Margarita Legaspi

Institut national de la recherche scientifique, Quebec City, Quebec, Canada

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Publications (9)20.34 Total impact

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    ABSTRACT: This study compares basic respiratory variables (rate, tidal and minute volumes) with time-, flow- and ratio-derived parameters obtained using head-out plethysmography in rats following administration of reference drugs (isotonic saline, 2.0 mL/kg, IV; albuterol, 400 μg/kg, inhalation; methacholine, 136 μg/kg, IV; and remifentanil, 14 μg/kg, IV) to identify respiratory variables with superior sensitivity. Paired t-tests by block-period, and analysis of covariance (ANCOVA) with baseline as covariate and a posteriori pair-wise comparisons using Dunnett's test were used. Variations in respiratory parameters observed over time justify the use of a control group in any respiratory safety pharmacology study for inter-groups comparison. Handling-, and slumbering-, induced perturbations were minimal. The system was sensitive and specific to detect changes in respiratory variables related to pharmacologically-induced bronchodilation, bronchoconstriction and central respiratory depression. The standard variables (respiratory rate, tidal and minute volumes) confirmed to be the cornerstone of respiratory safety pharmacology to detect pharmacological changes. Flow-derived parameters appeared as highly valuable complement for interpretation of respiratory response, whereas time- and ratio-derived parameters presented limited added value during interpretation.
    No preview · Article · Dec 2010 · Regulatory Toxicology and Pharmacology
  • Simon Authier · Margarita Legaspi · Dominique Gauvin · Eric Troncy
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    ABSTRACT: Rats are most frequently used to fulfill ICH S7A requirements for respiratory safety pharmacology. We hypothesized that the models used to assess respiratory safety pharmacology present different ventilatory responses to bronchoconstriction, bronchodilation and respiratory depression. Respiratory monitoring was performed with head-out plethysmographs for rats, masks for dogs and bias airflow helmets for monkeys. Respiratory rate (RR), tidal volume (TV) and minute volume (MV) were recorded. Forty rats, 18 dogs and 8 monkeys were acclimated to the respiratory monitoring equipment. Animals received saline (IV), albuterol (inhalation), methacholine (IV) and remifentanil (IV). Albuterol increased TV in all species. Methacholine decreased TV and MV in monkeys. In dogs, methacholine increased TV, RR and MV. In rats, methacholine increased TV and decreased RR. Remifentanil induced central respiratory depression in all species with decreased MV, except in rats. Dogs presented a biphasic response to remifentanil with hypoventilation followed by delayed hyperventilation. The monkeys presented similar responses to humans which may be due to biologic similarities. Dogs and rats presented clinically significant ventilatory alterations following positive control drugs. Although, the response to bronchoconstriction in dogs and rats was different from humans, the two species presented ventilatory changes that highlight the potential adverse effect of test articles.
    No preview · Article · Nov 2009 · Regulatory Toxicology and Pharmacology

  • No preview · Article · Sep 2008 · Journal of pharmacological and toxicological methods

  • No preview · Article · Sep 2008 · Journal of pharmacological and toxicological methods
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    ABSTRACT: Drug-induced cardiovascular effects identified in conscious cynomolgus monkeys equipped with tethers and prepared for radiotelemetry were compared with results from anesthetized non-human primate (cynomolgus and rhesus) models. Remifentanil (4.0 microg/kg, bolus), esmolol (2.0 mg/kg, bolus) and dopamine (0.05 mg/kg/min, 30 min infusion) were given intravenously to all models. Remifentanil decreased heart rate (HR), systolic, mean and diastolic systemic arterial pressures (SAP) in anesthetized animals while conscious monkeys presented an increase in HR, systolic, mean and diastolic SAP, as seen in humans for the respective state of consciousness (conscious and anesthetized). Esmolol decreased HR, systolic, mean and diastolic SAP in anesthetized monkeys while only HR, systolic and mean SAP achieved a statistically significant decrease in the conscious model. The amplitude of SAP reduction was greater in anesthetized models, while the amplitude of HR reduction was greater in the conscious and anesthetized cynomolgus models than in the anesthetized rhesus model. Dopamine induced a significant increase in HR, systolic, mean and diastolic SAP in anesthetized models without any statistically significant effect on HR and SAP in the conscious model. The amplitude of hemodynamic and chronotropic alterations induced by positive control drugs was generally greater in anesthetized than in conscious models and statistical significance was achieved more often with the anesthetized models. These results suggest that an anesthetized model may be valuable as part of a drug screening program for cardiovascular safety evaluations in addition to a conscious model.
    No preview · Article · Jul 2008 · Journal of pharmacological and toxicological methods
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    ABSTRACT: Installation, operation and performance qualifications were performed on a test system for respiratory monitoring. For performance qualification, conscious dogs received saline (0.2 mL/kg, iv, n=12), albuterol (100 microg/kg, inhalation, n=5), methacholine (2.0 and 8.0 microg/kg, iv, n=8) and remifentanil (4.0 microg/kg, iv, n=7). Following anesthesia with propofol infusion, dogs received saline (iv, n=15), albuterol (100 microg/kg, inhalation, n=8), methacholine (8.0 microg/kg, iv, n=8), remifentanil (4.0 microg/kg, iv, n=7), and cholecystokinine tetrapeptide (CCK-4) (10 microg/kg, iv, n=7) and were exposed to hypoxic gas mixture (10% oxygen) (n=12). Saline had no significant respiratory effect. Albuterol increased tidal volume (TV) (+28%, p<0.05) and minute ventilation (MV) (+96%, p<0.01) in conscious dogs. In anesthetized dogs, MV was significantly increased (+23%, p<0.05) but the difference was not statistically significant for TV and respiratory rate (RR). Methacholine at 2.0 microg/kg increased MV (+45%, p<0.01) in conscious animals while 8.0 microg/kg increased RR (+66%, p<0.01), TV (+24%, p<0.05) and MV (+88%, p<0.05). In anesthetized dogs, methacholine increased RR (+51%, p<0.05), MV (+34%, p<0.05), lung elastance (+36.9%, p<0.01), and resistance (+45.8%, p<0.01). Remifentanil decreased MV in conscious dogs (-68%, p<0.01) while transient apnea was observed in all anesthetized dogs. CCK-4 increased RR (+328%, p<0.01) and MV (+127%, p<0.05) and decreased TV (-58%, p<0.01). Exposure to hypoxic gas mixture increased MV and RR (p<0.01). Baseline MV was lower (p<0.05) in anesthetized than in conscious dogs. Arterial blood gas values, particularly SaO(2), presented a limited sensitivity to detect any ventilation disturbance, but allowed confirmation of both ventilatory compensatory phenomenon (when present) and initial pharmacologic drug effect. These results also highlight the greater sensitivity of the conscious model when compared to anesthetized dogs.
    No preview · Article · Feb 2008 · Journal of pharmacological and toxicological methods

  • No preview · Conference Paper · Feb 2008
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    ABSTRACT: The purpose of this study was to evaluate 3 anesthetic protocols for intraduodenal drug administration by endoscopy in rhesus monkeys (Macaca mulatta). Anesthesia was induced using intramuscular ketamine and midazolam, isoflurane (inhalant gas), or intravenous propofol in male and female rhesus monkeys. A noninvasive dosing line was placed in the duodenum by use of endoscopy, and 50% dextrose (3 ml/kg) was administered. Blood pressure, heart rate, body temperature, and reflexes (corneal, palpebral, pharyngeal) and myorelaxation (mandibular reflex and reaction to limb manipulation) were evaluated every 5 min. To estimate intestinal absorption, glycemia was evaluated prior to dextrose administration and at 2, 5, 10, 15, 20, 30, 45, and 60 min after dosing. All 3 protocols resulted in successful induction of anesthesia. Recovery from isoflurane and propofol was significantly faster than from ketamine-midazolam. Duration of the recovery period after isoflurane was less variable than with propofol, but isoflurane produced greater hypothermia. Isoflurane and propofol resulted in predictable glucose absorption after intraduodenal dextrose administration, whereas ketamine-midazolam led to an inconsistent increase in glycemia.
    No preview · Article · Dec 2006 · Journal of the American Association for Laboratory Animal Science: JAALAS
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    Margarita S.Legaspi
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    ABSTRACT: Le but de cette étude était d’évaluer les qualifications de performance du système FlexiWare® chez le rat male Sprague Dawley et le singe Cynomolgus éveillés, ainsi que chez le chien Beagle éveillé et anesthésié, suite à l’administration de produits ayant une activité pharmacologique connue. Les produits utilisés incluaient l’albutérol administré par inhalation, la méthacholine, et le rémifentanil administrés par voie intraveineuse. Une solution saline administré par voie intraveneuse, a été utilisée comme substance témoin. Différentes variables ont servi à évaluer la réponse des animaux (rats, chien, singe). Ces dernières comprenaient la fréquence respiratoire (RR), le volume courant (TV), la ventilation minute (MV). Des paramètres additionnels ont été évalués chez le rat, soit les temps d’inspiration (IT) et d’expiration (ET), le temps du pic de débit expiratoire, les pics de débits inspiratoire et expiratoire, le ratio inspiratoire:expiratoire (I:E), le ratio inspiratoire sur respiration totale (I:TB), et l’écoulement expiratoire moyen (EF50). Les résultats obtenus ont démontré que le système FlexiWare® était suffisamment sensible et spécifique pour dépister, chez les espèces animales utilisées, les effets bronchodilateur, bronchoconstricteur et dépresseur central des substances testées. Il pourrait faire partie des méthodes (ICH 2000) utilisées en pharmacologie de sécurité lors de l’évaluation de substances pharmacologiques sur le système respiratoire des animaux de laboratoire. Les espèces animales utilisées ont semblé s’adapter aisément aux procédures de contention. Les paramètres évalués, RR, TV et MV ont permis de caractériser la réponse des animaux suite à l’administration de produits pharmacologiques à effets connus, judicieusement complétés par les variables de débit. L’ajout de paramètres du temps n’était pas primordiale pour détecter les effets des drogues, mais offre des outils complémentaires d’interpréter les changements physiologiques. Cependant, chez le rat conscient, la période d’évaluation ne devrait pas s’étendre au-delà d’une période de deux heures post traitement. Ces études constituent une évaluation des qualifications de performance de cet appareil et ont démontré de manière originale, la validation concurrentielle, en terme de précision (sensibilité et spécificité) et fiabilité pour différentes variables et sur différentes espèces. The aim of this study was to evaluate the performance qualifications of the FlexiWare® system in conscious Sprague-Dawley rats, Cynomolgus monkeys, as well as awake and anesthetized Beagle dogs following the administration of pharmacological substances with known effects on the respiratory system. The pharmacological substances included albuterol administered by inhalation; methacholine and remifentanil, both administered intravenously. A preparation of saline solution administered intravenously was used as control. Respiratory monitoring included: respiratory rate (RR), tidal volume (TV), minute ventilation (MV), in rats, dogs and monkeys. Additional time-, flow-, and ratio-derived variables were used in the rat model. Those variables included inspiratory (IT) and expiratory (ET) times, time to peak expiratory flow, peak inspiratory and expiratory flows, mid-tidal expiratory flow (EF50), inspiratory:expiratory (I:E) and inspiratory to total breath (I:TB) ratios. The results of this study have proven that the FlexiWare® was a reliable method and should be considered in the core battery recommended in safety pharmacology studies (ICH 2000) to assess the broncho-dilative, -constrictive, and central depressant effects of drugs on the respiratory system of the common laboratory animal specie. The animals appeared to adapt well to the restraint unit. The variables evaluated, particularly RR, TV and MV, were adequate and allowed to characterize the response of the animals following the administration of the pharmacological substances. They are judiciously completed with flowderived variables. The addition of within-breath time parameters was not primordial to detect drug effects but offered complementary tools to interpret physiological changes. However the evaluation period should be limited to the first 2 hours post treatment. These studies represent a performance qualifications evaluation of the system and have originally demonstrated the precision (sensitivity and specificity) as well as repeatability for different variables and on different specie of interest.
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Publication Stats

65 Citations
20.34 Total Impact Points


  • 2010
    • Institut national de la recherche scientifique
      • National Experimental Biology Centre
      Quebec City, Quebec, Canada
  • 2006-2009
    • Université de Montréal
      • Faculty of Veterinary Medicine
      Montréal, Quebec, Canada