Simultaneous determination of niacin and its metabolites--nicotinamide, nicotinuric acid and N-methyl-2-pyridone-5-carboxamide--in human plasma by LC-MS/MS and its application to a human pharmacokinetic study

Identifying novel metabolites in children with attention-deficit hyperactivity disorder through metabolome profiling

Metabolomics research offers promising potential for identifying key metabolites and exploring the pathophysiological underpinnings of attention-deficit hyperactivity disorder (ADHD). However, serum metabolomics in ADHD remains largely uncharted. Our study aimed to search for metabolomic biomarkers in children with ADHD. 70 drug-naïve children diagnosed with ADHD according to DSM-5 criteria and 70 sex-, age-, IQ-matched healthy controls were recruited from the National Taiwan University Hospital. All participants were assessed for clinical and ADHD symptoms using the Clinical Global Impression Severity (CGI-S) and ADHD Rating Scale-IV (ADHDRS-IV), respectively. Serum-based metabolomic profiles were obtained through liquid chromatography-mass spectrometry. We performed the Wilcoxon test for univariate analysis, the orthogonal partial least squares discriminant analysis (OPLS-DA) for multivariate analysis, and Spearman correlation analyses for the associations between identified metabolites and clinical and ADHD measures. In our study, 156 metabolites were identified in peripheral blood samples using an untargeted metabolomics approach, among which cholic acid, homoveratric acid, inosine, and nicotinuric acid were significantly different between ADHD and controls. Children with ADHD had upregulated cholic acid and homoveratric acid levels and downregulated inosine and nicotinuric acid levels compared to controls. Notably, the upregulated metabolites positively correlated, and the downregulated metabolites negatively correlated with CGI-S and ADHDRS-IV scores. These metabolites and their mechanisms suggested that the pathophysiology of ADHD might involve connections between the gut-brain axis, oxidative stress, dopaminergic pathway, and purine salvage pathway. Our findings of four novel metabolite-behavior relationships in children with ADHD enhanced our understanding of the potential pathways underlying the pathophysiological mechanisms of ADHD.

Disordered Gut Microbiome and Alterations in Metabolic Patterns Are Associated With Hypertensive Left Ventricular Hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH) is most common when driven by hypertension, and it is a strong independent risk factor for adverse cardiovascular events and death. Some animal models support a role for gut microbiota and metabolites in the development of LVH, but cohort studies confirming these findings in populations are lacking.

METHODS AND RESULTS

We investigated the alterations of gut microbiota and metabolites in 30 patients with hypertension, 30 patients with hypertensive LVH, and 30 matched controls on the basis of 16S rDNA and metabolomic analyses. Thirty stool and 90 serum samples were collected in fasting conditions. ANOVA/Kruskal-Wallis/Pearson's χ2/Fisher's exact test and Bonferroni's correction were used (P<0.0167) for comparison among the 3 groups. A regression analysis and subgroup analysis were performed between gut microbiota and left ventricular mass index (LVMI) and metabolites and LVMI, respectively. Spearman correlation analysis was performed between metabolites and flora and metabolites and LVMI. We observed LVH-enriched Faecalitalea (β=6758.55 [95% CI, 2080.92-11436.18]; P=0.009), Turicibacter (β=8424.76 [95% CI, 2494.05-14355.47]; P=0.01), Ruminococcus torques group (β=840.88 [95% CI, 223.1-1458.67]; P=0.013), and Erysipelotrichaceae UCG-003 (β=856.37 [95% CI, 182.76-1529.98]; P=0.019) were positively correlated with LVMI. A total of 1141 (in sera) and 2657 (in feces) metabolites were identified. There was a sex-specific association between metabolites and LVMI. Significant changes in metabolic pathways in LVH were also observed, especially bile acid and lipid metabolism pathways.

CONCLUSIONS

Our study demonstrated the disordered gut microbiota and microbial metabolite profiles in LVH. This highlights the roles of gut bacteria and metabolite in this disease and could lead to new intervention, diagnostic, or management paradigms for LVH.

REGISTRATION

URL: https://www.chictr.org.cn; Unique Identifier: ChiCTR2200055603.

Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns

Recent research has unveiled an expansive role of NAD+ in cellular energy generation, redox reactions, and as a substrate or cosubstrate in signaling pathways that regulate health span and aging. This review provides a critical appraisal of the clinical pharmacology and the preclinical and clinical evidence for therapeutic effects of NAD+ precursors for age-related conditions, with a particular focus on cardiometabolic disorders, and discusses gaps in current knowledge. NAD+ levels decrease throughout life; age-related decline in NAD+ bioavailability has been postulated to be a contributor to many age-related diseases. Raising NAD+ levels in model organisms by administration of NAD+ precursors improves glucose and lipid metabolism; attenuates diet-induced weight gain, diabetes, diabetic kidney disease, and hepatic steatosis; reduces endothelial dysfunction; protects heart from ischemic injury; improves left ventricular function in models of heart failure; attenuates cerebrovascular and neurodegenerative disorders; and increases health span. Early human studies show that NAD+ levels can be raised safely in blood and some tissues by oral NAD+ precursors and suggest benefit in preventing nonmelanotic skin cancer, modestly reducing blood pressure and improving lipid profile in older adults with obesity or overweight; preventing kidney injury in at-risk patients; and suppressing inflammation in Parkinson disease and SARS-CoV-2 infection. Clinical pharmacology, metabolism, and therapeutic mechanisms of NAD+ precursors remain incompletely understood. We suggest that these early findings provide the rationale for adequately powered randomized trials to evaluate the efficacy of NAD+ augmentation as a therapeutic strategy to prevent and treat metabolic disorders and age-related conditions.

Defining NAD(P)(H) Catabolism

Dietary vitamin B3 components, such as nicotinamide and nicotinic acid, are precursors to the ubiquitous redox cofactor nicotinamide adenine dinucleotide (NAD⁺). NAD⁺ levels are thought to decline with age and disease. While the drivers of this decline remain under intense investigation, strategies have emerged seeking to functionally maintain NAD⁺ levels through supplementation with NAD⁺ biosynthetic intermediates. These include marketed products, such as nicotinamide riboside (NR) and its phosphorylated form (NMN). More recent developments have shown that NRH (the reduced form of NR) and its phosphorylated form NMNH also increases NAD⁺ levels upon administration, although they initially generate NADH (the reduced form of NAD⁺). Other means to increase the combined levels of NAD⁺ and NADH, NAD(H), include the inhibition of NAD⁺-consuming enzymes or activation of biosynthetic pathways. Multiple studies have shown that supplementation with an NAD(H) precursor changes the profile of NAD(H) catabolism. Yet, the pharmacological significance of NAD(H) catabolites is rarely considered although the distribution and abundance of these catabolites differ depending on the NAD(H) precursor used, the species in which the study is conducted, and the tissues used for the quantification. Significantly, some of these metabolites have emerged as biomarkers in physiological disorders and might not be innocuous. Herein, we review the known and emerging catabolites of the NAD(H) metabolome and highlight their biochemical and physiological function as well as key chemical and biochemical reactions leading to their formation. Furthermore, we emphasize the need for analytical methods that inform on the full NAD(H) metabolome since the relative abundance of NAD(H) catabolites informs how NAD(H) precursors are used, recycled, and eliminated.

What If Not All Metabolites from the Uremic Toxin Generating Pathways Are Toxic? A Hypothesis

The topic of uremic toxicity has received broad attention from the nephrological community over the past few decades. An aspect that is much less often considered is the possibility that the metabolic pathways that generate uremic toxins also may produce molecules that benefit body functions. Here, we discuss this dualism based on the example of tryptophan-derived metabolites, which comprise elements that are mainly toxic, such as indoxyl sulfate, kynurenine and kynurenic acid, but also beneficial compounds, such as indole, melatonin and indole-3-propionic acid, and ambivalent (beneficial for some aspects and harmful for others) compounds such as serotonin. This dualism can also be perceived at the level of the main receptor of the tryptophan-derived metabolites, the aryl hydrocarbon receptor (AHR), which has also been linked to both harm and benefit. We hypothesize that these beneficial effects are the reason why uremic toxin generation remained preserved throughout evolution. This duality is also not unique for the tryptophan-derived metabolites, and in this broader context we discuss the remote sensing and signaling theory (RSST). The RSST proposes that transporters (e.g., organic anion transporter 1—OAT1; ATP-binding cassette transporter G—ABCG2) and drug metabolizing enzymes form a large network of proteins interacting to promote small molecule remote communication at the inter-organ (e.g., gut–liver–heart–brain–kidney) and inter-organismal (e.g., gut microbe–host) levels. These small molecules include gut microbe-derived uremic toxins as well as beneficial molecules such as those discussed here. We emphasize that this positive side of uremic metabolite production needs more attention, and that this dualism especially needs to be considered when assessing and conceiving of therapeutic interventions. These homeostatic considerations are central to the RSST and suggest that interventions be aimed at preserving or restoring the balance between positive and negative components rather than eliminating them all without distinction.

In Vitro and In Vivo Studies of Anti-Lung Cancer Activity of Artemesia judaica L. Crude Extract Combined with LC-MS/MS Metabolic Profiling, Docking Simulation and HPLC-DAD Quantification

Artemisia judaica L. (Family: Asteraceae) exhibited antioxidant, anti-inflammatory, and antiapoptotic effects. The in vitro cytotoxic activity of A. judaica ethanolic extract was screened against a panel of cancer cell lines. The results revealed its cytotoxic activity against a lung cancer (A549) cell line with a promising IC50 of 14.2 μg/mL compared to doxorubicin as a standard. This was confirmed through the downregulation of antiapoptotic genes, the upregulation of proapoptotic genes, and the cell cycle arrest at the G2/M phase. Further in vivo study showed that a solid tumor mass was significantly reduced, with a tumor inhibition ratio of 54% relative to doxorubicin therapy in a Xenograft model. From a chemical point of view, various classes of natural products have been identified by liquid chromatography combined with tandem mass spectrometry (LC-MS/MS). The docking study of the detected metabolites approved their cytotoxic activity through their virtual binding affinity towards the cyclin-dependent kinase 2 (CDK-2) and epidermal growth factor receptor (EGFR) active sites. Finally, A. judaica is a fruitful source of polyphenols that are well-known for their antioxidant and cytotoxic activities. As such, the previously reported polyphenols with anti-lung cancer activity were quantified by high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD). Rutin, quercetin, kaempferol, and apigenin were detected at concentrations of 6 mg/gm, 0.4 mg/gm, 0.36 mg/gm, and 3.9 mg/gm of plant dry extract, respectively. It is worth noting that kaempferol and rutin are reported for the first time. Herein, A. judaica L. may serve as an adjuvant therapy or a promising source of leading structures in drug discovery for lung cancer treatment.

A validated liquid chromatography-tandem mass spectrometric method for the determination of co-administered ranitidine and metronidazole in plasma of human volunteers

This work describes the development, optimization and validation of a liquid chromatography-tandem mass spectrometric method (LC-MS/MS) for the simultaneous analysis of co-administered ranitidine (RAN) and metronidazole (MET) in plasma of healthy human volunteers. A simple protein precipitation procedure using 1 mL acetonitrile was applied to extract both drugs and metoclopramide as an internal standard (IS) from plasma. The chromatographic separation was achieved on a C₁₈ column with isocratic elution of the mobile phase consisting of acetonitrile and 0.1% formic acid (90 : 10, v/v) at a flow rate of 0.35 mL min^-1. The positive ionization mode was used for detecting the ions, by observing the pairs of transition m/z 314.82 < 176.06 for RAN, m/z 172.03 < 127.95 for MET and m/z 299.86 < 277.10 for IS. The linearity range was from 5-600 ng mL^-1 for RAN and 2-40 μg mL^-1 for MET. The method was found to be sensitive and accurate with good simple extraction recovery and matrix effect, according to FDA guidelines for bioanalytical methods. The developed method could be applied for further bioavailability studies that could be useful in therapeutic drug monitoring.

Recent trends in analytical methods for water-soluble vitamins

In this review, recent advances in the analysis of water-soluble vitamins (WSVs) have been reported considering the advantages and disadvantages of various extraction, separation and detection techniques, commonly used for their quantification. Acid hydrolysis, enzyme treatment, SPE based methods and some other extraction methods have been discussed. Particular attention has been devoted to the analytical techniques based on liquid chromatography and electrophoresis. Furthermore, suitability and selectivity of hydrophilic interaction liquid chromatography (HILIC) for WSVs has been discussed in detail. Problems related to these techniques and their possible solutions have also been considered. Special focus has been given to the applications of liquid chromatography (since 2014-2019) for the simultaneous analysis of WSVs and their homologous in complex food samples.

Effects of supplementing rumen-protected niacin on fiber composition and metabolism of skeletal muscle in dairy cows during early lactation

Nicotinic acid (NA) has been shown to induce muscle fiber switching toward oxidative type I fibers and a muscle metabolic phenotype that favors fatty acid (FA) utilization in growing rats, pigs, and lambs. The hypothesis of the present study was that supplementation of NA in cows during the periparturient phase also induces muscle fiber switching from type II to type I fibers in skeletal muscle and increases the capacity of the muscle to use free FA, which may help to reduce nonesterified fatty acid (NEFA) flow to the liver, liver triglyceride (TG) accumulation, and ketogenesis. Thirty multiparous Holstein dairy cows were allocated to 2 groups and fed a total mixed ration without (control group) or with ∼55 g of rumen-protected NA per cow per day (NA group) from 21 d before expected calving until 3 wk postpartum (p.p.). Blood samples were collected on d -21, -14, -7, 7, 14, 21, 35, and 63 relative to parturition for analysis of TG, NEFA, and β-hydroxybutyrate. Muscle and liver biopsies were collected on d 7 and 21 for gene expression analysis and to determine muscle fiber composition in the musculus semitendinosus, semimembranosus, and longissimus lumborum by immunohistochemistry, and liver TG concentrations. Supplementation of NA did not affect the proportions of type I (oxidative) or the type II:type I ratio in the 3 muscles considered. A slight shift from glycolytic IIx fibers toward oxidative-glycolytic fast-twitch IIa fibers was found in the semitendinosus, and a tendency in the longissimus lumborum, but not in the semimembranosus. The transcript levels of the genes encoding the muscle fiber type isoforms and involved in FA uptake and oxidation, carnitine transport, tricarboxylic acid cycle, oxidative phosphorylation, and glucose utilization were largely unaffected by NA supplementation in all 3 muscles. Supplementation of NA had no effect on plasma TG and NEFA concentrations, liver TG concentrations, and hepatic expression of genes involved in hepatic FA utilization and lipogenesis. However, it reduced plasma β-hydroxybutyrate concentrations in wk 2 and 3 p.p. by 18 and 26% and reduced hepatic gene expression of fibroblast growth factor 21, a stress hormone involved in the regulation of ketogenesis, by 74 and 56%. In conclusion, a high dosage of rumen-protected NA reduced plasma β-hydroxybutyrate concentrations in cows during early lactation, but failed to cause an alteration in muscle fiber composition and muscle metabolic phenotype.

Resolution and quantification challenge of modern chemometric models in the determination of anti-migraine tablets containing ergotamine, caffeine, acetaminophen, and metoclopramide

Unique mixture of ergotamine (ERG), metoclopramide (MET), caffeine (CAF) and the study presents a comparison between five multivariate models in the determination of the paracetamol (PAR) in laboratory mixtures and in pharmaceutical formulations.

N-methyl-2-pyridone-5-carboxamide (2PY)-Major Metabolite of Nicotinamide: An Update on an Old Uremic Toxin

N-methyl-2-pyridone-5-carboxamide (2PY, a major metabolite of nicotinamide, NAM) was recently identified as a uremic toxin. Recent interventional trials using NAM to treat high levels of phosphorus in end-stage renal disease have highlighted new potential uremic toxicities of 2PY. In the context of uremia, the accumulation of 2PY could be harmful-perhaps by inhibiting poly (ADP-ribose) polymerase-1 activity. Here, we review recently published data on 2PY's metabolism and toxicological profile.

Quantification of Niacin and Its Metabolite Nicotinuric Acid in Human Plasma by LC-MS/MS: Application to a Clinical Trial of a Fixed Dose Combination Tablet of Niacin Extended-Release/Simvastatin (500 mg/10 mg) in Healthy Chinese Volunteers

Our paper aimed to develop rapid, sensitive, and specific LC-MS/MS method for the quantification of niacin (NA) and its metabolite nicotinuric acid (NUA) in human plasma. Following protein precipitation with acetonitrile, the NA, NUA, and internal standard (5-fluorouracil) were separated on a Zorbax 300SB-C8 column (250 mm × 4.6 mm, 5 μm) with a mobile phase consisting of methanol-2 mM ammonium acetate (3 : 97, v/v) at a flow rate of 1 mL/min (split 1 : 1). A tandem mass spectrometer equipped with electrospray ionization source was used as the detector and operated in negative ion mode. The linear concentration ranges of the calibration curves were 5-800 ng/mL for NA and NUA. The intra-assay RSD for quality control (QC) samples were from 5.0% to 8.7% for NA, and 5.5% to 7.6% for NUA. The interassay RSD for QC samples were from 2.8% to 9.4% for NA, and 3.7% to 5.8% for NUA. The relative errors for QC samples were from -2.2% to 2.3% for NA, and -0.6% to 3.2% for NUA. The method was successfully applied to the investigation of the pharmacokinetic profiles of NA, NUA in human after single dose administration of Niacin extended-release/Simvastatin tablet (500 mg/10 mg).

Gender differences in pharmacokinetics of a combination tablet of niacin extended-release/simvastatin in healthy Chinese volunteers

The gender differences in pharmacokinetics of a combination tablet of niacin extended-release/simvastatin were evaluated in healthy Chinese volunteers. Thirty-six healthy male and female volunteers were enrolled in the study receiving a single oral dose of niacin extended-release/simvastatin 1,000/20 mg. The results indicated that the systemic exposure of simvastatin hydroxy acid and the total urine excretion of niacin were significantly higher for females compared with those for males, and the T max of niacin in plasma was significantly shorter for males than that for females. There were no significant differences in the systemic exposure of simvastatin, niacin, and NUA in plasma between males and females.

Nicotinuric acid: a potential marker of metabolic syndrome through a metabolomics-based approach

OBJECTIVE

Metabolic syndrome is a multiplex disorder and puts patients on the road to type 2 diabetes and atherosclerotic cardiovascular diseases. However, a surrogate biomarker in plasma or urine in fully reflecting features of metabolic syndrome has not been explored.

RESEARCH DESIGN AND METHODS

Urine metabolomics has potential utility in metabolic profiling because urine metabolites analysis reflects global outflux of metabolic change. Accordingly, we collected data on subjects (n = 99) with overweight, dyslipidemia, hypertension or impaired glucose tolerance and took a metabolomics approach to analyze the metabolites of urine revealed in metabolic syndrome by high-performance liquid chromatography-time-of-flight mass spectrometry and elicit potential biomarkers to picture metabolic syndrome.

RESULTS

Our results revealed that the urine nicotinuric acid value of subjects with diabetes (HbA1c ≥ 6.5% or those receiving diabetes medications) (n = 25) was higher than subjects without diabetes (n = 37) (221 ± 31 vs. 152 ± 13 × 10(3) mAU, P = 0.0268). Moreover, urinary nicotinuric acid level was positively correlated with body mass index, blood pressure, total cholesterol, low-density lipoprotein cholesterol, triacylglycerol and high sensitivity C-reactive protein, but negatively correlated with high-density lipoprotein cholesterol.

CONCLUSIONS

This is the first study, to our knowledge, to propose that nicotinuric acid represents an important pathogenic mechanism in process from metabolic syndrome to diabetes and atherosclerotic cardiovascular disease.

Simultaneous quantification of niacin and its three main metabolites in human plasma by LC-MS/MS

A sensitive and specific LC-MS/MS method for the simultaneous quantification of niacin (NA) and its three main metabolites nicotinamide (NAM), nicotinuric acid (NUA) and N-methyl-2-pyridone-5-carboxamide (2-Pyr) in human plasma has been developed and validated. Plasma samples (200 μL) were prepared by deproteinization with acetonitrile (500 μL), then the supernatant after centrifugation was evaporated and reconstituted. Chromatography was performed on a phenomenex synergi hydro-RP column with an isocratic elution of methanol-0.1% formic acid (5:95, v/v). The full separation of all analytes was achieved within 9 min. Multiple-reaction monitoring (MRM) using the fragmentation transitions of m/z 124.1 → 80.1, 123.1 → 80.0, 181.0 → 79.0 and 153.1 → 110.2 in positive electrospray ionization (ESI) mode was performed to quantify NA, NAM, NUA and 2-Pyr, respectively. The calibration curves were linear over the concentration range of 2.0-3000 ng/mL for NA and NUA, 10.0-1600 ng/mL for NAM and 50.0-5000 ng/mL for 2-Pyr. This method has been validated in accordance with the US FDA guidelines for bioanalytical method development and applied to the determination of NA and its three main metabolites in Chinese subjects following a single oral dose of niacin extended-release and simvastatin 1000 mg/20mg. In particular, because of the endogenous NAM and 2-Pyr in human plasma, the concentrations of NAM and 2-Pyr in human plasma after dosing were determined by subtracting blank values of them.

Voltammetric and amperometric determination of metoclopramide on boron-doped diamond film electrode

New methods for the determination of metoclopramide, antiemetic and gastroprokinetic pharmaceutical, were developed, using differential pulse voltammetry (DPV) and flow injection analysis (FIA) with amperometric detection on a boron-doped diamond film electrode. Electrode pretreatment necessary to ensure the stable results was investigated and it was found, that while DPV requires frequent electrode cleaning, FIA with a sufficiently high flow rate can maintain a stable signal with no signs of electrode passivation. The calculated quantification limits of the DPV and FIA with amperometric detection were 0.13 μmol L−1 and 0.015 mmol L−1, respectively. The applicability of the new methods was verified by the determination of metoclopramide in a pharmaceutical preparation. FIA with amperometic detection proved to be sensitive, accurate and, due to the resistance of the electrode to the passivation, also simple to handle.

Simultaneous determination of atorvastatin and niacin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study

A rapid, simple, sensitive and selective LC-MS/MS method has been developed and validated for quantification of the atorvastatin (AT) and niacin (NA) in 250 μL human plasma. The analytical procedure involves a liquid-liquid extraction method using nevirapine as an internal standard (IS). The chromatographic separation was achieved on a Hypurity Advance (4.6 × 50 mm, 5 µm) column using a mobile phase consisting of 0.1% formic acid buffer-acetonitrile (20:80, v/v) at flow rate of 0.8 mL/min. The API-4000 LC-MS/MS was operated in the multiple-reaction monitoring mode using electrospray ionization. The total run time of analysis was 3 min and elution of AT, NA and IS occurred at 1.06, 1.84 and 0.92 min, respectively. A detailed validation of the method was performed as per the US Food and Drug Administration guidelines and the standard curves found to be linear in the range of 0.10-30.0 ng/mL for AT and 20.2-6026 ng/mL for NA, with a coefficient of correlation of ≥ 0.99 for both the compounds. AT and NA were found to be stable in a battery of stability studies, viz. bench-top, autosampler, re-injection, wet-extract and repeated freeze-thaw cycles. The developed assay method was successfully applied to a pharmacokinetic study in humans.

Simultaneous determination of simvastatin, lovastatin and niacin in human plasma by LC-MS/MS and its application to a human pharmacokinetic study

A simple, sensitive and specific LC-MS/MS method for simultaneous determination of simvastatin (SV), lovastatin (LV) and niacin (NIA) in human plasma was developed and validated on API-4000 in positive ion mode. Nevirapine was used as internal standard (IS). The assay procedure involved a simple one-step liquid-liquid extraction of SV, LV, NIA and the IS from plasma into ethyl acetate. Separation of SV, LV, NIA and the IS was achieved on an Alltima C₁₈ column with a mobile phase consisting of 5 mm ammonium acetate (pH 4.5) and acetonitrile (20:80, v/v) pumped at a flow rate of 1 mL/min. Nominal retention times obtained for SV, LV, NIA and IS were 2.12, 1.67, 0.50 and 0.65 min, respectively. The lower limits of quantification (LLOQ) for SV, LV and NIA were 0.10, 0.10 and 25.2 ng/mL, respectively. The response function was established for the range of concentrations 0.10-101 ng/mL for SV and LV, and 25.2-5020 ng/mL for NIA, with a coefficient of correlation of >0.99 for all the compounds. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The proposed method was found to be applicable to clinical studies.

Niacin and its metabolites: role of LC-MS/MS bioanalytical methods and update on clinical pharmacology. An overview

Niacin (nicotinic acid), although an old drug, has seen a sudden surge in popularity for treatment of lipid disorders and other associated clinical conditions for the prevention of cardiovascular risk. Also, there has been considerable interest in clarifying the role of metabolic pathways of niacin in explaining the tolerability/adverse affect profile of the agent. Hence, it has become very important to quantify/monitor the levels of niacin and its metabolites in various clinical studies. This review describes the recent trends in the bioanalysis of niacin and its metabolites, where HPLC and LC-MS/MS assays have been successfully employed to measure the drug levels in various biological matrices arising from preclinical and clinical studies. In addition, this review encompass various considerations such as internal standard selection, extraction schemes, matrix effect, selectivity evaluation and optimization of mass spectral conditions to enable the development of sound bioanalytical methods for niacin alone or niacin along with its metabolites. Recent updates pertaining to the clinical pharmacology of niacin and ongoing debate for the clarification of adverse effects are also provided. Overall LC-MS/MS methods have proven to be choice of bioanalytical method for the quantification of niacin alone or with its metabolites in both preclinical and clinical studies.