1.
Bergman, Ebba, et al.
(author)
Pharmacokinetics of gefitinib in humans : the influence of gastrointestinal factors
2007
In: International Journal of Pharmaceutics. - : Elsevier BV. - 0378-5173 .- 1873-3476. ; 341:1-2, s. 134-142
Journal article (peer-reviewed) abstract
Purpose To investigate whether differences in plasma pharmacokinetic profiles of gefitinib between healthy subjects having normal (N; t1/2 > 20 h) and altered (A; t1/2 < 20 h) pharmacokinetic (PK) profiles might be explained by inter-individual variability in gastric emptying and/or precipitation/dissolution of gefitinib in the proximal small intestine. Methods One hundred healthy male subjects were screened to enable identification of subjects with the two PK profiles. Twenty five subjects from the screening were subsequently enrolled in an intubation study where a 250 mg gefitinib dispersion preparation (IRESSA®, AstraZeneca) was administered directly into the stomach. Intestinal fluid samples were withdrawn continuously for 180 min post-dose using the Loc-I-Gut catheter positioned in the jejunum. The crystalline form of gefitinib was determined using Raman microscopy. Results There were no differences between normal and altered subjects with regard to gastric emptying or the precipitation/dissolution of gefitinib in jejunal fluid. Due to difficulties in crystalline identification in the jejunal fluid samples, only the same crystalline form as the dosed form was identified. Conclusions There was no pronounced difference in gastric emptying, precipitation and re-dissolution of gefitinib in proximal human jejunum between normal and altered subjects. Other mechanism(s) are also likely to be important in explaining the inter-individual differences in plasma exposure to gefitinib, such as polymorphism in various metabolic enzymes and/or transport proteins. However, the difference between altered and normal subjects cannot be easily explained and it is likely a multifactorial explanation including low jejunal pH, increased expression of enzymatic and transporter activity and rapid small intestine transit.
2.
Persson, Eva M, et al.
(author)
A clinical single-pass perfusion investigation of the dynamic in vivo secretory response to a dietary meal in human proximal small intestine
2006
In: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 23:4, s. 742-751
Journal article (peer-reviewed) abstract
Purpose To investigate the gastrointestinal secretory and enzymatic responses to a liquid meal during in vivo perfusion of the proximal human jejunum. Methods Human intestinal fluid was collected from the proximal jejunum by single-pass in vivo perfusion (Loc-I-Gut). The fluid was quantitatively collected at 10-min intervals during 90 min while perfusing a nutritional drink at 2 mL/min. Quantification of lipids in the fluid leaving the segment was performed by using novel chromatographic methods. Results The overall bile acid concentration varied between 0.5 and 8.6 mM with a peak level 40 min after the start of the liquid meal perfusion. The total concentration of phospholipids was between 0.1 and 3.9 mM and there was a rapid degradation of phosphatidylcholine to lysophosphatidylcholine. The tri-, di-, monoglycerides and free fatty acid levels increased sharply in the beginning and reached steady-state levels between 7 and 9.5 mM. Conclusions There is a rapid secretion of bile in response to food. Most of the dietary lipids are found in the form of their degradation products in vivo in human jejunum. This novel in vivo characterization, based on direct and high-recovery sampling of intestinal fluids, forms a basis for further development of improved in vitro drug dissolution test media.
3.
Persson, Eva M., et al.
(author)
Improved understanding of the effect of food on drug absorption and bioavailability for lipophilic compounds using an intestinal pig perfusion model
2008
In: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 34:1, s. 22-29
Journal article (peer-reviewed) abstract
The purpose of this study was to investigate the relative importance of mechanisms behind the effect of food on the intestinal absorption and bioavailability for low solubility compounds by applying a porcine single-pass perfusion model. Nanoparticle suspensions of the model compounds, danazol and cyclosporine were perfused through the jejunum in isotonic fluid alone (control) and isotonic fluid with a P-glycoprotein (P-gp) inhibitor (verapamil) or dietary and endogenous lipids added. The drugs were also administered as saturated solutions in the isotonic fluid containing lipids. Administration of cyclosporine together with verapamil increased the absorption compared to the control (1.6 times) suggesting an effect on jejunal permeability. However, addition of dietary lipids to the media led to a 50% reduction in the absorption of cyclosporine indicating lack of major effects by P-gp inhibition by lipids in vivo. The absorption of danazol was increased (2.6 times) when administered as a nanosuspension in lipid containing media compared to the control, but decreased (60%) when administered as a solution in the same media. This shows how important dissolution of the drug nanoparticles is in drug absorption. The difference in the effect of lipids in the absorption of cyclosporine and danazol when administered as nanosuspensions may be due to different distribution to the colloidal structures present in the media, thereby rendering the drugs' different diffusion rates in the perfused segment. In conclusion, solubilisation seems to be a more important factor than P-gp inhibition as an explanation for the food-drug interaction observed for several low solubility drugs. In addition, the partition into different colloidal structures seems to play a major role in the dissolution and absorption of poorly soluble drugs.
4.
Persson, Eva M., et al.
(author)
Is there an effect of food on the biliary secretion of cyclosporine and three in vivo formed metabolites in a porcine model?
2007
In: Journal of Drug Delivery Science and Technology. - 1773-2247. ; 17:4, s. 253-258
Journal article (peer-reviewed) abstract
The aim of this study was to investigate the effect of lipids and P-glycoprotein (P-gp) inhibition on the biliary secretion of cyclosporine (CsA) and in vivo formed metabolites in pigs. A parallel group design including 12 pigs in four groups and a combined single-pass intestinal perfusion and bile collection method was employed. CsA was perfused through the jejunum in an isotonic fluid alone and with verapamil or lipids added. The study showed that there was no difference between the administration groups, except for the fraction of the absorbed dose that was excreted in bile was twice as high when CsA was administered together with lipids. In conclusion, CsA is excreted via the biliary route in pigs without any significant involvement of P-gp. Concomitant food-intake could increase the secretion to the bile, presumably by prolonged associations between the CsA and the lipid species.
5.
Persson, Eva M, et al.
(author)
The effects of food on the dissolution of poorly soluble drugs in human and in model small intestinal fluids
2005
In: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 22:12, s. 2141-2151
Journal article (peer-reviewed) abstract
Purpose This study was conducted to determine the effect of food on drug solubility and dissolution rate in simulated and real human intestinal fluids (HIF). Methods Dissolution rate obtained via the rotating disk method and saturation solubility studies were carried out in fed and fasted state HIF, fed dog (DIF), and simulated (FeSSIF) intestinal fluid for six aprotic low solubility drugs. The intestinal fluids were characterized with respect to physical–chemical characteristics and contents. Results Fed HIF provided a 3.5- to 30-times higher solubility compared to fasted HIF and FeSSIF, whereas fed DIF corresponded well (difference of less than 30%) to fed HIF. The increased solubility of food could mainly be attributed to dietary lipids and bile acids. The dissolution rate was also 2 to 7 times higher in fed HIF than fasted HIF. This was well predicted by both DIF and FeSSIF (difference of less than 30%). Conclusions Intestinal solubility is higher in fed state compared to fasted state. However, the dissolution rate does not increase to the same extent. Dog seems to be a good model for man with respect to dissolution in the small intestine after intake of a meal, whereas FeSSIF is a poorer means of determining intestinal saturation solubility in the fed state.
