Evaluation of respiratory function in freely moving Beagle dogs using implanted impedance technology

Safety Pharmacology Study of ET-26 Hydrochloride, a Potential Drug for Intravenous General Anesthesia, in Rats and Beagle Dogs

Background: ET-26 hydrochloride (ET-26HCl), a class 1 new drug, was developed to reserve the advantages of etomidate with a mild adrenocortical inhibition.

Purpose: this study was to evaluate the potential adverse effects on the cardiovascular system of beagle dogs and the respiratory and central nervous systems of rats.

Methods: three established methods, the whole-body plethysmography for respiratory function, the prototype telemetry transmitter for cardiovascular function, and the standardized functional observational battery for central nervous system function, were accomplished with Good Laboratory Practice standards.

Results: no significant difference in the tidal volume, but the respiratory rate and minute ventilation were reduced. The degree of inhibition was the most serious in the first 15 min after dosing and function fully recovered after 1 h. For male rats, the respiratory rate of male rats was reduced significantly at 15 min after injection with ET-26HCl (4 mg/kg, 28.6%, p ≤ 0.01; 8 mg/kg, 24.5%, p ≤ 0.01; 16 mg/kg, 44.5%, p ≤ 0.001), and the minute ventilation at 15 min was decreased by 20.1% (4 mg/kg, p = 0.034), 22.2% (8 mg/kg, p = 0.019), and 44.6% (16 mg/kg, p ≤ 0.001) as compared to control group. As with male rats, the respiratory rate of the female rats was reduced significantly at 15 min (4 mg/kg, 23.3%, p ≤ 0.01; 8 mg/kg, 29.2%, p ≤ 0.001; 16 mg/kg, 44.1%, p ≤ 0.001), and the minute ventilation was decreased by 25.2% (4 mg/kg, p ≤ 0.001), 23.0% (8 mg/kg, p ≤ 0.01), and 47.6% (16 mg/kg, p ≤ 0.001). Then, all the variations in cardiovascular functions were within the expected range for normal biological variation, we concluded that ET-26HCl, even at 10-fold ED₅₀, still does not exert toxicological effects on the cardiovascular system. For male beagle dogs, the systolic blood pressure after 24 h following administration of vehicle control or 8, 12, or 16 mg/kg ET-26HCl was 137.80 ± 5.55, 131.76 ± 10.03, 139.88 ± 8.35, and 141.28 ± 8.75 mmHg, respectively. The diastolic blood pressure was 71.16 ± 4.84, 66.52 ± 8.50, 73.64 ± 8.51, and 74.24 ± 8.68 mmHg, respectively. For female beagle dogs, the systolic blood pressure after 24 h following administration of vehicle control or 8, 12, or 16 mg/kg ET-26HCl was 128.28 ± 5.22, 124.76 ± 7.29, 134.88 ± 5.56, and 135.36 ± 8.72 mmHg, respectively. The diastolic blood pressure was 67.00 ± 4.10, 62.12 ± 7.87, 69.44 ± 6.40, and 70.20 ± 8.42 mmHg, respectively. In central nervous system function experiment, all the changes observed in the functional observational battery tests, including motor activity, behavior, coordination, and sensory and motor reflex responses, and reduced body temperature, were resulted in general anesthesia effect of ET-26HCl.

Conclusion: ET-26HCl exerts mild, reversible effects on respiratory, cardiovascular, and central nervous system function as verified by standard in vivo animal models.

Effects of Anisodine Hydrobromide on the Cardiovascular and Respiratory Functions in Conscious Dogs

Purpose

Anisodine hydrobromide (Ani) is isolated from the medicinal plant Anisodus tanguticus (Maxim.) Pascher for clinical use. Although considerable research regarding Ani has been reported, the safety profiles of Ani are currently unknown. This study investigated the cardiorespiratory effects of Ani in conscious dogs to provide clinicians a detailed safety profile of Ani on the cardiorespiratory system.

Materials and Methods

Using the Latin square design, the study was divided into six phases, where in each phase, six telemetered beagle dogs received one dose of normal saline or sotalol hydrochloride or Ani (0.1, 0.4, 1.6, or 6.4 mg/kg). Electrocardiogram, blood pressure (BP) and respiratory parameters were collected before and after administration for 24 hours. Statistical comparisons were performed at scheduled time-points.

Results

The heart rate was significantly increased, PR and QT_CV intervals were significantly shortened in Ani 0.4, 1.6, 6.4 mg/kg treatment group after drug administration. Compared with the saline group, a significant increase in heart rate and shortening of PR, QT_CV intervals were observed in the Ani 1.6, 6.4 mg/kg treatment groups from 5 min to 4 h time-points. Diastolic and mean BP were significantly increased in Ani 1.6, 6.4 mg/kg from 1 h to 2 h time-points compared to those of the saline control. Accelerated breathing was observed in the first 20 min after Ani 0.4, 1.6, and 6.4 mg/kg treatment, although not statistically significant. Furthermore, no significant differences were observed in any of the corresponding indexes of Ani 0.1 mg/kg treatment group at different time-points compared to those of the saline group.

Conclusion

Ani may have adverse effects on the cardio-respiratory systems of dogs at doses above 0.4 mg/kg, whereas Ani 0.1 mg/kg was devoid of potentially deleterious effects on cardiorespiratory function.

Comparison of respiratory inductive plethysmography versus head-out plethysmography for anesthetized nonhuman primates in an animal biosafety level 4 facility

For inhalational studies and aerosol exposures to viruses, head-out plethysmography acquisition has been traditionally used for the determination of estimated inhaled dose in anesthetized nonhuman primates prior to or during an aerosol exposure. A pressure drop across a pneumotachograph is measured within a sealed chamber during inspiration/exhalation of the nonhuman primate, generating respiratory values and breathing frequencies. Due to the fluctuation of depth of anesthesia, pre-exposure respiratory values can be variable, leading to less precise and accurate dosing calculations downstream. Although an anesthesia infusion pump may help stabilize the depth of sedation, pumps are difficult to use within a sealed head-out plethysmography chamber. Real-time, head-out plethysmography acquisition could increase precision and accuracy of the measurements, but the bulky equipment needed for head-out plethysmography precludes real-time use inside a Class III biological safety cabinet, where most aerosol exposures occur. However, the respiratory inductive plethysmography (RIP) acquisition method measures the same respiratory parameters by detecting movement of the chest and abdomen during breathing using two elastic bands within the Class III biological safety cabinet. As respiratory values are relayed to a computer for software integration and analysis real-time, adjustment of aerosol exposure duration is based on the depth of sedation of the animal. The objective of this study was to compare values obtained using two methodologies (pre-exposure head-out plethysmography and real-time RIP). Transitioning to RIP technology with real-time acquisition provides more consistent, precise, and accurate aerosol dosing by reducing reported errors in respiratory values from anesthesia variability when using pre-exposure head-out plethysmography acquisition.

Overview of Respiratory Studies to Support ICH S7A

Tests of pulmonary function are useful tools for evaluating the potential for compounds to produce toxicity affecting the pulmonary system. Insults to the pulmonary system (i.e., due to drugs, biologics, toxins) can cause detectable dysfunction through multiple mechanisms. Manifestation of the response to insults will depend on the component(s) involved and the compensatory mechanism(s) initiated. The purpose of this chapter is to introduce the concepts of pulmonary testing as it is applied to the preclinical evaluation of pharmaceutical test articles. The topics will include the techniques and methods that have been developed for use in nonclinical (animal) subjects and the parameters that are routinely measured.

Establishing clinical end points of respiratory function in large animals for clinical translation

Respiratory dysfunction due progressive weakness of the respiratory muscles, particularly the diaphragm, is a major cause of death in the neuromuscular disease (NMD) X-linked myotubular myopathy (XLMTM). Methods of respiratory assessment in patients are often difficult, especially in those who are mechanically ventilated. The naturally occuring XLMTM dog model exhibits a phenotype similar to that in patients and can be used to determine quantitative descriptions of dysfunction as clinical endpoints for treatment and the development of new therapies. In experiments using respiratory impedance plethysmography (RIP), XLMTM dogs challenged with the respiratory stimulant doxapram displayed significant changes indicative of diaphragmatic weakness.

Radio telemetry devices to monitor breathing in non-sedated animals

Radio telemetry equipment has significantly improved over the last 10-15 years and is increasingly being used in research for monitoring a variety of physiological parameters in non-sedated animals. The aim of this review is to provide an update on the current state of development of radio telemetry for recording respiration. Our literature review found only rare reports of respiratory studies via radio telemetry. Much of this article will hence report our experience with our custom-built radio telemetry devices designed for recording respiratory signals, together with numerous other physiological signals in lambs. Our current radio telemetry system allows to record 24 simultaneous signals 24h/day for several days. To our knowledge, this is the highest number of physiological signals, which can be recorded wirelessly. Our devices have been invaluable for studying respiration in our ovine models of preterm birth, reflux laryngitis, postnatal exposure to cigarette smoke, respiratory syncytial virus infection and nasal ventilation, all of which are relevant to neonatal respiratory problems.

Non-clinical models: validation, study design and statistical consideration in safety pharmacology

The current issue of the Journal of Pharmacological and Toxicological Methods (JPTM) focuses exclusively on safety pharmacology methods. This is the 7th year the Journal has published on this topic. Methods and models that specifically relate to methods relating to the assessment of the safety profile of a new chemical entity (NCE) prior to first in human (FIH) studies are described. Since the Journal started publishing on this topic there has been a major effort by safety pharmacologists, toxicologists and regulatory scientists within Industry (both large and small Pharma as well as Biotechnology companies) and also from Contract Research Organizations (CRO) to publish the surgical details of the non-clinical methods utilized but also provide important details related to standard and non-standard (or integrated) study models and designs. These details from core battery and secondary (or ancillary) drug safety assessment methods used in drug development programs have been the focus of these special issues and have been an attempt to provide validation of methods. Similarly, the safety pharmacology issues of the Journal provide the most relevant forum for scientists to present novel and modified methods with direct applicability to determination of drug safety-directly to the safety pharmacology scientific community. The content of the manuscripts in this issue includes the introduction of additional important surgical methods, novel data capture and data analysis methods, improved study design and effects of positive control compounds with known activity in the model.