A modified high performance liquid chromatographic method for simultaneous quantification of skatole and indole in porcine plasma

A simplified high-performance liquid chromatography method to measure skatole and indole in porcine plasma without the use of acetonitrile was developed and validated in this study. The mobile phase consisted of water and methanol used in a gradient programme. Fluorescence detection was performed on the supernatant obtained from plasma after protein precipitation with 100% acetone. Limits of quantification were 0.5 ng∙ml-1 for skatole and 1.0 ng∙ml-1 for indole. Accuracy and precision had less than 12% deviation in the linear ranges (0.5–256 ng∙ml-1 and R2 = 0.9999 for skatole, 1.0–256 ng∙ml-1 and R2 = 0.9999 for indole). The correlation between plasma and serum concentrations was strong for skatole (slope = 1.01, R2 = 0.999) and moderate for indole (slope = 0.65, R2 = 0.95). Analysis of skatole in plasma was in good accordance with our previous acetonitrile-based method (slope = 0.91, R2 = 0.988). The proposed method is suited for rapid routine analysis because of its high selectivity, accuracy and precision. Furthermore, it needs only simple sample preparation and the use of methanol instead of acetonitrile in the mobile phase. This method is of practical use to researchers in the field of boar taint.

Challenges of developing and validating immunogenicity assays to support comparability studies for biosimilar drug development

Imminent patent expiry for a number of biological products currently on the market (many of which are blockbusters) has created an increasing opportunity for the development of biosimilars in the biotechnology industry. The key for successful biosimilar development is to demonstrate biosimilarity to the originator drug. In addition to demonstrating the similarity of physical and chemical properties between biosimilar and originator compounds, regulatory agencies require that immunogenicity be evaluated in comparative studies between biosimilar and originator drugs. Immunogenicity assays are generally non-quantitative (qualitative) and proving similarity/comparability based on qualitative assays can be very challenging. This review will discuss the challenges of developing and validating immunogenicity assays to support preclinical and clinical comparative studies for biosimilar drug development as well as the challenges in association with the interpretation of the data.

Validation and verification of measurement methods in clinical chemistry

The present overview of validation and verification procedures in clinical chemistry focuses on the use of harmonized concepts and nomenclature, fitness-for-purpose evaluations and procedures for minimizing overall measurement and diagnostic uncertainty. The need for mutually accepted validation procedures in all fields of bioanalysis becomes obvious when they implement international accreditation and certification standards or their equivalents. The guide on bioanalytical method validation published by the US FDA in 2001 represents a sensible compromise between thoroughness and cost-effectiveness. Lacking comprehensive international agreements in the field, this document has also been successfully adapted in other fields of bioanalysis. European and international efforts aiming for consensus in the entire field of bioanalysis are currently being made. Manufacturers of highly automated in vitro diagnostic methods provide the majority of measurement methods used in unmodified in clinical chemistry. Validated by the manufacturers for their intended use and fitness-for-purpose, they need to be verified in the circumstances of the end-users. As yet, there is unfortunately no general agreement on the extent of the verification procedures needed.

A validated HPLC assay for the determination of R-(-)-gossypol in human plasma and its application in clinical pharmacokinetic studies

R-(-)-gossypol acetic acid (AT-101), a natural BH3 mimetic, is investigated in a Phase I/II clinical trial for the treatment of advanced solid tumor malignancies. Gossypol undergoes rapid degradation in solution phase, which causes major technical difficulty for its quantitation in plasma. We developed and validated a sensitive HPLC assay for pharmacokinetic evaluation of gossypol. Acetonitrile deproteinization method was chosen for sample preparation and Schiff's base derivative, R-(-)-gossypol-diamino-propanol (GDP), was used as internal standard. Chromatographic separation of gossypol in plasma was performed using a Zorbax Eclipse XDB column C(18) at 30 °C. The mobile phase consists of 10 mmol/L KH(2)PO(4) (pH 3.0) and acetonitrile (20:80) at 1.0 mL/min flow rate. Linearity ranged over 56-3585 ng/mL (R(2)=0.9997±0.0003, n=4), and the limit of detection was 28 ng/mL. The intra- and inter-assay precision was less than 13.7% and the bias ranged from -7.4 to 7.0%. The method was successfully applied to characterize the pharmacokinetics of AT-101 in a Phase I clinical trial. The validated assay is accurate, and sensitive with minimum loss and rapid analysis time and suitable for quantification of gossypol for pharmacokinetics evaluation.

A validated bioanalytical HPLC method for pharmacokinetic evaluation of 2-deoxyglucose in human plasma

2-Deoxyglucose (2-DG), an analog of glucose, is widely used to interfere with glycolysis in tumor cells and studied as a therapeutic approach in clinical trials. To evaluate the pharmacokinetics of 2-DG, we describe the development and validation of a sensitive HPLC fluorescent method for the quantitation of 2-DG in plasma. Plasma samples were deproteinized with methanol and the supernatant was dried at 45°C. The residues were dissolved in methanolic sodium acetate-boric acid solution. 2-DG and other monosaccharides were derivatized to 2-aminobenzoic acid derivatives in a single step in the presence of sodium cyanoborohydride at 80°C for 45 min. The analytes were separated on a YMC ODS C₁₈ reversed-phase column using gradient elution. The excitation and emission wavelengths were set at 360 and 425 nm. The 2-DG calibration curves were linear over the range of 0.63-300 µg/mL with a limit of detection of 0.5 µg/mL. The assay provided satisfactory intra-day and inter-day precision with RSD less than 9.8%, and the accuracy ranged from 86.8 to 110.0%. The HPLC method is reproducible and suitable for the quantitation of 2-DG in plasma. The method was successfully applied to characterize the pharmacokinetics profile of 2-DG in patients with advanced solid tumors.

Recommendations and requirements for the design of bioanalytical testing used in comparability studies for biosimilar drug development

With the imminent expiry of patents on a number of biological products on the market, the development of biosimilars (or 'follow-on biologics') creates an increasing opportunity in the biotechnology industry. Although general guidelines on the quality and safety of biological products also apply to biosimilars, there is a need to address specific requirements for developing biosimilar drugs. Since it is critical to show comparability of the biosimilar products to their reference (or innovator) products, developing the appropriate bioanalytical methods to support such preclinical and clinical comparability studies is of great importance. The present work recommends the requirements for the development and validation for both pharmacokinetic and immunogenicity assays to support the biosimilar drug development.

Insights in regulated bioanalysis of human insulin and insulin analogs by immunoanalytical methods

Despite the long and illustrious history of insulin and insulin analogs as important biotherapeutics, the regulated bioanalysis (in this article, regulated bioanalysis refers to the formalized process for generating bioanalytical data to support pharmacokinetic and toxicokinetic assessments intended for development of insulin and insulin analogs as biotherapeutics, as opposed to the analytical process used for measuring insulin as a biomarker) of these peptides remains a challenging endeavor for a number of reasons. Paramount is the fact that the therapeutic concentrations are often low in serum/plasma and not too dissimilar from the endogenous level, particularly in patients with insulin resistance, such as Type 2 diabetes mellitus. Accordingly, this perspective was written to provide helpful background information for the design and conduct of immunoassays to support regulated bioanalysis of insulin and insulin analogs. Specifically, it highlights the technical challenges for determination of insulin and insulin analogs by immunoanalytical methods that are intended to support evaluations of pharmacokinetics and toxicokinetics. In a broader sense, this perspective describes the general bioanalytical issues that are common to regulated bioanalysis of peptides and articulates some of the bioanalytical differences between conventional monoclonal antibodies and peptide therapeutics.

Case studies from the use of commercial biomarker/protein test kits

Large-molecule drugs (therapeutic proteins, peptides, various forms of antibodies) are more frequently being seen in drug-development pipelines, the majority of which are measured using immunochemical/ligand-binding techniques. The assays utilized for analysis of large-molecule drugs rely heavily upon the quality of the components (e.g., reference materials, antibodies) that are critical to the performance of the assays. Commercially available research-grade materials and kits offer a convenient and simple solution, but also present some unique challenges. This article will explore some examples of issues encountered while employing commercially available kits and reagents.

Liquid chromatography-tandem mass spectroscopic method for the determination of zerumbone in human plasma and its application to pharmacokinetics

A rapid, sensitive, specific and selective LC-MS/MS method for the determination of zerumbone (ZER) in human plasma using 2,4-diamino-6-(4-methoxyphenyl)-1,3,5-triazine (DMTZ) as an internal standard (IS) has been developed and validated. ZER was chromatographed on C8 column using a mobile phase of acetonitrile/water (80:20, v/v) at a flow rate of 0.25 ml min(-1) . Quantitation was achieved using ESI+ interface, employing multiple reaction monitoring (MRM) mode at m/z 219 > 81 and 218 > 134 for ZER and IS, respectively. The calibration standards were linear over a range of 5-3000 ng ml(-1) (r(2)=0.9994) with an LLOQ of 5 ng ml(-1) (RSD %; 11.4% and bias%; 9.5%). Intra- and inter-day precision of ZER assay ranged from 0.18 to 3.56% with accuracy (bias) that varied between -5.09 and 4.3%, demonstrating good precision and accuracy. Recoveries of ZER and the IS from human plasma were above 85%. The developed method was validated for the determination of ZER in rat plasma. Linearity, stability of ZER and the ME on rat plasma were discussed. The applicability of the developed method was demonstrated by measuring ZER in rat plasma samples following intravenous and intraperitoneal administration of ZER prepared in hydroxypropyl-β-cyclodextrin (HPβCD) and sodium carboxymethyl cellulose (CMC), respectively, in 20 mg kg(-1) and this study indicated a clear significant difference (p<0.05) in pharmacokinetic parameters of ZER in ZER/HPβCD complex compared with ZER in CMC preparation.

Benefits of an automated GLP final report preparation software solution

The final product of analytical laboratories performing US FDA-regulated (or GLP) method validation and bioanalysis studies is the final report. Although there are commercial-off-the-shelf (COTS) software/instrument systems available to laboratory managers to automate and manage almost every aspect of the instrumental and sample-handling processes of GLP studies, there are few software systems available to fully manage the GLP final report preparation process. This lack of appropriate COTS tools results in the implementation of rather Byzantine and manual processes to cobble together all the information needed to generate a GLP final report. The manual nature of these processes results in the need for several iterative quality control and quality assurance events to ensure data accuracy and report formatting. The industry is in need of a COTS solution that gives laboratory managers and study directors the ability to manage as many portions as possible of the GLP final report writing process and the ability to generate a GLP final report with the click of a button. This article describes the COTS software features needed to give laboratory managers and study directors such a solution.

Conducting remote bioanalytical data monitoring and review based on scientific quality objectives

For bioanalytical laboratories that follow GLP regulations and generate data for new drug filing, ensuring quality standards set by regulatory guidance is a fundamental expectation. Numerous guidelines and White Papers have been published by regulatory agencies, professional working groups and field experts in the past two decades, and have significantly improved the standards of good practices for bioanalysis. From a sponsor's perspective, continuous quality monitoring of the data generated by CRO laboratories, identifying adverse trends and taking corrective and preventative actions against issues encountered, are critical aspects of effective bioanalytical outsourcing management. This is especially important for clinical bioanalysis, where one validated assay is applied for analyzing a large number of samples of diverse demographics and disease states. This perspective article presents thoughts toward remote data monitoring and its merits for scientific quality oversight, and introduces a novel Bioanalytical Data Review software that was custom-developed and platform-neural, to conduct remote data monitoring on raw or processed LC-MS/MS data from CROs. Flexible, adaptive and user-customizable queries are applied for conducting project-, batch- and sample-level data review based on scientific quality performance factors commonly assessed for good bioanalytical practice.

Development and validation of LC-HRMS and GC-NICI-MS methods for stereoselective determination of MDMA and its phase I and II metabolites in human urine

3,4-Methylenedioxymethamphetamine (MDMA) is a racemic drug of abuse and its R- and S-enantiomers are known to differ in their dose-response curve. The S-enantiomer was shown to be eliminated at a higher rate than the R-enantiomer most likely explained by stereoselective metabolism that was observed in various in vitro experiments. The aim of this work was the development and validation of methods for evaluating the stereoselective elimination of phase I and particularly phase II metabolites of MDMA in human urine. Urine samples were divided into three different methods. Method A allowed stereoselective determination of the 4-hydroxy-3-methoxymethamphetamine (HMMA) glucuronides and only achiral determination of the intact sulfate conjugates of HMMA and 3,4-dihydroxymethamphetamine (DHMA) after C18 solid-phase extraction by liquid chromatography-high-resolution mass spectrometry with electrospray ionization. Method B allowed the determination of the enantiomer ratios of DHMA and HMMA sulfate conjugates after selective enzymatic cleavage and chiral analysis of the corresponding deconjugated metabolites after chiral derivatization with S-heptafluorobutyrylprolyl chloride using gas chromatography-mass spectrometry with negative-ion chemical ionization. Method C allowed the chiral determination of MDMA and its unconjugated metabolites using method B without sulfate cleavage. The validation process including specificity, recovery, matrix effects, process efficiency, accuracy and precision, stabilities and limits of quantification and detection showed that all methods were selective, sensitive, accurate and precise for all tested analytes.

Pharmacokinetics of p-Aminohippuric Acid and Inulin in Rabbits with Aristolochic Acid Nephropathy

The characteristics of aristolochic acid nephropathy (AAN) are interstitial fibrosis and atrophy of the proximal tubules, but with no change in glomeruli. To investigate the effects of AA on renal functions and the pharmacokinetics (PKs) of p-aminohippuric acid (PAH) and inulin, New Zealand white rabbits were used in this study. The plasma concentrations of PAH and inulin were determined by validated HPLC methods. After a single intravenous administration of 0.5 mg/kg aristolochic acid sodium (AANa), rabbits exhibited mild to moderate nephrotoxicity on the 7th day. Significant tubulointerstitial damage to kidney specimens was found, but there were no remarkable glomerular changes. Clearance rates of PAH and inulin both significantly decreased in AANa-treated rabbits. In addition, there was a significant correlation among the degree of tubulointerstitial changes and PK parameters of PAH after AANa administration, but no correlation was noted with the PKs of inulin. With mild to moderate AAN in rabbits, the renal plasma flow significantly decreased by 55%, and the glomerular filtration rate also significantly decreased by 85%. In conclusion, major renal lesions were found on proximal tubules after AANa administration. The PKs of PAH and inulin significantly changed, and kidney functions, including the RPF and GFR, were reduced.

GlaxoSmithKline’s experience of incurred sample reanalysis for dried blood spot samples

Dried blood spots are becoming a popular alternative to plasma for many different applications. This has been driven by animal ethics but also by ease of use and cost savings. Recent regulatory guidance now has a requirement for incurred sample reanalysis. This article details three examples of incurred sample reanalysis using dried blood spot samples.

Incurred sample reanalysis (ISR): a decisive tool in bioanalytical research

The AAPS Workshop 2008 on Current Topics in GLP Bioanalysis: Assay Reproducibility for Incurred Samples was the defining moment in establishing incurred sample reanalysis (ISR) as a mandatory exercise in demonstrating assay reproducibility using incurred (study) samples. The importance of ISR can be envisaged from its role in clinical as well as non-clinical studies. Incurred samples can differ significantly in their composition when compared with the calibration standards and quality control samples that are used to validate the developed method. The present article attempts to summarize five troubleshooting cases encountered in the analyses of incurred samples for bioanalytical methods developed in our laboratory for mesalamine, hydrochlorothiazide, clopidogrel, sildenafil and rabeprazole. The issues identified were related to: sample inhomogeneity, sample processing error, impact of buffer pH during sample preparation, instability of metabolite and change in laboratory environment. The steps taken to trace and correct these incidents are discussed with adequate data. These examples will further broaden the scope and emphasize the significance of ISR. We believe this investigation will help to develop more reliable and efficient bioanalytical methods.

Historical perspective on the development and evolution of bioanalytical guidance and technology

Bioanalytical methods employed for the quantitative determination of drugs and their metabolites in biological fluids provide essential regulatory data for bioavailability, bioequivalence, pharmacokinetic and toxicokinetic studies. The quality of these studies is directly related to the underlying bioanalytical data. Data generated by a typical bioanalytical laboratory is submitted to not only the local regulatory agency, but also to multiple regulatory agencies worldwide. Many pharmaceutical companies and CROs are now performing bioanalytical work for global submissions and the regulatory agencies are often reviewing the bioanalytical work performed in other countries. The bioanalytical workplace has become global and therefore needs universal rules for quality and compliance of bioanalysis. This paper provides a historical perspective and insight into the development and evolution of the regulatory guidance for bioanalytical method validation and analysis of samples.

Quality assessment of bioanalytical quantification of monoclonal antibody drugs

Monoclonal antibody biotherapeutics are developed to bind to a specific target to affect the target’s biological effect. Reliable measurements of monoclonal antibodies in biological fluids using ligand-binding assays are vital for understanding the pharmacokinetic and pharmacodynamic relationships for efficacy/safety evaluations and dose-regimen selection. The method should be properly characterized and demonstrate adequate assay performance to generate credible data for the right decision making at each specific stage, with considerations on the constraints of timeline, reagent availability and assay caveats. Quality assessment of the assay performance should be based on whether the method is ‘fit-for-use’ to meet the objectives of the study. The basic industrial requirements and recent trends in method and data quality of ligand-binding assays for drug exposure studies at various development stages are discussed.

Unique challenges of providing bioanalytical support for biological therapeutic pharmacokinetic programs

Regulatory recommendations for providing bioanalytical support for biological therapeutics have co-evolved with the increasing success of these unique pharmaceuticals. Immunoassays have been used to quantify biological macromolecules for more than 50 years. These assays rely on the use of antigen-specific antibodies. More recently, LC–MS methods have being adapted to quantitate biologics. LC–MS has attributes that complement the limitations encountered by immunoassays. Whether employing immunoassay or LC–MS methods, compared with traditional chemical-based therapeutics, biological therapeutics present unique analytical challenges to analysts. In this article, we review bioanalytical strategies for supporting biologics and discuss the regulatory and analytical challenges that must be met.

Identifying trends and developing solutions for incurred sample reanalysis failure investigations in a bioanalytical CRO

In 2007, the US FDA recommended that pharmaceutical companies and CROs conduct incurred sample reanalysis (ISR) following the analysis of study samples using validated methods. Between January 2008 and Deccember 2009, over 250 separate analytes were tested for ISR in our laboratory (a bioanalytical CRO). Among these, nine analytes initially failed for ISR. While thorough investigations were conducted to identify the root cause of ISR failure for each study, these investigations were often painfully tedious and very costly, both financially and in terms of project timelines. In this paper, three representative studies are presented to showcase the detailed investigation processes, methodologies and final conclusions of the ISR investigations. Additionally, all nine ISR failures are analyzed to identify trends or common elements of the studies or methods that might help identify potential problems before they occur. Furthermore, suggestions and recommendations to minimize future ISR failures are provided.

Bioequivalence of venlafaxine modified-release capsule revisited with an innovative approach using experimental and predictive models

Background: To evaluate the venlafaxine:O-desmethyl venlafaxine (active metabolite) in vivo formation ratio (MR) in three independent bioequivalence (BE) studies consisting of single-dosed (under fasted and fed conditions) and multiple-dosed clinical trials on healthy subjects. The pooled data pharmacokinetic (PK) analysis demonstrates a model to conduct enantiomer/racemate/active metabolite bioanalysis for regulatory submission of bioavailability/bioequivalence (BA/BE) studies using an interesting MR concept. Results: BE was established for all three studies. Moreover, the venlafaxine:O-desmethyl venlafaxine MR for Cmax and AUClast differed by more than 50% for fasted and fed single-dosed studies, while pooled data analysis found the MR for Cmax to be approximately 0.63 and the AUC to be approximately 0.36 for both test and reference drugs. However, negligible variation was observed for both rate and extent of drug and active metabolite absorption into the systemic circulation at steady state, as the MR for both Cmax and AUC was approximately 0.62. Conclusions: The applications/consequences of the above results are immense. First, an achiral assay for venlafaxine and O-desmethyl venlafaxine estimation in human plasma has been justified for the regulatory acceptance of BA/BE studies, supported with both single- and multiple-dosed PK data showing negligible variation in terms of MR at Cmax. Second, the current investigation shows the MR to be within ±10% when compared with the single-dosed reported study on a western population. Third, the racial effect would not lead to any significant clinical outcome using an interchangeable venlafaxine 150-mg capsule manufactured by Ranbaxy with an Efexor 150-mg capsule manufactured by Wyeth. Furthermore, a decision tree is proposed to evaluate if a racemate or an enantiomer drug and active metabolite bioanalysis should be executed for BA/BE regulatory submission using respective achiral or chiral assays when the drug moiety is a racemate or an enantiomer, formulated in modified-release dosage forms.

Enhanced oral bioavailability of etodolac by self-emulsifying systems: in-vitro and in-vivo evaluation

OBJECTIVES

The objective of this study was to prepare a self-emulsifying drug delivery system (SEDDS) for oral bioavailability enhancement of a poorly water-soluble drug, etodolac. The SEDDS formulations were optimized by evaluating their ability to self-emulsify when introduced to an aqueous medium under gentle agitation, and by determination of the particle size of the resulting emulsion.

METHODS

An optimized formulation of SEDDS (composed of 20% etodolac, 30% oil Labrafac WL1349, 10% Lauroglycol 90 and 40% Labrasol) was selected for bioavailability assessment in rabbits. The anti-inflammatory effect was also determined in rats, and compared with powder drug and etodolac suspension in water (50 mg/kg).

KEY FINDINGS

The peak plasma concentration of 16.4 +/- 1.1 microg/ml appeared after 1.3 +/- 0.2 h, whereas with powder drug and etodolac suspension the values were 7.5 +/- 0.5 and 10.6 +/- 0.7 microg/ml at 4.2 +/- 0.4 and 2.4 +/- 0.2 h, respectively. The AUC(0-8) of the etodolac SEDDS formulation was 2.3 times that of the pure drug and 1.4 times that of the suspension form. SEDDS formulation exhibits a 21% increase in paw thickness compared with a 39% increase on oral administration of etodolac suspension after 4 h at the same dose of the drug (20 mg/kg).

CONCLUSIONS

The result indicates the utility of SEDDS for the oral delivery of etodolac and potentially other lipophilic drugs.

Multiplex ultra-performance liquid chromatography-tandem mass spectrometry method for simultaneous quantification in human plasma of fluconazole, itraconazole, hydroxyitraconazole, posaconazole, voriconazole, voriconazole-N-oxide, anidulafungin, and caspofungin

Therapeutic drug monitoring (TDM) may contribute to optimizing the efficacy and safety of antifungal therapy because of the large variability in drug pharmacokinetics. Rapid, sensitive, and selective laboratory methods are needed for efficient TDM. Quantification of several antifungals in a single analytical run may best fulfill these requirements. We therefore developed a multiplex ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method requiring 100 μl of plasma for simultaneous quantification within 7 min of fluconazole, itraconazole, hydroxyitraconazole, posaconazole, voriconazole, voriconazole-N-oxide, caspofungin, and anidulafungin. Protein precipitation with acetonitrile was used in a single extraction procedure for eight analytes. After reverse-phase chromatographic separation, antifungals were quantified by electrospray ionization-triple-quadrupole mass spectrometry by selected reaction monitoring detection using the positive mode. Deuterated isotopic compounds of azole antifungals were used as internal standards. The method was validated based on FDA recommendations, including assessment of extraction yields, matrix effect variability (<9.2%), and analytical recovery (80.1 to 107%). The method is sensitive (lower limits of azole quantification, 0.01 to 0.1 μg/ml; those of echinocandin quantification, 0.06 to 0.1 μg/ml), accurate (intra- and interassay biases of -9.9 to +5% and -4.0 to +8.8%, respectively), and precise (intra- and interassay coefficients of variation of 1.2 to 11.1% and 1.2 to 8.9%, respectively) over clinical concentration ranges (upper limits of quantification, 5 to 50 μg/ml). Thus, we developed a simple, rapid, and robust multiplex UPLC-MS/MS assay for simultaneous quantification of plasma concentrations of six antifungals and two metabolites. This offers, by optimized and cost-effective lab resource utilization, an efficient tool for daily routine TDM aimed at maximizing the real-time efficacy and safety of different recommended single-drug antifungal regimens and combination salvage therapies, as well as a tool for clinical research.

Evaluation of an isochronic study design for long-term frozen stability investigation of drugs in biological matrices

Long-term stability is a basic parameter in bioanalytical method validation; however, no criteria for conducting long-term stability studies are specified in current guidelines. We present an evaluation of a modified statistical approach applied to a study design utilizing an isochronic analysis (collection of samples to be analyzed at one time point) to determine the long-term stability and, further, a comparison with the most widely used continuous design. The presented approach has been used in regulated bioanalysis at Lundbeck for the past 7 years and has, in this period, been applied to 121 studies; all providing conclusive data. The isochronic approach eliminates day-to-day variation, reduces labor and adds to the flexibility in the laboratory. The statistical evaluation used is based on the relative difference between baseline samples and stability test samples as well as 90% confidence intervals for the mean concentration for each of the stability test points.

Spectrophotometric and spectrodensitometric methods for the determination of rivastigmine hydrogen tartrate in presence of its degradation product

Three sensitive, selective and precise stability-indicating methods for the determination of the anti-Alzheimer's drug, rivastigmine hydrogen tartrate (RIV) in the presence of its alkaline degradation product (major metabolite, NAP 226-90) and in pharmaceutical formulation were developed and validated. The first method is a second derivative (D(2)) spectrophotometric one, which allows the determination of RIV in the presence of its degradate at 262 nm (corresponding to zero crossing of the degradate) over a concentration range of 50-500 microg/ml with mean percentage recovery 100.18 +/- 0.628. The second method is the first derivative of the ratio spectra (DD(1)) by measuring the peak amplitude at 272 nm over the same concentration range as (D(2)) spectrophotometric method, with mean percentage recovery 99.97 +/- 0.641. The third method is a TLC-densitometric one, where RIV was separated from its degradate on silica gel plates using methanol:butanol:H(2)O:ammonia (5:4:1:0.01 v:v:v) as a developing system. This method depends on the quantitative densitometric evaluation of thin layer chromatogram of RIV at 263 nm over a concentration range of 20-160 microg/spot, with mean percentage recovery 100.19 +/- 1.344. The selectivity of the proposed methods was tested using laboratory-prepared mixtures. The proposed methods have been successfully applied to the analysis of RIV in pharmaceutical dosage forms without interference from other dosage form additives and the results were statistically compared with reference method.

Interleukin-2 treatment effect on imatinib pharmacokinetic, P-gp and BCRP expression in mice

The aim of this study was to investigate the effect that recombinant interleukin-2 (rIL-2) (0.16 MUI/injection) had on the pharmacokinetics of imatinib (IM) in plasma. In this study, IM was given orally to mice at a dose of 150 mg/kg once a day for 11 days (from day 1 to 11) either alone or in combination with intraperitoneal injections of rIL-2 twice a day from day 8 to 11. Pharmacokinetic parameters were determined using WinNonLin software. Areas under the curve were compared using Bailer's method. The repeated administration of the rIL-2+IM combination was shown to have two pharmacokinetic advantages compared with repeated IM doses alone. In addition to the pharmacodynamic interest of this treatment, we found that the combined treatment significantly increased the IM Cmax (P<0.05) and significantly increased the IM trough concentration (C(24 h)) (P<0.01), which was always above the minimum therapeutic IM concentration (1 mumol/l) in plasma. Those pharmacokinetic modifications may be explained, in part, by a decrease in the P-glycoprotein expression in the three intestinal segments of the mice (duodenum, P<0.01; jejunum, P<0.05; and ileum, P<0.05) and a decrease in BCRP expression in the duodenum segment (P<0.05) due to rIL-2. In another experiment, we found a significant induction of intestinal P-glycoprotein expression in mice that had been given IM orally (150 mg/kg) twice a day for 11 days. It would be interesting to further investigate the IM disposition associated with rIL-2 treatment for clinical applications.

A history of biopharmaceutics in the Food and Drug Administration 1968-1993

The history of biopharmaceutics is reviewed, beginning with its origin out of the Division of Clinical Research in The Bureau of Medicine. The reason for the creation of the Division of Biopharmaceutics, the certification of Food and Drug Administration authority over the functions it was to have, and the implementation of that authority are described. The determination of bioequivalence, the bioavailability decision rules, pharmacokinetics, and drug metabolism are explained. The reason for the development of the Scale-Up and Post Approval Regulations and how they were developed are also explained.

An evolutionary view of chromatography data systems used in bioanalysis

This is a personal view of how chromatographic peak measurement and analyte quantification for bioanalysis have evolved from the manual methods of 1970 to the electronic working possible in 2010. In four decades there have been major changes from a simple chart recorder output (that was interpreted and quantified manually) through simple automation of peak measurement, calculation of standard curves and quality control values and instrument control to the networked chromatography data systems of today that are capable of interfacing with Laboratory Information Management Systems and other IT applications. The incorporation of electronic signatures to meet regulatory requirements offers a great opportunity for business improvement and electronic working.