The purified extract of steamed Panax ginseng protects cardiomyocyte from ischemic injury via caveolin-1 phosphorylation-mediating calcium influx.

Background: Caveolin-1, the scaffolding protein of cholesterol-rich invaginations, plays an important role in store-operated Ca2+ influx and its phosphorylation at Tyr14 (p-caveolin-1) is vital to mobilize protection against myocardial ischemia (MI) injury. SOCE, comprising STIM1, ORAI1 and TRPC1, contributes to intracellular Ca2+ ([Ca2+]i) accumulation in cardiomyocytes. The purified extract of steamed Panax ginseng (EPG) attenuated [Ca2+]i overload against MI injury. Thus, the aim of this study was to investigate the possibility of EPG affecting p-caveolin-1 to further mediate SOCE/[Ca2+]i against MI injury in neonatal rat cardiomyocytes and a rat model. Methods: PP2, an inhibitor of p-caveolin-1, was used. Cell viability, [Ca2+]i concentration were analyzed in cardiomyocytes. In rats, myocardial infarct size, pathological damages, apoptosis and cardiac fibrosis were evaluated, p-caveolin-1 and STIM1 were detected by immunofluorescence, and the levels of caveolin-1, STIM1, ORAI1 and TRPC1 were determined by RT-PCR and Western blot. And, release of LDH, cTnI and BNP was measured. Results: EPG, ginsenosides accounting for 57.96%, suppressed release of LDH, cTnI and BNP, and protected cardiomyocytes by inhibiting Ca2+ influx. And, EPG significantly relieved myocardial infarct size, cardiac apoptosis, fibrosis, and ultrastructure abnormality. Moreover, EPG negatively regulated SOCE via increasing p-caveolin-1 protein, decreasing ORAI1 mRNA and protein levels of ORAI1, TRPC1 and STIM1. More importantly, inhibition of the p-caveolin-1 significantly suppressed all of the above cardioprotection of EPG. Conclusions: Caveolin-1 phosphorylation is involved in the protective effects of EPG against MI injury via increasing p-caveolin-1 to negatively regulate SOCE/[Ca2+]i.

[Pathogenesis of steroid-resistant asthma and the influence of vitamin D].

Glucocorticoid (GC) is currently the most effective drug for controlling persistent asthma; however, there is a significant difference in the response to GC among patients with asthma. Steroid-resistant asthma is one of the subtypes of asthma and has poor response to high-dose GC treatment. It may affect the quality of life of patients and even threaten their lives. Therefore, it is of great significance to explore the pathogenesis of steroid-resistant asthma and related targeted treatment strategy. In recent years, a variety of pathogeneses have been found to participate in the development and progression of steroid-resistant asthma, including the reduction in the binding between GC receptor and GC, the increase in the expression of GC receptor ß, over-activation of nuclear transcription factor activating protein 1 and nuclear factor-κB, abnormality in histone acetylation, and immune-mediated cytokine dysregulation. In addition, many studies have shown that vitamin D can improve the sensitivity to GC among patients with steroid-resistant asthma. This article reviews the pathogenesis of steroid-resistant asthma and the influence of vitamin D.

Preparation of lactoferrin-modified nanostructured lipid carriers and evaluation of its brain targeting efficiency / 中国药学杂志

OBJECTIVE: To construct receptor-mediated lactoferrin-modified curcumin-loaded nanostructured lipid carriers (Lf-Cur-NLCs) and investigate its in vitro physicochemical properties and in vivo brain targeting efficiency. METHODS: Cur-NLCs were prepared by melt-emulsification method, and then lactoferrin(Lf) was adsorbed onto the surface of Cur-NLCs via electrostatic interaction to form Lf-Cur-NLCs. Lf-Cur-NLCs with different concentrations of Lf were characterized in terms of shape, diameter, Zeta potential, serum stability and in vitro release of Lf-Cur-NLCs in saline containing 1% Tween 80. Additionally, Lf-NLCs labeled with NIRD-15, a fluorescent imaging agent, were prepared with Lf at concentrations of 0.5, 1.5 and 2.0 mg · mL-1 (marked for Lf1, -NLC, Lf3-NLC, and Lf4-NLC, respectively). After iv injection in mice, living animal imaging system was used to observe the fluorescence intensity of NIRD-15 in the living animals and isolated organs to evaluate the brain targeting of Lf-NLCs. RESULTS: Cur-NLCs were spherical with average particle size of(187.5 ±4.7) nm and Zeta potential of(- 23.7 ± 2.9) mV. The average diameter of Lf-Cur-NLCs with spherical shape was between 167.8-299.9 nm. The Zeta potential was between -26.87 - -13.03 mV. When the concentration of Lf was 2.0 mg · mL-1 and the incubated time was 6 h, the adsorption of Lf at the surface of the Cur-NLCs was saturated. Lf-Cur-NLCs were stable in serum, and the release of Cur from Lf-Cur-NLCs was slowed down. Compared with NLCs, there was a strong fluorescence in the brain after iv injection of Lf-NLCs, indicating that Lf-NLCs were more effective than NLCs in brain targeting, while Lf3-NLCs were the most effective one. CONCLUSION: Lf-NLCs are constructed successfully for brain targeting via electrostatic adsorption. The established process avoids chemical synthesis in the targeting drug delivery system design. However, the ability of brain targeting of the carriers is related with the amount of Lf.

Preparation and in vitro characterizations of cyclosporine A ocular nanostructured lipid carriers / 中国药学杂志

OBJECTIVE: To develop an appropriate nanostructured lipid carrier (CsA-NLC) for ocular drug delivery of cyclosporine A and its in vitro physicochemical properties and ocular irritation studies were investigated. METHODS: The melt-emulsification method was chosen to prepare CsA-NLC. The formulation was optimized by orthogonal design. The morphology of CsA-NLC was observed by transmission electron microscopy (TEM). The mean particle size and Zeta potential were measured by laser particle size analyzer. The state of drug in NLC was confirmed by DSC. Drug loading and encapsulation efficiency were determined by HPLC. Dialysis method at 34°C was employed to investigate the in vitro release of CsA-NLC. The topical ocular irritation study of CsA-NLC was made in rabbits. RESULTS: The obtained CsA- NLC was approximately spherical in shape with average particle size of (35.9 ± 0.21) nm and zeta potential of (- 13.9 ± 0.21) mV. The drug loading and encapsulation efficiency were (16.2 ± 0.09)% and (97.5 ± 0.58)%, respectively. The in vitro release of CsA-NLC was slowed down and fitted well single exponential distribution model. There was no irritation for CsA-NLC to rabbits eye. CONCLUSION: CsA-NLC with small particle sizes and high drug loading, slow release would be a promising nanocarrier for ocular drug delivery to improve drugs bioavailability. Copyright 2012 by the Chinese Pharmaceutical Association.

Preparation of bioadhesive cyclosporine a ocular nanostructured lipid carriers and its ocular distribution in rabbits / 中国药学杂志

OBJECTIVE: To develop a bioadhesive nanostructured lipid carrier (P407-NLC) for ocular delivery of cyclosporine A and investigate its ocular distribution in rabbits. METHODS: Melt-emulsification method was chosen to prepare CsA-NLC. Poloxamer 407 (P407) was dissolved in borate buffer solution (pH 8.0), then added into CsA-NLC to prepare P407-NLC. The morphology of P407-NLC was observed by transmission electron microscopy (TEM). The mean particle size and Zeta potential were measured by laser particle size analyzer. The viscosity was measured by rheometer. Dialysis method was employed to investigate the in vitro release of CsA from P407-NLC at 34°C. The concentrations of CsA in ocular tissues were studied by RP-HPLC, and the pharmacokinetic parameters were calculated by linear trapezoidal method. The topical ocular irritation study of P407-NLC was carried out in rabbits. RESULTS: The obtained P407-NLC was approximately spherical in shape with average particle size of (41.2 ± 0.2) nm and Zeta potential of (-15.2 ± 0.21) mV, and P407 was coated on the appearance of NLC. P407-NLC was non-newtonian fluids. The in vitro release of CsA from P407-NLC was slowed down and fitted well with single exponential distribution model. AUC0-24h of CsA in cornea, aqueous humor and iris after ocular administration of P407-NLC containing 6.0% P407 were 10.75, 4.45 and 4.62 times higher than that of CsA oil solution, and 2.77, 1.22 and 1.54 times higher than that of CsA-NLC, respectively. MRTs in aqueous humor, cornea and iris were 3.28, 2.26 and 3.46 times higher, respectively, than that of CsA oil solution, and 1.69, 1.50 and 1.62 times higher than CsA-NLC, respectively. There was no irritation for P407-NLC to rabbit eyes. CONCLUSION: P407-NLC can be used to increase the level of CsA in ocular tissues and would be a promising nanocarrier for ocular drug delivery. Copyright 2012 by the Chinese Pharmaceutical Association.

Water in oil microemulsions containing NaCl for transdermal delivery of fluorouracil / 药学学报

This study is to prepare the W/O microemulsion containing NaCl and fluorouracil (5-Fu) as a model drug to investigate the transdermal characteristics and skin irritation of the microemulsion in vitro. Isopropylmyristate (IPM) acting as oil phase, Aerosol-OT (AOT) as surfactant, Tween 85 as cosurfactant, NaCl solution was added dropwise to the oil phase to prepare W/O microemulsion at room temperature using magnetic stirring, and then 5-Fu powder was added. According to the area of microemulsion based on the pseudo-tertiary phase diagrams, the optimum formulation was screened initially. And the permeation flux of fluorouracil across excised mice skin was determined in vitro using Franz diffusion cells to study the influence of the amount of water and the drug loading capacity and optimize the formulation further. Refer to 5-Fu cream, the irritation of microemulsion on the rat skin was studied. The optimum formulation was composed of 0.7% (w/v) 5-Fu, 50% NaCl solution (0.05 mol x L(-1)), 20% mix-surfactant (AOT/Tween 85, K(m) = 2) and 29.3% oil (IPM). The cumulative amount of fluorouracil permeated in 12 h was (2 013.4 +/- 41.6) microg x cm(-2), 20.23 folds and 10.38 folds more than 0.7% fluorouracil aqueous solution and 2.5% (w/w) fluorouracil cream, respectively. Microemulsion exhibited some irritation, but could be reversed after drug withdrawal. The addition of NaCl significantly increased the content of water and the drug loading in microemulsion systems. The NaCl/AOT-Tween 85/IPM microemulsion system promoted the permeation of fluorouracil greatly, which may be a promising vehicle for the transdermal delivery of fluorouracil and other hydrophilic drug.

Socioeconomic status is a critical risk factor for human rabies post-exposure prophylaxis.

The socioeconomic status of the patients is the important factor for post-exposure prophylaxis (PEP). However, few investigations were designed to study the correlation between the socioeconomic status and PEP. This study set out to determine the importance of socioeconomic status for PEP. All of the 11,670 at-risk populations of rabies in the public health centre of San Sheng County in Chengdu from January 2002 to December 2009 were reviewed retrospectively. We identified 11,350 patients on vaccination and 550 patients with rabies immunoglobulin. RIG was administered to 4.85% bite victims attending the rabies prevention clinics, while 61.36% had a category III exposure. The incidence of receiving RIG in the population of the high level of income (49.38%) was much higher than the groups of the medium level (8.08%) and the low level of income (1.46%) (P<0.05). The incidence of receiving RIG with above high school (23.08%) was much higher than the groups of the primary school (3.01%), the junior school (12.56%) and the illiteracy (2.08%) (P<0.05). In the logistic regression analysis by stepwise approach, the socioeconomic status was the most important factor for PEP (95% CI 1.20-2.04). Vaccination and immunoglobulin proved to be the most prominent two factors for PEP but whether receiving Vaccination and immunoglobulin treatment or not is determined by the socioeconomic status. So, the socioeconomic status was the most important factor for PEP.

Microemulsion-based gel of fluorouracil for transdermal delivery / 药学学报

This study is to prepare the microemulsion-based gel based on the W/O microemulsion and fluorouracil (5-Fu) as a model drug to study the transdermal characterization and observe its skin irritation of the microemulsion-based gel in vitro. IPM acted as oil phase, AOT as surfactant, Tween 85 as cosurfactant, water was added dropwise to the oil phase to prepare W/O microemulsion at room temperature using magnetic stirring, then 5-Fu powder was added. The gelatin was used as substrate to prepare 5-Fu microemulsion-based gel. The permeation flux of 5-Fu from 5-Fu microemulsion-based gel across excised mice skin was determined in vitro using Franz diffusion cell to study the influence of the amount of gelatin and the drug loading capacity. Refer to 5-Fu cream, the irritation of microemulsion and microemulsion-based gel on the rat skin was studied. Based on the water/AOT/Tween 85/IPM microemulsion, only the gelatin can form the microemulsion-based gel. At 25 degrees C, 32 degrees C and 40 degrees C, the amount of gelatin required for the formation of microemulsion-based gel were 7%, 14% and more than 17%, respectively. The 12 h transdermal cumulated permeation amount of 5-Fu from microemulsion-based gel containing 14% gelatin and 0.5% drug loading were (876.5 +/- 29.1) microg x cm(-2), 12.3 folds and 4.5 folds more than 0.5% 5-Fu aqueous solution and 2.5% (w/w) 5-Fu cream, respectively. Microemulsion-based gel exhibited some irritation, but could be subsided after drug withdrawal. Microemulsion-based gel may be a promising vehicle for transdermal delivery of 5-Fu and other hydrophilic drug.

Water in oil microemulsions for transdermal delivery of fluorouracil / 药学学报

An Aersol-OT (AOT) included microemulsion containing fluorouracil was prepared by using appropriate proportion of oil, co-surfactant and water for increasing the drug transdermal delivery ability. According to the area of microemulsion basing on the pseudo-tertiary phase diagrams, the optimum formulation was screened initially. And the permeation flux of fluorouracil across excised mice skin was determined in vitro using Franz diffusion cell to optimize the formulation further. The effect of the kind of co-surfactant, the content of water, the content of mixed surfactant, the mass ratio of surfactant/cosurfactant (Km) and the drug load on skin permeation of fluorouracil were evaluated. The optimum formulation was composed of 0.5% (w/v) fluorouracil, 30% water, 20% mix-surfactant (AOT/Tween 85, Km = 2) and 49.5% oil (IPM). The cumulative amount permeated of fluorouracil in 12 hour was 1 355.5 microg x cm(-2), 19.1 folds and 7 folds more than 0.5% fluorouracil aqueous solution and 2.5% (w/w) fluorouracil cream, respectively. The permeation of this microemulsion accorded with first-order model. The water/AOT/Tween 85/IPM microemulsion system promoted the permeation of fluorouracil greatly, which may be a promising vehicle for the transdermal delivery of fluorouracil and other hydrophilic drug.

The enhancing effect of borneol on the absorption of tetramethylpyrazine / 药学学报

To explore the mechanism of the absorption enhancement of borneol, the effect of borneol on the intestinal absorption and the pharmacokinetics of tetramethylpyrazine phosphate after oral administration were investigated. In situ intestinal recirculation was performed to study the effect of various concentrations of borneol on the absorption of tetramethylpyrazine phosphate at duodenum, jejunum, ileum and colon. After oral administration of tetramethylpyrazine phosphate, the mixture of tetramethylpyrazine phosphate and borneol and the mixture of tetramethylpyrazine phosphate and verapamil in rats, the concentrations of tetramethylpyrazine phosphate in plasma were determined by RP-HPLC at predesigned time. The pharmacokinetic parameters were compared based on the results of the three animal experiments, and analyzed with software program 3p97. The result showed that tetramethylpyrazine phosphate could be absorbed at all of the four intestinal segments with increasing absorption amount per unit as follows: colon > duodenum > jejunum > ileum, but without saturation, which demonstrated that tetramethylpyrazine phosphate was absorbed via simple diffusion. Borneol could enhance the intestinal absorption of tetramethylpyrazine phosphate, however, not in proportion. There was no obvious difference between the test group and the control group when 10 microg x mL(-1) borneol was added (P > 0.05), while when the concentration comes to 25 microg x mL(-1) and 50 microg x mL(-1), significant differences were observed (P < 0.05). Borneol and verapamil did enhance the bioavailability of tetramethylpyrazine phosphate after oral administration in rats. The enhancing effect of borneol showed only when the concentration came to a certain level but with no specific sites existed in the intestine. One of the mechanisms of borneol on the enhancing effect on absorption of tetramethylpyrazine phosphate might be the inhibition of the metabolism of CYP 3A and exocytosis of P-gp.

A simple gas chromatographic method for the simultaneous determination and pharmacokinetic study of tetramethylpyrazine phosphate and borneol in mouse plasma and brain tissue after oral administration of the fufang tetramethylpyrazine phosphate tablets.

A rapid, sensitive, and simple gas chromatographic method with flame ionization detection is developed for the simultaneous determination of tetramethylpyrazine phosphate (TMPP) and borneol in mouse plasma and brain tissue. Sample preparations are carried out by deproteinization with an internal standard solution in methanol. The analytes and internal standard (dimethyl sulfoxide) are well-separated on an HP-5 MS capillary column. The analytical curves are linear over a wide concentration range of 0.02-40 microg/mL for both TMPP and borneol in plasma and brain tissue, with the intra- and inter-day precision (the relative standard deviation values) at less than 15%. TMPP and borneol are both stable under different conditions. The method described is successfully applied to the pharmacokinetic study of mouse plasma and brain tissue after oral administration of the Fufang TMPP and TMPP tablets to mice.

The enhancing effect of synthetical borneol on the absorption of tetramethylpyrazine phosphate in mouse.

The main purpose of this study was to illustrate the effect of synthetical borneol (SB) on the plasma and brain concentration profile of tetramethylpyrazine phosphate (TMPP) in mice after oral administration of TMPP without or with different amounts of SB. The concentrations of TMPP on the plasma and brain in mice were determined by GC-FID. The pharmacokinetic parameters were computed by software program 3p97. Our data showed that after oral administration of 15, 30, 90 mg kg(-1) of SB, oral bioavailability of TMPP in plasma was 1.52, 2.21, 2.95 times increase, respectively, than that without SB, and 1.12, 1.62, 1.93 times increase, respectively, in brain tissue. The pharmacokinetic data were simulated by non-linear least squares. The results showed that both open two-compartment model and one-order absorption were fitted to TMPP plasma and brain concentration-time course in vivo in mice. The MRT of TMPP showed same results under the conditions without or with SB. SB did enhance the oral absorption of TMPP and the concentration of TMPP in brain tissue, especially in the early period. But the use of SB did not change the behavior in vivo of TMPP.

Preparation of silymarin proliposome: a new way to increase oral bioavailability of silymarin in beagle dogs.

The aim of the present study was to find a method to increase oral bioavailability of silymarin, that is to say, by the preparation of silymarin proliposome and to compare the pharmacokinetic characteristics and bioavailability after oral administration of silymarin proliposome and silymarin in beagle dogs. Silymarin proliposome was prepared by the film-deposition on carriers. After the proliposome was contacted with water, the silymarin liposome suspensions formed automatically. The tests of physicochemical properties including SEM, TEM, encapsulation efficiency, dissolution studies, particle size of the reconstituted liposome and stability of the silymarin proliposome were determined by laser-particle-sizer, HPLC, etc. The concentrations of silymarin in plasma of beagle dogs and its pharmacokinetic behaviors after oral administration of silymarin liposome suspensions and silymarin were studied by RP-HPLC. The pharmacokinetic parameters were computed by software program 3p97. The encapsulation efficiency of silymarin liposome could be more than 90%, with an average particle size of about 196.4 nm and the proliposome appeared a very stability at 40 degrees C during 3 months. It was found that mean plasma concentration-time curves of silymarin after oral administration of liposome suspensions and silymarin in beagle dogs were both in accordance with open two-compartments model and first-order absorption. Pharmacokinetic parameters of silymarin proliposome and silymarin in beagle dogs were Tmax both 30 min; Cmax 472.62 and 89.78 ng mL(-1); and AUC0-infinity 2606.21 and 697 ng mL(-1)h, respectively. The high bioavailability of silymarin proliposome could be obtained by oral administration. Silymarin proliposome was stable and did enchance the gastrointestinal absorption of silymarin.

Preparation of verapamil hydrochloride controlled-onset extended-release pellets and its pharmacokinetics in dogs / 药学学报

<p><b>AIM</b>To prepare verapamil hydrochloride controlled-onset extended-release pellets (VH-COERP) and study its release behavior in vitro. To compare the pharmacokinetic characteristics and bioavailability in six Beagle dogs after oral administration of VH-COERP and verapamil hydrochloride delayed-release pellets (VH-DRP) as reference.</p><p><b>METHODS</b>The core of VH-COERP were prepared in the fluidized bed (mini-glatt) by spraying water solution containing drugs onto sucrose-starch pellets with hydroroxy propyl methyl cellulose (HPMC) as the inner coating swelling layer and ethylcellulouse aqueous dispersion as the outer coating controlled layer. Through modifying the coating level of inner and outer layer, the VH-COERP with the optimized cumulative release profile was obtained. The concentration of VH in plasma of six dogs and its pharmacokinetic behaviors after oral administration of VH-COERP and VH-DRP at different times were studied by RP-HPLC. The pharmacokinetic parameters were computed by software program 3P97.</p><p><b>RESULTS</b>The lag time, the release behavior and the amount of VH from VH-COERP within 24 hours were not influenced by the pH of dissolution medium and post-process, but obviously influenced by the different kinds of added material in swelling layer and the coating level of the inner swelling layer and the outer controlled layer. In vitro the lag time of release profile of VH from VH-COERP was 5 h and then VH was extended release from VH-COERP in the following time. Compared with the VH-DRP, VH-COERP in vivo has an obviously lag time (4 h) , Tmax was also delayed (8 h) and the relative bioavailability was (94.56 +/- 7.64)%.</p><p><b>CONCLUSION</b>The release profile of VH from VH-COERP was shown to be extended-release after an conspicuous lag time in vitro and in vivo. So the drug can be taken by the patient before bed time and begin to work at the morning.</p>

Preparation of silymarin proliposomes and its pharmacokinetics in rats / 药学学报

<p><b>AIM</b>To study the preparation of silymarin proliposomes. To study its physicochemic properties, its pharmacokinetical characteristics and bioavailability in rats after oral administration.</p><p><b>METHODS</b>Silymarin proliposomes were prepared by film-deposition on carriers. When the proliposomes were contacted with water to form liposome suspensions, the tests of physicochemical properties including encapsulation efficiency, particle size and stability of the formed liposome suspensions were determined by HPLC, laser-particle-sizer and etc. The concentrations of non-conjugated and overall silymarin in plasma of rats and their pharmacokinetic behaviors after oral administration were studied by RP-HPLC. The pharmacokinetic parameters were computed by software program 3P97.</p><p><b>RESULTS</b>The encapsulation efficiency of silymarin liposomes could be more than 90%, with an average particle size of about 238.8 nm and a very good stability. The high bioavailability of silymarin proliposomes could be gotten by oral administration.</p><p><b>CONCLUSION</b>Compared with silymarin, silymarin proliposome is a stable and easily industrialized preparation and did enchance the gastrointestinal absorption of silymarin.</p>

Preparation of silybin-phospholipid complex and its bioavailability in rats / 药学学报

<p><b>AIM</b>To prepare silybin-phospholipid complex and study its physicochemical properties. To compare the pharmacokinetic characteristics and bioavailability after oral administration of silybinphospholipid complex and silybin material in rats.</p><p><b>METHODS</b>Using acetone as a reaction medium, silybin and phospholipid were resolved into the medium, when the organic solvent was clear, then removed under vacuum evaporation, silybin-phospholipid complex was obtained. The new complex' s physicochemical properties including DSC, UV, IR were determined. The concentrations of non-conjugated and total silybin after oral administration of silybin-phospholipid complex and silybin material at different time in rats were determined by RP-HPLC. The pharmacokinetic parameters were computed by software program 3P97.</p><p><b>RESULTS</b>Experiment results showed that silybin and phospholipid in the silybin-phospholipid complex were combined by non-covalent-bond, not forming a new compound and the solubility of silybin-phospholipid complex in water and n-octanol was effectively enhanced. It was found that mean plasma concentration-time curve of silybin after oral administration of silybin-phospholipid complex in rats was in accordance with one-compartment model with first-order absorption. Pharmacokinetic parameters of non-conjugated and total silybin in rats were respectively T(max) 10 min and 2 h; C(max) 0.11 and 1.08 microg x mL(-1); T1/2 2.18 and 3.84 h; AUC(0-infinity) 1.71 and 12.94 microg x mL(-1) x h. However, after oral administration of silybin material, plasma levels of both non-conjugated and total silybin were within the analytical detection limit.</p><p><b>CONCLUSION</b>It was concluded that after oral administration of silybin-phospholipid complex in rats the bioavailability of silybin increased greatly. This was mainly due to an obvious improvement of the lipophilic property of silybin-phospholipid complex compared with silybin material and an increase in gastrointestinal absorption.</p>