Bioavailability assessment of a brompheniramine taste-masked pediatric formulation in a juvenile porcine model.

A brompheniramine taste-masked pediatric formulation was developed as part of the National Institutes of Health Pediatric Formulation Initiative to help address low patient compliance caused by the bitter taste of many adult formulations. To confirm that the taste-masked formulation can provide a similar pharmacological effect to the previous marketed adult formulations, a juvenile porcine model was used to screen the model pediatric formulation to compare the bioavailability between the marketed brompheniramine maleate and the taste-masked maleate/tannate formulation. Pigs were dosed orally with both formulations and blood samples were obtained from 0 to 48 h. Plasma samples were prepared and extracted using solid-phase extraction. The mass spectrometer was operated under selected ion monitoring mode. The selected ion monitoring channels were set to m/z 319.1 for brompheniramine and m/z 275.2 for the internal standard chlorpheniramine. Calibration curves were linear over the analytical range 0.2-20 ng/ml (r2 > 0.995) for brompheniramine in plasma. The intra- and inter-day accuracies were between 98.0 and 105% with 5.73% RSD precision. The bioanalytical method was successfully applied to a preclinical bioavailability study. The bioavailability profiles were not significantly different between the two formulations, which demonstrates that taste-masking with tannic acid is a promising approach for formulation modification for pediatric patients.

A Spike-Control Approach that Evaluates High Resolution Mass Spectrometry-Based Sequence Variant Analytical Method Performance for Therapeutic Proteins.

An amino acid sequence variant (SV) is defined as an unintended amino acid substitution in protein drug products. SVs contribute to product heterogeneity and can potentially impact product quality, safety, immunogenicity, and efficacy. The analysis of biotherapeutics for SVs is important throughout the product life cycle including clone selection, development of nutrient feed strategies, commercial manufacturing process, and post-approval changes to monitor product quality. The proposed analytical procedure for SVs consists of both qualitative (identification of SVs) and quantitative (quantitation of identified SVs) components. The complexities of SV analysis and the variety of current procedures highlight the need for a systematic approach for assessing the capability of these methodologies to reliably identify and quantitate SVs in biotherapeutics. We described here a "spike-control" approach for evaluating SV analytical procedure. The concept was adopted from quality control samples routinely used in analytical procedure validation. One FDA approved monoclonal antibody (mAb) was spiked with accurate amounts of highly homologous mAb to create mAb samples containing low yet accurate levels of "artificial" SVs. Spike-control samples were denatured, reduced, alkylated, digested and then analyzed by high resolution Orbitrap mass spectrometry. In silico analysis revealed four single amino acid differences between the two mAbs that could be used to represent SVs in the spike-control samples. All four "artificial" SVs were reliably identified by the current workflow. Analytical range (0.01% to 2%), accuracy and precision of identified SVs have also been evaluated. Overall, spike-control sample(s) helped to demonstrate that the SV analytical procedure (i.e., sample preparation, LC separation, mass spectrometry determinations and bioinformatic software) was fit for purpose and suitable for the identification and quantitation of SVs at a pre-determined threshold.

An advanced automation platform coupled with mass spectrometry for investigating in vitro human skin permeation of UV filters and excipients in sunscreen products.

RATIONALE: Systemic absorption of UV-filtering chemicals following topical application of sunscreens may present a safety concern. The Food and Drug Administration (FDA) had recommended an in vitro skin permeation test (IVPT) to evaluate the potential of this safety risk for the evaluation of sunscreens prior to clinical studies. Therefore, a sensitive and robust bioanalytical method(s) were required for IVPT studies of different topical sunscreen products. METHODS: An analytical procedure to quantitate sunscreen UV-filtering components and excipients in IVPT samples including avobenzone, octocrylene, oxybenzone, ecamsule, methylparaben and propylparaben was developed employing a RapidFire 360 robotic sample delivery system coupled with a triple quadrupole mass spectrometer. The analytical procedure was developed and validated according to the requirements of the FDA Bioanalytical Method Validation Guidance for Industry (2018). RESULTS: The analytical method provided a turnaround time of 12 seconds per sample and was determined to be accurate, precise, specific, and linear over the corresponding analytical ranges. The validated method was successfully applied for two IVPT studies for evaluating the skin permeation potential of UV-filtering chemicals and assisting with the selection of the sunscreen products for the clinical study conducted by the FDA. CONCLUSIONS: This work highlights the first analytical procedure that has applied a non-chromatographic-MS/MS automation platform to an in vitro biopharmaceutics study. The analytical platform simultaneously quantitated four UV filters and two excipients in complex media to evaluate their permeation in IVPT studies. The sample throughput and analytical performance of advanced automation platforms indicate their analytical procedure has the potential to significantly advance the efficiency of IVPT studies to evaluate permeation of a wide variety of UV chemical filters and excipients for topical OTC sunscreen products.

In Vitro Testing of Sunscreens for Dermal Absorption: Method Comparison and Rank Order Correlation with In Vivo Absorption.

Evaluating the dermal absorption of sunscreen UV filters requires the development of a bio-predictable in vitro permeation test (IVPT). This work describes the comparison of two IVPT methods and rank order correlations of in vitro absorption (skin permeation and retention) with the in vivo absorption (AUC and skin retention) of sunscreens. The IVPT was compared regarding the following elements: (1) application of a single finite dose vs. an infinite dose and (2) the use of heat-separated human epidermis vs. dermatomed skin models. The IVPT was used to evaluate dermal absorption of six UV filters (avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone) in commercial sunscreens. Both the in vivo and in vitro permeation studies demonstrated that all UV filters were absorbed following a single-dose application. Sunscreens were rank ordered by the amount of the UV filters absorbed. Data obtained from the IVPT method using a single finite dose and heat-separated human epidermis was found to correlate with the clinical data. Rank orders of the cumulative in vitro skin permeation and the in vivo AUC were found comparable for oxybenzone, homosalate, octisalate, and octinoxate. Rank orders of the in vitro and in vivo skin retention of oxybenzone and octinoxate were also comparable. Additional IVPT parameters may be optimized to enhance the discriminatory power for UV filters with low skin permeation potential (e.g., avobenzone and octocrylene).

Zinc supplementation improves the harvest purity of ß-glucuronidase from CHO cell culture by suppressing apoptosis.

The variability of trace metals in cell culture media is a potential manufacturing concern because it may significantly affect the production and quality of therapeutic proteins. Variability in trace metals in CHO cell culture has been shown to impact critical production metrics such as cell growth, viability, nutrient consumption, and production of recombinant proteins. To better understand the influence of excess supplementation, zinc and copper were initially supplemented with 50-µM concentrations to determine the impact on the production and quality of ß-glucuronidase, a lysosomal enzyme, in a parallel bioreactor system. Ethylenediaminetetraacetic acid (EDTA), a metal chelator, was included as another treatment to induce a depletion of trace metal bioavailability to examine deficiency. Samples were drawn daily to monitor cell growth and viability, nutrient levels, ß-glucuronidase activity, and trace zinc flux. Cell cycle analysis revealed the inhibition of sub-G0/G1 species in zinc supplemented cultures, maintaining higher viability compared to the control, EDTA-, and copper-supplemented cultures. Enzyme activity analysis in the harvests revealed higher specific activity of ß-glucuronidase in reactors supplemented with zinc. A confirmation run was conducted with supplementations of zinc at concentrations of 50, 100, and 150 µM. Further cell cycle analysis and caspase-3 analysis demonstrated the role of zinc as an apoptosis suppressor responsible for the enhanced harvest purity of ß-glucuronidase from zinc-supplemented bioreactors.

Development and validation of an ultra-high-performance liquid chromatography-tandem mass spectrometry method to determine the bioavailability of warfarin and its major metabolite 7-hydroxy warfarin in rats dosed with oral formulations containing different polymorphic forms.

A simple, sensitive and rapid ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated for the quantification of warfarin and 7-hydroxy warfarin in Sprague Dawley (SD) rats. Animals were administered a single dose of warfarin sodium formulations (crystalline and amorphous) at 12 mg/kg via oral gavage and blood was drawn over a 96-h time course. Sample process recoveries, matrix effect and analyte stability were determined. The linearity for warfarin and 7-hydroxy warfarin was from 5 to 2000 ng/mL in blank SD rat plasma. Correlation coefficients (r2 ) for standard calibration curves were >.98 and analytes quantified within ±15% of target at all calibrator concentrations. The average percent accuracy and precision for intra- and inter-day were 93.7%-113.8% and ≤12.1%, respectively, for warfarin and 7-hydroxy warfarin, across the quality control standards (5, 10, 500, 1800 and 2000 ng/mL). Acceptable analytical recovery (>55%) was achieved with process efficiencies >41.5% and matrix effects <139.9% over the analytical range. Both analytes were stable in stock solution, autosampler, benchtop and three cycles of freeze-thaw with percent accuracy ≥90.2% and precision (percent relative standard deviation) ≤14%. The validated method was successfully applied to a pre-clinical bioavailability study of crystalline and amorphous warfarin sodium formulations in SD rats.

Development and validation of a UPLC-MS method for the determination of galantamine in guinea pig plasma and its application to a pre-clinical bioavailability study of novel galantamine formulations.

To evaluate the bioavailability and pharmacokinetic profiles of two novel galantamine formulations as medical countermeasure products, an ultra-performance liquid chromatography-single quadrupole mass spectrometry (UPLC-MS) method was developed and validated for quantifying galantamine in guinea pig plasma using solid-phase extraction with a mixed mode strong cation exchange reversed-phase cartridge. Chromatographic separation was achieved on a Waters Acquity UPLC BEH C18 column maintained at 40°C. The mobile phases were solution A, acetonitrile-water, 5:95 (v/v) and solution B, acetonitrile-water 90:10 (v/v), both containing 2 mM ammonium formate and 0.2% formic acid. The mobile phase was delivered utilizing a 3 min gradient program start with 95%A-5%B at a flow rate of 0.6 mL/min. The analyte and internal standard, galantamine-d3, were detected by selected ion monitoring mode on a Waters 3100 single quadrupole mass spectrometer with positive electrospray ionization. The method was validated according to the US Food and Drug Administration bioanalytical guidance. The method was selective and was linear over the analytical range of 2-2000 ng/mL. Accuracy and precision were acceptable with intra- and inter-day accuracies between 96.8 and 101% and precisions (RSD) <4.88%. The method was successfully implemented to measure galantamine plasma levels in a series of pre-clinical bioavailability studies for the evaluation of novel galantamine formulations.

Rapid Quantitation of Four Nitrosamine Impurities in Angiotensin Receptor Blocker Drug Substances.

Starting in July 2018, the FDA alerted patients and health care professionals to the recall of ARBs such as valsartan by several pharmaceutical companies because of their potential contamination with carcinogenic nitrosamine impurities, including: (1) N-nitrosodimethylamine (NDMA), (2) N-nitrosodiethylamine (NDEA), (3) N-nitrosoethylisopropylamine (NEIPA), (4) N-nitrosodiisopropylamine (NDIPA), (5) N-nitrosodibutylamine (NDBA) and (6) N-nitroso-N-methyl-4-aminobutyric acid (NMBA). The FDA initiated a laboratory investigation to develop analytical procedures to test multiple lots of marketed ARB drugs to determine the possible presence of carcinogenic impurities and, if present, quantitate the levels of these impurities. Here the FDA laboratory developed and validated an automated micro-solid phase extraction MS/MS method, where all the analytes are not separated prior to elution to the MS, to simultaneously quantify NEIPA, NDIPA, NDBA and NMBA in ARB drug substances with an instrument sample analysis time of 12 seconds. The method was validated according to the ICH Q2(R1) guideline, and was determined to be specific, accurate, precise and linear over the corresponding nitrosamine analytical ranges. The method has been successfully implemented to quantitate the four nitrosamine impurities in 129 generic losartan, valsartan, olmesartan, irbesartan and telmisartan drug substance samples from 32 lots; and 32 losartan and valsartan drug product samples from 6 lots.

Asymmetrical Flow Field Flow Fractionation for Molar Mass Characterization of Polyethylene Oxide in Abuse-Deterrent Formulations.

High molar mass polyethylene oxide (HM-PEO) is commonly used to enhance the mechanical strength of solid oral opioid drug products to deter abuse. Because the properties of PEO depend on molar mass distribution, accurately determining the molar mass distribution is a necessary part of understanding PEO's role in abuse-deterrent formulations (ADF). In this study, an asymmetrical flow field-flow fractionation (AF4) analytical procedure was developed to characterize PEO polymers with nominal molar masses of 1, 4 or 7 MDa as well as those from in-house prepared placebo ADF. The placebo ADF were manufactured using direct compress or hot-melt-extrusion methods, and subjected to physical manipulation, such as heating and grinding before measurement by AF4 were performed. The molar mass distribution characterized by AF4 revealed that PEO was sensitive to thermal stress, exhibiting decreased molar mass with increased heat exposure. The optimized AF4 method was deemed suitable for characterizing HM-PEO, offering adequate dynamic separation range for PEO with molar mass from 100 kDa to approximately 10 MDa.

Bumetanide as a Model NDSRI Substrate: N-nitrosobumetanide Impurity Formation and its Inhibition in Bumetanide Tablets.

Nitrosamine compounds are classified as potential human carcinogens, the origin of these impurities can be broadly classified in two categories, nitrosamine impurity found in drug products that are not associated with the Active Pharmaceutical Ingredient (API), such as N-nitrosodimethylamine (NDMA) or nitrosamine impurities associated with the API, such as nitrosamine drug substance-related impurities (NDSRIs). The mechanistic pathway for the formation of these two classes of impurities can be different and the approach to mitigate the risk should be tailored to address the specific concern. In the last couple of years number of NDSRIs have been reported for different drug products. Though, not the only contributing factor for the formation of NDSIRs, it is widely accepted that the presence of residual a nitrites/nitrates in the components used in the manufacturing of the drug products can be the primary contributor to the formation of NDSRIs. Approaches to mitigate the formation of NDSRIs in drug products include the use of antioxidants or pH modifiers in the formulation. The primary objective of this work was to evaluate the role of different inhibitors (antioxidants) and pH modifiers in tablet formulations prepared in-house using bumetanide (BMT) as a model drug to mitigate the formation of N-nitrosobumetanide (NBMT). A multi-factor study design was created, and several bumetanide formulations were prepared by wet granulation with and without sodium nitrite spike (100 ppm) and different antioxidants (ascorbic acid, ferulic acid or caffeic acid) at three concentrations (0.1%, 0.5% or 1% of the total tablet weight). Formulations with acidic and basic pH were also prepared using 0.1 N hydrochloric acid and 0.1 N sodium bicarbonate, respectively. The formulations were subjected to different storage (temperature and humidity) conditions over 6 months and stability data was collected. The rank order of N-nitrosobumetanide inhibition was highest with alkaline pH formulations, followed by formulations with ascorbic acid, caffeic acid or ferulic acid present. In summary, we hypothesize that maintaining a basic pH or the addition of an antioxidant in the drug product can mitigate the conversion of nitrite to nitrosating agent and thus reduce the formation of bumetanide nitrosamines.

Simultaneous quantification of dexamethasone and 6ß-hydroxydexamethasone in rabbit plasma, aqueous and vitreous humor, and retina by UHPLC-MS/MS.

Aim: To develop and validate a fit for purpose method for the simultaneous determination of dexamethasone and its major metabolite, 6ß-hydroxydexamethasone, in rabbit plasma and ocular matrices to measure the in vivo release and distribution profile of dexamethasone from intravitreal implants. Materials & methods: An UHPLC-MS/MS system was employed to perform the bioanalysis. The method was validated according to the US FDA Bioanalytical Method Validation Guidance for Industry. Results & conclusion: The method was found to be fit-for-purpose for the described biological matrices and had a LLOQ of 0.1 ng/ml.

In Vitro Testing of Sunscreens for Dermal Absorption: A Platform for Product Selection for Maximal Usage Clinical Trials.

Sunscreen products contain UV filters as active ingredients for the protection of the skin against UVR. The US Food and Drug Administration (FDA) issued a new proposed rule in 2019 (84.FR.6204) for sunscreens and identified the need for additional safety data for certain UV filters including their dermal absorption data. Dermal absorption data reveal systemic exposure of UV filters in humans, which can be obtained from clinical maximal usage trials. FDA guidance recommends conducting in vitro skin permeation tests (IVPTs) to help select formulations for maximal usage clinical trials as IVPT results may be indicative of in vivo absorption. This case study reports in vitro methodologies used for the selection of sunscreen products for an FDA-sponsored proof-of-concept maximal usage clinical trial. An IVPT method was developed using human cadaver skin. Commercially available sunscreen products were tested to determine the skin absorption potential of common UV filters using the IVPT. All the studied sunscreen products demonstrated a certain degree of skin absorption of UV filters using IVPT, and a formulation rank order was obtained. These sunscreen products were also characterized for several formulation properties including the globule size in emulsions, which was found to be an indicator for the rank order.

Quantitative evaluation of the thallium binding of soluble and insoluble Prussian blue hexacyanoferrate analogs: A scientific comparison based on their critical quality attributes.

There has been a long-standing discussion in the scientific literature on the thallium (Tl) binding capacity of ferric hexacyanoferrate (insoluble) and potassium hexacyanoferrate (soluble) forms of Prussian blue (PB). The literature sometime suggests that the soluble form of PB should be used to treat thallium poisoning, instead of the FDA approved insoluble form of PB. The literature debate is further complicated by the lack of fundamental characterization data such as critical quality attributes (CQAs) that clearly define the analog forms. The purpose of this study is to compare, the binding capacity of soluble and insoluble PB analogs with the same CQAs (particle size/distribution and water content). Water content and particle size/particle distribution were determined by TGA, and solid-state laser diffraction particle sizing. Thallium binding studies were conducted at physiological pH to determine the maximal binding capacity (MBC) at equilibrium. Multiple linear regression and principal component analysis was also used for multivariate data analysis. Results indicate that insoluble and soluble analogs, with similar quality attributes, have nearly identical, MBC binding capacities of (441.5 mg/g) for insoluble vs soluble (458.4 mg/g). However, when both analog forms with different CQAs such as water, particle size were compared, results indicated significantly higher or lower thallium binding levels. In conclusion, it is essential that the FDA approved iron form with well-defined CQAs is used to treat thallium poisoning and radioactive thallium metal contamination for consistent therapeutic outcomes.

An ICP-MS platform for metal content assessment of cell culture media and evaluation of spikes in metal concentration on the quality of an IgG3:κ monoclonal antibody during production.

Metal ions can be enzyme cofactors and can directly influence the kinetics of biochemical reactions that also influence the biological production and quality attributes of therapeutic proteins, such as glycan formation and distribution. However, the concentrations of metals in commercially available chemically defined media can range from 1 to 25,000 ppb. Because such concentration changes can impact cell growth, manufacturing yield and product quality the alteration/fluctuation in media composition should be well controlled to maintain product quality. Here, we describe a platform of analytical methods to determine the composition of several metals in different sample matrices using an advanced automated Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). These methods, validated to ICH Q2R1 regulatory validation parameters, were successfully applied to- (a) screen cell culture media; (b) determine changes in the metal concentration during cell growth in spinner flasks, and, (c) determine effect on the glycosylation pattern and homogeneity of an IgG3:κ produced from a murine-hybridoma cell line in bench-top parallel bioreactors due to a spike in copper and iron concentration. Our results show that maintenance of metal content in the cell culture media is critical for product consistency of the IgG3:κ produced.

Comparison of the stability of split and intact gabapentin tablets.

The purpose of this study was to determine the stability differences between split and intact gabapentin tablets. Gabapentin tablets from three different manufacturers (G1, G2 and G3) were tested for a period of 9 weeks under long-term (25 degrees C/60% RH) and intermediate stability (30 degrees C/60% RH) storage conditions after storage in closed amber pharmacy dispensing containers. Samples were analyzed for dissolution and potency using validated HPLC methods. Potency test also included the quantitation of gabapentin's main degradation product. Tablets from all manufacturers and at all time points had potency >90%. At 9 weeks, a statistically significant decrease (p<0.02) in gabapentin potency was observed for the whole and split G2 and G3 tablets under the intermediate storage conditions. At the end of 9 weeks, all samples also showed slightly higher levels of degradation product which was statistically significant (p<0.01) for samples stored under intermediate stability storage conditions and exceeded the proposed USP (PF, 2006) limit for the G3 split and intact tablets. No difference was observed between the potency and dissolution of the intact and the split tablets from the same manufacturer and the three products tested remained stable throughout the study period. The results suggest that splitting of gabapentin tablets did not affect the stability of these particular drug products tested as part of this study when stored under normal storage conditions for a period of up to 9 weeks. However, the results should not be extrapolated to other gabapentin drug products and to other tablet dosage forms.

Quantitative determination of thallium binding to ferric hexacyanoferrate: Prussian blue.

Ferric hexacyanoferrate, (Fe(4)(III)[Fe(II)(CN)(6)](3)), also known as insoluble Prussian blue (PB), is the active pharmaceutical ingredient (API) of Radiogardase which is the first approved drug product (DP) for treatment of thallium and radiocesium poisoning. The aim of this study is (1) to determine the in vitro thallium binding capacity and binding rates of insoluble PB; and (2) to evaluate the effect of physiological pH conditions, PB particle size and storage conditions on the binding to PB. Experimental pH levels from 1.0 to 7.5 were used to cover the range of pH levels that PB may encounter when traveling through the gastrointestinal (GI) tract in humans. Measurements of thallium binding were made between 1 and 24h, to cover gastric and intestinal tract residence time. PB was found to have a binding capacity of approximately 1400 mg/g at pH 7.5. When the pH decreased, the binding decreased as well. The results indicated that the hydration state of PB influences the thallium binding process. It was also found that there exits a direct correlation between the moisture loss in PB and the thallium binding rate constant. The PB with 17 mol of water had a binding rate constant of 0.52, which was reduced to 0.32 when PB was dehydrated to 2.5 mol of water. Significant differences were observed in both binding capacity and binding rate constant among PB fractions with different particle size ranges. PB fraction with particle size of 220-1000 microm had a binding rate constant of 0.43, which increased to 0.64 when the particle size was reduced to 32-90 microm. Batch-to-batch variation in thallium binding was also observed among the APIs and the DPs and this was related to particle size and hydration state. These findings can be utilized to evaluate and predict drug product quality under certain manufacturing and dry storage conditions.

Development and application of a validated HPLC method for the analysis of dissolution samples of gabapentin drug products.

A simple isocratic reversed-phase HPLC method was developed and validated for the analysis of dissolution samples of gabapentin tablets and capsules. Separation of gabapentin from its major degradation impurity, 3,3-pentamethylene-4-butyrolactam was achieved on a Phenomenex Luna Cyano column using a methanol-acetonitrile-20 mM KH(2)PO(4) (pH 2.2) (5:5:90, v/v/v) mobile phase. The compounds were eluted isocratically at a flow rate of 1.25 mL/min. Both compounds were analyzed with UV detection at 210 nm. The method was validated according to USP Category I requirements for gabapentin. The validation characteristics included accuracy, precision, linearity, range, specificity and limit of quantitation. Robustness testing was also conducted to evaluate the effect of minor changes to the chromatographic system and to establish appropriate system suitability parameters. Validation acceptance criteria were met in all cases. This method was used successfully for the quality assessment of five gabapentin drug products.

Quantitative determination of cesium binding to ferric hexacyanoferrate: Prussian blue.

Ferric hexacyanoferrate (Fe4III[FeII(CN)6]3), also known as insoluble Prussian blue (PB) is the active pharmaceutical ingredient (API) of the drug product, Radiogardase. Radiogardase is the first FDA approved medical countermeasure for the treatment of internal contamination with radioactive cesium (Cs) or thallium in the event of a major radiological incident such as a "dirty bomb". A number of pre-clinical and clinical studies have evaluated the use of PB as an investigational decorporation agent to enhance the excretion of metal cations. There are few sources of published in vitro data that detail the binding capacity of cesium to insoluble PB under various chemical and physical conditions. The study objective was to determine the in vitro binding capacity of PB APIs and drug products by evaluating certain chemical and physical factors such as medium pH, particle size, and storage conditions (temperature). In vitro experimental conditions ranged from pH 1 to 9, to cover the range of pH levels that PB may encounter in the gastrointestinal (GI) tract in humans. Measurements of cesium binding were made between 1 and 24h, to cover gastric and intestinal tract residence time using a validated atomic emission spectroscopy (AES) method. The results indicated that pH, exposure time, storage temperature (affecting moisture content) and particle size play significant roles in the cesium binding to both the PB API and the drug product. The lowest cesium binding was observed at gastric pH of 1 and 2, whereas the highest cesium binding was observed at physiological pH of 7.5. It was observed that dry storage conditions resulted in a loss of moisture from PB, which had a significant negative effect on the PB cesium binding capacity at time intervals consistent with gastric residence. Differences were also observed in the binding capacity of PB with different particle sizes. Significant batch to batch differences were also observed in the binding capacity of some PB API and drug products. Our results suggest that certain physiochemical properties affect the initial binding capacity and the overall binding capacity of PB APIs and drug products during conditions that simulated gastric and GI residence time. These physiochemical properties can be utilized as quality attributes to monitor and predict drug product quality under certain manufacturing and storage conditions and may be utilized to enhance the clinical efficacy of PB.

A headspace-gas chromatography method for isopropanol determination in warfarin sodium products as a measure of drug crystallinity.

Coumadin® a nd s everal generic products of warfarin s odium (WS) contain the crystalline form (clathrate) in which WS and isopropanol (IPA) are associated in a 2:1 molar ratio. IPA is critical in maintaining the WS crystalline structure. Physicochemical properties of the drug and drug product may change when the crystalline drug transforms to amorphous form. A headspace-gas chromatography (HS-GC) method was developed and validated for IPA determination in the WS drug product. n-propanol (NPA) was used as internal standard and the method was validated for specificity, system suitability, linearity, accuracy, precision, range, limits of detection and quantification, and robustness. The method was specific, with good resolution between IPA and NPA peaks. Chromatographic parameters (retention time, IPA/NPA area ratio, tailing factor, theoretical plates, USP symmetry, capacity factor, selectivity and resolution) were consistent over three days of validation. The analytical method was linear from 2-200 µg mL-1 (0.1- 10 % IPA present in the drug product). LOD and LOQ were 0.1 and 2 µg mL-1, respectively. Accuracy at low (2 µg mL-1) and high (200 µg mL-1) IPA concentrations of the calibration curve was 103.3-113.3 and 98.9-102.2 % of the nominal value, resp. The validated method was precise, as indicated by the RSD value of less than 2 % at three concentration levels of the calibration curve. The method reported here was utilized to determine accurately and precisely the IPA content in in-house formulations and commercial products. In summary, IPA determination by HS-GC provides an indirect measure of WS crystallinity in the drug product. Nevertheless, it should be confirmed by another analytical method since IPA from the drug substance is not distinguishable from IPA that may be present outside the drug crystals in a dosage form when prepared by wet granulation with IPA.