Dextran sulfate sodium-induced colitis and ginseng intervention altered oral pharmacokinetics of cyclosporine A in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Application of cyclosporine A (CsA) as a rescue treatment in acute severe ulcerative colitis (UC) is limited by its narrow therapeutic window and great interpatient variability. As a substrate of cytochrome P450 3A enzyme (CYP3A) and P-glycoprotein (P-gp), the oral pharmacokinetics of CsA is susceptible to disease status and concomitant medications. Combined treatment with ginseng, a famous medicinal herb frequently prescribed for ameliorating abnormal immune response in many diseases including UC, showed immunologic safety in CsA-based immunosuppression. AIM OF THE STUDY: Since the therapeutic levels of CsA can be achieved within 24 h, this study first assessed the impact of acute colitis and ginseng intervention on the single oral dose pharmacokinetics of CsA and explored the underlying mechanisms in dextran sulfate sodium (DSS)-induced colitis rats and Caco-2 cells. MATERIALS AND METHODS: Rats received drinking water (normal group), 5% DSS (UC group), or 5% DSS plus daily oral ginseng extract (GS+UC group). On day 7, GS+UC group only received an oral dose of CsA (5 mg/kg), while animals of normal or UC group received an oral, intravenous (1.25 mg/kg), or intraperitoneal dose of CsA (1.25 mg/kg), respectively. Blood, liver/intestine tissues and fecal samples were collected for determining CsA and main hydroxylated metabolite HO-CsA or measuring hepatic/intestinal CYP3A activity. Caco-2 cells were incubated with gut microbial culture supernatant (CS) of different groups or ginseng (decoction or polysaccharides), and then CYP3A, P-gp and tight junction (TJ) proteins were determined. RESULTS: Oral CsA exhibited enhanced absorption, systemic exposure and tissue accumulation, and lower fecal excretion, while intravenous or intraperitoneal CsA showed lower systemic exposure and enhanced distribution, in colitis rats. Diminished intestinal and hepatic P-gp expression well explained the changes with DSS-induced colitis. Moreover, blood exposures of HO-CsA in both normal and colitis after oral dosing were significantly higher than intravenous/intraperitoneal dosing, supporting the dominant role of intestinal first-pass metabolism. Interestingly, colitis reduced CYP3A expression in intestine and liver but only potentiated intestinal CYP3A activity, causing higher oral systemic exposure of HO-CsA. Oral ginseng mitigated colitis-induced down-regulation of CYP3A and P-gp expression, facilitated HO-CsA production, biliary excretion and colonic sequestration of CsA, while not affected CsA oral systemic exposure. In Caco-2 cells, gut microbial CS from both colitis and GS+UC group diminished P-gp function, while ginseng polysaccharides directly affected ZO-1 distribution and suppressed TJ proteins expression, explaining unaltered oral CsA systemic exposure. CONCLUSIONS: DSS-induced colitis significantly altered oral CsA disposition through regulating intestinal and hepatic P-gp and CYP3A. One-week ginseng treatment enhanced colonic accumulation while not altered the systemic exposure of CsA after single oral dosing, indicating pharmacokinetic compatibility between the two medications.

Inhibition effect of epigallocatechin-3-gallate on the pharmacokinetics of calcineurin inhibitors, tacrolimus, and cyclosporine A, in rats.

BACKGROUND: Epigallocatechin-3-gallate (EGCG) is the most biologically active catechin of green tea. Tacrolimus (TAC) and cyclosporine A (CsA) are immunosuppressive agents commonly used in clinical organ transplantation. The present study investigated the effect of EGCG on the pharmacokinetics of TAC and CsA in rats and its underlying mechanisms. RESEARCH DESIGN AND METHODS: Either TAC or CsA was administered to rats intravenously or orally with or without concomitant EGCG. Polymerase Chain Reaction and Western Blot were used to determine the effect of EGCG on drug-metabolizing enzymes (DMEs), drug transporters (DTs) and nuclear receptors (NRs). RESULTS: The Cmax and AUC of TAC were reduced, and V/F and CL/F of TAC were enhanced after co-administration of EGCG. EGCG increased the Cmax, AUC of CsA at 3 ~ 30 mg∙kg-1 dosages, while decreased those parameters at the dosage of 100 mg∙kg-1. EGCG inhibited the mRNA and protein expressions of DMEs and DTs, such as CYP3A1, A2, UGT1A1, Mdr1 and Mrp2, but upregulated the expressions of Car, Pxr and Fxr. CONCLUSIONS: These results revealed consumption of high dose EGCG may cause a significant alteration in pharmacokinetics of TAC and distribution/elimination profiles of CsA through the regulation of DMEs, DTs and NRs.

Absorption and Disposition of Coproporphyrin I (CPI) in Cynomolgus Monkeys and Mice: Pharmacokinetic Evidence to Support the Use of CPI to Inform the Potential for Organic Anion-Transporting Polypeptide Inhibition.

Despite a recent expansion in the recognition of the potential utility of coproporphyrin (CP) as an endogenous biomarker of organic anion-transporting polypeptide (OATP) 1B activity, there have been few detailed studies of CP's pharmacokinetic behavior and an overall poor understanding of its pharmacokinetic fate from tissues and excretion. Here, we describe the pharmacokinetics of octadeuterium-labeled coproporphyrin I (CPI-d8) in cynomolgus monkeys following oral and intravenous administration. CPI-d8 has a half-life and bioavailability of 7.6 hours and 3.2%, respectively. Cynomolgus monkeys received oral cyclosporin A (CsA) at 4, 20, and 100 mg/kg which yielded maximum blood concentrations (C max) and area under the plasma concentration-time curve (AUC) values of 0.19, 2.5, and 3.8 µM, and 2.7, 10.5, and 26.6 µM·h, respectively. The apparent CsA-dose dependent increase in the AUC ratio of CPI-d8 (1.8, 6.2, and 10.5), CPI (1.1, 1.4, and 4.4), and CPIII (1.1, 1.8, and 4.6) at 4, 20, and 100 mg, respectively. In contrast, the plasma concentrations of CPI and CPIII were generally not affected by intravenous administration of the renal organic anion and cation transporter inhibitors (probenecid and pyrimethamine, respectively). In addition, tritium-labeled coproporphyrin I ([3H]CPI) showed specific and rapid distribution to the liver, intestine, and kidney after an intravenous dose in mice using quantitative whole-body autoradiography. Rifampin markedly reduced the liver and intestinal uptake of [3H]CPI while increasing the kidney uptake. Taken together, these results suggest that hepatic OATP considerably affects the disposition of CPI in animal models, indicating CPI is a sensitive and selective endogenous biomarker of OATP inhibition. SIGNIFICANCE STATEMENT: This study demonstrated that coproporphyrin I (CPI) has favorable oral absorption, distribution, and elimination profiles in monkeys and mice as an endogenous biomarker. It also demonstrated its sensitivity and selectivity as a probe of organic anion-transporting polypeptide (OATP) 1B activity. The study reports, for the first time, in vivo pharmacokinetics, tissue distribution, sensitivity, and selectivity of CPI as an OATP1B endogenous biomarker in animals. The data provide preclinical support for exploration of its utility as a sensitive and selective circulating OATP biomarker in humans.

The Pharmacokinetic Prediction of Cyclosporin A after Coadministration with Wuzhi Capsule.

We aim to describe the influence of principal ingredients of Wuzhi capsule, schisandrin A (SIA) and schisantherin A (STA), on the pharmacokinetics of cyclosporin A (CsA) and to quantify the herb-drug interactions (HDIs) between SIA, STA, and CsA. CsA is a first-line immunosuppressant for anti-rejection therapy after solid organ transplantation, while narrow therapeutic window associated with strong hepatotoxicity largely limited its use. Wuzhi capsule, a liver-protective drug, was approved for coadministration with CsA to reduce the hepatotoxicity. There are few studies exploring HDIs of CsA when coadministered with Wuzhi capsule. The essential adjusted physicochemical data and pharmacokinetic parameters of SIA, STA, and CsA were collected. Then physiologically based pharmacokinetic (PBPK) models of SIA, STA, and CsA were built and verified in healthy subjects using Simcyp respectively. The refined PBPK models were used to estimate potential HDIs between CsA and SIA, STA. The simulated plasma concentration-time curves of CsA, SIA, and STA were in good accordance with the observed profiles respectively. CsA pharmacokinetics were improved after coadministration. After a single dose and multiple doses, the area under the plasma concentration-time curve (AUC) of CsA was increased by 47% and 226% when coadministered with STA, respectively, and by 8% and 36% when coadministered with SIA, respectively. PBPK models sufficiently described the pharmacokinetics of CsA, SIA, and STA. Compared with SIA, STA inhibited CsA metabolism to a greater extent. Our result revealed the dose of CsA can be reduced to maintain similar profile when used concomitantly with Wuzhi capsule.

Activation of P-glycoprotein and CYP 3A by Coptidis Rhizoma in vivo: Using cyclosporine as a probe substrate in rats.

Coptidis Rhizoma (CR), the rhizome of Coptis chinensis FRANCH, is a popular Chinese herb. CR contains plenty of isoquinoline alkaloids such as berberine, coptisine and palmatine. Cyclosporine (CSP), an important immunosuppressant with narrow therapeutic window, is employed as a probe substrate of P-glycoprotein (P-gp) and CYP3A4 in order to investigate the in vivo modulation effect of CR on P-gp and CYP3A4. Three groups of rats were orally administered CSP without and with single dose or repeated dosing of CR in a parallel design. Blood samples were collected at specific time points and the blood CSP concentration was determined by a specific monoclonal fluorescence polarization immunoassay. The results showed that a single dose (1.0 g/kg) and the 7th dose (1.0 g/kg) of CR significantly decreased the Cmax of CSP by 56.9% and 70.4%, and reduced the AUC0-540 by 56.4% and 68.7%, respectively. Cell study indicated that CR decoction, berberine, coptisine, palmatine all activated the efflux transport of P-gp. Ex-vivo study showed that the serum metabolites of CR activated CYP 3A4. In conclusion, through using CSP as an in vivo probe substrate, we have verified that oral intake of CR activated the functions of P-gp and CYP3A based on in vivo and in vitro studies.

Porous mannitol carrier for pulmonary delivery of cyclosporine A nanoparticles.

This study employed the ultrasonic spray-freeze-drying technique to prepare porous mannitol carriers that incorporated hydrophobic cyclosporine A (CsA) nanoparticles (NPs) for pulmonary delivery. Two nanosuspension stabilization systems, (1) a combination of lecithin and lactose system and (2) a D-α-tocopheryl polyethylene glycol succinate (TPGS) system, were investigated. The ability of the lecithin and TPGS in anchoring the hydrophobic CsA NPs to the porous hydrophilic mannitol structure was first reported. Formulations stabilized by TPGS provided a much better dose uniformity, suggesting that TPGS is a better anchoring agent compared with lecithin. The effects of mannitol carrier density and CsA loading (4.9-27%) on aerosol performance and dissolution profiles were assessed. The fine particle fraction (FPF) increased from 44 to 63% as the mannitol concentration decreased from 1 to 5%. All formulations achieved full dissolution within an hour without significant influence from the mannitol content and CsA loading. The initial dissolution rates of the present formulations were almost double than that of the spray-dried counterpart, with 90% of the drug dissolved in 10 min. Overall, the CsA NPs were successfully incorporated into the porous mannitol which demonstrated good aerosol performance and enhanced dissolution profiles. These spray-freeze-drying (SFD) powders were stable after 2-year storage under desiccation at 20 ± 3°C.

Enhanced colonic delivery of ciclosporin A self-emulsifying drug delivery system encapsulated in coated minispheres.

OBJECTIVES: Investigate the potential of coated minispheres (SmPill®) to enhance localized Ciclosporin A (CsA) delivery to the colon. METHODS: CsA self-emulsifying drug delivery systems (SEDDS) were encapsulated into SmPill® minispheres. Varying degrees of coating thickness (low, medium and high) were applied using ethylcellulose and pectin (E:P) polymers. In vitro CsA release was evaluated in simulated gastric and intestinal media. Bioavailability of CsA in vivo following oral administration to pigs of SmPill® minispheres was compared to Neoral® po and Sandimmun® iv in a pig model. CsA concentrations in blood and intestinal tissue were determined by HPLC-UV. RESULTS: In vitro CsA release from coated minispheres decreased with increasing coating thickness. A linear relationship was observed between in vitro CsA release and in vivo bioavailability (r(2) = 0.98). CsA concentrations in the proximal, transverse and distal colon were significantly higher following administration of SmPill®, compared to Neoral® po and Sandimmun® iv (p < 0.05). Analysis of transverse colon tissue subsections also revealed significantly higher CsA concentrations in the mucosa and submucosa using SmPill® minispheres (p < 0.05). CONCLUSIONS: Modulating E:P coating thickness controls release of CsA from SmPill® minispheres. Coated minispheres limited CsA release in the small intestine and enhanced delivery and uptake in the colon. These findings demonstrate clinical advantages of an oral coated minisphere-enabled CsA formulation in the treatment of inflammatory conditions of the large intestine.

Pharmacokinetic and nephroprotective benefits of using Schisandra chinensis extracts in a cyclosporine A-based immune-suppressive regime.

Cyclosporine A (CsA) is a powerful immunosuppressive drug. However, nephrotoxicity resulting from its long-term usage has hampered its prolonged therapeutic usage. Schisandra chinensis extracts (SCE) have previously been used in traditional Chinese medicine and more recently coadministered with Western medicine for the treatment of CsA-induced side effects in the People's Republic of China. This study aimed to investigate the possible effects of SCE on the pharmacokinetics of CsA in rats and elucidate the potential mechanisms by which it hinders the development of CsA-induced nephrotoxicity. A liquid chromatography/tandem mass spectrometry method was developed and validated for determining the effect of SCE on the pharmacokinetics of CsA. Male Sprague Dawley rats, which were administered with CsA (25 mg/kg/d) alone or in combination with SCE (54 mg/kg/d and 108 mg/kg/d) for 28 days, were used to evaluate the nephroprotective effects of SCE. Our study showed that SCE increased the mean blood concentration of CsA. Furthermore, we found that the concomitant administration of SCE alongside CsA prevented the disruption of catalase activity and reduction in creatinine, urea, renal malondialdehyde, and glutathione peroxidase levels that would have otherwise occurred in the absence of SCE administration. SCE treatment markedly suppressed the expression of 4-hydroxynonenal, Bcl-2-associated X protein, cleaved caspase 3, and autophagy-related protein LC3 A/B. On the other hand, the expression of heme oxygenase-1, nuclear factor erythroid 2-related factor 2 (Nrf2), and P-glycoprotein was enhanced by the very same addition of SCE. SCE was also able to increase the systemic exposure of CsA in rats. The renoprotective effects of SCE were thought to be mediated by its antiapoptotic and antioxidant abilities, which caused the attenuation of CsA-induced autophagic cell death. All in all, these findings suggest the prospective use of SCE as an effective adjunct in a CsA-based immunosuppressive regimen.

Pomelo enhances cyclosporine bioavailability in healthy male Thai volunteers.

The aim of this study was to investigate the effect of pomelo pulp on the pharmacokinetics of cyclosporine in healthy male Thai volunteers. The study design was an open-label, randomized, single dose, crossover study with a 2-week washout period. A single oral dose of 2 × 100 mg cyclosporine was administered with 200 mL of water. Each subject received 250 g of pomelo pulp or 250 mL of water 1 hour before drug administration and once again 10 minutes following drug administration. Blood samples were collected over a 24 hour period. The point estimates (90% confidence intervals) of the test/control ratio using logarithmic transformed data for the area under the curve (AUC) for blood concentration from time 0 to infinity (AUC(0- ∞)) and the observed maximum concentration (C(max)) were 128.8% (120.6-137.6) and 136.1% (126.0-146.8), respectively. These 90% confidence intervals were higher than the accepted bioequivalence range defined by the European Medicines Agency guidelines for narrow therapeutic index drugs (90%-111% for AUC and 80%-125% for C(max)). However, the apparent terminal half-life (t(1/2)) was not significantly different. In conclusion, co-administration of cyclosporine and pomelo pulp increased the relative bioavailability of cyclosporine.

Herbal tea extracts inhibit Cytochrome P450 3A4 in vitro.

OBJECTIVES: Ciclosporin and sirolimus, two immunosuppressive agents with narrow therapeutic windows, are mainly metabolized by Cytochrome 3A4 (CYP3A4). A clinical case of toxic blood levels of these drugs after the consumption of a '24-flavours' tea was reported. This study aims to identify the causative ingredients of the 24-flavour herbal tea in the inhibition of CYP3A4 metabolism. METHODS: Two commercially available 24-flavour tea products purchased in Hong Kong and the six plant constituents were tested for their CYP3A4 inhibitory effects utilizing an in-vitro fluorometric assay. KEY FINDINGS: Of the commercially available teas available in Hong Kong, the most potent inhibitory effect was observed with the tea consumed in the initial clinical case. Of the six universal constituents, chrysanthemum exhibited the greatest inhibitory effect, with an IC50 of 95.7 µg/ml. Dandelion, liquorice and bishop's weed have IC50 of 140.6, 148.4 and 185.5 µg/ml, respectively. Field mint and Japanese honeysuckle have weaker inhibitory effect on CYP3A4 with IC50 of 1153.3 and 1466.3 µg/ml. CONCLUSIONS: This study confirms the possible implication of herbal tea constituents in the inhibition of ciclosporin and sirolimus' CYP3A4 metabolism. Combined usage of herbal teas with drug should be closely monitored.

Pharmacokinetic interaction studies of fenugreek with CYP3A substrates cyclosporine and carbamazepine.

The present study investigated the effect of fenugreek seed powder on disposition of CYP3A substrates, cyclosporine and carbamazepine. Rabbits were treated with fenugreek seed powder (300 mg/kg p.o.) for 8 days and on 8th day the single dose of cyclosporine (30 mg/kg, p.o.) and carbamazepine (40 mg/kg, p.o.) were administered to the corresponding group after 1 h of fenugreek administration. Blood samples were drawn at several time points and analyzed by using UPLC-MS (cyclosporine) and HPLC (carbamazepine). Pharmacokinetic parameters were calculated by using PK Solver. The present investigation reveals that there was no statistically significant difference between pre- and post-treated pharmacokinetic parameters such as AUC(o-t), AUC(o-∞), C(max), T(max), T(1/2), K(el), MRT(o-∞) , V(z/F), and Cl/F for cyclosporine and carbamazepine. Two tailed "P" values for all these pharmacokinetic parameters were more than 0.05, indicating insignificant impact of fenugreek treatment on the disposition of cyclosporine and carbamazepine. Further, fenugreek may also not have any significant effect on the functionality of P-glycoprotein as cyclosporine is a substrate to P-glycoprotein. The outcomes of present study suggested that fenugreek may not likely to interfere cyclosporine and carbamazepine pharmacokinetics, when co-administered with these drugs.

Acute drug toxicity related to drinking herbal tea in a kidney transplant recipient.

Calcineurin and mTOR inhibitors are commonly used immunosuppressive agents with narrow therapeutic range. As the drugs are mainly metabolized by the P450 cytochrome system, the interaction between food and herbs are also commonly seen and affect the drug levels. We present a case of a kidney transplant recipient with toxic therapeutic levels of cyclosporine A and sirolimus due to interaction between the immunosuppressive agents and Chinese herbal tea. Ingredients within the herbal tea were reported to have inhibitory effect on cytochrome CYP3A4 in-vitro studies. Transplant recipients should be alert that there may be potent interaction between the immunosuppressive drugs and herbs resulting in adverse effect on allograft function.

Capsaicin pretreatment increased the bioavailability of cyclosporin in rats: involvement of P-glycoprotein and CYP 3A inhibition.

Capsaicin (CAP), the main ingredient responsible for the hot pungent taste of chilli peppers. This study investigated the effect of CAP on the pharmacokinetics of Cyclosporin A (CyA) in rats and the mechanism of this food-drug interaction. The results indicated that after 7 days of low or middle dose of CAP (0.3 or 1.0 mg/kg), the blood concentration of CyA was not significantly changed compared with that of vehicle-treated rats, whereas the blood concentration of CyA in high dose group (3.0 mg/kg) was significantly increased. The total clearance (CL/F) of CyA was decreased, and the bioavailability was significantly increased to about 1.44-fold of that in vehicle-treated rats after 7 days of high dose CAP treatment. At this time, the P-gp and CYP3A1/2 in the liver and intestine were decreased at both the mRNA and protein levels. These results demonstrated that chronic ingestion of high doses of CAP will increase the bioavailability of CyA to a significant extent in rats and the food-drug interaction between CAP and CyA appears to be due to modulation of P-gp and CYP3A gene expression by CAP, with differential dose-dependence.

Effects of Nigella sativa and Lepidium sativum on cyclosporine pharmacokinetics.

The present study was conducted to investigate the effects of Nigella sativa and Lepidium sativum on the pharmacokinetics of cyclosporine in rabbits. Two groups of animals were treated separately with Nigella sativa (200 mg/kg p.o.) or Lepidium sativum (150 mg/kg p.o.) for eight consecutive days. On the 8th day, cyclosporine (30 mg/kg p.o.) was administered to each group one hour after herbal treatment. Blood samples were withdrawn at different time intervals (0.0, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0, 8.0, 12, and 24 hrs) from marginal ear vein. Cyclosporine was analyzed using UPLC/MS method. The coadministration of Nigella sativa significantly decreased the C(max) and AUC(0-∞) of cyclosporine; the change was observed by 35.5% and 55.9%, respectively (P ≤ 0.05). Lepidium sativum did not produce any significant change in C(max) of cyclosporine, although its absorption was significantly delayed compared with control group. A remarkable change was observed in T(max) and AUC(0-t) of Lepidium sativum treated group. Our findings suggest that concurrent consumption of Nigella sativa and Lepidium sativum could alter the pharmacokinetics of cyclosporine at various levels.

Potential risk of mulberry-drug interaction: modulation on P-glycoprotein and cytochrome P450 3A.

Mulberry is a fruit containing polyphenol antioxidants. Cyclosporine (CSP), a potent immunosuppressant with a narrow therapeutic range, is widely used in transplant patients. This study investigated the effect of co-administration of mulberry on the bioavailability of CSP, a probe drug of P-glycoprotein (P-gp)/cytochrome P450 3A4 (CYP 3A4), in rats and relevant mechanisms. CSP (2.5 mg/kg) was orally administered with and without a single dose or the seventh dose of mulberry (2 g/kg) to rats. The results showed that a single dose of mulberry significantly decreased the area under the curve of concentration (AUC(0-540)) and the maximum blood concentration (Cmax) of CSP by 53.2 and 65.8%, respectively. Repeated dosing of mulberry significantly decreased the AUC(0-540) and Cmax of CSP by 23.7 and 39.7%, respectively. Mechanism studies indicated that mulberry significantly increased the activities of P-gp and CYP 3A. In conclusion, mulberry significantly reduced the bioavailability of CSP through activating the functions of P-gp and CYP 3A.

Effect of Wuzhi tablet (Schisandra sphenanthera extract) on the pharmacokinetics of cyclosporin A in rats.

In our previous reports, Wuzhi tablet (an herbal preparation of ethanol extract of Wuweizi (Schisandra sphenanthera)) can significantly increase the blood concentration of tacrolimus and paclitaxel in rats by inhibiting the CYP3A-mediated metabolism and the P-gp-mediated efflux. Cyclosporin A (CsA), a well-known immunosuppressant agent, is also a substrate of CYP3A and P-gp. Therefore, this study aimed to investigate whether and how WZ affects pharmacokinetics of CsA in rats. The AUC0-48 h and Cmax of CsA were increased by 40.1% and 13.1%, respectively, with a single oral co-administration of WZ and high dose of CsA (37.8 mg/kg). Interestingly, after a single oral co-administration of WZ and low dose of CsA (1.89 mg/kg), the AUC0-36 h and Cmax of CsA were dramatically increased by 293.1% (from 1103.2 ± 293.0 to 4336.5 ± 1728.3 ng.h/mL; p < 0.05) and 84.1% (from 208.5 ± 67.9 to 383.1 ± 92.5 ng/mL; p < 0.05), respectively. The CL/F was decreased from 1.7 L/h/kg to 0.5 L/h/kg. Thus, the effect of WZ on high dose of CsA was not significant, but pharmacokinetic parameters of CsA at low dose were significantly influenced by co-administration of WZ. The herb-drug interaction should be taken into consideration at this situation.

Liquorice reduced cyclosporine bioavailability by activating P-glycoprotein and CYP 3A.

Liquorice (root of Glycyrrhiza uralensis FISCH) is an ingredient of candies and used as a popular medicine in Europe and oriental countries. Cyclosporine (CsA), an immunosuppressant with narrow therapeutic window, is widely used in transplant patients. The absorption and disposition of CsA were associated with P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4). This study investigated the effects of liquorice extract (LE) and its major ingredient, glycyrrhizin (GZ), on CsA pharmacokinetics in rats. The results indicated that LE and GZ significantly decreased the peak blood concentration and the areas under the curves of CsA in rats. Mechanism studies revealed that glycyrrhetic acid (GA), the major metabolite of GZ, significantly activated the functions of P-gp and CYP3A4. In conclusion, liquorice significantly reduced the oral bioavailability of CsA through activating P-gp and CYP3A4.

Comparative evaluation of cyclosporine A/HPßCD-incorporated PLGA nanoparticles for development of effective ocular preparations.

To improve poor water solubility of cyclosporine A (CsA), hydroxypropyl-beta-cyclodextrin (HPßCD) was incorporated into the nanoparticle formulation. Solid complexes of CsA with HPßCD in different ratios were prepared by the kneading method. CsA containing alone or in combination with HPßCD in poly-lactide-co-glycolide (P-CsA or P-CsA-HPßCD) nanoparticles were prepared by the emulsification solvent evaporation method. The mean size of CsA-loaded NPs was found to be approximately 220 nm. The solubility of CsA was significantly improved and the phase solubility diagram of CsA-HPßCD systems showed an A(L) type phase. Nanoparticles showed high CsA encapsulation efficiency (88%) and production yield (89%). Release rate was increased by the presence of HPßCD and total cumulative release ranged from 75% to 96% in 24 h. In vitro cytotoxicity study assay resulted in a low toxicity for all types of nanoparticles. After 6 h incubation period, the cellular uptake was found at 33% and 32% for P-CsA and P-HPßCD-CsA nanoparticles, respectively.

Time-course effects of St John's wort on the pharmacokinetics of cyclosporine in dogs: interactions between herbal extracts and drugs.

To clarify the interaction between St John's wort (SJW) and cyclosporine (CsA) in dogs, the pharmacokinetics of CsA before and during the repeated administration of SJW were analyzed. In the SJW group, SJW (300 mg) was given orally to four dogs every 24 h for 14 days. A single dose of CsA (5 mg/kg) was given orally 7 days before and 7 and 14 days after the initiation of the repeated administration of SJW. In the Control group, a single dose of CsA (5 mg/kg) was given orally to four other dogs in accordance with that in the SJW group. Blood samples from both groups were collected, and whole-blood concentrations of CsA were determined using high-performance liquid chromatography with UV detection. The maximum whole-blood concentration and AUC(0-∞) of the SJW group were significantly lower and the CL(tot) /F and V(d) /F were significantly higher than those in the Control group 7 and 14 days after the initiation of repeated SJW. Thus, repeated administrations of SJW affect the pharmacokinetic profiles of CsA in dogs. Further studies are necessary to elucidate the mechanisms of interaction between SJW and CsA in dogs.

Steroid withdrawal based on lymphocyte sensitivity to endogenous steroid in renal transplant recipients.

Though steroid withdrawal is done in many renal transplant recipients, some patients must restart steroids. Little report has investigated steroid withdrawal under pharmacodynamic monitoring. We assessed lymphocyte sensitivity to endogenous cortisol as a biomarker for determining the safety of steroid withdrawal in renal transplant patients, as we hypothesized that patients hyposensitive to cortisol could not be sufficiently immunosuppressed by their intrinsic cortisol as a substitute for the reduced or withdrawn steroid. Lymphocyte sensitivity to cortisol was examined in 30 long stable renal transplant recipients. Lymphocyte sensitivity to cortisol and its relationship with the clinical outcome after steroid reduction and withdrawal was investigated. The lymphocyte sensitivities to cortisol were estimated as IC(50) of lymphocyte blastogenesis. The lymphocyte proliferation rate for concentration of serum cortisol compared between incident and non-incident groups. Serum creatinine levels (S-Cr) increased in a significantly higher number of patients hyposensitive to cortisol (IC(50)≧10000 ng/ml) than in normally sensitive patients (IC(50)<10000 ng/ml). The incidences of steroid withdrawal syndrome and necessity for increasing steroid dose or restarting steroid administration were also higher in the patients hyposensitive to cortisol. The patients in whom the lymphocyte proliferation rate was less than 60% did not show increase in S-Cr, experience steroid withdrawal symptoms, or require an increase in the steroid dose or restart of steroid administration. The patients who have the normal IC(50) values of cortisol, can withdraw steroid more safely. The lymphocyte sensitivity to cortisol may be a useful biomarker for selecting patients who can sustain steroid withdrawal.