were determined using the multiple depletion curves method (MDCM), the traditional initial formation rate of metabolite method (IFRMM), and the "in vitro t(1/2)" method, and the parameter estimates that were derived from the three methods were compared. The impact of a change in enzyme activity during the incubation period on the parameter estimates and the possibility to correct for this were also investigated. The MDCM was in good overall agreement with the IFRMM. Correction for a change in enzyme activity was possible and resulted in a better concordance in CL(int) estimates. The robustness of the method in coping with different rates of substrate turnover and variable starting concentrations were also demonstrated through Monte Carlo simulations. Furthermore, the limitations imposed by assumptions inherent in the in vitro t(1/2) method were demonstrated both experimentally and by simulations. This study demonstrates that the MDCM is a robust and efficient method for estimating enzyme kinetic variables with high accuracy and precision. The method may potentially be used in a wide range of applications, from pure enzyme kinetics to in vitro-based predictions of the pharmacokinetics of compounds with multiple and/or unknown metabolic pathways.
10.
Thörn, Helena Anna, et al.
(författare)
Different effects of ketoconazole on the stereoselective first-pass metabolism of R/S-verapamil in the intestine and the liver : important for the mechanistic understanding of first-pass drug-drug interactions
2009
Ingår i: Drug Metabolism And Disposition. - : American Society for Pharmacology & Experimental Therapeutics (ASPET). - 0090-9556 .- 1521-009X. ; 37:11, s. 2186-2196
Tidskriftsartikel (refereegranskat) abstract
In this acute study a pig jejunal intestinal perfusion model with multiple plasma sampling sites and three different administration routes was used to investigate the quantitative contribution of the intestine versus liver to the first-pass extraction of each enantiomer of verapamil (VER). A subclinical dose of ketoconazole (8 mg) was coadministered in the perfusion solution to selectively inhibit gut wall CYP3A. Both enantiomers of VER and its main metabolite norverapamil (NOR) as well as the inhibitor ketoconazole were quantified in all plasma compartments by liquid chromatography-tandem mass spectrometry. The overall first-pass metabolic extraction of VER and the metabolite NOR was shown to be stereoselective with the S-isomer being more extensively extracted. For VER the ratio of R- enantiomer to S-enantiomer was greater in the hepatic vein than in the portal vein (approximately 2.2 versus 1.4), indicating that the stereoselective metabolism of VER in pigs mainly occurs on the first pass through the liver and not in the intestine. Ketoconazole increased the area under the curve from time 0 to 6 h and C(max) of R- and S-VER at least 3-fold in the portal vein, most likely explained by inhibition of gut wall metabolism. Conversely, hepatic extraction was increased because the effect of gut wall metabolism was not observed at the peripheral sampling sites. In conclusion, this study provided novel and more direct information on the contribution of the intestine and the liver, respectively, to the overall first-pass extraction of racemic VER.
