Effect of nebicapone on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects

OBJECTIVE

Nebicapone is a new catechol-O-methyltransferase inhibitor. In vitro, nebicapone has showed an inhibitory effect upon CYP2C9, which is responsible for the metabolism of S-warfarin. The objective of this study was to investigate the effect of nebicapone on warfarin pharmacokinetics and pharmacodynamics in healthy subjects.

METHODS

Single-centre, open-label, randomised, two-period crossover study in 16 healthy volunteers. In one period, subjects received nebicapone 200 mg thrice daily for 9 days and a racemic warfarin 25-mg single dose concomitantly with the nebicapone morning dose on day 4 (test). In the other period, subjects received a racemic warfarin 25-mg single dose alone (reference). The treatment periods were separated by a washout of 14 days.

RESULTS

For R-warfarin, mean +/- SD C(max) was 1,619 +/- 284 ng/mL for test and 1,649 +/- 357 ng/mL for reference, while AUC(0-t ) was 92,796 +/- 18,976 ng x h/mL (test) and 73,597 +/- 11,363 ng x h/mL (reference). The R-warfarin test-to-reference geometric mean ratio (GMR) and 90% confidence interval (90%CI) were 0.973 (0.878-1.077) for C(max) and 1.247 (1.170-1.327) for AUC(0-t ). For S-warfarin, mean +/- SD C(max) was 1,644 +/- 331 ng/mL for test and 1,739 +/- 392 ng/mL for reference, while AUC(0-t ) was 66,627 +/- 41,199 ng x h/mL (test) and 70,178 +/- 42,560 ng x h/mL (reference). The S-warfarin test-to-reference GMR and 90%CI were 0.932 (0.845-1.028) for C(max) and 0.914 (0.875-0.954) for AUC(0-t ). No differences were found for the pharmacodynamic parameter (INR).

CONCLUSION

Nebicapone showed no significant effect on S-warfarin pharmacokinetics or on the coagulation endpoint (INR). A mild inhibition of the R-warfarin metabolism was found but is unlikely to be of clinical relevance.

Dopamine 5 receptor mediates Ang II type 1 receptor degradation via a ubiquitin-proteasome pathway in mice and human cells

Hypertension is a multigenic disorder in which abnormal counterregulation between dopamine and Ang II plays a role. Recent studies suggest that this counterregulation results, at least in part, from regulation of the expression of both the antihypertensive dopamine 5 receptor (D5R) and the prohypertensive Ang II type 1 receptor (AT1R). In this report, we investigated the in vivo and in vitro interaction between these GPCRs. Disruption of the gene encoding D5R in mice increased both blood pressure and AT1R protein expression, and the increase in blood pressure was reversed by AT1R blockade. Activation of D5R increased the degradation of glycosylated AT1R in proteasomes in HEK cells and human renal proximal tubule cells heterologously and endogenously expressing human AT1R and D5R. Confocal microscopy, Förster/fluorescence resonance energy transfer microscopy, and fluorescence lifetime imaging microscopy revealed that activation of D5R initiated ubiquitination of the glycosylated AT1R at the plasma membrane. The regulated degradation of AT1R via a ubiquitin/proteasome pathway by activation of D5R provides what we believe to be a novel mechanism whereby blood pressure can be regulated by the interaction of 2 counterregulatory GPCRs. Our results therefore suggest that treatments for hypertension might be optimized by designing compounds that can target the AT1R and the D5R.

A new approach on the purification of recombinant human soluble catechol-O-methyltransferase from an Escherichia coli extract using hydrophobic interaction chromatography

Catechol-O-methyltransferase (COMT) is a significant target in protein engineering due to its role not only in normal brain function but also to its possible involvement in some human disorders. In this work, a new approach was employed for the purification of recombinant human soluble COMT (hSCOMT) using hydrophobic interaction chromatography, as the main isolation method, from an Escherichia coli culture broth. A simplified overall process flow is proposed. Indeed, with an optimized heterologous expression system for recombinant hSCOMT production, such as E. coli, it was possible to produce and recover the active monomeric enzyme directly from the cell crude culture broth either by a freeze/thaw or ultrasonication lysis step. The recombinant enzyme present in the bacterial soluble fraction, exhibited similar affinity for epinephrine (K(m) 276 [215; 337] microM) and the methyl donor (S-adenosyl-L-methionine, SAMe) (K(m) 36 [30; 41]microM) as human SCOMT. After the precipitation step by 55% of ammonium sulphate, a HIC step on the butyl-sepharose resin was found to be highly effective in selectively eluting a range of contaminating key proteins present in the concentrate soluble extract. Consequently, the partially purified eluate from HIC could then be loaded and polished by gel filtration in order to increase the process efficiency. The final product appeared as a single band in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The procedure resulted in a global 10.9-fold purification with a specific activity of 5500 nmol/h/mg of protein. The widespread applicability of the process, here described, to different COMT sources could make this protocol highly useful for all studies requiring purified and active COMT proteins.

Overexpression of Na(+)/K (+)-ATPase parallels the increase in sodium transport and potassium recycling in an in vitro model of proximal tubule cellular ageing

Na(+)/K(+)-ATPase plays a key role in the transport of Na(+) throughout the nephron, but ageing appears to be accompanied by changes in the regulation and localization of the pump. In the present study, we examined the effect of in vitro cell ageing on the transport of Na(+) and K(+) ions in opossum kidney (OK) cells in culture. Cells were aged by repeated passing, and Na(+)/K(+)-ATPase activity and K(+) conductance were evaluated using electrophysiological methods. Na(+)K(+)-ATPase alpha(1)- and beta(1)-subunit expression was quantified by Western blot techniques. Na(+)/H(+) exchanger activity, changes in membrane potential, cell viability, hydrogen peroxide production and cellular proliferation were determined using fluorimetric assays. In vitro cell ageing is accompanied by an increase in transepithelial Na(+) transport, which results from an increase in the number of Na(+)/K(+)-ATPase alpha(1)- and beta(1)-subunits, in the membrane. Increases in Na(+)/K(+)-ATPase activity were accompanied by increases in K(+) conductance as a result of functional coupling between Na(+)/K(+)-ATPase and basolateral K(+) channels. Cell depolarization induced by both KCl and ouabain was more pronounced in aged cells. No changes in Na(+)/H(+) exchanger activity were observed. H(2)O(2) production was increased in aged cells, but exposure for 5 days to 1 and 10 microM: of H(2)O(2) had no effect on Na(+)/K(+)-ATPase expression. Ouabain (100 nM: ) increased alpha(1)-subunit, but not beta(1)-subunit, Na(+)/K(+)-ATPase expression in aged cells only. These cells constitute an interesting model for the study of renal epithelial cell ageing.

Dopamine D2 receptor polymorphisms in inflammatory bowel disease and the refractory response to treatment

Dopamine and its receptors may be involved in inflammatory reaction. The availability of this molecule depends on its receptors. The DRD2 gene, which codifies for the D2 dopamine receptor, has several polymorphisms. In this study, the DRD2 TaqIA polymorphism, which confers a decreased receptor density, was evaluated in 313 individuals including 220 inflammatory bowel disease patients (143 patients with Crohn's disease and 77 with ulcerative colitis) and in 93 healthy blood donors. The analysis was carried out by PCR-RFLP techniques. The frequencies of A (1) A (1) and A (2) A (2) genotypes were similar among Crohn's disease, ulcerative colitis patients, and health controls. Also, the genotype frequency was similar in different groups of disease localization, behavior, and age of disease onset. However, the Crohn's disease patients carriers of A (2) A (2) genotype showed a lower risk for development refractory Crohn's disease (37 out 65) than A (1) A (1) and A (1) A (2) carriers (28 out of 65) [(OR=0.4, 95% CI 0.21-0.87; p=0.02)]. Our results support an involvement of the dopamine receptor in inflammatory bowel disease and suggest a new potential target for therapy in refractory Crohn's disease patients.

Comparative Study ofortho-andmeta-Nitrated Inhibitors of Catechol-O-methyltransferase: Interactions with the Active Site and Regioselectivity ofO-Methylation

In this work, we present a comparative case study of "ortho-" and "meta-nitrated" catecholic inhibitors of catechol-O-methyltransferase (COMT), with regard to their interaction with the catalytic site of the enzyme and the in vitro regioselective formation of their mono-O-methyl ether metabolites. In particular, the effects of altering the attachment position of the inhibitors' side-chain substituent, within the classic nitrocatechol pharmacophore, were investigated. For this purpose, we compared two simple regioisomeric nitrocatechol-type inhibitors of COMT, BIA 3-228 and BIA 8-176, which contain the benzoyl substituent attached at the meta and ortho positions, respectively, relative to the nitro group. The two compounds were slowly O-methylated by COMT in vitro, but the particular substitution pattern of each compound was shown to have a profound impact on the regioselectivity of their O-methylation. To provide a plausible interpretation of these results, a comprehensive analysis of the protein-inhibitor interactions and of the relative chemical susceptibility to O-methylation of the catechol hydroxyl groups was performed by means of docking simulations and ab initio molecular orbital calculations. The major structural and chemical factors that determine the enzyme regioselectivity of O-methylation were identified, and the X-ray structure of the complex of COMT with S-adenosyl-l-methionine and BIA 8-176 is herein disclosed. This is the first reported structure of the soluble form of COMT complexed with a nitrocatecholic inhibitor having a bulky substituent group in adjacent position (ortho) to the nitro group. Structural and dynamic aspects of this complex are analyzed and discussed, in the context of the present study.

Increases in transepithelial vectorial Na+ transport facilitates Na+-dependent L-DOPA transport in renal OK cells

The present study evaluated the hypothesis of whether increases in vectorial Na+ transport translate into facilitation of Na+-dependent L-DOPA uptake in cultured renal epithelial tubular cells. Increases in vectorial Na+ transport were obtained in opossum kidney (OK) cells engineered to overexpress Na+-K+-ATPase after transfection of wild type OK cells with the rodent Na+-K+-ATPase alpha1 subunit. The most impressive differences between wild type and transfected OK cells are that the latter overexpressed Na+-K+-ATPase accompanied by an increased activity of the transporter. Non-linear analysis of the saturation curve for l-DOPA uptake revealed a Vmax value (in nmol mg protein/6 min) of 62 and 80 in wild type and transfected cells, respectively. The uptake of a non-saturating concentration (0.25 microM) of [14C]-L-DOPA in OK-WT cells was not affected by Na+ removal, whereas in OK-alpha1 cells accumulation of [14C]-L-DOPA was clearly dependent on the presence of extracellular Na+. When Na+ was replaced by choline, the inhibitory profile of neutral l-amino acids, but not of basic and acidic amino acids, upon [14C]-L-DOPA uptake in both cell types, was significantly greater than that observed in the presence of extracellular Na+. It is concluded that enhanced ability of OK cells overexpressing Na+-K+-ATPase to translocate Na+ from the apical to the basal cell side correlates positively with their ability to accumulate L-DOPA, which is in agreement with the role of Na+ in taking up the precursor of renal dopamine.

Intestinal 5-hydroxytryptamine and mast cell infiltration in rat experimental colitis

The present study evaluated the extent of dysfunction of the 5-hydroxytryptaminergic system in inflamed (distal colon) and noninflamed segments (jejunum and ileum) after intrarectal administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) in the rat. Dexamethasone was administered to control rats and TNBS-treated animals before and for 7 days after TNBS treatment. Tissue levels of 5-hydroxytryptamine (5-HT) in the inflamed colon were higher than in controls. The density of mast cells was also markedly increased. Treatment with dexamethasone attenuated the inflammatory response but did not prevent the increase in colonic 5-HT. In the noninflamed jejunum and terminal ileum, 5-HT tissue levels were markedly increased, but treatment with dexamethasone prevented this increase. It is concluded that the increase in 5-HT levels in the inflamed colon in TNBS-induced colitis may result from mast cell infiltration. In the noninflamed intestine, 5-HT tissue levels were also increased, favoring the view of a generalized mast cell infiltration.

Synthesis and Biological Evaluation of Novel, Peripherally Selective Chromanyl Imidazolethione-Based Inhibitors of Dopamine β-Hydroxylase

A novel series of dopamine beta-hydroxylase (DBH) inhibitors was designed and synthesized incorporating modifications to the core structure of nepicastat 3, with the principal aim of discovering potent DBH inhibitors exerting minimal effects on dopamine (DA) and noradrenaline (NA) levels in the central nervous system. This study resulted in the identification of a potent, peripherally selective DBH inhibitor, (R)-5-(2-aminoethyl)-1-(6,8-difluorochroman-3-yl)-1,3-dihydroimidazole-2-thione hydrochloride 54 (BIA 5-453). In experiments in mice and rats at T(max) (9 h after administration), 54 reduced NA levels in a dose-dependent manner in both the left atrium and the left ventricle, with the maximal inhibitory effect attained at a dose of 100 mg/kg. In contrast to that found in the heart, 54 failed to affect NA tissue levels in the brain. Compound 54 is thus presented as a candidate for clinical evaluation for the treatment of chronic heart failure and hypertension.

Angiotensin-II type 1 receptor-mediated hypertension in D4 dopamine receptor-deficient mice

Dopamine receptors are important in systemic blood pressure regulation. D4 receptors are expressed in the kidney and brain, but their role in cardiovascular regulation is unknown. In pentobarbital-anesthetized mice, systolic and diastolic blood pressures were elevated in sixth-generation D4 receptor-deficient (D4(-/-)) mice and in tenth-generation D4(-/-) mice compared with D4 wild-type (D4(+/+)) littermates. The conscious blood pressures measured via a chronic arterial (femoral) catheter or telemetry (carotid) were also higher in D4(-/-) mice than in D4 littermates. Basal renal and plasma renin concentrations were similar in the 2 mouse strains. The protein expression of angiotensin II type 1 receptor was increased in homogenates of kidney (330+/-53%, n=5) and brain (272+/-69%, n=5) of D4(-/-) mice relative to D4(+/+) mice (kidney: 100+/-12%, n=5; brain: 100+/-32%, n=5). The expression of the receptor in renal membrane was also increased in D4(-/-) mice (289+/-28%, n=8) relative to D4(+/+) mice (100+/-14%, n=10). In contrast, the expression in the heart was similar in the 2 strains. Bolus intravenous injection of angiotensin II type 1 receptor antagonist losartan initially decreased mean arterial pressures to a similar degree in D4(-/-) and D4(+/+) littermates. However, the hypotensive effect of losartan dissipated after 10 minutes in D4(+/+) mice, whereas the effect persisted for >45 minutes in D4(-/-) mice. We conclude that the absence of the D(4) receptor increases blood pressure, possibly via increased angiotensin II type 1 receptor expression.

Apical and basolateral 4F2hc and the amino acid exchange of L-DOPA in renal LLC-PK1 cells

The present study aimed to examine the presence and define the role of 4F2hc, a glycoprotein associated with the LAT2 amino acid transporter, in L-DOPA handling by LLC-PK1 cells. For this purpose we have measured the activity of the apical and basolateral inward and outward transport of [14C] L-DOPA in cell monolayers and examined the influence of 4F2hc antisense oligonucleotides on [14C] L-DOPA handling. The basal-to-apical transepithelial flux of [14C] L-DOPA progressively increased with incubation time and was similar to the apical-to-basal transepithelial flux. The spontaneous and the L-DOPA-stimulated apical fractional outflow of [14C] L-DOPA were identical to that through the basal cell side. The L-DOPA-induced fractional outflow of [14C] L-DOPA through the apical or basal cell side was accompanied by marked decreases in intracellular levels of [14C] L-DOPA. In cells treated with an antisense oligonucleotide complementary to 4F2hc mRNA for 72 h, [14C] L-DOPA inward transport and 4F2hc expression were markedly reduced. Treatment with the 4F2hc antisense oligonucleotide markedly decreased the spontaneous fractional outflow of [14C] L-DOPA through the apical or the basal cell side. It is likely that the Na+-independent and pH-sensitive uptake of L-DOPA include the hetero amino acid exchanger LAT2/4F2hc, which facilitates the trans-stimulation of L-DOPA and its outward transfer at both the apical and basal cell sides.

Expression and function of LAT1, a neutral amino acid exchanger, in renal porcine epithelial cell line LLC-PK1

AIM

The present study examined the expression of LAT1 and the functional characteristics of the inward and outward [14C] l-leucine transporter in the renal porcine epithelial cell line LLC-PK1.

METHODS

LLC-PK1 cells were cultured in polycarbonate filters and accumulation and transepithelial flux of the substrate monitored with [14C] l-leucine. LAT1 transcripts were examined by RT-PCR. LAT1 protein was detected by immunoblotting.

RESULTS

The accumulation of [14C] l-leucine in the cell and the [14C] l-leucine transepithelial flux were four- and twofold, respectively, when the substrate was added from the basal cell side, suggesting that the basolateral membrane is endowed with a high density of transport units, when compared with the apical membrane. Increases in the transepithelial flux of [14C] l-leucine by unlabelled l-leucine were also more pronounced when unlabelled l-leucine was added from the basolateral membrane. In the absence of Na+, unlabelled l-leucine increased the basal and apical fractional outflow of [14C] l-leucine, this being similar at pH 7.4 and pH 6.2. RT-PCR and immunoblotting detected LAT1 transcript and protein, respectively.

CONCLUSION

LLC-PK1 cells are endowed with the LAT1 transcript and protein and transport l-leucine through the Na+-independent and pH-insensitive LAT1 transporter. The density of transporter units in LLC-PK1 cells may be higher at the basolateral membranes, although be also present in the apical membranes.

Expression of LAT1 and LAT2 amino acid transporters in human and rat intestinal epithelial cells

The present study evaluated the presence of LAT1 and LAT2 amino acid transporters in human Caco-2 cells and rat IEC-6 cells along the mucosa of the rat digestive tract. The LAT1 cDNA was amplified by PCR using two sets of primers (one specific for rat LAT1 and another simultaneously specific for human, rat and mice). The LAT2 cDNA was amplified by PCR using one set of primers simultaneously specific for human, rat and mice LAT2. The presence of LAT1 and LAT2 protein was examined by means of immunoblotting using an antibody raised against the rat LAT1 and mouse LAT2. Caco-2 and IEC-6 cells, as well as the rat intestinal mucosa, are endowed with both LAT1 and LAT2 transporter transcripts and protein. LAT1 protein is most abundant in IEC-6 cells, which is in agreement with functional data previously reported. The findings in the rat intestinal mucosa indicate that LAT1 protein is most abundant in the colon and its abundance markedly decreases at the level of jejunum and ileum, which contrast with relative homogeneous presence of LAT2 across the digestive tract. In conclusion, Caco-2 and IEC-6 cells, as well as the rat intestinal mucosa, are endowed with both LAT1 and LAT2 amino acid transporter transcripts and protein.

Regional intestinal adaptations in Na+,K+-ATPase in experimental colitis and the contrasting effects of interferon-gamma

AIMS

This study evaluated Na+,K+-ATPase activity and the abundance of alpha1 subunit Na+,K+-ATPase in experimental colitis and gathered evidence on the effects of interferon-gamma (IFN-gamma) on intestinal Na+,K+-ATPase.

METHODS

Colitis was induced by the intrarectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS, 30 mg/250 microL). Na+,K+-ATPase activity was determined as the difference between total and ouabain-insensitive ATPase. The abundance of Na+,K+-ATPase was analysed by immunoblotting.

RESULTS

Na+,K+-ATPase activity was markedly reduced in the proximal colonic mucosa of TNBS-treated rats, whereas upstream in the terminal ileal mucosa a marked increase in sodium pump activity was observed. At the jejunal level no significant changes in Na+,K+-ATPase activity were observed between TNBS-treated rats and corresponding controls (ethanol-treated rats). No changes were observed in the abundance of alpha1 subunit Na+,K+-ATPase in the proximal colon, terminal ileum and jejunum. The administration of IFN-gamma (50,000 U) 48 h before sacrifice reduced both Na+,K+-ATPase activity and the abundance of alpha1 subunit Na+,K+-ATPase in the proximal colon. Dexamethasone prevented colonic inflammation and decreases in proximal colonic Na+,K+-ATPase activity in TNBS-treated rats, but did not affect the INF-gamma-induced decrease in colonic Na+,K+-ATPase activity.

CONCLUSIONS

The increase in ileal Na+,K+-ATPase activity upstream to the lesioned colonic mucosa, where Na+,K+-ATPase activity was markedly reduced, might indicate a compensatory process to counteract the decrease in water and electrolyte absorption at the colonic level. This decrease in colonic Na+,K+-ATPase activity is likely not related to INF-gamma-induced downregulation of Na+,K+-ATPase.

Over-expression of renal LAT1 and LAT2 and enhanced L-DOPA uptake in SHR immortalized renal proximal tubular cells

BACKGROUND

Spontaneously hypertensive rats (SHR) may have an increased renal production of dopamine. LAT2 promotes L-DOPA renal uptake, and this may determine the rate of dopamine synthesis. The present study evaluated L-DOPA inward and outward transfer in immortalized renal proximal tubular epithelial cells of SHR and Wistar-Kyoto rats (WKY).

METHODS

Uptake of [(14)C]-L-DOPA was initiated by the addition of 1 mL Hanks' medium with a given concentration of the substrate. The apical fractional outflow of intracellular [(14)C]-L-DOPA was evaluated in cells loaded with [(14)C]-L-DOPA for 6 minutes, and then the corresponding efflux was monitored over 12 minutes. The presence of LAT1 and LAT2 transcripts and protein in WKY and SHR cells was examined, respectively, by reverse transcription-polymerase chain reaction (RT-PCR) and immunobloting.

RESULTS

LAT2 in WKY cells contributed almost exclusively for [(14)C]-L-DOPA uptake. In SHR cells [(14)C]-L-DOPA uptake was 25% through system B(0), 25% through LAT2 (resulting from inhibition by 1 mmol/L glycine, L-alanine, L-serine, and L-threonine), and the remaining 50% through LAT1. The efflux of [(14)C]-L-DOPA from WKY and SHR cells corresponded to approximately 65% and approximately 25%, respectively, of the amount accumulated in the cells. The LAT1 and LAT2 transcripts were present in both SHR and WKY cells, but the abundance of both LAT1 and LAT2 proteins in SHR cells was greater than in WKY cells.

CONCLUSION

Differences in L-DOPA handling between SHR and WKY cells may result from over-expression of LAT1 and LAT2 transporters in the former. The unique role of Na(+)-dependent transporters (system B(0)) in SHR cells also contributes to the enhanced L-DOPA uptake in these cells.

Effect of Food on the Pharmacokinetic Profile of Eslicarbazepine Acetate (BIA 2-093)

OBJECTIVE

To investigate the effect of food on the pharmacokinetics of eslicarbazepine acetate (BIA 2-093), a new voltage-gated sodium channel antagonist.

MATERIAL AND METHODS

Single-centre, open-label, randomised, two-way crossover study in 12 healthy subjects. The study consisted of two consecutive treatment periods separated by a washout of 14 days or more. In each of the study periods subjects were administered a single dose of eslicarbazepine acetate 800 mg following either a standard high-fat content meal or 10 hours of fasting.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolised to BIA 2-005. Maximum BIA 2-005 plasma concentrations (C(max)) in fed (test) and fasting (reference) conditions were, respectively, 12.8 +/- 1.8 microg/mL and 11.3 +/- 1.9 microg/mL, and the areas under the plasma concentration time curve from 0 to infinity (AUC(infinity)) were, respectively, 242.5 +/- 32.1 microg.h/mL and 243.6 +/- 31.1 microg.h/mL (arithmetic mean +/- SD). The point estimate (PE) and 90% confidence interval (90% CI) of the test/reference C(max )geometric mean ratio were 1.14 and 1.04, 1.25, respectively; for the AUC(infinity) ratio, the PE and 90% CI were 1.00 and 0.95, 1.04, respectively. Bioavailability of eslicarbazepine acetate administered in fed and fasting conditions was similar and bioequivalence is accepted for both AUC(infinity) and C(max) because the 90% CI lies within the acceptance range of 0.80-1.25. No statistically significant differences were found in time of occurrence of C(max).

CONCLUSION

The presence of food had no significant effect on the pharmacokinetics of eslicarbazepine acetate and therefore this new voltage-gated sodium channel antagonist may be administered without regard to meals.

Eslicarbazepine Acetate (BIA 2-093)

PURPOSE

To investigate the bioavailability and bioequivalence of three different formulations of eslicarbazepine acetate (BIA 2-093): 50 mg/mL oral suspension (test 1), 200mg tablets (test 2) and 800mg tablets (reference).

DESIGN, SUBJECTS AND METHODS

Single-centre, open-label, randomised, three-way crossover study in 18 healthy subjects. The study consisted of three consecutive periods separated by a washout period of 7 days or more. Each subject received a single dose of eslicarbazepine acetate 800mg on three different occasions: 16mL of oral 50 mg/mL suspension, four 200mg tablets or one 800mg tablet.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolised to BIA 2-005. Maximum BIA 2-005 plasma concentrations (Cmax) and area under the plasma concentration-time curve from time 0 to infinity (AUCinfinity) were, respectively (arithmetic mean +/- SD), 18.0 +/- 4.6 microg/mL and 325.7 +/- 64.9 microg x h/mL for test 1, 16.0 +/- 4.0 microg/mL and 304.2 +/- 66.0 microg x h/mL for test 2, and 17.0 +/- 4.1 microg/mL and 301.1 +/- 60.0 microg x h/mL for the reference formulation. Point estimate (PE) and 90% confidence intervals (CIs) for AUCinfinity test 1/reference geometric mean ratio were 1.09 and 1.01, 1.15; for Cmax ratio, PE and 90% CI were 1.07 and 0.97, 1.15. When test 2 and the reference formulations were compared, the PE and 90% CI were 0.99 and 0.94, 1.07 for the AUCinfinity ratio, and 0.94 and 0.86, 1.02 for the Cmax ratio. Bioequivalence of test versus reference formulations is thus accepted for both AUCinfinity and Cmax because the 90% CIs lie within the acceptance range of 0.80-1.25.

CONCLUSION

The pharmacokinetic profiles of eslicarbazepine acetate oral 50 mg/mL suspension, 200mg tablet and 800mg tablet formulations were essentially similar, and the formulations can be considered bioequivalent.

Bioavailability and Bioequivalence of??Two Enteric-Coated Formulations of??Omeprazole in Fasting and Fed Conditions

OBJECTIVE

To investigate the relative bioavailability and bioequivalence, in fasting and fed conditions, of repeated doses of two omeprazole enteric-coated formulations in healthy volunteers.

MATERIAL AND METHODS

Open label, single-centre study consisting of two consecutive randomised, two-way crossover trials (a fasting trial and a fed trial). Each trial consisted of two 7-day treatment periods in which subjects received one daily dose of the test (Ompranyt((R))) or reference (Mopral((R))) formulations. At day 7 and day 14 (fasting trial), products were administered in fasting conditions and blood samples were taken for omeprazole plasma assay over 12 hours. At day 21 and day 28 (fed trial), products were administered after a standard high-calorie and high-fat meal and 12-hour blood samples taken. Omeprazole plasma concentrations were quantified by a validated method using a reverse-phase high performance liquid chromatography with UV detection (HPLC-UV).

RESULTS

Twenty-four subjects were enrolled and 23 completed the study. Under fasting conditions, the mean +/- SD maximum omeprazole plasma concentration (C(max)) was 797 +/- 471 mug/L for Ompranyt((R)) and 747 +/- 313 mug/L for Mopral((R)) with a point estimate (PE) of 1.01 and a 90% confidence interval (CI) of 0.88, 1.16. The mean +/- SD area under the plasma concentration curve from administration to last observed concentration (AUC(0-12)) was 1932 +/- 1611 mug . h/L and 1765 +/- 1327 mug . h/L for Ompranyt((R)) and Mopral((R)), respectively (PE = 1.09; 90% CI 0.95, 1.25). In the presence of food, the C(max) was 331 +/- 227 mug/L and 275 +/- 162 mug/L (PE = 1.21; 90% CI 0.92, 1.59) and AUC(0-12) was 1250 +/- 966 mug . h/L and 1087 +/- 861 mug . h/L (PE = 1.16; 90% CI 0.92, 1.47) for Ompranyt((R)) and Mopral((R)), respectively. Bioequivalence of the formulations in the fasting condition was demonstrated both for AUC(0-12) and for C(max) because the 90% CI lay within the acceptance range of 0.80-1.25. In contrast with the fasting condition, there were significant reductions in rate (C(max)) and extent (AUC(0-12)) of systemic exposure when test and reference formulations were administered with food. The food effect was more marked with Mopral((R)) than with Ompranyt((R)), and the bioequivalence criterion was not fulfilled because the 90% CI fell out of the acceptance range of 0.80, 1.25, for both C(max) and AUC(0-12). The two formulations were similarly well tolerated.

CONCLUSION

Bioequivalence of Ompranyt((R)) (test formulation) and Mopral((R)) (reference) formulations was demonstrated after repeated dosing in the fasting condition. Following a high-calorie and high-fat meal, there was a significant reduction in rate and extent of systemic exposure for both products, with Ompranyt((R)) being less affected than Mopral((R)) by the presence of food.

Crystallization and preliminary X-ray diffraction studies of a catechol-O-methyltransferase/inhibitor complex

Inhibitors of the enzyme catechol-O-methyltransferase (COMT) are used as co-adjuvants in the therapy of Parkinson's disease. A recombinant form of the soluble cytosolic COMT from rat has been co-crystallized with a new potent inhibitor, BIA 8-176 [(3,4-dihydroxy-2-nitrophenyl)phenylmethanone], by the vapour-diffusion method using PEG 6K as precipitant. Crystals diffract to 1.6 A resolution on a synchrotron-radiation source and belong to the monoclinic space group P2(1), with unit-cell parameters a = 52.77, b = 79.63, c = 61.54 A, beta = 91.14 degrees.

Decreased availability of intestinal dopamine in transmural colitis may relate to inhibitory effects of interferon-gamma upon L-DOPA uptake

AIMS

The present study aimed to evaluate the relationship between intestinal inflammation, interferon-gamma (IFN-gamma) levels and intestinal levels of dopamine, its precursor l-3,4-dihydroxyphenylalanine (L-DOPA), and the activity of aromatic L-amino acid decarboxylase (AADC) activity along the digestive tract in a rat experimental model of colitis.

METHODS

Colitis was induced by rectal administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS). Catechol derivatives were assayed by means of HPLC-EC.

RESULTS

It is shown that dopamine and noradrenaline levels in the distal colon (inflamed mucosa), but not in the ileum (non-inflamed mucosa), of TNBS-treated rats were markedly lower than in control animals. A slight decrease in L-DOPA tissue levels, no changes in AADC activity and an increase in plasma IFN-gamma levels accompanied this decrease in dopamine levels. Exposure of Caco-2 cells, a human intestinal epithelial cell line, to human IFN-gamma resulted in a concentration-dependent and long-lasting inhibition of L-DOPA uptake, which most likely explains the decrease in dopamine levels in the inflamed mucosa.

CONCLUSION

Changes in tissue levels of noradrenaline and dopamine in experimental colitis in the rat follow a similar pattern to that observed in patients with Crohn's disease and ulcerative colitis. In this model of experimental colitis, the decrease in dopamine levels is most likely explained by the inhibitory effect of IFN-gamma on L-DOPA uptake by intestinal epithelial cells.