Evidence of 13 C-lactate oxidation in the human brain from hyperpolarized 13 C-MRI.

PURPOSE: To test the hypothesis that lactate oxidation contributes to the 13 $$ {}^{13} $$ C-bicarbonate signal observed in the awake human brain using hyperpolarized 13 $$ {}^{13} $$ C MRI. METHODS: Healthy human volunteers (N = 6) were scanned twice using hyperpolarized 13 $$ {}^{13} $$ C-MRI, with increased radiofrequency saturation of 13 $$ {}^{13} $$ C-lactate on one set of scans. 13 $$ {}^{13} $$ C-lactate, 13 $$ {}^{13} $$ C-bicarbonate, and 13 $$ {}^{13} $$ C-pyruvate signals for 132 brain regions across each set of scans were compared using a clustered Wilcoxon signed-rank test. RESULTS: Increased 13 $$ {}^{13} $$ C-lactate radiofrequency saturation resulted in a significantly lower 13 $$ {}^{13} $$ C-bicarbonate signal (p = 0.04). These changes were observed across the majority of brain regions. CONCLUSION: Radiofrequency saturation of 13 $$ {}^{13} $$ C-lactate leads to a decrease in 13 $$ {}^{13} $$ C-bicarbonate signal, demonstrating that the 13 $$ {}^{13} $$ C-lactate generated from the injected 13 $$ {}^{13} $$ C-pyruvate is being converted back to 13 $$ {}^{13} $$ C-pyruvate and oxidized throughout the human brain.

Age-associated change in pyruvate metabolism investigated with hyperpolarized 13 C-MRI of the human brain.

In this study, hyperpolarized 13 C MRI (HP-13 C MRI) was used to investigate changes in the uptake and metabolism of pyruvate with age. Hyperpolarized 13 C-pyruvate was administered to healthy aging individuals (N = 35, ages 21-77) and whole-brain spatial distributions of 13 C-lactate and 13 C-bicarbonate production were measured. Linear mixed-effects regressions were performed to compute the regional percentage change per decade, showing a significant reduction in both normalized 13 C-lactate and normalized 13 C-bicarbonate production with age: - 7 % ± 2 % per decade for 13 C-lactate and - 9 % ± 4 % per decade for 13 C-bicarbonate. Certain regions, such as the right medial precentral gyrus, showed greater rates of change while the left caudate nucleus had a flat 13 C-lactate versus age and a slightly increasing 13 C-bicarbonate versus age. The results show that both the production of lactate (visible as 13 C-lactate signal) as well as the consumption of monocarboxylates to make acetyl-CoA (visible as 13 C-bicarbonate signal) decrease with age and that the rate of change varies by brain region.

Retrospective multicentre matched cohort study comparing safety and efficacy outcomes of intermittent-infusion versus continuous-infusion vancomycin.

BACKGROUND: Patients with good renal function receiving intermittent-infusion vancomycin (IIV) may require total daily doses ≥4 g to achieve trough concentrations of 15-20 mg/L, increasing the risk of vancomycin-associated nephrotoxicity. Continuous-infusion vancomycin (CIV) may be associated with a lower risk of vancomycin-associated nephrotoxicity compared with IIV, but studies comparing safety of both dosing strategies are lacking. OBJECTIVES: To compare the risk of nephrotoxicity with CIV versus IIV when target concentration ranges were the same with both dosing modalities. METHODS: A retrospective multicentre matched cohort study of admitted patients between 1 January 2010 and 31 December 2016 was completed. Adult patients who received ≥48 h of vancomycin with at least one steady-state vancomycin concentration were eligible. The primary outcome was to compare the rates of nephrotoxic risk and renal injury, defined by the RIFLE criteria, between CIV and IIV. RESULTS: Of 2136 patients who received vancomycin during the study period, 146 CIV patients were eligible and matched to 146 IIV patients. After adjustment of potential confounders, CIV was found to have a lower odds of developing nephrotoxic risk (OR 0.42, 95% CI 0.21-0.98, P = 0.025) and renal injury (OR 0.19, 95% CI 0.05-0.59, P = 0.004). CONCLUSIONS: CIV is associated with a lower odds of nephrotoxicity compared with IIV when targeting the same concentration range and should be an alternative dosing strategy for patients who will receive prolonged therapy or require >4 g/day to achieve therapeutic levels.

Development and validation of a screening tool for early identification of bloodstream infection in older patients - a retrospective case-control study.

BACKGROUND: Delayed diagnosis of bloodstream infection (BSI) occurs in > 20% of older patients, with misdiagnosis in 35%. Our objective was to develop and validate a clinically useful screening tool to identify older patients with a high probability of having a BSI. METHODS: Hospitalized patients > 80 years old with BSI (n = 105/group) were evaluated for the tool development in this retrospective matched case-controlled study (learn cohort). The tool was validated in different retrospectively matched case and control patients > 80 years old (n = 120/group) and 65 to 79 years old (n = 250/group) (test cohort). Binary logistic regression was used to develop a screening tool using laboratory and clinical parameters that were significantly associated with BSI (P < 0.05; adjusted odds ratio (OR) > 1); and Classification and Regression Tree (CART) analysis was used to identify parameter breakpoints. Performance metrics were used to evaluate and validate the tool. RESULTS: The significant parameters associated with BSI were maximum temperature (Tmax)(> 37.55C)(OR = 42.575), neutrophils (> 7.95)(OR = 1.923), a change in level of consciousness (LOC) (Yes = 1, No = 0)(OR = 1.571), blood urea nitrogen (BUN)(> 10.05)(OR = 1.359), glucose (> 7.35)(OR = 1.167), albumin (< 33.5)(OR = 1.038) and alanine aminotransferase (ALT) (> 19.5)(OR = 1.005). The optimal screening tool [Ln (odds of BSI) = - 150.299 + 3.751(Tmax) + 0.654(neutrophils) + 0.452(change in LOC) + 0.307(BUN) + 0.154(glucose) + 0.038(albumin) + 0.005(ALT)] had favorable performance metrics in the learn and test cohorts (sensitivity, specificity and accuracy of 95% in the learn cohort and 77, 89, and 81% in the total test cohort); and performed better than using only temperature and neutrophil count. CONCLUSIONS: The validated tool had high predictive value which may improve early identification and management of BSI in older patients.

Task Activation Results in Regional 13 C-Lactate Signal Increase in the Human Brain.

Hyperpolarized- 13 C magnetic resonance imaging (HP- 13 C MRI) was used to image changes in 13 C-lactate signal during a visual stimulus condition in comparison to an eyes-closed control condition. Whole-brain 13 C-pyruvate, 13 C-lactate and 13 C-bicarbonate production was imaged in healthy volunteers (N=6, ages 24-33) for the two conditions using two separate hyperpolarized 13 C-pyruvate injections. BOLD-fMRI scans were used to delineate regions of functional activation. 13 C-metabolite signal was normalized by 13 C-metabolite signal from the brainstem and the percentage change in 13 C-metabolite signal conditions was calculated. A one-way Wilcoxon signed-rank test showed a significant increase in 13 C-lactate in regions of activation when compared to the remainder of the brain ( p = 0.02, V = 21). No significant increase was observed in 13 C-pyruvate ( p = 0.11, V = 17) or 13 C-bicarbonate ( p = 0.95, V = 3) signal. The results show an increase in 13 C-lactate production in the activated region that is measurable with HP- 13 C MRI.

Chemical Stability of Epinephrine 10 mcg/mL Diluted in 0.9% Sodium Chloride and Stored in Polypropylene Syringes at 4 degrees C and 25 degrees C.

Studies have evaluated epinephrine stability in higher concentrations and shorter durations than we require. The objective of this study was to evaluate the chemical stability of epinephrine in syringes at concentrations of 10 mcg/mL in 0.9% sodium chloride at 4°C and 25°C. Solutions of 10 mcg/mL epinephrine in 0.9% sodium chloride were prepared and stored in 10-mL Becton, Dickinson and Company syringes. Three units of each container were stored at 4°C and 25°C. Concentration analysis was completed on study days 0, 2, 7, 14, 21, 28, 42, 56, 72, and 91 using a validated stability-indicating liquid chromatographic method with ultraviolet detection. Chemical stability was based on the intersection of the lower limit of the 95% confidence interval of the observed degradation rate and the time to achieve 90% of the initial concentration (T-90). The analytical method separated degradation products from epinephrine to measure concentration specifically, accurately, and reproducibly. During the study period, all solutions at 4°C retained more than 89.62% of the initial concentration for 91 days. Solutions stored at 25°C retained more than 90% for 21 days. Multiple linear regression revealed significant differences in percent remaining due to study day (P<0.001) and temperature (P=0.002). The calculated T-90, with 95% confidence, was 71.40 days for solutions stored at 4°C but only 12.77 days for solutions stored at 25°C. We conclude that 10 mcg/mL epinephrine solution diluted in 0.9% sodium chloride stored at 4°C is chemically and physically stable for 64 days, with 95% confidence. The syringe may be held at room temperature for up to 24 hours during this period and still retain more than 90% of the initial concentration.

Stability of Generic Formulations of Bortezomib 1.0 and 2.5 mg/mL in Vials and Syringes Stored at 4°C and Room Temperature (23°C or 25°C).

BACKGROUND: The availability of generic versions of bortezomib raises questions about the reliability of extrapolating stability data from one brand to another. OBJECTIVE: To evaluate the stability of bortezomib formulations available from Janssen, Teva Canada, Actavis Pharma, Dr. Reddy's Laboratories, Apotex, and MDA, reconstituted with 0.9% sodium chloride (normal saline) to produce solutions of either 1.0 or 2.5 mg/mL and stored over at least 21 days under refrigeration (4°C) or at room temperature (either 23°C or 25°C) in the manufacturer's original glass vials or in polypropylene syringes. METHODS: On study day 0, solutions with concentration 1.0 mg/mL or 2.5 mg/mL of the Teva, Actavis, Dr. Reddy's, Apotex, and MDA generic formulations were prepared. Three units of each type of container (glass vials and syringes) were stored at 4°C and 3 units at room temperature. Concentration and physical inspection were completed on at least 8 study days (including day 0) over a 21- to 84-day study period. Bortezomib concentrations were determined by a validated stability-indicating liquid chromatographic method with ultraviolet detection. The end point of these studies was the time to reach 90% of the initial concentration (T-90) with 95% confidence, which is expressed as "T-9095%CI", where CI refers to the confidence interval. In addition to estimating the T-9095%CI, differences in stability among products from all manufacturers were compared using multiple linear regression. Previously published data for the Janssen product were included in the overall comparisons. RESULTS: In all of the studies, the analytical method separated degradation products from bortezomib, such that the concentration of bortezomib was measured specifically, accurately (deviations < 2.5%), and reproducibly (average replicate error 2.5%). During all studies, solutions retained more than 94% of the initial concentration at 4°C. The T-9095%CI exceeded the study period for all formulations under all combinations of concentration, container, and temperature, except the 84-day study for the MDA product. Multiple linear regression showed no significant differences among manufacturers (p = 0.57). CONCLUSIONS: In this study, formulations of bortezomib currently marketed in Canada (by Janssen, Teva Canada, Actavis Pharma, Dr. Reddy's Laboratories, Apotex, and MDA) were pharmaceutically equivalent and interchangeable. Given that there was no difference in stability related to manufacturer, nominal concentration, or container, we conclude that these formulations are physically and chemically stable for at least 35 days under refrigeration and at least 25 days at room temperature.

CONTEXTE: La disponibilité de versions génériques de bortezomib soulève des questions relatives à la fiabilité de l'extrapolation des données concernant la stabilité d'une marque à l'autre. OBJECTIF: Évaluer la stabilité des formules de bortezomib de Janssen, de Teva Canada, d'Actavis Pharma, des Laboratoires du Dr Reddy, d'Apotex et de MDA, reconstituées avec 0,9 % de chlorure de sodium (solution saline normale) pour produire des solutions de 1 ou de 2,5 mg/mL et réfrigérées au moins 21 jours à 4 °C ou à température ambiante (23 °C ou 25 °C), dans des fioles en verre du fabricant ou dans des seringues en polypropylène. MÉTHODES: La préparation des solutions avec une concentration de 1 mg/mL ou 2,5 mg/mL des formules génériques de Teva, d'Actavis, du Dr Reddy, d'Apotex et de MDA a eu lieu le jour 0 de l'étude. Trois unités de chaque contenant (fioles en verre et seringues) étaient stockées à 4 °C et 3 unités, à température ambiante. L'inspection de la concentration et l'inspection physique ont été réalisées pendant au moins 8 jours (y compris le jour 0) de l'étude qui a duré de 21 à 84 jours. Les concentrations de bortezomib ont été déterminées par une méthode chromatographique liquide validée, indiquant la stabilité à l'aide d'une détection par rayons ultraviolets. Le point final de ces études était le temps nécessaire pour que le produit atteigne 90 % de la concentration initiale (T-90) avec un seuil de confiance de 95 %, exprimé par T-90IC 95 %, IC indiquant l'intervalle de confiance. En plus de l'estimation du T-90IC 95 %, les différences de stabilité des produits de tous les fabricants ont été comparées à l'aide d'une régression linéaire multiple. Les données publiées précédemment sur le produit Jansen sont incluses dans les comparaisons globales. RÉSULTATS: La méthode analytique de toutes les études qui ont été menées a séparé les produits de dégradation du bortezomib de telle manière que la concentration était mesurée de manière spécifique, précise (déviations < 2,5 %) et reproductible (erreur de réplique 2,5 %). Tout au long des études, les solutions ont retenu plus de 94 % de la concentration initiale à 4 °C. Le T-90IC 95 % de toutes les formules dans toutes les combinaisons de concentration, de contenant et de température, dépassait la durée des études, à l'exception du produit MDA dans l'étude de 84 jours. La régression linéaire multiple n'a indiqué aucune différence importante parmi les fabricants (p = 0,57). CONCLUSIONS: Dans cette étude, les formules de bortezomib actuellement commercialisées au Canada (par Janssen, Teva Canada, Actavis Pharma, les Laboratoires du Dr Reddy, Apotex et MDA) étaient équivalentes et interchangeables d'un point de vue pharmaceutique. Puisqu'aucune différence de stabilité, de concentration nominale ou de contenant liée à l'un ou l'autre des fabricants n'a été révélée, nous concluons que ces formules sont physiquement et chimiquement stables pendant au moins 35 jours sous réfrigération et au moins 25 jours à température ambiante.

Development of Stable and Simple Finasteride 333-µg/mL Suspensions that Minimize Occupational Exposure.

Finasteride is not commercially available in a liquid format, which stimulated the development of a stable and simple finasteride suspension formulation. The objectives of this work were to develop and test a finasteride suspension for 1) simplicity to compound, 2) pharmaceutical acceptability, 3) stability, and 4) potential for occupational exposure. The stability of commercial 5-mg finasteride tablets (50 mg/150 mL) was evaluated in water, Oral Mix, and OralMix SF in amber polyethylene terephthalate bottles at 25°C or 4°C. Additional stability studies were carried out using sugar-free Finasteride Powder USP in amber polyethylene terephthalate bottles and tablets in water in polypropylene oral syringes. On study days 0, 1, 3, 7, 14, 28, 38, 49, 63, and 90, the finasteride concentration was determined using a validated stability-indicating liquid chromatographic method. The potential occupational airborne exposure was evaluated by attempting to measure finasteride in 1000 liters of room air following shaking and nebulization. Finasteride suspension/dispersion formulations were prepared in water, Oral Mix, and Oral Mix SF from tablets and pure powder. All formulations retained more than 94.3% of the initial finasteride concentration, with 95% confidence, when stored for up to 90 days at room temperature or 4°C. Simulations of occupational exposure failed to demonstrate the presence of finasteride in room air following attempts to nebulize finasteride mixtures. We conclude that 333-µg/mL suspension/dispersions of finasteride in water or Oral Mix products will have more than 94.3% of the initial finasteride concentration remaining after 90 days, regardless of the formulation, container, or storage temperature. Although we could not detect finasteride in room air, given the analytical limits of the study, we estimate that exposure would unlikely exceed 3.6-µg/1000 liters of room air. Nevertheless, since current regulations are based on "no safe limit," use of primary engineering controls and personal protective equipment as appropriate is recommended.