The Effects of Special Patient Population Plasma on Pharmacokinetic Quantifications Using LC-MS/MS

BACKGROUND

Clinical development of lesinurad, a selective uric acid reabsorption inhibitor, required analysis of lesinurad in plasma from special patient populations.

METHODS

EMA and FDA bioanalytical method validation guidance have recommended studying matrix effects on quantitation if samples from special patient populations are to be analyzed. In addition to lesinurad (plasma protein binding 98.2%), the matrix effects from special population plasma on the quantitation of verapamil (PPB 89.6%), allopurinol and oxypurinol (PPB negligible) were also investigated.

RESULTS

The plasma from special population patients had no matrix effects on the three quantification methods with stable isotope labeled internal standard, protein precipitation extraction, and LC-MS/MS detection. The validated lesinurad plasma quantification method was successfully applied for the pharmacokinetic evaluations to support the clinical studies in renal impaired patients.

CONCLUSION

Special population plasma did not affect quantitation of drugs with a wide range of plasma protein binding levels in human plasma. With the confirmation that there is no impact on quantification from the matrix, the bioanalytical method can be used to support the pharmacokinetic evaluations for clinical studies in special populations.

Efficacy and Safety of Non-Vitamin K Antagonist Oral Anticoagulants in Atrial Fibrillation Patients With Impaired Liver Function: A Retrospective Cohort Study

Background Patients with impaired liver function ( ILF ) were excluded from clinical trials that investigated non-vitamin K antagonist oral anticoagulants ( NOAC s) for stroke prevention in patients with atrial fibrillation. The aim of this study was to evaluate the efficacy and safety of NOAC s in atrial fibrillation patients with ILF . Methods and Results A cohort study based on electronic medical records was conducted from 2009 to 2016 at a multicenter healthcare provider in Taiwan and included 6451 anticoagulated atrial fibrillation patients (aged 76.7±7.0 years, 52.5% male). Patients were classified into 2 subgroups: patients with normal liver function (n=5818) and patients with ILF (n=633, 9.8%). Cox regression analysis was performed to investigate the risks of thromboembolism, bleeding, and death associated with use of NOAC s and warfarin in patients with normal liver function and ILF , respectively. In patients with normal liver function, compared with warfarin therapy (n=2928), NOAC therapy (n=4048) was associated with significantly lower risks of stroke or systemic embolism (adjusted hazard ratio: 0.75; 95% confidence interval, 0.65-0.88; P<0.001) and death (adjusted hazard ratio: 0.69; 95% confidence interval, 0.60-0.80; P<0.001) with no difference in major bleeding or gastrointestinal bleeding. In patients with ILF , compared with warfarin therapy (n=394), NOAC therapy (n=342) was associated with significantly lower risk of death (adjusted hazard ratio: 0.64; 95% confidence interval, 0.49-0.83; P<0.001), but no difference in stroke or systemic embolism, major bleeding, or gastrointestinal bleeding. Conclusions In atrial fibrillation patients with ILF , NOAC therapy and warfarin therapy were associated with similar risks of stroke or systemic embolism, major bleeding, and gastrointestinal bleeding.

Altered cytokine profile under control of the serotonergic system determines the regulation of CYP2C11 and CYP3A isoforms

The aim of this study is to assess a potential mechanism by which the serotonergic system can control the expression and activity of cytochrome (CYP) 2C11 and CYP3A isoforms during liver insufficiency. A rat model of diethylnitrosamine (DEN)-induced liver insufficiency was developed by administering 50 mg/kg of DEN twice a week for 7 weeks. Dysfunction of the serotonergic system was evoked by feeding the rats with a tryptophan-free diet for three weeks. Dysfunction of the serotonergic system during liver insufficiency decreased the level of proinflammatory cytokines (TGF-β and IL-1β) and increased the level of an anti-inflammatory cytokine (IL-4). Simultaneously, activation of the repressive mechanism IL-4/JAK1/STAT6/SOCS1 of the JAK2/STAT5b-mediated signal transduction pathway and the pERK1/2/GR/STAT6 signal transduction pathway resulted in the suppression of the CYP2C11 and CYP3A isoforms. Moreover, dysfunction of the serotonergic system during liver insufficiency equalized the level of testosterone to the basal level, did not change the steady state of the corticosterone level and significantly enhanced the reduced level of growth hormone. An altered cytokine profile under control of the serotonergic system determines the regulation of CYP2C11 and CYP3A isoforms during liver insufficiency through mechanisms based on posttranscriptional and posttranslational processes.

Neonatal Citrulline Supplementation and Later Exposure to a High Fructose Diet in Rats Born with a Low Birth Weight: A Preliminary Report

A low birth weight (LBW) leads to a higher risk of metabolic syndrome in adulthood. Literature suggests that citrulline supplementation in adulthood prevents the effect of a high fructose diet on energy metabolism. Whether neonatal citrulline supplementation would alter early growth or energy metabolism in the long-term in rats with LBW is unknown. LBW pups born from dams fed a low (4%) protein diet, were nursed by normally-fed dams and received isonitrogenous supplements of either l-citrulline or l-alanine by gavage from the sixth day of life until weaning, and were subsequently exposed to 10%-fructose in drinking water from weaning to 90 days of age. The oral glucose tolerance was tested (OGTT) at 70 days of age, and rats were sacrificed at 90 days of age. Pre-weaning citrulline supplementation failed to alter the growth trajectory, OGTT, plasma triglycerides, or fat mass accretion in adulthood; yet, it was associated with increased liver triglycerides, decreased liver total cholesterol, and a distinct liver lipidomic profile that may result in a predisposition to liver disease. We conclude that pre-weaning supplementation with citrulline does not impact early growth, but might impact liver fat metabolism in adulthood upon exposure to a high fructose diet.

[Effect of liver cirrhosis on pharmacokinetics and pharmacodynamics of drugs]

Metabolic liver functions are significantly involved in the total clearance of a number of drugs. In liver cirrhosis the reduced drug elimination is a result of the blood flow through the liver, hepatocytes function and volume of hepatic tissue. Pharmacokinetic and pharmacodynamic changes depend on the nature and degree of hepatic impairment and on the characteristics of the dosed drug. Hepatocytes have a different extraction ability with respect to the individual drugs. The following are examples of drugs with high hepatic extraction: anodyne, propranolol, metoprolol, verapamil and lidocaine. These drugs are significantly dependent on the first passage through the liver. Intrahepatic and extrahepatic collateral blood flows significantly increase their bio-logical availability and reduce the clearance. The reduction in hepatic clearance of drugs with low extraction coefficient, such as chlordiazepoxide, diazepam or furosemide, is a result of its own limited functional capacity to eliminate the drug. Predicting a hepatic metabolic disorder based on a common bio-chemical assessment of enzyme activities is not sufficient. In advanced liver cirrhosis a higher risk is demonstrated for drugs with a narrow therapeutic width. It is always necessary to take into account whether the pharmacotherapy is necessary, use small doses and cautiously monitor the patient.

In vivo antioxidant and biochemical evaluation of Sphenocentrum jollyanum leaf extract in P. berghei infected mice

Recent approach in treatment and drug development suggested that the control of oxidative stress in malarial infected patients may be an added advantage. In this study, effect of methanolic leaf extract of Sphenocentrum jollyanum pier (S. jollyanum) on liver damage, markers of oxidative stress and alteration in lipid profile in P. berghei infected mice was assessed. Oxidative stress was induced by intravenously inoculation of mice with 1 × 10⁷ sporozoites P. berghei. Treatment of parasitized mice with leaf extract of S. jollyanum had a significant (p<0.05) reductions in elevated levels of total protein, globulin, AST, ALT, ALP, GGT and total bilirubin, serum, kidney and liver malondialdehyde (MDA) concentrations, but caused a significant (p<0.05) increased in the activities of serum and liver catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) level when compared with parasitized non-treated group (PNT). The extract treated group also showed significant (p<0.05) improvement in the levels of HDLc, total cholesterol, LDL and reduction in triglyceride compared with parasitized non treated group. Our results revealed that the protective capacity and antioxidant activity of the extract is dose dependant. The findings suggest that antioxidant property of Sphenocentrum jollyanum leave extract might be an added advantage to it anti-malarial activity.

Pharmacokinetics of Nelfinavir in Subjects With Hepatic Impairment

HIV-seronegative subjects with hepatic impairment (6 mild, 6 moderate) and 12 matched healthy controls received nelfinavir 1250 mg every 12 hours with food for 2 weeks. Mild impairment did not significantly change nelfinavir or major metabolite (M8) steady-state exposures compared with controls. In subjects with moderate impairment, steady-state area under the plasma concentration time-curve over the dosing interval and maximum observed plasma concentrations were 62% and 22% higher for nelfinavir than for controls, and for M8 were 46% and 35% of control values. With increasing degree of impairment, no trend toward increase in unbound nelfinavir was observed, but there was an increase in unbound M8 levels. Nelfinavir was safe and well tolerated. One subject with moderate impairment was discontinued because of transient leucopenia. Observed changes are unlikely to affect nelfinavir efficacy or markedly influence safety. Dose reduction of nelfinavir does not appear necessary for subjects with mild/moderate impairment. Further long-term evaluations of nelfinavir pharmacokinetics and safety in HIV-seropositive subjects with hepatic impairment may be useful.

Anidulafungin Does Not Require Dosage Adjustment in Subjects With Varying Degrees of Hepatic or Renal Impairment

Two open-label studies assessed the effects of hepatic and renal impairment on anidulafungin pharmacokinetics. A single 50-mg dose was administered intravenously to subjects with varying degrees of hepatic or renal insufficiency or with end-stage renal disease; all were matched to normal healthy controls. Anidulafungin was well tolerated. AUC, CL, C(max), t(max), t(1/2), and V(ss) between renally impaired subjects and controls were not significantly different (P>.05), and no measurable amounts of drug were found in dialysate. The same pharmacokinetic parameters were also not affected (P>.05) by mild or moderate hepatic insufficiency, with respective mean AUCs of 50.6 +/- 11.7 microg x h/mL and 68.6 +/- 14.5 microg x h/mL, compared to 70.0 +/- 13.4 microg x h/mL in controls. Statistically significant decreases (P<05) of AUC (33% change) and C(max) (36% change) in severely hepatically impaired subjects compared to controls--most likely secondary to ascites and edema--were not clinically relevant. Anidulafungin can be safely administered to patients with any degree of hepatic or renal impairment without dosage adjustment and without regard to hemodialysis schedules.

Gastric estrogen increases pituitary estrogen receptor α and prolactin mRNAs during the different pathological conditions of the liver

Mammalian liver is an estrogen-responsive tissue mediated by hepatic estrogen receptors. Although Ueyama et al. (Endocrinology 143:3162-3170, 2002) have reported the presence of aromatase and active production of gastric 17β-estradiol in parietal cells, there are a few studies on gastric 17β-estradiol exploring the relationship between gastro-hepato function and the gastro-pituitary-gonadal axis. The alteration of gastric 17β-estradiol flow into the systemic circulation by portal vein ligation (PVL) or partial hepatectomy (PH), and the effect of gastric 17β-estradiol on the pituitary function was investigated. In the PVL rats, arterial 17β-estradiol increased 9.5 times that of controls on day 3, and gradually decreased near to control levels in the portal vein by 4 weeks, which was still 5 times higher than those in the arteries of the control rats. In the PH rats, arterial 17β-estradiol increased 2 times that of controls on day 3, and gradually decreased to the control levels. Regeneration and growth of the liver remnants were observed about 2 weeks after PH. In the PVL and PH animals, pituitary ERα and prolactin mRNAs levels increased, positively correlating with an increase of arterial 17β-estradiol levels. Both reduced LHβ mRNA. It is apparent that hepatic dysfunction causes changes in gastric 17β-estradiol levels in the systemic circulation; and that elevated gastric 17β-estradiol affects pituitary function(s). This data suggest that gastric 17β-estradiol has a pivotal role in the regulation of the gastro-hepato-pituitary axis.

[Effect of domestic gas on morphological and functional state of parenchymatous organs in rats]

The work is devoted to a study of morphological and functional changes in liver and kidneys in the simulation of subacute toxic exposure of rats to domestic gas in the experiment. In the course of studies found that the subacute intoxication by domestic gas and its metabolites were shown to causes profound structural and metabolic lesions of the liver and kidneys that can progress to develop the chronic liver and kidney insufficiency.

From chronic overfeeding to hepatic injury: role of endoplasmic reticulum stress and inflammation

We analyse how chronic overfeeding, by increasing circulating fatty acids, might lead to inflammation, insulin resistance (IR) and injury in the liver. Chronic overfeeding causes an increase in adipose tissue depots and is characterised by an increased presence of hypertrophic adipocytes when adipose tissue expandability is inadequate. Adipocyte hypertrophy is a possible stress condition for the endoplasmic reticulum (ER), which will activate inflammatory and apoptotic pathways and cause IR in adipose tissue. Insulin-resistant adipocytes, being more lipolytic and less liposynthetic, induce an increase in circulating free fatty acids. Moreover, the strongly compromised secretion/function of the adipocyte hormones, adiponectin and leptin, decreases lipid oxidation, particularly in the liver, causing lipid accumulation, ER stress and IR in hepatocytes. ER stress may lead to reduced very-low-density lipoprotein (VLDL) secretion and increased lipogenic gene expression despite the presence of IR. These events and reduced lipid oxidation may lead to further hepatic lipid accumulation. When the triglyceride storage capacity of hepatocytes is exceeded, hepatic injury may occur. ER-stressed steatotic hepatocytes activate apoptotic and inflammatory pathways, which trigger IR and the release of chemokines and cytokines, and these, in turn, elicit an increased influx of Kupffer cells (KCs) and hepatic stellate cells (HSCs) around dying hepatocytes. Soluble mediators, secreted mainly by ER-stressed steatotic hepatocytes and activated KCs, induce the transdifferentiation of HSCs to myofibroblasts, which secrete fibrogenic cytokines and matrix components that trigger fibrosis. In conclusion, chronic lipid overloading due to inadequate fat-storing capacity of adipose tissue can induce hepatic injury when triglyceride storage capacity of hepatocytes is exceeded.

[The role of biliary decompression and correction of dysbiosis in the treatment of obstructive jaundice]

The article providing in-depth analysis of pathogenesis of obstructive jaundice shows that this disease is manifest not only as changes at the hepatic level (cholestasis, cholehemia, cholangitis, cholangio- and lymphovenous shunts, hepatic encephalopathy) but also as marked dysbiotic disturbances due to anacholia and toxic metabolites that cause bacterial translocation and endotoxemia complicating liver insufficiency. Based on the literary data and original observations, a new scheme for the treatment of obstructive jaundice is proposed including simultaneous correction of both components of hepatoenteric turnover, also, it permits to improve the outcome of the postoperative period.

Role of STAT3 in liver regeneration: survival, DNA synthesis, inflammatory reaction and liver mass recovery

The hepatoprotective effect of interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) has been well documented. However, reports on the role of IL-6/STAT3 in liver regeneration are conflicting probably due to the fact that the model of Stat3 knockout mice were complicated with obesity and fatty liver, which may cause some secondary effects on liver regeneration. To study the direct role of STAT3 and to circumvent the problems of obesity and fatty liver in liver regeneration, we generated conditional STAT3 knockout in the liver (L-Stat3(-/-)) using a transthyretin-driven Cre-lox method. The L-Stat3(-/-) mice were born with the expected Mendelian frequency and showed no obesity or other obvious phenotype. After partial hepatectomy, mortality in the L-Stat3(-/-) mice was significantly higher than the littermate Stat3(f/+) controls in the early time points (<24 h). Hepatocyte DNA synthesis in the survived L-Stat3(-/-) mice slightly decreased as compared with Stat3(f/+) mice at 40 h after partial hepatectomy, whereas similar hepatocyte DNA synthesis was found at other time points and liver mass could be completely recovered in the L-Stat3(-/-) mice. In another model of liver regeneration induced by subcutaneous injection of carbon tetrachloride (CCl(4)), hepatocyte DNA synthesis in the CCl(4)-treated L-Stat3(-/-) mice also decreased as compared with Stat3(f/+) mice at 40 h after injection but not at other time points. In addition, infiltration of neutrophils and monocyte increased in the liver of CCl(4)-treated L-Stat3(-/-) mice compared to wild-type mice. In conclusion, STAT3 is required for survival in the acute stage after 70% hepatectomy and plays a role in inflammatory reaction after hepatocyte necrosis. However, the hepatocytic STAT3 may have limited role in liver mass recovery although DNA synthesis may be impaired.

Single- and multiple-dose administration of caspofungin in patients with hepatic insufficiency: implications for safety and dosing recommendations

This report investigated safety and dosing recommendations of intravenous caspofungin in hepatic insufficiency. In the single-dose study, 8 patients each with mild and moderate hepatic insufficiency received 70 mg of caspofungin. In the multiple-dose study, 8 patients with mild hepatic insufficiency and 13 healthy matched controls received 70 mg on day 1 and 50 mg daily on days 2 through 14. Eight patients with moderate hepatic insufficiency received 70 mg on day 1 and 35 mg daily on days 2 through 14. Caspofungin was generally well tolerated with no discontinuations due to serious or nonserious adverse experiences. The area under the concentration-time profile over the interval of last quantifiable point to infinity (AUC(0-infinity)) geometric mean ratio (GMR) (90% confidence interval [CI]) for mild hepatic insufficiency/historical controls was 1.55 (1.32-1.86) in the single-dose study and for mild hepatic insufficiency/concurrent controls was 1.21 (1.04-1.39) for day 14 area under the concentration-time profile calculated over the interval 0 to 24 hours (AUC(0-24h)) following multidose. The AUC(0-infinity) GMR (90% CI) for moderate hepatic insufficiency/historical controls was 1.76 (1.51-2.06) following 70 mg; AUC(0-24h) GMR (90% CI) for moderate hepatic insufficiency/concurrent controls was 1.07 (0.90-1.28) on day 14 after 35 mg daily. No dosage adjustment is recommended for patients with mild hepatic insufficiency. A dosage reduction to 35 mg daily following the 70-mg loading dose is recommended for patients with moderate hepatic insufficiency.

Hydranencephaly with cholestasis and giant hepatitis

We present a rare case of hydranencephaly with cholestasis and giant hepatitis. Studies for infectious agents were all negative including for the detection of virus in liver tissue by using polymerase chain reaction. Although the anterior pituitary functions (cortisol, thyroid stimulating hormone, free T4, human growth hormone) were normal, the patient revealed massive cholestasis and giant hepatitis.

[Morphometric and immunohistochemical patterns of duodenal CCK-cells in rats with portacaval shunts]

INTRODUCTION

End-to-side portacaval shunt (PCS) performed in rats is an appropriate experimental model of chronic liver insufficiency. Functional hepatic injury followed by numerous metabolic and endocrine disorders develops, as well. Due to impaired functional hepatic activity in PCS and to the well known role of the liver in CCK metabolism and elimination, delayed CCK bloodstream elimination may be responsible for increased CCK-A receptor activity. Therefore, we investigated immunohistochemical and morphometric features of duodenal CCK-cells in rats with PCS.

MATERIAL AND METHODS

Male Wistar rats (180 - 250g body weight) were used in this experiment. The animals were divided into two groups: PCS-animals (experimental group (n=27) which underwent an operation) and C - unoperated animals [control group (n=11)].

SURGICAL TECHNIQUE

End-to-side portacaval anastomosis was created using the technique of Lee and Fisher, modified by Bismuth et al. Eight weeks, after the operation, animals were sacrificed. Pancreatic and hepatic weights were measured and samples taken from appropriate segments of the small intestine were used for morphometric and immunohistochemical CCK-cells determination. IMMUNOHISTOCHEMICAL TECHNIQUE: Peroxidase-antiperoxidase (PAP) technique described by Stenberger was applied for detection of intestinal CCK-immunoreactive cells.

RESULTS

Our results indicate that eight weeks after operation liver weight was reduced in animals with PCS compared to control animals (p<0.01). To the contrary, in comparasion with control animals, the pancreatic wight was increased (p<0.01). In the exocrine pancreas of rats with PCS there were lipid droplets and hypertrophy of the acinus cells. The morphometric analysis of CCK-immunoreactive cells in different small intestine segments indicates that in the duodenum of animals with PCS there was a significant cell increase compared to control, unoperated animals.

CONCLUSION

In liver cirrhosis, plasma CCK-8 concentration increases. In PCS, performed in rats, as an experimental model of chronic liver insufficiency, proliferation of CCK-cells in the small intestine leads to pancreatic hypertrophy and hyperplasia.

The Effect of Hepatic Insufficiency on the Safety and Pharmacokinetics of Paricalcitol (Zemplar®)

BACKGROUND/AIMS

Paricalcitol is highly protein bound, extensively metabolized and eliminated primarily by hepatobiliary excretion. This study was designed to determine if hepatic disease alters the pharmacokinetics or affects the safety of paricalcitol.

METHODS

Subjects with mild (n = 5) or moderate (n = 5) hepatic impairment, and subjects with normal hepatic function (n = 10) enrolled in and completed the study. Each subject was administered a single 0.24 microg/kg intravenous dose of paricalcitol, injected within 1 min.

RESULTS

For both total and unbound paricalcitol, there were no statistically significant differences in the pairwise comparisons between hepatic function groups in paricalcitol concentration at 5 min postdose (C5) or area under the plasma concentration-time curve from time zero to infinity (AUC(0-infinity), except C5 of total paricalcitol between mild and moderate impairment groups (p = 0.02). Paricalcitol binding to plasma proteins was extensive in all hepatic function groups (mean values >99.7%); unbound fraction was greater in subjects with moderate impairment than either healthy subjects or subjects with mild impairment (p < 0.01). Paricalcitol appeared to be well tolerated both by healthy subjects and subjects with mild to moderate hepatic insufficiency.

CONCLUSION

No adjustment of paricalcitol dose is required for subjects with mild to moderate hepatic impairment. However, caution should be exercised in extrapolating the results from this study to subjects with severe hepatic impairment.

Pharmacokinetic Profile of the Somatostatin Analogue Lanreotide in Individuals with Chronic Hepatic Insufficiency

BACKGROUND AND OBJECTIVES

The somatostatin analogue lanreotide is indicated for the treatment of acromegaly and to relieve the symptoms of neuroendocrine tumours. The objective of the present study was to compare the pharmacokinetic profile and safety of intravenous lanreotide in healthy volunteers and individuals with hepatic impairment.

METHODS

Immediate-release lanreotide was administered at 7 microg/kg during a 20-minute intravenous infusion. Blood samples were collected over 24 hours and lanreotide serum levels determined by radioimmunoassay. Pharmacokinetic parameters were estimated by non-compartmental analyses.

RESULTS

Two study centres recruited 53 individuals. Study A comprised 10 individuals with hepatic insufficiency Child-Pugh grade A (mild), 7 with grade B (moderate) and 12 healthy volunteers - all Caucasian. Study B comprised 4 individuals with hepatic insufficiency Child-Pugh grade A, 6 with grade B, 2 with grade C (severe) and 12 healthy volunteers - all Chinese. All participants were included in the safety analysis. The pharmacokinetic analysis included all participants from study B, but only 12 with hepatic impairment and 11 healthy volunteers from study A. Combined analysis of both studies showed an increased serum elimination half-life (57%; p < or = 0.001), mean residence time (53%; p < or = 0.001) and volume of distribution (at steady state, 57%; at terminal disposition phase, 64%; both p < or = 0.001) in individuals with mild hepatic insufficiency compared with healthy volunteers. These differences were more pronounced in individuals with moderate-to-severe hepatic insufficiency compared with healthy volunteers; additionally, the area under the serum concentration-time curve from time zero to infinity (AUC(infinity)) was increased (23%; p < or = 0.05) and clearance (CL) decreased (19%; p < or = 0.05) compared with healthy volunteers. The peak serum concentration of lanreotide tended to be lower in individuals with hepatic insufficiency than in healthy volunteers (statistically non-significant). There were no pharmacokinetic differences between the two groups of healthy volunteers. Lanreotide was well tolerated with only two mild adverse events that were considered to be possibly related to treatment (both nausea and headache with either vomiting or dizziness). There were no clinically relevant changes in laboratory parameters or vital signs during the study.

CONCLUSION

The pharmacokinetic profile of lanreotide depends on the severity of hepatic insufficiency with CL and AUC(infinity), which are only slightly altered with moderate-to-severe insufficiency. The changes in exposure do not, however, require dosage adjustment. Moreover, lanreotide is usually given as a prolonged-release microparticle or Autogel formulation, and terminal half-life and serum concentrations depend on the release properties of the formulation. Dosing is also adapted for each patient, based on therapeutic response. Thus, hepatic insufficiency does not require additional dosage adjustments.

Assessment of branched-chain amino Acid status and potential for biomarkers

BCAAs are not synthesized in the body in humans, but they are crucial in protein and neurotransmitter synthesis. The protein anabolic role of BCAAs seems to be mediated not only by their important role as a promoter of the translation process (and possibly acting at the transcription level) but also by inhibition of protein degradation. Leucine may play a critical role in these signaling pathways. Supplementation with BCAAs spares lean body mass during weight loss, promotes wound healing, may decrease muscle wasting with aging, and may have beneficial effects in renal and liver disease. BCAA supplementation is extensively used in the athletic field with the assumption of improved performance and muscle mass. Measuring serum BCAAs has limited clinical utility beyond the controlled setting because levels are affected by a variety of clinical states, and optimal levels in these scenarios have not been completely elucidated. We discuss the effects diet, hormones, stress, aging, and renal or liver dysfunction have on BCAA levels and how understanding the biological effects of BCAAs may help to develop biomarkers of BCAA status. We also discuss potential biomarkers of BCAA status.

Pharmacokinetic Profile of Dexloxiglumide

Dexloxiglumide is a potent and selective cholecystokinin type 1 (CCK1) receptor antagonist currently under development in a variety of diseases affecting the gastrointestinal tract such as gastro-oesophageal reflux disease, irritable bowel syndrome (IBS), functional dyspepsia, constipation and gastric emptying disorders. In female patients with constipation-predominant IBS, clinical efficacy has been demonstrated following administration of dexloxiglumide 200 mg three times daily. Dexloxiglumide is rapidly and extensively absorbed after single oral administration in humans with an absolute bioavailability of 48%. The incomplete bioavailability is due to both incomplete absorption and hepatic first-pass effect. Following multiple-dose administration of 200 mg three times daily, the accumulation is predictable, indicating time-independent pharmacokinetics. In addition, dexloxiglumide pharmacokinetics are dose-independent after both single and repeated oral three-times-daily doses in the dose range 100-400 mg. Dexloxiglumide absorption window extends from the jejunum to the colon and the drug is a substrate and a weak inhibitor of P-glycoprotein and multidrug resistance protein 1. Plasma protein binding of dexloxiglumide is 94-98% and the drug has a moderate to low volume of distribution in humans. Systemic clearance of dexloxiglumide is moderate and cytochrome P450 (CYP) 3A4/5 and CYP2C9 have been implicated in the metabolism of dexloxiglumide to produce O-demethyl dexloxi-glumide. This metabolite is further oxidised to dexloxiglumide carboxylic acid. These two major metabolites (accounting for up to 50% of dexloxiglumide elimination) have been identified. However, in human plasma the unchanged drug represents the major (up to 91%) component of the metabolic profile. The parent drug is believed to be the major contributor to the efficacy of the compound, since its major metabolites are pharmacologically inactive. In addition, the drug is a single isomer chiral drug (eutomer) that does not undergo chiral inversion into its pharmacologically inactive enantiomer (distomer). After oral administration of (14)C-dexloxiglumide, radioactivity is mainly excreted in bile and in faeces (74% of dose) with much lower excretion in urine (20% of dose). Renal excretion of unchanged dexloxiglumide is low (7% of dose in urine and faeces, 1% of dose in urine) and is dose-independent in the dose range 100-400 mg. As the kidney is a minor contributor to the elimination of dexloxiglumide and/or its metabolites in humans, the pharmacokinetics of the drug should not be affected in patients with renal insufficiency. The pharmacokinetics of dexloxiglumide are also not affected by age, sex and administration with a high-fat breakfast. Mild and moderate liver impairment do not affect the pharmacokinetics of dexloxiglumide but severe liver impairment causes increases in systemic exposure to dexloxiglumide and O-demethyl dexloxiglumide. Thus, the drug should be prescribed with caution in patients with severe hepatic impairment even though no dose adjustment is warranted. The results of different drug interaction studies have indicated that no clinically relevant metabolic and concomitant drug-drug interactions are expected during the clinical use of dexloxiglumide.