Serum metabolite profiling of ST-segment elevation myocardial infarction using liquid chromatography quadrupole time-of-flight mass spectrometry.

ST segment elevation myocardial infarction (STEMI) is one of the most common global causes of cardiovascular disease-related death. Several metabolites may change during STEMI. Hence, analysis of metabolites in body fluid may be considered as a rapid and accurate test for initial diagnosis. This study has therefore attempted to determine the variation in metabolites identified in the serum of STEMI patients (n = 20) and 15 controls. Samples collected from the Cardiology Department, Medical Faculty, Ataturk University, were extracted by liquid-liquid extraction and analysed using liquid chromatography quadrupole time-of-flight mass spectrometry. The METLIN database was used for the identification and characterization of metabolites. According to Q-TOF/MS measurements, 231 m/z values, which were significantly different between groups (P < 0.01 and fold analysis >1.5) were detected. Metabolite identification was achieved via the Human Metabolome database. According to the multivariate data analysis, leucine, isoleucine, l-proline, l-alanine, glycine, fumaric acid, citrate, succinate and carnitine levels were decreased, whereas levels of propionic acid, maleic acid, butyric acid, urea, oleic acid, palmitic acid, lysoPC [18:2(9Z)], glycerol, phoshpatidylethanolamine, caffeine and l-lactic acid were increased in STEMI patients compared with controls. In conclusion, malonic acid, maleic acid, fumaric acid and palmitic acid can be used as biomarkers for early risk stratification of patients with STEMI.

Serum metabolites are associated with all-cause mortality in chronic kidney disease.

Chronic kidney disease (CKD) involves significant metabolic abnormalities and has a high mortality rate. Because the levels of serum metabolites in patients with CKD might provide insight into subclinical disease states and risk for future mortality, we determined which serum metabolites reproducibly associate with mortality in CKD using a discovery and replication design. Metabolite levels were quantified via untargeted liquid chromatography and mass spectroscopy from serum samples of 299 patients with CKD in the Modification of Diet in Renal Disease (MDRD) study as a discovery cohort. Six among 622 metabolites were significantly associated with mortality over a median follow-up of 17 years after adjustment for demographic and clinical covariates, including urine protein and measured glomerular filtration rate. We then replicated associations with mortality in 963 patients with CKD from the African American Study of Kidney Disease and Hypertension (AASK) cohort over a median follow-up of ten years. Three of the six metabolites identified in the MDRD cohort replicated in the AASK cohort: fumarate, allantoin, and ribonate, belonging to energy, nucleotide, and carbohydrate pathways, respectively. Point estimates were similar in both studies and in meta-analysis (adjusted hazard ratios 1.63, 1.59, and 1.61, respectively, per doubling of the metabolite). Thus, selected serum metabolites were reproducibly associated with long-term mortality in CKD beyond markers of kidney function in two well characterized cohorts, providing targets for investigation.

Circulating tricarboxylic acid cycle metabolite levels in citrin-deficient children with metabolic adaptation, with and without sodium pyruvate treatment.

Citrin deficiency causes adult-onset type II citrullinemia (CTLN-2), which later manifests as severe liver steatosis and life-threatening encephalopathy. Long-standing energy deficit of the liver and brain may predispose ones to CTLN-2. Here, we compared the energy-driving tricarboxylic acid (TCA) cycle and fatty acid ß-oxidation cycle between 22 citrin-deficient children (age, 3-13years) with normal liver functions and 37 healthy controls (age, 5-13years). TCA cycle analysis showed that basal plasma citrate and α-ketoglutarate levels were significantly higher in the affected than the control group (p<0.01). Conversely, basal plasma fumarate and malate levels were significantly lower than those for the control (p<0.001). The plasma level of 3-OH-butyrate derived from fatty acid ß-oxidation was significantly higher in the affected group (p<0.01). Ten patients underwent sodium pyruvate therapy. However, this therapy did not correct or attenuate such deviations in both cycles. Sodium pyruvate therapy significantly increased fasting insulin secretion (p<0.01); the fasting sugar level remained unchanged. Our results suggest that citrin-deficient children show considerable deviations of TCA cycle metabolite profiles that are resistant to sodium pyruvate treatment. Thus, long-standing and considerable TCA cycle dysfunction might be a pivotal metabolic background of CTLN-2 development.

Development and validation of a HPLC-PDA bioanalytical method for the simultaneous estimation of Aliskiren and Amlodipine in human plasma.

A simple, unique and selective HPLC-PDA method was developed and validated for the simultaneous estimation of aliskiren (ALS) and amlodipine (AML) in human plasma. Extraction of the sample was accomplished by protein precipitation. Plasma proteins were precipitated by employing acetonitrile containing hydrochlorothiazide as internal standard. The compounds were analyzed by HPLC by using PDA detector on a Hibar C18 (250 × 4.6 mm) column with a mobile phase comprising acetonitrile and phosphate buffer (pH 4.2 and 25 mm; 60:40 v/v) with a flow rate of 0.8 mL/min. Different sample pretreatment techniques were evaluated but protein precipitation was found to be satisfactory, offering good recovery values of 97.11-98.45% for ALS and 97.5-99.12% for AML. The within-day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively, and for AML they were 97.27, 99.54 and 99.31% at 3.3, 8.8 and 17.6 ng/mL, respectively. The between-day precisions for ALS were 96.66, 99.16 and 99.41% at 90, 240 and 480 ng/mL, respectively and the between-day precisions for AML were 98.18, 99.20 and 99.40% at 3.3, 8.8 and 17.6 ng/mL, respectively. The limit of quantitation was 30 and 1.0 ng/mL for ALS and AML respectively. Different constituents of plasma proteins did not interfere with the absolute recovery of ALS and AML.

Analysis of Concentrations of Monomethyl Fumarate in Patients with Multiple Sclerosis: Result from Routine Health Care

BACKGROUND: Dimethyl fumarate is used to treat patients with relapsing-remitting multiple sclerosis. After ingestion, it is rapidly hydrolyzed to the active primary metabolite monomethyl fumarate. OBJECTIVE: The main objective of our study was to analyze serum concentrations of monomethyl fumarate during routine health care in patients with multiple sclerosis treated with a fixed dose of dimethyl fumarate. METHODS: In the pilot cross-sectional study, data from 42 patients treated with dimethyl fumarate at a dose of 240 mg twice daily were collected. Concentrations of the active metabolite monomethyl fumarate were determined at 1-8 h (median, 3 h) or 10-14 h (median, 13 h) after taking the dose. The relationship between monomethyl fumarate concentrations and absolute lymphocyte count was evaluated. RESULTS: Concentrations of monomethyl fumarate ranged from 2.5-3177.9 µg/L, with most concentrations being undetectable approximately 10 hours after administration. In the 1-8 h (median, 3 h) post-dose subgroup, the concentration/dose ratio ranged widely from 0.04-6.62. The median concentration of monomethyl fumarate in the group with the absolute lymphocyte count <0.8 x 10^9/l was more than four times higher than in the group with the absolute lymphocyte count ≥0.8 x 10^9/l (median 440.1 µg/L versus 98.4 µg/L). CONCLUSION: The wide interindividual variability in monomethyl fumarate pharmacokinetics could contribute to the differential response to dimethyl fumarate in multiple sclerosis patients. A nonsignificant but noticeable trend was observed in the relationship of higher serum monomethyl fumarate concentrations to absolute lymphocyte counts.

Determination of aliskiren in human serum quantities by HPLC-tandem mass spectrometry appropriate for pediatric trials.

The orally active direct renin inhibitor aliskiren is approved for the treatment of essential hypertension in adults. Analytical methods utilized in clinical studies on efficacy and safety have not been fully described in the literature but need a large sample volume ranging from 200 to 700 µL, rendering them unsuitable particularly for pediatric applications. In the assay presented only 100 µL of serum is needed for mixed-mode solid-phase extraction. The chromatographic separation was performed on Xselect(TM) C18 CSH columns with mobile phase consisting of methanol-water-formic acid (75:25:0.005, v/v/v) and a flow rate of 0.4 mL/min. Running in positive electrospray ionization and multiple reaction monitoring the mass spectrometer was set to analyze precursor ion 552.2 m/z [M + H](+) to product ion 436.2 m/z during a total run time of 5 min. The method covers a linear calibration range of 0.146-1200 ng/mL. Intra-run and inter-run precisions were 0.4-7.2 and 0.6-12.9%. Mean recovery was at least 89%. Selectivity, accuracy and stability results comply with current European Medicines Agency and Food and Drug Administration guidelines. This successfully validated LC-MS/MS method with a wide linear calibration range requiring small serum amounts is suitable for pharmacokinetic investigations of aliskiren in pediatrics, adults and the elderly.

Liquid chromatography-tandem mass spectrometric assay for aliskiren, a novel renin inhibitor in micro-volumes of human plasma: a pharmacokinetic application in healthy South Indian male subjects.

This paper describes a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry assay for the determination of aliskiren in human plasma using nevirapine as an internal standard. Analyte and the internal standard were extracted from 100 µL of human plasma via liquid-liquid extraction using tert-butyl methyl ether. The chromatographic separation was achieved on a C18 column using a mixture of acetonitrile and 0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.9 mL/min. The calibration curve obtained was linear (r(2) ≥ 0.99) over the concentration range of 0.10-1013 ng/mL. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. A run time of 2.2 min for each sample made it possible to analyze a greater number of samples in a short time, thus increasing the productivity. The proposed method was found to be applicable to clinical studies.

[Comparative efficacy of nitrofurans in children and adolescents with pyelonephritis in presence of crystalluria].

AIM: To evaluate the efficacy of nitrofurans in children and adolescents with pyelonephritis in the presence of crystalluria. SUBJECTS AND METHODS: The study included 50 patients aged 4-14 years with chronic pyelonephritis in the presence of dysmetabolism. The patients underwent general blood test, general urinalysis with an urocytogram, bacteriological examination of urine, biochemical test of serum (uric acid, calcium, phosphorus, magnesium, urea, and creatinine) and 24-hour urinary excretion (uric acid, oxalates, calcium, phosphorus, and magnesium) at hospital admission and over time. The treatment regimen for Group 1 patients after antibiotic therapy involved furamag, Group 2 received furagin. The drugs were used in a dosage of 2 mg/kg/day in 2 divided doses for 14 days. Complaints, major clinical manifestations, crystalluria patterns, and a number of laboratory findings were analyzed over time. RESULTS: The urinary sediment showed leukocyturia and bacteriuria in all the patients, oxaluria in 70% of the patients, uraturia in 10%, and mixed crystalluria in 20%. The main etiological agent of pyelonephritis was Escherichia coli (48.4%). Increased serum uric acid concentrations were revealed in 14% of the patients. Daily urine tests revealed hyperoxaluria, hyperuricosuria, and hypercalciuria in 86, 18, and 8% of the patients, respectively; urinary magnesium excretion was reduced in 86%. After treatment, Group 1 patients showed a more marked therapeutic effect in terms of a number of indicators (leukocyturia, crystalluria, uricosuria, magnesuria). CONCLUSION: The results of the study showed that the antibacterial therapy involving antibiotics and nitrofurans for an exacerbation of chronic pyelonephritis in the presence of crystalluria not only provides an anti-inflammatory effect, but also leads to reductions in the level of crystalluria and the urinary content of uric acid and calcium. There was a significantly marked reduction in crystalluria, serum uric acid, and urinary oxalates and calcium in the children taking furamag. Out of nitrofurans, furamag may be recommended as the drug of choice to treat urinary tract infections in the presence of crystalluria.

Spectrofluorimetric determination of aliskiren in tablets and spiked human plasma through derivatization with dansyl chloride.

A simple and sensitive method has been developed and validated for the determination of aliskiren (ALS) in its dosage forms and spiked plasma. The method was based on the reaction of the drug with dansyl chloride in the presence of bicarbonate solution of pH 10.5 to give a highly fluorescent derivative which was measured at 501 nm with excitition at 378 nm in dichloromethane. Different experimental parameters affecting the development of the method and stability were carefully studied and optimized. The calibration curves were linear over the concentration ranges of 100-700 and 50-150 ng/mL for standard solution and plasma, respectively. The limits of detection were 27.52 ng/mL in standard solution, 4.91 ng/mL in plasma. The developed method was successfully applied to the analysis the drug in the commercial tablets and spiked plasma samples. The mean recovery of ALS from tablets and plasma was 100.10 and 97.81%, respectively. A proposal of the reaction pathway was presented.

Intestinal OATP1A2 inhibition as a potential mechanism for the effect of grapefruit juice on aliskiren pharmacokinetics in healthy subjects.

PURPOSE: To conduct a mechanistic investigation of the interaction between aliskiren and grapefruit juice in healthy subjects. METHODS: Twenty-eight subjects received an oral dose of aliskiren 300 mg (highest recommended clinical dose) with 300 mL of either water or grapefruit juice in a two-way crossover design. Safety and pharmacokinetic analyses were performed. In vitro studies were performed in HEK293 cells to investigate the role of organic anion transporting polypeptide (OATP) transporter-mediated uptake of aliskiren. RESULTS: Co-administration of a single dose of aliskiren with grapefruit juice decreased the plasma concentration of aliskiren, with mean decreases in the AUC(inf), AUC(last), and C(max) of 38, 37, and 61%, respectively. The uptake of [¹4C]aliskiren into OATP2B1-expressing cells was essentially the same as that into control cells, and the inhibitor combination atorvastatin and rifamycin had no effect on [¹4C]aliskiren accumulation in either cell type. The uptake of [¹4C]aliskiren and [³H]fexofenadine was linear in OATP1A2-expressing cells and was reduced by naringin, with IC50 values of 75.5 ± 11.6 and 24.2 ± 2.0 µM, respectively. CONCLUSIONS: Grapefruit juice decreases exposure of aliskiren partially via inhibition of intestinal OATP1A2.

Orange and apple juice greatly reduce the plasma concentrations of the OATP2B1 substrate aliskiren.

AIM: The aim of this study was to investigate the effects of orange juice and apple juice on the pharmacokinetics and pharmacodynamics of aliskiren. METHODS: In a randomized crossover study, 12 healthy volunteers ingested 200 ml of orange juice, apple juice or water three times daily for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h and plasma renin activity up to 24 h. RESULTS: Orange and apple juice reduced aliskiren peak plasma concentrations by 80% (95% CI 63%, 89%, P < 0.001) and 84% (95% CI 72%, 91%, P < 0.001), and the area under the plasma aliskiren concentration-time curve (AUC) by 62% (95% CI 47%, 72%, P < 0.001) and 63% (95% CI 46%, 74%, P < 0.001), respectively, but had no significant effect on its elimination half-life or renal clearance. The decreases in aliskiren AUC by orange and apple juice correlated with aliskiren AUC during the water phase (r= 0.98, P < 0.001). Plasma renin activity was 87% and 67% higher at 24 h after aliskiren during the orange juice and apple juice phases, respectively, than during the water phase (P < 0.05). CONCLUSIONS: Orange juice and apple juice greatly reduce the plasma concentrations and renin-inhibiting effect of aliskiren, probably by inhibiting its OATP2B1-mediated influx in the small intestine. Concomitant intake of aliskiren with orange or apple juice is best avoided.

Effect of ABCB1 haplotypes on the pharmacokinetics and renin-inhibiting effect of aliskiren.

PURPOSE: This study aimed to investigate the possible effects of ABCB1 haplotypes on the pharmacokinetics and renin-inhibiting effect of aliskiren. METHODS: Eleven healthy volunteers homozygous for the ABCB1 c.1236C-c.2677G-c.3435C (CGC) haplotype and 11 homozygous for the c.1236T-c.2677T-c.3435T (TTT) haplotype ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h, its excretion into urine up to 12 h, and plasma renin activity up to 24 h. RESULTS: The ABCB1 haplotypes had no significant effect on the pharmacokinetics or renin-inhibiting effect of aliskiren. The geometric mean ratio (95% confidence interval) of aliskiren peak plasma concentration and area under the plasma concentration-time curve from 0 h to infinity in participants homozygous for the TTT haplotype to those in participants homozygous for the CGC haplotype were 1.14 (0.66, 1.96; P = 0.631) and 1.01 (0.58, 1.76; P = 0.960) respectively. CONCLUSIONS: These data suggest that the ABCB1 c.1236C-c.2677G-c.3435C and c.1236T-c.2677T-c.3435T haplotypes have no clinically meaningful effect on the pharmacokinetics of aliskiren.

Rifampicin reduces the plasma concentrations and the renin-inhibiting effect of aliskiren.

PURPOSE: This study aimed to investigate the effect of rifampicin, an inducer of CYP3A4 and P-glycoprotein, on the pharmacokinetics and pharmacodynamics of aliskiren, a renin inhibitor used in the treatment of hypertension. METHODS: In a randomized crossover study, 12 healthy volunteers took 600 mg rifampicin or placebo once daily for 5 days. On day 6, they ingested a single 150-mg dose of aliskiren. Plasma aliskiren concentrations were measured up to 72 h and urine concentrations up to 12 h; pharmacodynamic variables were measured up to 24 h. RESULTS: Rifampicin reduced the peak plasma aliskiren concentration (C(max)) by 39% (95% confidence interval 0.41, 0.90; P = 0.017) and the area under the plasma aliskiren concentration-time curve AUC(0-infinity) by 56% (95% confidence interval 0.35, 0.56; P < 0.001). Rifampicin had no significant effect on aliskiren elimination half-life (t(1/2)) or its renal clearance (Cl(renal)). Plasma renin activity 24 h after aliskiren intake was 61% higher during the rifampicin phase than during the placebo phase (P = 0.008). CONCLUSIONS: Rifampicin considerably reduces the plasma concentrations and the renin-inhibiting effect of aliskiren by decreasing its oral bioavailability.

First orally active DRI Aliskiren--a new prospect in management of hypertension and beyond.

Hypertension is a major public health problem and leading cause for diseases involving cardiovascular & renal system. It is fourth largest contributor for premature deaths in developed countries and seventh largest in developing world. The major pharmacological strategies currently utilized for hypertension management include volume control with diuretics, suppression of central and peripheral sympathetic nervous system activity, vasodilatation with ion channel manipulation and blockade of renin-angiotensin-aldosterone system. Activation of the renin-angiotensin-aldosterone system in the pathogenesis of cardiovascular diseases and renal disease is well established. It also has been established that inhibition of renin-angiotensin-aldosterone system, is an effective way to intervene with pathogenesis of these disorders. Therapies like beta blockers, renin inhibitors, angiotensin converting enzyme inhibitors, angiotensin receptor blockers and aldosterone inhibitors, that inhibit renin-angiotensin-aldosterone system have proven to be highly successful for treatment of hypertension & related cardiovascular diseases. Renin inhibitors block the renin-angiotensin-aldosterone system at its origin, and thus offer a new approach to pharmacotherapy of Hypertension. Aliskiren is the first in a new class of orally active, non-peptide, low molecular weight direct renin inhibitor available for clinical use and potential new approach to the blockade of the renin-angiotensin-aldosterone system. Studies in humans demonstrate to an effectual blood Pressure lowering effect of aliskiren with placebo like tolerability, when used as monotherapy or in combination with other agents and has the potential to be useful in this wide spectrum of conditions

Renal and hormonal responses to direct renin inhibition with aliskiren in healthy humans.

BACKGROUND: Pharmacological interruption of the renin-angiotensin system focuses on optimization of blockade. As a measure of intrarenal renin activity, we have examined renal plasma flow (RPF) responses in a standardized protocol. Compared with responses with angiotensin-converting enzyme inhibition (rise in RPF approximately 95 mL x min(-1) x 1.73 m(-2)), greater renal vasodilation with angiotensin receptor blockers (approximately 145 mL x min(-1) x 1.73 m(-2)) suggested more effective blockade. We predicted that blockade with the direct oral renin inhibitor aliskiren would produce renal vascular responses exceeding those induced by angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. METHODS AND RESULTS: Twenty healthy normotensive subjects were studied on a low-sodium (10 mmol/d) diet, receiving separate escalating doses of aliskiren. Six additional subjects received captopril 25 mg as a low-sodium comparison and also received aliskiren on a high-sodium (200 mmol/d) diet. RPF was measured by clearance of para-aminohippurate. Aliskiren induced a remarkable dose-related renal vasodilation in low-sodium balance. The RPF response was maximal at the 600-mg dose (197+/-27 mL x min(-1) x 1.73 m(-2)) and exceeded responses to captopril (92+/-20 mL x min(-1) x 1.73 m(-2); P<0.01). Furthermore, significant residual vasodilation was observed 48 hours after each dose (P<0.01). The RPF response on a high-sodium diet was also higher than expected (47+/-17 mL x min(-1) x 1.73 m(-2)). Plasma renin activity and angiotensin levels were reduced in a dose-related manner. As another functional index of the effect of aliskiren, we found significant natriuresis on both diets. CONCLUSIONS: Renal vasodilation in healthy people with the potent renin inhibitor aliskiren exceeded responses seen previously with angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. The effects were longer lasting and were associated with significant natriuresis. These results indicate that aliskiren may provide more complete and thus more effective blockade of the renin-angiotensin system.

Renin inhibition with aliskiren.

1. Initial attempts to inhibit renin in humans have faced numerous difficulties. Molecular modelling and X-ray crystallography of the active site of renin have led to the development of new orally active renin inhibitors, such as aliskiren. 2. Aliskiren has a low bioavailability (between 2.6 and 5.0%) compensated by its high potency to inhibit renin (IC50: 0.6 nmol/L) and a long plasma half-life (23-36 h), which makes it suitable for once-daily dosing. 3. The once-daily administration of aliskiren to hypertensive patients lowers BP as strongly as standard doses of established angiotensin II type 1 (AT1) receptor blockers (losartan, valsartan, irbesartan), hydrochlorothiazide, angiotensin converting enzyme inhibitors (ramipril and lisinopril) or long acting calcium channel blockers (amlodipine). In combination therapy, aliskiren further decreases blood pressure when combined with either hydrochlorothiazide, amlodipine, irbesartan or ramipril. 4. The biochemical consequences of renin inhibition differ from those of angiotensin I-converting enzyme (ACE) inhibition and Ang II antagonism, particularly in terms of angiotensin profiles and interactions with the bradykinin-nitric oxide-cyclic guanosine monophosphate pathway and possibly the (pro)renin receptor. 5. Blockade of the renin angiotensin system (RAS) with ACE inhibitors, AT1 receptor blockers or a combination of these drugs has become one of the most successful therapeutic approaches in medicine. However, it remains unclear how to optimize RAS blockade to maximize cardiovascular and renal benefits. In this context, renin inhibition to render the RAS fully quiescent is a new possibility requiring further study.

Pharmacokinetics, safety, and tolerability of the oral Renin inhibitor aliskiren in patients with hepatic impairment.

Aliskiren is the first in a new class of orally active, direct renin inhibitors for the treatment of hypertension. This open-label, nonrandomized, single-center, parallel-group study compared the pharmacokinetics and safety of a single 300-mg oral dose of aliskiren in patients with mild, moderate, or severe hepatic impairment to that in healthy subjects. When pooled across subgroups, there were no significant differences between patients with hepatic impairment and healthy subjects in aliskiren AUC(0-infinity) (ratio of geometric means, 1.12; 90% confidence interval, 0.85, 1.48) or Cmax (mean ratio, 1.19; 90% confidence interval, 0.84, 1.68), and there was no correlation between severity of hepatic impairment and either AUC(0-infinity) or Cmax. Aliskiren was well tolerated by healthy subjects and patients with hepatic impairment. In conclusion, hepatic impairment has no significant effect on the pharmacokinetics of aliskiren following single-dose administration, and dosage adjustment is unlikely to be needed in patients with liver disease.

Pharmacokinetics, safety, and tolerability of the novel oral direct renin inhibitor aliskiren in elderly healthy subjects.

This open-label, multicenter study compared the pharmacokinetics and safety of the oral direct renin inhibitor aliskiren in 29 elderly (>or=65 years) and 28 young (18-45 years) healthy subjects. Plasma drug concentrations were determined for up to 168 hours following a single 300-mg oral dose of aliskiren. In elderly compared with young subjects, AUC(0-infinity) was 57% higher (ratio of geometric means 1.57, 90% confidence interval: 1.19, 2.06; P = .008) and C(max) was 28% higher (1.28, 90% confidence interval: 0.91, 1.79; P=.233). Other parameters, including t(max) and Vd/F, were similar between age groups. No differences in aliskiren exposure were observed between subjects ages 65 to 74 years (n=16) and >or=75 years (n=13). Aliskiren was well tolerated by all age groups, including the very elderly. In conclusion, aliskiren exposure is modestly increased in elderly subjects. Based on its wide therapeutic index and shallow dose response for blood pressure lowering, no initial dose adjustment should be needed for elderly patients.

Bioanalysis of monomethyl fumarate in human plasma by a sensitive and rapid LC-MS/MS method and its pharmacokinetic application.

Dimethyl fumarate (DMF) is the methyl ester of fumaric acid, after oral administration completely converts to its active metabolite monomethyl fumarate (MMF). A simple, rapid and sensitive LC-MS/MS method was developed and validated for the quantification of MMF in human plasma. Monomethyl fumarate d3 was used as an internal standard (IS). The analyte and the IS were extracted from plasma using a selective solid phase extraction technique. The clean samples were chromatographed on a C18 column using formic acid and acetonitrile (25:75, v/v) as mobile phase. An API-4000 LC-MS/MS system equipped with turbo ion spray (TIS) source and operated in multiple reactions monitoring (MRM) mode was used for the study. The method was validated for linearity in the range of 5.03-2006.92ng/mL. Also, a number of stability tests were conducted to evaluate the stability of analyte, IS in plasma samples and in neat samples, the results comply with recent bioanalytical guidelines. A shortest run time helped us to analyze more than 300 samples in a day. The method was applied to a pharmacokinetic study in ten healthy male Indian subjects and the study data was authenticated by conducting incurred sample reanalysis (ISR).

A comparative pharmacokinetic and tolerability analysis of the novel orotic acid salt form of tenofovir disoproxil and the fumaric acid salt form in healthy subjects.

A novel orotic acid salt form of tenofovir disoproxil (DA-2802) was developed and is expected to replace the fumaric acid salt form. The pharmacokinetic (PK) characteristics and tolerability profiles of DA-2802 were compared to those of tenofovir disoproxil fumarate (TDF, Viread®) in healthy subjects. A randomized, open-label, single-dose study was conducted in 36 healthy subjects using a two-treatment, two-period, and two-sequence crossover design. Subjects received a single oral dose of 319 mg DA-2802 or 300 mg TDF, during each period, with a 7-day washout. Serial blood samples were collected pre-dosing and up to 72 hours post-dosing in each period, for determination of serum tenofovir concentration, which was measured by ultra-performance liquid chromatography-tandem mass spectrometry. A non-compartmental method was used to obtain PK parameters of tenofovir. For comparison between the two tenofovir disoproxil salts, the 90% confidence intervals (90% CIs) of geometric mean ratios of DA-2802 to TDF for the maximum concentration (Cmax) and the area under the concentration-time curve to the last quantifiable concentration (AUC0-t) were determined. The tolerability profiles of tenofovir were assessed by evaluation of adverse events and vital signs, physical examination, ECG, and clinical laboratory tests. The serum tenofovir concentration-time profiles of DA-2802 or TDF were comparable in 32 subjects who completed the study. In both profiles, a two-compartmental elimination with first-order elimination kinetics in the terminal phase was reported in a few subjects, showing a secondary peak in the initial phase of elimination. The geometric mean ratio (90% CI) of DA-2802 to TDF was 0.898 (0.815-0.990) for Cmax and 0.904 (0.836-0.978) for AUC0-t. There were no clinically significant findings in the tolerability assessments. DA-2802 showed comparable PK characteristics and tolerability profiles to TDF.