Effects of tasipimidine premedication with and without methadone and dexmedetomidine on cardiovascular variables during propofol-isoflurane anaesthesia in Beagle dogs.

OBJECTIVE: To evaluate cardiovascular effects of oral tasipimidine on propofol-isoflurane anaesthesia with or without methadone and dexmedetomidine at equianaesthetic levels. STUDY DESIGN: Prospective, placebo-controlled, blinded, experimental trial. ANIMALS: A group of seven adult Beagle dogs weighing (mean ± standard deviation) 12.4 ± 2.6 kg and a mean age of 20.6 ± 1 months. METHODS: The dogs underwent four treatments 60 minutes before induction of anaesthesia with propofol. PP: placebo orally and placebo (NaCl 0.9%) intravenously (IV); TP: tasipimidine 30 µg kg-1 orally and placebo IV; TMP: tasipimidine 30 µg kg-1 orally and methadone 0.2 mg kg-1 IV; and TMPD: tasipimidine 30 µg kg-1 orally with methadone 0.2 mg kg-1 and dexmedetomidine 1 µg kg-1 IV followed by 1 µg kg-1 hour-1. Isoflurane in oxygen was maintained for 120 minutes at 1.2 individual minimum alveolar concentration preventing motor movement. Cardiac output (CO), tissue blood flow (tbf), tissue oxygen saturation (stO2) and relative haemoglobin content were determined. Arterial and mixed venous blood gases, arterial and pulmonary artery pressures and heart rate (HR) were measured at baseline; 60 minutes after oral premedication; 5 minutes after IV premedication; 15, 30, 60, 90 and 120 minutes after propofol injection; and 30 minutes after switching the vaporiser off. Data were analysed by two-way anova for repeated measures; p < 0.05. RESULTS: Tasipimidine induced a significant 20-30% reduction in HR and CO with decreases in MAP (10-15%), tbf (40%) and stO2 (43%). Blood pressure and oxygenation variables were mainly influenced by propofol-isoflurane-oxygen anaesthesia, preceded by short-lived alterations related to IV methadone and dexmedetomidine. CONCLUSIONS AND CLINICAL RELEVANCE: Tasipimidine induced mild to moderate cardiovascular depression. It can be incorporated into a common anaesthetic protocol without detrimental effects in healthy dogs, when anaesthetics are administered to effect and cardiorespiratory function is monitored.

Anaesthetic-sparing effect of the anxiolytic drug tasipimidine in Beagle dogs.

OBJECTIVE: To evaluate the effect of oral tasipimidine on dog handling, ease of catheter placement and propofol and isoflurane requirements for anaesthesia. STUDY DESIGN: Placebo-controlled, randomized, blinded, experimental trial. ANIMALS: A group of seven adult Beagle dogs weighing (mean ± standard deviation) 13.1 ± 2.7 kg with a mean age of 18.6 ± 1 months. METHODS: The dogs underwent four treatments before induction of anaesthesia with propofol. PP: placebo orally (PO) 60 minutes before induction of anaesthesia followed by placebo (NaCl 0.9%) intravenously (IV). TP: tasipimidine 30 µg kg-1 (PO) 60 minutes before induction of anaesthesia followed by placebo (NaCl 0.9%) IV. TMP: tasipimidine 30 µg kg-1 PO 60 minutes before induction of anaesthesia followed by methadone 0.2 mg kg-1 IV. TMPD: tasipimidine 30 µg kg-1 PO 60 minutes before induction of anaesthesia followed by methadone 0.2 mg kg-1 and dexmedetomidine 1 µg kg-1 IV followed by a dexmedetomidine constant rate infusion of 1 µg kg-1 hour-1. Sedation, response to catheter placement, intubation quality, time to loss of consciousness, time to intubation, required dose of propofol and minimum alveolar isoflurane concentration preventing motor movement (MACNM) were determined. A mixed-model analysis or the Friedman and Mann-Whitney test were used; p-value < 0.05. RESULTS: Response to catheter placement did not differ between treatments. Tasipimidine alone reduced the propofol dose by 30%. Addition of methadone or methadone and dexmedetomidine reduced the propofol dose by 48% and 50%, respectively. Isoflurane MACNM was reduced by 19% in tasipimidine-medicated dogs, whereas in combination with methadone or methadone and dexmedetomidine, isoflurane MACNM was reduced by 35%. CONCLUSIONS AND CLINICAL RELEVANCE: An anxiolytic dose of tasipimidine induced mild signs of sedation in dogs and reduced propofol and isoflurane requirements to induce and maintain anaesthesia, which needs to be considered in an anaesthetic plan.

How to stop disproportionation of a hydrochloride salt of a very weakly basic compound in a non-clinical suspension formulation.

Our objectives were to stabilize a non-clinical suspension for use in toxicological studies and to develop methods to investigate the stability of the formulation in terms of salt disproportionation. The compound under research was a hydrochloride salt of a practically insoluble discovery compound ODM-203. The first of the three formulation approaches was a suspension prepared and stored at room temperature. The second formulation was stabilized by pH adjustment. In the third approach cooling was used to prevent salt disproportionation. 5 mg/mL aqueous suspension consisting of 20 mg/mL PVP/VA and 5 mg/mL Tween 80 was prepared for each of the approaches. The polymer was used as precipitation inhibitor to provide prolonged supersaturation while Tween 80 was used to enhance dissolution and homogeneity of the suspension. The consequences of salt disproportionation were studied by a small-scale in vitro dissolution method and by an in vivo pharmacokinetic study in rats. Our results show that disproportionation was successfully suppressed by applying cooling of the suspension in an ice bath at 2-8 °C. This procedure enabled us to proceed to the toxicological studies in rats. The in vivo study results obtained for the practically insoluble compound showed adequate exposures with acceptable variation at each dose level.

European Bioanalysis Forum recommendation on the best practices to demonstrate processed sample stability.

The European Bioanalysis Forum is providing a proposal on experiments to be conducted if processed samples are to be stored for a period of time, either after an initial injection or if processed samples are to be stored for a period of time prior to their first injection. Using survey information and extensive discussion an insight was gained as to whether the current practices employed during method validation were conducted to scientifically validate actual sample handling conditions or to simply meet a perceived regulatory expectation. The goal of this report is to recommend the adoption of scientifically justified validation experiments that exactly reproduce and processed test sample handling and storage procedures and to introduce some uniformity across the industry.

Bioanalysis for plasma protein binding studies in drug discovery and drug development: views and recommendations of the European Bioanalysis Forum.

Plasma protein binding (PPB) is an important parameter for a drug's efficacy and safety that needs to be investigated during each drug-development program. Even though regulatory guidance exists to study the extent of PPB before initiating clinical studies, there are no detailed instructions on how to perform and validate such studies. To explore how PPB studies involving bioanalysis are currently executed in the industry, the European Bioanalysis Forum (EBF) has conducted three surveys among their member companies: PPB studies in drug discovery (Part I); in vitro PPB studies in drug development (Part II); and in vivo PPB studies in drug development. This paper reflects the outcome of the three surveys, which, together with the team discussions, formed the basis of the EBF recommendation. The EBF recommends a tiered approach to the design of PPB studies and the bioanalysis of PPB samples: 'PPB screening' experiments in (early) drug discovery versus qualified/validated procedures in drug development.

Best practices in a tiered approach to metabolite quantification: views and recommendations of the European Bioanalysis Forum.

The relationship between the exposure to drug metabolites and overall drug safety has become an integral part of the drug-development process. In-depth discussions in the scientific community, as well as recent guidelines on Drug Safety Testing of Metabolites from the US FDA (often referred to as the MIST guidance and ICH M3(R2) from the International Conference on Harmonization (ICH), has brought clarity to the regulatory requirements of the sponsor company in providing documentation on circulating levels of qualifying metabolites. However, less attention has been given to the challenges now faced by the bioanalytical community in supporting these new guidance policies. In this paper, the European Bioanalysis Forum (EBF) is providing a recommendation on which quality standards to apply when assessing the (relative) abundance or absolute concentrations of metabolites. This paper is the result of both an intensive consultation within the EBF (through internal surveys amongst EBF member companies and discussions) and consultation of the broader bioanalytical community (through discussions at international conferences). These recommendations will provide an increased understanding of how to apply a tiered approach to metabolite quantification as part of the bioanalytical strategy. As such, it aims to provide support to the bioanalytical community on the appropriate level of validation required at each stage of the drug-development process.

Incurred sample reproducibility: views and recommendations by the European Bioanalysis Forum.

Following intensive discussions, review, alignment of procedures and multiple surveys among their member companies, the European Bioanalysis Forum (EBF) is providing a recommendation on how to integrate incurred sample reproducibility (ISR) in the bioanalytical process. The recommendation aims to provide guidance throughout the lifecycle of a validated method, including the application of the method in study support. In its recommendation, the EBF considers both the internal discussions with EBF member companies, as well as the input provided in international meetings where ISR was discussed. The ultimate goal of the EBF recommendation is to ensure that bioanalytical methods can provide accurate and reproducible concentration data for pharmacokinetic and/or toxicokinetic evaluation, without any compromise, while safeguarding the optimal use of laboratory resources.

Effect of synthesis parameters of the sol-gel-processed spray-dried silica gel microparticles on the release rate of dexmedetomidine.

The objective of this study was to evaluate the possibilities to control the release rate of dexmedetomidine (DMED) from different spray-dried silica gel microparticle formulations. Microparticles were prepared by spray drying a silica sol polymer solution containing the drug. Drug release was investigated both in vitro and in vivo. The influence of sol-gel synthesis parameters, like pH and the water/alkoxide ratio (r) of the sol, on the release behaviour of the drug was studied. Silica gel microparticles had a smooth surface. Microparticles prepared from diluted sol, however, were more aggregated and clustered. The drug release conformed to zero order release from microparticles prepared near the isoelectric point of silica (pH 2.3 and pH 3) and to the square root of time kinetics from microparticles prepared at pH 1 and pH 5. The release also showed a dual-phasic profile with an initial burst and after that a slower release period. The dexmedetomidine release conformed to zero order kinetics from microparticles prepared at water/ alkoxide ratios between r = 6 and r = 35 (at pH 2.3). The release rate was the slowest from microparticles prepared with water/ alkoxide ratio 35. The bioavailability of dexmedetomidine in dogs showed that the release was sustained from silica gel microparticles as compared with a subcutaneously administered reference dose of 0.1 mg.