Pharmacodynamics in horses refers to the study of how drugs affect the equine body, encompassing the mechanisms of action, the relationship between drug concentration and effect, and the duration of these effects. This field examines how drugs interact with biological systems in horses to produce therapeutic or adverse effects. Key aspects include receptor binding, post-receptor effects, and chemical interactions. Understanding pharmacodynamics is essential for determining appropriate dosages, predicting drug interactions, and assessing therapeutic outcomes in equine medicine. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacodynamic properties of various drugs in horses, focusing on their effects, efficacy, and safety profiles.
Robinson NE, Derksen FJ, Berney C, Goossens L.The airway response to aerosol administration of the anticholinergic agent ipratropium bromide was determined in 8 horses with recurrent airway obstruction (heaves). The reversibility of airway obstruction was confirmed by measuring lung function before and during stabling; and by determining the response to atropine administration (0.02 mg/kg bwt intravenously). The dose-response to ipratropium bromide was determined using a Williams square design experiment in which 25, 50 or 75 micrograms ipratropium bromide/ml (4 ml/100 kg bwt) or the same volume of vehicle was administered to each horse b...
Tolliver SC, Lyons ET, Drudge JH, Stamper S, Granstrom DE.Critical tests were conducted in horses (n = 11) with naturally acquired infections of benzimidazole (BZ)-resistant population-B small strongyles in 1989 and 1990. Anthelmintics administered were thiabendazole (44 mg/kg of body weight, n = 4), oxibendazole (10 mg/kg, n = 3), and oxfendazole (OFZ, 10 mg/kg; n = 4). All compounds were paste formulations administered orally except for 1 of the OFZ treatments, which was a suspension formulation given by stomach tube. Aggregate mean efficacy was calculated for all species of small strongyles, drug-resistant and non-resistant. The highest efficacy w...
Kohn CW, Sams R, Kowalski JJ, Powers J, Wallace S.The disposition of rifampin in six healthy mares after single intravenous (i.v.) and oral (p.o.) doses and after seven oral doses of 10 mg/kg administered twice a day was investigated using a high performance liquid chromatographic (HPLC) method. Pharmacokinetic variables for rifampin determined using the HPLC method were comparable to variables reported from earlier studies utilizing a microbiological assay. Desascetylrifampin, a major metabolite of the parent compound, could not be detected in the serum but was detected at low concentrations in urine. Mean trough concentrations of rifampin i...
LeBlanc PH, Eberhart SW, Robinson NE.In horses with noninduced, reversible airway obstruction (heaves), pulmonary function is improved after sedation with the alpha 2-adrenergic agonist xylazine. The mechanism of this effect is undetermined. Because the predominant excitatory innervation of equine airways is cholinergic, the influence of alpha 2-adrenergic receptor stimulation on the response of isolated distal airways to cholinergic stimulation was determined. Distal bronchial segments from 22 healthy horses were suspended in isolated organ baths where their mechanical responses to various stimuli could be studied. Each tissue w...
Cervantes CC, Brown MP, Gronwall R, Merritt K.Each of 5 healthy mares was given 5 consecutive IM injections of ceftiofur sodium (2 mg/kg of body weight; 50 mg/ml) at 12-hour intervals. Ceftiofur concentrations were measured serially in serum, synovial fluid, peritoneal fluid, and urine, and were measured in CSF and endometrial tissue after the fifth dose. Mean elimination rate constant was 0.354 +/- 0.101 h-1 and elimination half-life was 2.49 +/- 0.49 hour. Mean serum ceftiofur concentrations peaked approximately 1 hour after each injection. The highest mean ceftiofur concentration was 5.09 micrograms/ml at 1 hour after the fifth dose fo...
Carrick JB, Morris DD, Moore JN.Platelet-activating factor (PAF) is an important mediator of endotoxaemia and various PAF receptor antagonists prevent many of the adverse effects of experimental endotoxaemia in laboratory animals. In this study a specific PAF receptor antagonist was used to investigate the role of PAF in equine endotoxaemia. At an interval of not greater than 10 days, 6 horses were each challenged with endotoxin and endotoxin with concurrent administration of SRI 63-441, a PAF receptor antagonist. The order of the treatments was randomised. Clinical signs, serum biochemical and coagulation profiles, and plat...
Sarasola P, McKellar QA.A regime for administration of ampicillin sodium by continuous intravenous infusions to horses was designed. The aim was to achieve plasma ampicillin concentrations between 5 and 10 micrograms/ml over a 4-h period. A 2 mg/kg bodyweight loading dose of ampicillin sodium was administered intravenously at the beginning of the infusion in order to achieve steady-state plasma concentrations rapidly. The infusion system subsequently administered ampicillin at a rate of approximately 19.2 micrograms/min/kg bodyweight. The plasma concentrations obtained over the infusion period correlated very well wi...
Rubie S, Robinson NE, Stoll M, Broadstone RV, Derksen FJ.Six horses that developed acute airway obstruction (heaves) when housed in a barn and fed poor-quality hay were studied. Airway obstruction was verified by a maximal change in pleural pressure during tidal breathing (delta Pplmax) of at least 15 cmH2O. Frusemide (1.0 mg/kg bwt) or an equivalent volume of vehicle was then administered intravenously (iv) and lung function was measured 15, 30, 60, 120, 180, 240 and 300 mins after drug administration. The effect of frusemide on lung function was also studied after treatment of horses with the cyclooxygenase inhibitor flunixin meglumine (1.1 mg/kg ...
Delatour P, Benoit E, Bourdin M, Gobron M, Moysan F.After the administration of racemic ketoprofen and carprofen to man, both enantiomers of each compound exhibit similar plasma profiles. This contrasts with the rat where the active S(+) enantiomer is predominant. For carprofen, regardless of the route of administration, the R(-) enantiomer is predominant in the plasma of all investigated animal species. The S(+)/R(-) ratio of the "areas under the curves" during the time course of the kinetics, is: 0.60 in dogs, 0.53 in Yucatan micro-pigs, 0.48 in mini-goats, 0.67 in calves and 0.19 in horses. For ketoprofen, the S(+) enantiomer is predominant ...
Wilson DV, Eberhart SW, Robinson NE, Rice R, Gray PR.The effects of exogenous platelet-activating factor (PAF) were determined in anesthetized ponies. Administration of PAF induced a decrease in cardiac index that resulted in systemic hypotension. This was followed by tachycardia, hypertension, and a return of cardiac index to baseline. Pulmonary arterial pressure increased markedly because of pulmonary vasoconstriction. Exogenous PAF also caused leukopenia and thrombocytopenia. The specific PAF receptor antagonist (WEB 2086) blocked all PAF-induced changes. Flunixin meglumine, a cyclooxygenase inhibitor, abolished the pulmonary hypertension and...
Eades SC, Moore JN.Changes in lateral cecal arterial blood flow, mean internal carotid arterial pressure, and heart rate caused by nasogastric administration of fenoldopam (3, 6, and 9 mg/kg of body weight), a selective agonist of dopaminergic receptors, were recorded in 7 healthy horses. Cecal arterial blood flow was significantly increased within 30 minutes after administration of fenoldopam at all 3 dosages, with the peak increases from baseline (67.8 +/- 17.5 ml/min) being 125 +/- 28, 120 +/- 22, and 153 +/- 32 ml/min for 3, 6, and 9 mg/kg, respectively. Although carotid arterial pressure did not change sign...
Orsini JA, Ramberg CF, Benson CE, Dreyfuss DJ, Vecchione JA, Kunz CC.Vancomycin hydrochloride was infused intravenously (i.v.) over a 30-min period in five horses at doses of 6.6, 11.0 and 15.4 mg/kg. Vancomycin concentration in plasma and synovial fluid samples was measured using a polarization immunoassay. A pharmacokinetic model was developed to accommodate the special features of the present study. The data were described by a two compartment open model with synovial fluid as an additional compartment in exchange with plasma. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) were measured for Staphylococcus aureus and Enteroco...
Clarke CR, Burrows GE, MacAllister CG, Spillers DK, Ewing P, Lauer AK.Single-dose pharmacokinetic variables of pyrimethamine were studied in horses. Pyrimethamine (1 mg/kg of body weight) was administered IV and orally to 6 adult horses, and plasma samples were obtained at frequent intervals thereafter. Plasma pyrimethamine concentration was assayed by gas chromatography, and concentration-time data were analyzed, using a pharmacokinetic computer program. The IV and oral administration data were best described by 3-compartment and 1-compartment models, respectively. The median volume of distribution at steady state after IV administration was 1,521 ml/kg and the...
Gaynor JS, Bednarski RM, Muir WW.The effect of xylazine on the arrhythmogenic dose of epinephrine (ADE) was studied in 9 horses. Anesthesia was induced by administration of guaifenesin (50 mg/kg of body weight, IV) followed by thiamylal (4 to 6 mg/kg, IV) and was maintained at 1 minimal alveolar concentration (MAC) of halothane (0.89%). Base apex ECG and facial artery pressure were recorded. Epinephrine was infused in a sequence of arithmetically spaced increasing rates (initial rate 0.25 micrograms/kg/min) for a maximum of 10 minutes. The ADE was defined as the lowest epinephrine infusion rate to the nearest 0.25 micrograms/...
Clarke CR, MacAllister CG, Burrows GE, Ewing P, Spillers DK, Burrows SL.Pharmacokinetics, CSF penetration, and hematologic effects of oral administration of pyrimethamine were studied after multiple dosing. Pyrimethamine (1 mg/kg of body weight) was administered orally once a day for 10 days to 5 adult horses, and blood samples were collected frequently after the first, fifth, and tenth doses. The CSF samples were obtained by cisternal puncture 4 to 6 hours after administration of the first, third, seventh, and tenth doses. Pyrimethamine concentration in plasma and CSF was quantified by gas chromatography, and plasma concentration-time data were analyzed, using a ...
Guthrie AJ, Beadle RE, Bateman RD, White CE.This paper presents a method for on-line determination of pulmonary mechanics in standing, non-sedated horses during and following inhalation of aerosolized drug solutions. This method was used to evaluate the temporal effects of inhaled histamine and methacholine aerosols on pulmonary mechanics in 18 Thoroughbred horses. The following were concluded from this study. The extremely large between-breath variation, for all variables used to evaluate pulmonary mechanics in the horse, limits the usefulness of these variables for modeling the non-specific pulmonary responses to inhaled stimulants on...
Geor RJ, Weiss DJ, Burris SM, Smith CM.The effects of furosemide and pentoxifylline on blood flow properties in horses were investigated. Hematologic and rheologic changes were examined in 4 horses before and 3 minutes after administration of epinephrine (1 mg, IV). The next day, hemorheologic changes were determined before and 3 hours after administration of furosemide (1 mg/kg of body weight, IM), and after administration of epinephrine at the sampling at 3 hours. Hematologic and rheologic changes were evaluated weekly in 3 horses given pentoxifylline (8.5 mg/kg, q 12 h, PO) for 28 days. In addition, hemorheologic responses to ep...
Coyne CP, Smith JE, Keeton K.A selected group of pharmaceutical compounds were evaluated for the ability to inhibit the biochemical activity of fibrinoligase (coagulation factor XIIIa*) in pooled equine plasma. Criteria for the pharmaceuticals selected were based on the mechanism of the transglutamination biochemical reaction mediated by coagulation factor XIIa*. These criteria were complemented by recognition of the molecular configuration and chemical composition of amino acid residue side chains involved in the process of covalent fibrin monomer polymerization (cross-linking, transglutamination) mediated by this enzyme...
Broadstone RV, Gray PR, Robinson NE, Derksen FJ.The effect of IV administration of the alpha 2-adrenoceptor agonist xylazine hydrochloride (0.5 mg/kg of body weight) was examined in ponies with recurrent obstructive pulmonary disease, commonly called heaves. Six ponies with the disease (principals) were studied during clinical remission and during an acute attack of airway obstruction precipitated by stabling and feeding of dusty hay. Six control ponies were also studied. In principal ponies with airway obstruction, xylazine administration significantly (P < 0.05) decreased pulmonary resistance and increased dynamic compliance, but did n...
Weiss DJ, Geor RJ, Burris SM, Smith CM.Pentoxifylline has been reported to improve peripheral vascular circulation by altering the flow properties of blood. To determine if the hemorrheological effects of pentoxifylline were mediated by alterations in neutrophil function and/or flow properties, we evaluated the drug's effects on equine neutrophils in vitro. Pentoxifylline, at a concentration of 1 x 10(-1) M, but not at concentrations of 1 x 10(-6) M to 1 x 10(-2) M, markedly suppressed neutrophil superoxide production, zymosan phagocytosis and adherence to nylon wool. Pentoxifylline failed to improve neutrophil filterability throug...
Sojka JE, Weiss JS, Samuels ML, You GM.The effect of the somatostatin analogue, octreotide, on gastric fluid pH was investigated in 4 ponies. Gastric fluid pH was determined after SC administration of octreotide or physiologic saline solution (control). A baseline sample of fluid was obtained, the agent was given, and 8 additional samples were collected hourly. Administration of octreotide at all dosages tested (0.1, 0.5, 1.0, and 5.0 micrograms/kg of body weight) increased gastric pH to > 5.0. Baseline values were consistently 4.0 for 2.4 +/- 1.2, 4.8 +/- 0.8, 5.7 +/- 1.3, and 5.4 +/- 2.6 (mean +/- SD) continuous hours, respec...
Dixon PM.The structure and possible functions of respiratory secretions are reviewed. In the equine, goblet (mucus producing) cells are the main source but little information is available on the volume or composition of equine respiratory secretions. Airway mucus has complex and incompletely understood physical characteristics which can be partially assessed by a wide range of in vitro and biological techniques. The complex relationship between mucus structure and its propulsion by the airway cilia are discussed, both in health and with pulmonary disease. Mucokinesis in the horse has been assessed visu...
Chen CL, Sailor JA, Collier J, Wiegand J.Seven mature thoroughbred horses, weighing between 400 and 541 kg, were each injected intra-articularly into three joints with 6 mg/joint of triamcinolone acetonide (Vetalog). The fourth joint, the control, was injected with saline. Synovial fluid was taken from all four legs of the horses on days 1, 2, 3, 4, 5, 6, 7, 8, 11, and 15 following the injections. Triamcinolone acetonide was assayed by a radioimmunoassay. Blood was collected at 1, 2, 4, 6, 12 h and on days 1, 2, 3, 4, 5, 6, 7, 8, 11, and 15 following injection of either triamcinolone or saline. Both cortisol and triamcinolone were as...
MacAllister CG, Sangiah S, Mauromoustakos A.Using video gastroscopy, the efficacy of a Histamine-H2 type receptor antagonist (WY 45, 727) was investigated in young ponies with spontaneous and experimentally induced gastric ulcers. Oral administration of WY 45, 727 at 2 mg/kg and 10 mg/kg of body weight every 12 hours for 14 days resulted in complete healing of spontaneous gastric ulcers in the non-glandular portion of the stomach in 2/5 (40%) and 3/4 (75%) of the ponies, respectively, compared (P < 0.05) to 0/5 (0%) placebo-treated ponies. After intramuscular administration of flunixin meglumine at 1.5 mg/kg body weight every 8 hours...
Sarasola P, McKellar QA.The effect of an oral dose of probenecid on the disposition kinetics of ampicillin was determined in four horses. An intravenous bolus dose (10 mg/kg) of ampicillin sodium was administered to the horses on two occasions. On the first occasion the antibiotic was administered on its own, and on the second occasion it was administered one hour after an oral dose of 75 mg/kg probenecid. The plasma concentration of probenecid reached a mean (+/- se) maximum concentration (Cmax) of 188-6 +/- 19.3 micrograms/ml after 120.0 +/- 21.2 minutes and concentrations greater than 15 micrograms/ml were present...
Light GS, Hellyer PW, Swanson CR.We investigated the influence of parasympathetic tone on the arrhythmogenicity of graded dobutamine infusions in horses anesthetized under clinical conditions. Six horses were used in 9 trials. Two consecutive series of graded dobutamine infusions were given IV; each continuous graded dobutamine infusion was administered for 20 minutes. The dobutamine infusion dosage (5, 10, 15, and 20 micrograms/kg of body weight/min) was increased at 5-minute intervals. Isovolumetric saline solution vehicle (v) or atropine (A; 0.04 mg/kg) was administered IV, or bilateral vagotomy (VG) was performed as a tre...
Whitehair KJ, Blevins WE, Fessler JF, Van Sickle DC, White MR, Bill RP.Regional perfusion of carpal tissues by forced intramedullary administration of fluids was evaluated in 10 horses. Results of subtraction radiography after perfusion with a contrast medium demonstrated that perfusate was delivered to the carpal tissues by the venous system. Perfused India ink was distributed uniformly in the antebrachiocarpal and middle carpal synovial membranes. Histologically, the ink was within the venules of the synovial villi. Immediately after perfusion with gentamicin sulfate (1 g), the gentamicin concentrations in the synovial fluid and synovial membrane of the antebra...
Baggot JD.The route of administration and formulation of the dosage form affect the bioavailability (rate and extent of absorption) of a drug and may thereby influence the intensity and duration of the pharmacological effect. Location of injection site may affect the plasma concentration profile of drugs administered as aqueous suspensions or sustained release parenteral preparations (procaine penicillin G). When absorption influences the rate of elimination ('flip-flop' phenomenon), the apparent half-life of the drug will be increased (cefazolin sodium, i.m.; meclofenamic acid, p.o.). Absorption genera...
Court MH, Engelking LR, Dodman NH, Anwer MS, Seeler DC, Clark M.The pharmacokinetics of dantrolene sodium were investigated in horses following both intravenous (2 mg/kg) and intragastric (4 mg/kg) administration. Two ponies also received dantrolene sodium intravenously (2 mg/kg) in a pilot study to obtain preliminary kinetic data and to determine urinary and biliary excretion of the intact drug. Distribution and elimination of dantrolene was rapid, resulting in an elimination half-life of 129 +/- 8 (SEM) min and a whole body clearance of 4.16 +/- 0.52 ml/min/kg. Following intragastric administration, dantrolene rapidly acheived peak concentrations within ...
Maes A, Baert K, Croubels S, De Clercq D, van Loon G, Deprez P, De Backer P.A rapid method for the quantification of amiodarone and desethylamiodarone in animal plasma using high-performance liquid chromatography combined with UV detection (HPLC-UV) is presented. The sample preparation includes a simple deproteinisation step with acetonitrile. In addition, a sensitive method for the quantification of amiodarone and desethylamiodarone in horse plasma and urine using high-performance liquid chromatography combined with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) is described. The sample preparation includes a solid-phase extraction (SPE) with a SCX c...
Ellerbrock RE, Curcio BR, Zhong L, Honoroto J, Wilkins P, Lima FS, Giguere S, Canisso IF.Enrofloxacin may be an alternative antimicrobial for unresponsive cases of severe bacterial infections in pregnant mares. As pregnancy may affect drug bioavailability, distribution, metabolism and excretion, dose adjustment might be necessary. Objective: To determine the disposition of orally and intravenously administered enrofloxacin in pregnant and non-pregnant mares. Methods: Randomised cross-over experiment. Methods: Six light-breed, healthy pregnant mares (260Â days gestation) were given a single dose of either intravenous (5Â mg/kg bwt) or oral compounded (7.5Â mg/kg bwt) enrofloxacin, ...
Beasley AM, Coleman GT, Kotze AC.The use of macrocyclic lactone drugs for control of equine cyathostomins is threatened by increasing levels of resistance. Detection of changes in drug sensitivity is important for effective and sustainable management of cyathostomins, however, at present such detection relies on the use of the faecal egg count reduction test, which is known to be an insensitive method. The present study therefore aimed to examine the use of a 96-well plate larval migration inhibition test for detection of resistance to macrocyclic lactone drugs in cyathostomins. We optimised conditions for migration of larvae...
Wakuno A, Aoki M, Kushiro A, Mae N, Maeda T, Yamazaki Y, Minamijima Y, Nagata SI, Ohta M.To investigate the clinical pharmacokinetics and pharmacodynamics of intravenous alfaxalone in young Thoroughbred horses, seven Thoroughbred horses were randomly anaesthetised twice with either 1 or 2 mg/kg of intravenous alfaxalone after premedication with medetomidine (6 µg/kg intravenous) and midazolam (20 µg/kg intravenous). Blood samples were collected at predetermined time points up to two hours after administration. Plasma alfaxalone concentrations were quantified by a liquid chromatography tandem-mass spectrometry method and analysed by non-compartmental pharmacokinetic analy...
McCandless EE, Rai SK, Mwangi D, Sly L, Franz LC.Hydrocortisone is widely accepted as an anti-inflammatory agent and there are many products available containing hydrocortisone as an active ingredient. Surprisingly, there is little data available specifically on the immunological effects of hydrocortisone in large animals. Glucocorticoids are well-characterized for their ability to repress inflammation via a wide variety of mechanisms including suppression of cytokine production. In this study the effects of hydrocortisone on IFN-γ production by equine, bovine, and ovine PBMCs were assessed using flow cytometric or ELISpot analysis. Hydroco...
Heath MF, Evans RJ, Poole AW, Hayes LJ, McEvoy RJ, Littler RM.The responses of equine blood platelets in citrated platelet-rich plasma to arachidonic acid, U44069 (prostaglandin endoperoxide analogue), adenosine 5'-diphosphate, platelet-activating factor or collagen were investigated by turbidimetric aggregometry. Pre-treatment of the platelets with aspirin (1 mmol/l) or paracetamol (1.3 mmol/l) abolished shape change and aggregation in response to arachidonic acid; decreased the rate of aggregation in response to collagen, with no separate effect on shape change; had no marked effect on aggregation caused by the other agonists; but in no case transforme...
Giorgi M, Mengozzi G, Raffaelli A, Saba A.Tepoxalin is a veterinary drug registered for use in the dog as a dual inhibitor (cyclooxygenase-5 lipoxygenase). In the horse, it predominantly triggers a strong cyclooxygenase inhibition; this bias seems to be due to the action of its metabolite(s). Among these, only the RWJ-20142 is well known, while to the best of our knowledge no information is available on the other metabolites produced in vivo. Hence, the identification of its main metabolic pathway is pivotal to better understand its clinical activity. A suitable high performance liquid chromatography method has been applied to liquid ...
Delatour P, Garnier F, Maire R.After administration of the racemic drug, the stereoselective quantification of the enantiomers of free and conjugated carprofen was performed in human plasma and in plasma, urine and bile of dogs and horses. In humans, the plasma profile of free carprofen and its glucuronides is not stereoselective and the glucuronides excreted in urine are close to a racemate. In dogs and horses on the contrary, the R(-) enantiomer of the free drug is predominant in plasma, while urine and/or bile concentrations of the glucuronides are high in comparison to plasma with a strong selectivity for the S(+) enant...
Knych HK, Steinmetz SJ, McKemie DS.The anti-anxiety and calming effects following activation of the GABA receptor have been exploited in performance horses by administering products containing GABA. The primary goal of the study reported here was to describe endogenous concentrations of GABA in horses and the pharmacokinetics, selected pharmacodynamic effects, and CSF concentrations following administration of a GABA-containing product. The mean (±SD) endogenous GABA level was 36.4 ± 12.5 ng/mL (n = 147). Sixteen of these horses received a single intravenous and oral dose of GABA (1650 mg). Blood, urine, and cerebrospin...
Garcia Filho SG, de Andrade FSRM, Dos Santos RST, Gonçalves LA, Pereira MAA, de Souza AF, Ambrósio AM, Fantoni DT.The objective of this study was to compare the hemodynamic effects of dobutamine and ephedrine during the management of anesthesia-related hypotension in healthy horses. Thirteen horses underwent general anesthesia with isoflurane and were randomly divided into two different groups, one of which received a dobutamine constant rate infusion (CRI) (1 µg/kg bwt/min) and the other received an ephedrine CRI (20 µg/kg bwt/min) when hypotension ( 0.05); however, the heart rate was higher in the ephedrine group (p = 0.0098), and sinus bradyarrhythmia occurred in the dobutamine group. Furthermore, bo...
Ayres JW, Pearson EG, Riebold TW, Chang SF.The pharmacokinetics of theophylline and dyphylline were determined after IV administration in horses. In a preliminary experiment, the usual human dosage (milligram per kilogram) of each drug was given to 1 horse. Results were used to calculate dosages for a cross-over study, using 6 horses for each drug. Theophylline plasma concentrations decreased triexponentially in 5 of 6 healthy horses after IV infusion of 10 mg of aminophylline/kg of body weight for 16 to 32 minutes. In the 6 horses, total body elimination rate constants were variable, and the half-life of theophylline was 9.7 to 19.3 h...
Spallek A, Recknagel S, Breuer J, Koeller G, Schusser GF.The use of laxatives is crucial in the treatment of horses with large colon impaction. To reach the impacted mass, the laxative must leave the stomach and pass through the small intestine. The aim of this study was to determine whether the most frequently used saline and lubricant laxatives influence gastric emptying. Six fasted normal adult Warmblood horses were used in a randomized study design with five laxative trials (1.8% sodium sulfate [1.8% Na2SO4], 4.2% magnesium sulfate [4.2% MgSO4], mineral oil [MOil], 25% sodium sulfate [25% Na2SO4], 25% magnesium sulfate [25% MgSO4]) and two trial...
Zscherpe P, Kalbitz J, Weber LA, Paschke R, Mäder K, von Rechenberg B, Cavalleri JV, Meißner J, Klein K.Gray horses are predisposed to equine malignant melanoma (EMM) with advancing age. Depending on the tumor's location and size, they can cause severe problems (e.g., defaecation, urination, feeding). A feasible therapy for EMM has not yet been established and surgical excision can be difficult depending on the location of the melanoma. Thus, an effective and safe therapy is needed. Naturally occurring betulinic acid (BA), a pentacyclic triterpene and its synthetic derivate, NVX-207 (3-acetyl-betulinic acid-2-amino-3-hydroxy-2-hydroxymethyl-propanoate) are known for their cytotoxic properties ag...
Nelson GR, Mama KR, Weiner D, McKemie DS, Kass PH, Steinmetz SJ, Knych HK.This study describes the pharmacokinetics and pharmacodynamics, including antinociceptive effects, of a transdermal buprenorphine solution in horses. It was hypothesized that transdermal application would lead to sustained blood concentrations and antinociceptive effects with fewer adverse effects compared with intravenous (IV) injection. Methods: Prospective nonrandomized four-part parallel experimental study. Methods: A group of eight horses (three mares and five geldings) aged 6-12 years. Methods: Horses were administered incremental doses of 15, 30 and 45 μg kg of buprenorphine transderma...
Hubbell JAE, Muir WW, Gorenberg E, Hopster K.Horses are the most challenging of the common companion animals to anesthetize. Induction of anesthesia in the horse is complicated by the fact that it is accompanied by a transition from a standing position to recumbency. The purpose of this article is to review the literature on induction of anesthesia with a focus on the behavioral and physiologic/pharmacodynamic responses and the actions and interactions of the drugs administered to induce anesthesia in the healthy adult horse with the goal of increasing consistency and predictability.
Wong ASY, Yuen BP, Wong COL, Kong FK, So YM, Kwok WH, Brooks L, Wan TSM, Ho EN.Bisphosphonates and myo-inositol trispyrophosphate (ITPP) are two classes of difficult-to-detect polar drugs that are prohibited under the rules of racing. ITPP is a drug capable of increasing the amount of oxygen in hypoxic tissues, and studies have shown that administration of ITPP increases the maximal exercise capacity in mice. The properties of ITPP make it an ideal candidate as a doping agent to enhance performance in racehorses. In recent years, ITPP had indeed been detected in racehorses and confiscated items. As for bisphosphonates, it is especially critical to control their use as si...
Lehman ML, Domenig O, Ames MK, Morgan JM.Furosemide, a commonly used diuretic, activates the renin-angiotensin-aldosterone system (RAAS) in other species. Little is known about RAAS peptide activation in horses. Objective: To evaluate equilibrium analysis as a practical method for RAAS quantification in horses and describe the RAAS response to a single dose of furosemide. We hypothesize that furosemide would cause transient increase in RAAS peptides in horses. Methods: 14 healthy adult thoroughbreds from a university teaching herd. Methods: Horses received either furosemide (1 mg/kg IV) or saline IV in a crossover study design. Pro...
Wong AM, Schier MF, Hosgood G, Drynan E, Raisis AL.To explore the influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine. Methods: Prospective randomised clinical trial. Methods: A total of 18 horses undergoing elective arthroscopy were enrolled, of which 12 horses requiring dobutamine were included. Methods: Horses were randomised to receive acepromazine 0.02 mg kg (Group A+) intravenously (IV) or none (Group A-), 35 minutes before anaesthesia. Horses received xylazine 0.2 mg kg concurrently to facilitate IV access. Horses were premedicated with romifidine 0.08 mg ...
Adler DMT, Nielsen AT, Olsen C, Verwilghen D, Damborg P, Olsen RH.To investigate the in vitro efficacy of antibiotics (amikacin, ceftiofur, and gentamicin) in combination with local anesthetics (LAs; bupivacaine hydrochloride, lidocaine hydrochloride, and mepivacaine hydrochloride), a combination commonly performed for IA injectate and regional limb perfusion (RLP) in horses. Unassigned: 17 equine clinical isolates were tested by the checkerboard method for their minimum inhibitory concentration (MIC) against a combination of concentrations of LAs and antibiotics from August 2020 through December 2023. Unassigned: For the majority of combinations, the antibi...
Oyaneder L, Lagos N, Dörner C.The present study was conducted to evaluate the safety and the long-lasting anesthetic properties of Neosaxitoxin (NeoSTX) when injected into the intercoccygeal space in standing horses. A group of eighteen (n = 18) healthy client-owned mature crossbreed horses were enrolled in this study. Caudal epidural injection was ascertained by two methods, the "hanging drop" technique and radiographs. Horses were allocated into three groups (n = 6) each group receiving different dosages of NeoSTX. To assess the onset of action and duration of anesthesia, six horses received 20 μg in 2 mL, six 20Â...
Kazama T, Hector RC, Hess AM, Rezende ML.To determine the cardiopulmonary effects of oral trazodone before isoflurane anesthesia in systemically healthy horses. Unassigned: 12 horses donated for euthanasia (from August 2022 through June 2023) due to conditions unrelated to the cardiovascular system were included in this prospective, randomized, controlled trial. Horses were assigned to receive oral trazodone (6 mg/kg; n = 7) or corn syrup (n = 5) 1 hour before xylazine (1 mg/kg, IV) sedation, ketamine (2.2 mg/kg, IV) and propofol (0.7 mg/kg, IV) induction, and anesthetic maintenance with inhaled isoflurane (target 1.6% expired) for 7...
Maldonado Moreno N, Alves Moreira J, Araujo De Oliveira L, Sanches Gontijo A, Castilho Baldi ML, Rocha Wenceslau R, Beier SL.A multimodal approach is recommended to optimize perioperative pain control in animals, although opioid use in horses remains limited due to the risks of central nervous system (CNS) stimulation and reduced intestinal motility. A group of 19 healthy, male, mixed-breed horses were divided into two groups and medicated with acepromazine (0.05 mg kg) and detomidine (10 µg kg), with methadone (0.05 mg kg) (ADM) or saline (ADS) administered intravenously (IV). Physiological variables, intestinal motility, gastric distention, and facial pain (EQUUS-FAP) were evaluated one day before (DB), before th...
Arantes JA, Rabelo IP, Bermudes L, Lacerenza MD, Mendes RP, Corrêa RR, Yamada DI, Valadão CAA, Dória RGS.This study aimed to compare the sedation quality and cardiorespiratory and behavioral effects of detomidine administered intravenously, either in intermittent boluses or as a continuous rate infusion, with butorphanol in horses pre-medicated with acepromazine for odontoplasty procedures. Unassigned: A prospective clinical study was conducted with fifteen adult horses randomly assigned to two groups: Bolus group (BG, = 7) and Infusion group (IG, = 8). Both groups received acepromazine premedication, followed by detomidine administration (bolus or infusion). Butorphanol was administered either...
McDonnell SM, Kenney RM, Meckley PE, Garcia MC.Pony stallions were given sexual behavior trials in experimental "home" and "novel" environments, similar in all major features except location. In the novel environment, erection latency was increased and erection time decreased. Treatment with an anxiolytic benzodiazepine derivative (diazepam) appeared to block these effects.
Klein LV.In summary, neuromuscular blocking agents can be used safely and to advantage in equine anesthesia. Muscle-relaxant use in equine anesthesia has been helped by the development of new relaxants such as atracurium, which has a reliable and reproducible duration of action. There are certain cases that benefit particularly by the use of relaxants but their use is not limited to these cases. These cases involve horses that experience persistent movement and hypotension during anesthesia, are undergoing ophthalmic or abdominal surgery or fracture repair, or are severely ill. Horses receiving muscle ...
