Tacrolimus In Rats Research Articles

Implications of an Altered Gut Microbiome in Rat Experimental Vascularized Composite Transplantation.

Vascularized composite allotransplantation is a reconstructive option after severe injury but is fraught with complications, including transplant rejection due to major histocompatibility complex mismatch in the context of allogeneic transplant, which in turn is due to altered immuno-inflammation secondary to transplant. The immunosuppressant tacrolimus can prevent rejection. Because tacrolimus is metabolized predominantly by the gut, this immunosuppressant alters the gut microbiome in multiple ways, thereby possibly affecting immunoinflammation. We performed either allogeneic or syngeneic transplant with or without tacrolimus in rats. We quantified protein-level inflammatory mediators in the skin, muscle, and plasma and assessed the diversity of the gut microbiome through 16S RNA analysis at several timepoints over 31 days posttransplant. Statistical analysis highlighted a complex interaction between major histocompatibility complex and tacrolimus therapy on the relative diversity of the microbiome. Time-interval principal component analysis indicated numerous significant differences in the tissue characteristics of inflammation and gut microbiome that varied over time and across experimental conditions. Classification and regression tree analysis suggested that both inflammatory mediators in specific tissues and changes in the gut microbiome are useful in characterizing the temporal dynamics of posttransplant inflammation. Dynamic network analysis highlighted unique changes in Methanosphaera that were correlated with Peptococcusin allogeneic transplants with and without tacrolimus versus Prevotella in syngeneic transplant with tacrolimus, suggesting that alterations in Methanosphaera might be a biomarker of vascularized composite allotransplant rejection. Our results suggest a complex interaction among major histocompatibility complex, local and systemic immuno-inflammation, and tacrolimus therapy and highlight the potential for novel insights into vascularized composite allotransplant from computational approaches.

Effects of clarithromycin on the pharmacokinetics of tacrolimus and expression of CYP3A4 and P-glycoprotein in rats.

The objective of this study was to investigate the effect of clarithromycin on the pharmacokinetics of tacrolimus in rats and better understand its mechanism. In the control group (n = 6), rats received a single oral dose of 1mg tacrolimus on day 6. In the experimental group (n = 6), rats received 0.25 g of clarithromycin daily for five consecutive days and then a single oral dose of 1mg tacrolimus on day 6. Orbital venous blood (250 μL) was collected at 0, 0.25, 0.50, 0.75, 1, 2, 4, 8, 12, and 24 h before and after tacrolimus administration. Blood drug concentrations were detected via mass spectrometry. Small intestine and liver tissue samples were collected after rats were euthanized via dislocation, and CYP3A4 and P-glycoprotein (P-gp) protein expression was determined using western blotting. Clarithromycin increased the blood tacrolimus concentration and affected its pharmacokinetic properties in rats. Compared with those in the control group, the AUC0-24 , AUC0-∞ , AUMC(0-t) , and AUMC(0-∞) of tacrolimus in the experimental group were significantly increased, whereas the CLz/F was significantly lower (P < 0.01). Simultaneously, clarithromycin significantly inhibited CYP3A4 and P-gp expression in the liver and intestine. Protein expression of CYP3A4 and P-gp in the liver and the intestinal tract was significantly downregulated in the intervention group compared with that in the control group. Clarithromycin significantly inhibited the protein expression of CYP3A4 and P-gp in the liver and intestine, thereby increasing the mean blood concentration and significantly increasing the AUC of tacrolimus.

Effect of histone deacetylase inhibitor (vorinostat) on new-onset diabetes induced by tacrolimus

ObjectiveThe immunosuppressant tacrolimus is a major cause of new-onset diabetes after transplantation. The aim of this study was to evaluate whether a low dose of the histone-deacetylase inhibitor (vorinostat) might ameliorate tacrolimus-induced new-onset diabetes. MethodsThirty 8-week-old male Wistar rats were randomly divided into five groups: a control group, tacrolimus group (1.5 mg/kg intraperitoneally for 28 days), vorinostat group (15 mg/kg orally for 28 days), a group receiving tacrolimus with vorinostat for 28 days; and a group receiving coadministration of tacrolimus for 28 days and vorinostat for 14 days. Diabetes development was assessed on the basis of serum glucose, insulin, HOMA-IR and C-peptide. To investigate the mechanism of vorinostat, we assessed inflammatory markers (tumor necrosis factor-α and interleukin-1β), an antioxidant marker (glutathione), an oxidant marker (nicotinamide adenine dinucleotide phosphate hydrogen oxidase) and an apoptosis marker (caspase-3). Kidney functions (creatinine and blood urea nitrogen) were also assessed. ResultsThe administration of tacrolimus for 28 days resulted in significantly increased serum glucose and decreased C-peptide and insulin levels than those in the control group. However, coadministration of vorinostat significantly decreased hyperglycemia and increased C-peptide and insulin levels. Moreover, combined treatment with tacrolimus and vorinostat, compared with tacrolimus treatment alone, resulted in significantly reduced inflammatory and oxidant markers, and increased glutathione. Additionally, vorinostat improved the kidney parameters. ConclusionVorinostat at a low dose (15 mg/kg) induces anti-inflammatory and antioxidative effects that protect the pancreas and kidney against the development of new-onset diabetes due to tacrolimus in rats. This experimental study provides insights supporting further clinical trials to improve the post-kidney transplantation protocol through addition of vorinostat to the immunosuppressive regimen.

Inhibitory effects of traditional Chinese medicine colquhounia root tablet on the pharmacokinetics of tacrolimus in rats

Ethnopharmacological relevanceTacrolimus (TAC) was widely used in various renal diseases while high recurrence rate and high expense restricted its applications. Traditional herbal medicine has become increasingly popular as an adjuvant therapy to minimize the adverse effects of TAC. Colquhounia root tablet (CRT), a prescribed drug prepared from the water extract of the peeled root of Tripterygium hypoglaucum (H. Lév.) Hutch., showed excellent anti-inflammatory, analgesic and immunosuppressive pharmacological properties. TAC used in combination with CRT was substantially more efficacious and safer than the monotherapy for the treatment of nephrotic syndrome. However, studies on their herb-drug interaction were scanty. Aim of the studyThe study was proposed to examine the effect of CRT on the pharmacokinetics of TAC in rats and identify the key natural constituents in CRT that affected the metabolism of TAC. Materials and methodsTAC was orally and intravenously administered to rats alone or in combination with CRT and the pharmacokinetic parameters of TAC were compared. After pretreatment with CRT for 15 d, the expressions of the drug-metabolizing enzymes (DMEs), drug transporters (DTs) and nuclear receptors (NRs) were determined by polymerase chain reaction and western blotting and compared with the control group. The hepatic microsomal incubation system was employed to confirm the inhibitory effects of CRT and its major components on rat cytochrome P450 (CYP) 3A2. The roles of the primary components in the regulation of human CYP3A4 and mouse P-gp activities were evaluated by using docking analysis. ResultsThe blood concentrations of TAC were significantly increased in a dose- and pretreatment time-dependent manner after combined administration of CRT. The maximal effect was found at 300 mg/kg (43.70 ± 8.77 ng/mL and 141.45 ± 21.58 h·ng/mL) in a single dose run and the pharmacokinetic parameters gradually returned to the normal levels at 24 h interval of long-term CRT pretreatment. In contrast, CRT had no effect on the pharmacokinetics of intravenous TAC. Further study indicated that the mRNA and protein expressions of DMEs and DTs, such as CYP3A1, CYP3A2, P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 in rat intestine and liver were down-regulated, whereas the expressions of NRs like constitutive androstane receptor and pregnane X receptor were up-regulated after multiple oral doses of CRT. Molecular docking showed the binding potency of five CRT major constituents with both human CYP3A4 and mouse P-gp. Celastrol, wilforgine and wilforine were the strongest inhibitors towards midazolam metabolism in rat liver microsomes, with the 50% inhibition concentrations being at 8.33 μM, 22.18 μM and 22.22 μM, respectively. ConclusionsOur results revealed that co-dosing of CRT could lead to a significant increase in blood concentration of TAC and this effect could be ascribed to the resultant co-regulation of DMEs, DTs and NRs. Our study provided an experimental basis for the combination use of CRT and TAC in clinical practice.

Inhibitory Effects of Traditional Chinese Medicine Colquhounia Root Tablet on the Pharmacokinetics of Tacrolimus in Rats

Inhibitory Effects of Traditional Chinese Medicine Colquhounia Root Tablet on the Pharmacokinetics of Tacrolimus in Rats

Co-administration of Wuzhi tablet (Schisandra sphenanthera extract) alters tacrolimus pharmacokinetics in a dose- and time-dependent manner in rats

Ethnopharmacology relevanceTacrolimus is a well-known potent but expensive immunosuppressant. We previously clarified the herb-drug interaction between tacrolimus and Wuzhi tablet (WZ), a prescribed drug of ethanol extract of Schisandra sphenanthera, and showed the ideal effect of WZ on maintaining therapeutic level of tacrolimus and reducing the total drug expense. However, WZ possesses a biphasic effect on regulating CYP3A (the major metabolizing enzyme of tacrolimus), which could induce the mRNA and protein expression after long-term treatment while transiently inhibit the activity of CYP3A. In clinic, clinicians are confused about the relationship between the blood concentration of tacrolimus and the dose and the duration of pretreatment of WZ. Therefore, the effects of the pretreatment time and the dose of WZ on the pharmacokinetics of tacrolimus is urgently needed to be clarified to better combine the use of WZ and tacrolimus in clinic. Aim of the study and methodThis study aimed to investigate the effects of the pretreatment time and the dose of WZ on the pharmacokinetics of tacrolimus in rats. Results and conclusionsAfter pretreated rats with WZ for 0, 0.5, 2, 6, 12 or 24 h, the area under the curve (AUC) of tacrolimus was 2.27 ± 0.59, 1.87 ± 1.14, 2.86 ± 0.64, 1.62 ± 0.70, 1.54 ± 1.06 and 1.12 ± 0.69-fold of that of the tacrolimus alone group, respectively. The ratio of AUC of tacrolimus to that of the co-administration group with 0, 62.5, 125, 250, 500 or 750 mg/kg of WZ was 1.00: 1.07: 1.44: 2.60: 2.32: 2.42, respectively. These findings suggested that WZ increased tacrolimus AUC in a pretreatment time- and dose-dependent manner. In line with the in vivo findings, WZ extract inhibited CYP3A activity in a pre-treatment time- and concentration-dependent manner in human liver microsomes. In conclusion, the pharmacokinetics of tacrolimus was significantly affected by the pretreatment time and the dose of WZ. Oral pretreatment with WZ for 0–2 h or co-dosing of 250 mg/kg of WZ most significantly increased the blood concentration of tacrolimus. These findings would be helpful for guiding the reasonable use of WZ and tacrolimus in clinic.

Effects of the combined administration of risedronate and menatetrenone on bone loss induced by tacrolimus in rats.

Tacrolimus, a calcineurin inhibitor, affects bone metabolism and increases the risk of fracture due to marked bone loss. Bisphosphonates increase the bone mineral density (BMD) in osteoporosis patients. Menatetrenone has less positive effects on BMD but reduces the risk of fracture by improving bone quality. In this study, we investigated the effectiveness of the combined administration of risedronate and menatetrenone against bone loss induced by tacrolimus. Wistar rats were divided into four groups: [1] control, [2] tacrolimus at 1.5 mg/kg, [3] tacrolimus + risedronate at 1.0 mg/kg, and [4] tacrolimus + risedronate + menatetrenone at 20 mg/kg. After the drugs were administered for 4 weeks, bone histomorphometric analysis was performed and bone strength was evaluated using a three point bending method. BMD was measured using quantitative computed tomography. Tacrolimus significantly reduced the BMD and strength properties of the lower limb bones. These tacrolimusinduced decreases were suppressed by risedronate treatment. The combined administration of risedronate and menatetrenone more significantly improved bone strength properties than risedronate alone. Bone histomorphometric analysis revealed a significant increase in bone resorption with tacrolimus. Risedronate alone significantly suppressed the tacrolimus-induced increase in bone resorption but simultaneously reduced bone formation. On the other hand, the combined administration of risedronate and menatetrenone suppressed the tacrolimus-induced increase in bone resorption, in addition to the significant risedronate-induced decrease in bone formation. This study suggests that the combined administration of risedronate and menatetrenone improves bone strength in tacrolimus-treated rats by preventing and ameliorating the risedronate-induced suppression of bone formation.

The Role of Cytochrome P450 3A5 Enzyme on the Metabolism of Tacrolimus in Rats

Purpose: The present study was designed to determine the effect ratio of CYP3A5 on the metabolism of tacrolimus that is used as an immunosuppressant for tissue transplantation.Methods: To determine the role of CYP3A4 and CYP3A5 on tacrolimus metabolism, rats were divided into five groups as: group 1 control group, tacrolimus only 1 mg/kg i.v. , group 2 pretreated with ritonavir 5 mg/kg, i.v. 1 h before administration of tacrolimus , group 3 pretreated with indinavir 10 mg/kg, i.v. 1 hour before administration of tacrolimus , groups 4 and 5, in addition to the protocol of groups 2 and groups 3. Dexamethasone 100 mg/kg, p.o. was administered for 2 days before the experimental study to each group. To estimate the area under curve AUC of tacrolimus, the blood samples were collected after 15, 30, 60, 75, and 90 min and after 2, 3, 4, 8, and 24 h, and MEIA method was used to determine whole blood levels of tacrolimus.Results: Although the AUCs of tacrolimus in group 2 533.5±139.85 ng.h/mL and group 3 3428±683 ng.h/mL were higher than the control group 394±127 ng.h/mL , the only significant difference was found in ritonavir pretreated group group 3 . In dexamethasone pretreated groups, the AUC values were similar to control group.Conclusion: These results suggest that the role of CYP3A5 enzyme has to be taken into account for probable drug interactions and sufficient immunosuppression in patients who are treated with tacrolimus

Release mechanisms of tacrolimus-loaded PLGA and PLA microspheres and immunosuppressive effects of the microspheres in a rat heart transplantation model

The objective of this study was to elucidate the release and absorption mechanisms of tacrolimus loaded into microspheres composed of poly(lactic-co-glycolic acid) (PLGA) and/or polylactic acid (PLA). Tacrolimus-loaded microspheres were prepared by the o/w emulsion solvent evaporation method. The entrapment efficiency correlated with the molecular weight of PLGA, and the glass transition temperature of PLGA microspheres was not decreased by the addition of tacrolimus. These results indicate that intermolecular interaction between tacrolimus and the polymer would affect the entrapment of tacrolimus in the microspheres. Tacrolimus was released with weight loss of the microspheres, and the dominant release mechanism of tacrolimus was considered to be erosion of the polymer rather than diffusion of the drug. The whole-blood concentration of tacrolimus in rats was maintained for at least 2 weeks after a single subcutaneous administration of the microspheres. The pharmacokinetic profile of tacrolimus following subcutaneous administration was similar to that following intramuscular administration, suggesting that the release and dissolution of tacrolimus, rather than the absorption of the dissolved tacrolimus, were rate-limiting steps. Graft-survival time in a heart transplantation rat model was prolonged by the administration of tacrolimus-loaded microspheres. The microsphere formulation of tacrolimus would be expected to precisely control the blood concentration while maintaining the immunosuppressive effect of the drug.

Solid self-nanoemulsifying drug delivery system (SNEDDS) for enhanced oral bioavailability of poorly water-soluble tacrolimus: physicochemical characterisation and pharmacokinetics

To develop a novel self-nanoemulsifying drug delivery system (solid SNEDDS) with better oral bioavailability of tacrolimus, the solid SNEDDS was obtained by spray-drying the solutions containing the liquid SNEDDS and colloidal silica. Its reconstitution properties were determined and correlated to solid state characterisation of the powder. Moreover, the dissolution and pharmacokinetics in rats was done in comparison to the commercial product. Among the liquid SNEDDS formulations tested, the liquid SNEDDS comprised of Capryol PGMC, Transcutol HP and Labrasol (10:15:75, v/v/v) presented the highest dissolution rate. In the solid SNEDDS, this liquid SNEDDS was absorbed in the pores and attached onto the surface of the colloidal silica. Drug was present in the amorphous state in it. The solid SNEDDS with 5% w/v tacrolimus produced the nanoemulsions and improved the oral bioavailability of tacrolimus in rats. Therefore, this solid SNEDDS would be a potential candidate for enhancing the oral bioavailability of tacrolimus.

Preparation and pharmaceutical evaluation of new tacrolimus-loaded solid self-emulsifying drug delivery system.

The purpose of this study was to develop a novel tacrolimus-loaded solid self-emulsifying drug delivery system (SEDDS) using Labrafac as an oil phase. The ternary phase diagram was plotted with Labrafac, Labrasol and Lauroglycol used as an oil, surfactant and co-surfactant, respectively. The liquid SEDDS formulated with Labrasol, Lauroglycol and Labrafac (70:15:15, volume ratio) furnished the smallest emulsion globule size. The solid SEDDS was obtained by spray-drying the liquid mixture containing the liquid SEDDS with 5 % tacrolimus and silicon dioxide. Furthermore, dissolution of tacrolimus from the solid SEDDS and pharmacokinetics in rats was studied compared to the commercial product. The solid SEDDS produced relatively larger emulsion globule size than that exhibited by the corresponding liquid SEDDS. However, this size variation was not significantly different. The solid SEDDS with approximately 280 nm emulsion droplet size improved the dissolution of the drug compared to drug power and the commercial product. It resulted in significantly higher plasma concentration, AUC and Cmax, and shorter Tmax values than did the commercial product (p < 0.05). The enormously enhanced oral bioavailability of tacrolimus in rats was attributed to relatively faster absorption due to accelerated dissolution of the drug from the solid SEDDS. Therefore, this novel solid SEDDS prepared with Labrafac as an oil phase is an excellent way to achieve better bioavailability of tacrolimus given via the oral route.

Effects of Traditional Chinese MedicineWuzhiCapsule on Pharmacokinetics of Tacrolimus in Rats

Wuzhi capsule (WZC) is a preparation of an ethanol herbal extract of Schisandra sphenanthera (Nan-Wuweizi), with its main active ingredients that include schisandrin, schizandrol B, schisantherin A, schisanhenol, and deoxyschizandrin. WZC and tacrolimus are often coadministered for the treatment of drug-induced hepatitis in organ transplant recipients in China. Recently, it was reported that WZC could significantly increase the blood concentration of tacrolimus. The purpose of this study was to investigate whether and how WZC affects the pharmacokinetics of tacrolimus in rats. Liquid chromatography-tandem mass spectrometry method was used to determine the plasma concentration of tacrolimus. The results showed that WZC increased the mean plasma concentration of tacrolimus. Compared with administration of tacrolimus alone [maximum plasma concentration (C(max)), 18.87 ± 10.29 ng/ml; area under the plasma concentration-time curve from time zero to last sampling time (AUC(0→t)), 40.98 ± 37.07 ng h/ml], a single intragastric administered dose of WZC increased the pharmacokinetic parameters of tacrolimus (C(max), 59.42 ± 30.32 ng/ml; AUC(0→t), 239.71 ± 28.86 ng h/ml) by 5-fold in rat plasma. After pretreatment with WZC for 12 days, there were still significant increases in AUC(0→t) (from 40.98 ± 37.07 to 89.21 ± 26.39 ng h/ml; P < 0.05) and C(max) (from 18.87 ± 10.29 to 43.16 ± 10.61 ng/ml; P < 0.05) of tacrolimus, compared with oral of tacrolimus alone, suggesting that WZC increased the exposure of tacrolimus by one or more mechanisms. The increase in tacrolimus C(max) by WZC was dose-dependent. The effect of WZC on tacrolimus AUC(0→t) also increased with dose, with a maximal effect observed at 450 mg/kg (825.34 ng h/ml). No further increases in tacrolimus AUC(0→t) were observed at WZC dose above 450 mg/kg. It is suggested that, because of the effect of WZC on the pharmacokinetics of tacrolimus, the herb-drug interaction between WZC and tacrolimus should be taken into consideration in clinical practice.

Effect of amlodipine on the pharmacokinetics of tacrolimus in rats

1. The immunosuppressant tacrolimus (TAC) is a substrate of cytochrome P450 3A2 (CYP3A2) and P-glycoprotein (P-gp) in rats. Amlodipine (AML) is an inhibitor of CYP3A2 in rats. We investigated the effect of AML on the pharmacokinetics of TAC in rats.2. When co-administered with TAC orally or intravenously, AML decreased the oral clearance and raised the blood concentration of TAC in rats, but the T1/2 of TAC was not significantly affected by AML. Upon oral administration of TAC, the effect of 15 mg/kg of AML on the AUC of TAC was lower than that seen with 5 or 10 mg/kg. However, upon intravenous TAC administration, the effect of 15 mg/kg of AML on the AUC of TAC was higher than that seen with 5 mg/kg.3. AML is an inhibitor of P-gp and CYP3A2 in rats. If AML and TAC are co-administered orally, AML elicits greater inhibition in P-gp than CYP3A2 during first-pass metabolism. If AML is given orally and TAC given intravenously concurrently, AML mainly inhibits CYP3A2 activity and increases the blood concentration of TAC. There are significant pharmacokinetic interactions between TAC and AML. AML raises the blood concentration of TAC in rats probably by inhibiting P-gp and CYP3A2.

Effects of bile duct stricture on the pharmacokinetics of the immunosuppressant tacrolimus in rats

Abstract Background: To investigate the effects of bile duct stricture on the pharmacokinetics of the immunosuppressant tacrolimus, the pharmacokinetics of tacrolimus in rats with bile duct ligation were evaluated and

Effect of long-term co-administration of Wuzhi tablet (Schisandra sphenanthera extract) and prednisone on the pharmacokinetics of tacrolimus

Tacrolimus (TAC) is an immunosuppressant that has been widely used alone or in combination with prednisone (PRED) to prevent acute rejection after organ transplantation. Wuzhi tablet (WZ, Schisandra sphenanthera extract) is often prescribed with TAC to prevent drug-induced hepatitis. We recently reported that WZ could significantly increase TAC blood exposure by inhibiting P-gp-mediated efflux and CYP3A-mediated metabolism of TAC. PRED is also a substrate of P-gp and is a weak inducer of CYP3A, and drug-drug interactions within this combination therapy might occur. Therefore, the purpose of this study was to investigate the effect of long-term treatment of WZ and PRED on the pharmacokinetics of TAC in rats. After 14 days of co-administration of WZ and PRED, the AUC0–24h of oral TAC was increased (from 59.6±37.3 to 95.3±39.4 ngh/ml, p=0.18) and the clearance was decreased (from 38.4±28.4 to 17.7±6.4l/h/kg, p=0.15). When only co-administered with WZ, AUC0–24h of TAC was demonstrated a significantly increase (from 59.6±37.3 to 135.9±34.8 ngh/ml, p<0.05). The concomitant administration of PRED resulted in a reduction in the systemic exposure of TAC and an increase in its clearance, though neither was statistically significant. Thus, our study suggested that the presence of WZ and PRED still could increase the systemic exposure of TAC in rats. The drug–drug interactions among this combination therapy should still be taken into consideration in clinical practice.

Food-drug Interaction of Tacrolimus with Pomelo, Ginger, and Turmeric Juice in Rats

Tacrolimus is a well-known potent immunosuppressant agent, which has various drug-drug or food-drug interactions. Previously, we found a renal transplant recipient who increased tacrolimus blood concentrations after ingestion of pomelo as a rare case. So, we investigated the effect of pomelo after its administration for one day or 3 consecutive days on the pharmacokinetics of tacrolimus in rats. We also confirmed the effects of grapefruit, turmeric, and ginger. The tacrolimus blood concentrations of the rats pre-treated with 100% pomelo juice were significantly higher than those pre-treated with water. On the other hand, the tacrolimus blood concentrations of the rats pre-treated with 50% pomelo juice were not significantly different from those pre-treated with water. The pomelo-tacrolimus interaction showed concentration dependency. Even low concentration of pomelo juice could enhance the blood concentrations of tacrolimus by repeated administration. The inhibitory effect of 100% pomelo juice disappeared 3 days after intake. The AUC values of tacrolimus in the rats pre-treated with grapefruit juice, ginger juice, and turmeric juice were significantly larger than those pre-treated with water. We could confirm the pomelo-tacrolimus interaction, which we discovered in a case study, quantitatively. We newly found the influence of turmeric and ginger on tacrolimus pharmacokinetics, comparable to pomelo.

Enhanced oral bioavailability of tacrolimus in rats by self-microemulsifying drug delivery systems

A new self-microemulsifying drug delivery system (SMEDDS) has been developed to increase the solubility, dissolution rate and oral bioavailability of tacrolimus (TAC). The formulations of TAC-SMEDDS were optimized by solubility assay, compatibility tests, and pseudo-ternary phase diagrams analysis. In order to inhibit the efflux of P-glycoprotein (P-gp) for tacrolimus, which is the substrate of P-gp, the excipients which show the inhibition effect to P-gp, such as tocopheryl polyethylene glycol succinate (TPGS) and Cremophor EL40, were chosen in the SMEDDS formulations. According to particle size and the rate of self-emulsification, two optimized formulations were selected: Miglyol 840 as oil phase, Transcutol P as cosurfactant, TPGS as surfactant (TPGS-SMEDDS) or Cremophor EL40 as surfactant (Crem-SMEDDS), respectively. The ratio of oil phase, surfactant and cosurfactant is 1:7.2:1.8. The mean droplet size distribution of the optimized SMEDDS was less than 20 nm. The in vitro dissolution test indicated a significant improvement in release characteristics of TAC. The prepared SMEDDS was compared with the homemade solution by administering the hard capsule to fasted rats. The absorption of TAC from TPGS-SMEDDS and Crem-SMEDDS form resulted in about sevenfold and eightfold increase in bioavailability compared with the homemade solution. Our study illustrated the potential use of SMEDDS for the delivery of hydrophobic compounds, such as TAC by the oral route.

Effect of the antiresorptive treatment on development of skeletal changes induced by the combined immunosuppressive treatment with azathioprine and tacrolimus in rats

Effect of the antiresorptive treatment on development of skeletal changes induced by the combined immunosuppressive treatment with azathioprine and tacrolimus in rats

Inhibitory Effect of Chinese Patent Medicines and Natural Pure Compounds on the Catalytic Activities of Drug Metabolism Enzymes

Chinese Patent Medicines are commonly used in combined with other drugs, including western drugs and Chinese drugs. To predict the potential for herb-drug interactions, the effects of over 23 Chinese Patent Medicines on the catalytic activities of five main drug metabolism enzymes of human liver microsomes, CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP 3A4, were assessed. Human liver microsomes were incubated and phenacetin, tolbutamide, S-mephenytoin, dextromethorphane as well as midazolam were used as the specific substrates of these five enzymes. After incubation, the metabolite of each substrate was quantified by an LC-MS/MS method. The inhibitory effect was calculated by comparing formation velocities of metabolites of probes with or without test drugs. The effects of Shuang-huang-lian Injection, Nuo-di-kang Capsule and Wu-zhi Capsule on the pharmacokinetics of clindamycin, omeprazole and tacrolimus in rats based on the inhibition of CYP3A, CYP2C and CYP3A were also evaluated. 21 of 23 tested drugs showed significant inhibitory effect on the catalytic activities of one or more enzymes. Shuang-huang-lian Injection inhibited the metabolism of clindamycin with a 1.34-fold increase in the t1/2 and a 1.37-fold increase in AUC value. In the rats pretreated with Nuo-di-kang Capsule, the AUC of omeprazole was increased by 1.19-fold (P&lt;0.05). Wu-zhi Capsule enhanced the oral absorption of tacrolimus with 5.0-fold increase in AUC. These results indicated that Chinese Patent Medicine had the potential to induce herb-drug interactions, and special attention should be paid when they are used in combined with other drugs.

Evaluation of increased bioavailability of tacrolimus in rats with experimental renal dysfunction.

The effects of renal failure on the hepatic and intestinal extraction of tacrolimus were evaluated to examine the mechanisms for the increased bioavailability of this drug in cisplatin-induced renal failure model rats. Tacrolimus extractions in the liver and intestine were evaluated by intravenous, intraportal and intraintestinal infusion. The intestinal metabolism and absorption rate were estimated by incubating the isolated intestine with drug solution and by an in situ loop method, respectively. Blood concentrations of tacrolimus following the intraintestinal infusion were significantly increased in rats with renal failure compared with those in normal rats. The blood concentration of tacrolimus during intraportal infusion in rats with renal failure showed non-linearity against dose, and was increased as compared with that in normal rats. The intestinal metabolism was not altered, but the absorption rate was significantly increased in the intestine from rats with renal dysfunction. These results suggest that the hepatic metabolism of tacrolimus is impaired in rats with renal failure, and that the accelerated absorption rate in the intestine in renal dysfunction is followed by partial saturation of hepatic extraction, which may be one of the mechanisms of increased bioavailability of tacrolimus.