Pharmacology in horses involves the study and application of drugs and medications to diagnose, treat, and prevent diseases and conditions in equine species. This field encompasses the understanding of pharmacokinetics and pharmacodynamics specific to horses, including how drugs are absorbed, distributed, metabolized, and excreted by the equine body. Commonly studied pharmacological agents in horses include non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, sedatives, and anthelmintics. Research in equine pharmacology focuses on determining appropriate dosages, understanding drug interactions, and minimizing adverse effects. This page compiles peer-reviewed research studies and scholarly articles that investigate the efficacy, safety, and regulatory aspects of pharmacological interventions in equine veterinary practice.
Cuervo-Arango J, Newcombe JR.The objective of this study was to establish and characterize the relationship between the dose of cloprostenol (37.5, 250, 500 and 750 μg) and the age of the early corpus luteum (CL) (80, 88, 96, 104 and 112 h) on the luteolytic response of mares. Behavioural oestrus and ultrasonographic signs of return to oestrus were considered as the occurrence of full luteolysis. A total of 298 mares were divided into groups according to dose of cloprostenol and CL age. There was an effect of dose of cloprostenol (p < 0.001) and age of the CL at the time of treatment (p 0.05); and that of 500 similar...
Lyons ET, Tolliver SC.Macrocyclic lactones (MLs) revolutionized parasite control in horses and other animals. They are unique in that they are effective against arthropods and nematodes. The first of the widely used avermectins was ivermectin. In 1983, it was marketed for use in horses as an injectable formulation but was withdrawn in 1984 after about a year and half on the market because of adverse problems. It was replaced by a paste formulation and an oral/stomach tube liquid formulation. Ivermectin is highly active on bots, ascarids, large and small strongyles, pinworms, strongyloides, stomach worms, and some o...
Guschlbauer M, Feige K, Geburek F, Hoppe S, Hopster K, Pröpsting MJ, Huber K.To determine whether administration of lidocaine during ischemia and reperfusion in horses results in concentrations in smooth muscle sufficient to protect against the negative consequences of ischemia-reperfusion injury on smooth muscle motility. Methods: 12 horses. Methods: Artificial ischemia and reperfusion injury of jejunal segments was induced in vivo in conjunction with lidocaine treatment during ischemia (IRL) or without lidocaine treatment (IR). Isometric force performance was measured in vitro in IRL and IR smooth muscle preparations with and without additional in vitro application o...
Wearn JG, Suagee JK, Crisman MV, Corl BA, Hulver MW, Hodgson DR, Geor RJ, McCutcheon LJ.Equine metabolic syndrome (EMS) is a condition of obese horses characterized by insulin resistance, systemic inflammation, and an increased risk of laminitis. The pathogenesis of EMS is thought, in part, to be due to inflammatory proteins produced by adipose tissue. Reducing inflammation may decrease the incidence of laminitis in horses with EMS. Pioglitazone hydrochloride, a thiazolidinedione, has efficacy to reduce obesity associated inflammation in humans. Eight normal, adult, horses were administered 1mg/kg pioglitazone for 14 days, and eight horses served as controls. Physical examination...
Benbarek H, Ayad A, Deby-Dupont G, Boukraa L, Serteyn D.The purpose of this study was to explore the potential modulation of equine neutrophil oxidative burst by a series of classical NSAIDs which was subsequently monitored by the luminol or lucigenin-enhanced chemiluminescence (CL) technique. A significant dose-dependent inhibition of the luminol CL was observed with the majority of investigated drugs. This inhibition was very significant for phenylbutazone and Indomethacin; while for aspirin, a higher concentration is required. The action of Ketoprofen was significant during the first 5 min and only when the concentration was above 1 mM. Indometh...
Vidyashankar AN, Hanlon BM, Kaplan RM.Anthelmintic resistance (AR) is a serious problem for the control of equine gastrointestinal nematodes, particularly in the cyathostomins. The fecal egg count reduction test (FECRT) is the most common method for diagnosing AR and serves as the practical gold standard. However, accurate quantification of resistance and especially accurate diagnosis of emerging resistance to avermectin/milbemycin (A/M) drugs, is hampered by a lack of accepted standards for study design, data analysis, and data interpretation. In order to develop rational evidence-based standards for diagnosis of resistance, one ...
Garcia P, Paris AC, Leufroy A, Popot MA, Bonnaire Y.A quantitative method, using LC/ESI-MS(n) with a quadrupole linear ion trap mass analyzer, has been developed for the analysis of ipratropium cation in horse plasma and urine. The method applies solid-phase extraction with WCX cartridges for plasma and MM2 cartridges for urine, prior to analysis by LC/ESI-MS(n). The efficiency of extraction combined with the sensitivity and the selectivity of MS(n) allows for the quantification of ipratropium cation at picogram per milliliter levels. The analytical capabilities of the method have been successfully checked by the quantitative analysis of ipratr...
Appolonova SA, Baranov PA, Mesonzhnik NV, Brazhnikova DO, Rodchenkov GM.A method is described for the determination of mesocarb abuse in equestrian sport by combining gradient liquid chromatography and electrospray ionization tandem mass spectrometry. Mesocarb was administrated orally to two horses at a dose of 50 µg/kg. Urine samples were collected up to 120 h post administration. Hydrolyzed and conjugated urine fractions were handled using liquid-liquid extraction (LLE). The identity of the parent drug and metabolites was confirmed using liquid chromatography combined with tandem mass spectrometry (MS/MS). Mesocarb and seven metabolites were detected in horse...
Pietra M, Cinotti S, Ducci A, Giunti M, Peli A.During an 18 day test, we measured the cytokine mRNA expression (Interleukin-1beta [IL-1beta], Interleukin-8 [IL-8], Interferon-gamma [IFN-gamma], Tumor Necrosis Factor-alpha [TNF-alpha]) of cells from bronchoalveolar lavage fluid [BALF] in five horses previously diagnosed with RAO, before and during challenge exposure, and after the desensitization phase which involved dexamethasone treatment and environmental modification. Simultaneously, the same cytokine mRNA expression of cells from BALF in four asymptomatic RAO-affected horses maintained outdoors was analyzed. An evident respiratory dist...
Lippert-Gruner M, Svestkova O.The acute management of spasticity following ABI is challenging. Contractures can occur during the acute phases of illness. The joints most affected are the shoulders and the ankles. Methods: A case study of a 48-year-old female patient who received local chemoneurolytic anti-spasticity therapy following a severe subarachnoid haemorrhage for pes equines deformity is presented to illustrate the role of focal neurotoxin therapy. Methods: The increasing spasticity in her legs was observed and could not be effectively treated with oral anti-spasticity agents or intensive physiotherapy. As spastici...
Bailey CS, Sper RB, Schewmaker JL, Buchanan CN, Beachler TM, Pozor MA, Whitacre MD.The objective of this study was to use Doppler ultrasound technology to determine whether pentoxifylline administration increased uterine blood flow in normal pregnant pony mares. Thirteen pregnant pony mares between 18 and 190 d of gestation (mean ± SEM, 101 ± 55) were utilized for the study during two trial periods. In each trial, pentoxifylline (17 mg/kg by mouth every 12h, diluted in syrup) was administered to half of the mares for 3 d, while the other mares were treated with syrup only. Doppler measurements were obtained from the right and left uterine arteries from each mare for 2 d pr...
Baker WT, Frederick J, Giguere S, Lynch TM, Lehmkuhl HD, Slone DE.To evaluate the outcome in horses treated with a rolling technique or surgically for nephrosplenic entrapment of the large colon (NSE) and to examine the benefit of phenylephrine (PE) HCl on the efficacy of nonsurgical (rolling) management of NSE. Methods: Case series. Methods: Horses (n = 211) diagnosed with NSE by rectal palpation with or without ultrasonography, or at the time of exploratory celiotomy or necropsy. Methods: Medical records (January 1, 2001-September 1, 2008) were collected from horses diagnosed with NSE at 2 referral centers. Records were used to obtain signalment, physical ...
Stewart AJ, Behrend EN, Wright JC, Martin LG, Kemppainen RJ, Busch KA, Hanson RR.To determine the lowest ACTH dose that would induce a maximum increase in serum cortisol concentration in healthy adult horses and identify the time to peak cortisol concentration. Methods: Evaluation study. Methods: 8 healthy adult horses. Methods: Saline (0.9% NaCl) solution or 1 of 4 doses (0.02, 0.1, 0.25, and 0.5 μg/kg [0.009, 0.045, 0.114, and 0.227 μg/lb]) of cosyntropin (synthetic ACTH) were administered IV (5 treatments/horse). Serum cortisol concentrations were measured before and 30, 60, 90, 120, 180, and 240 minutes after injection of cosyntropin or saline solution; CBCs were per...
Casella S, Giudice E, Giannetto C, Marafioti S, Piccione G.The purpose of this study was to evaluate in vitro the effects of hydrocortisone and aminophylline on adenosine diphosphate (ADP)-induced platelet aggregation in horses. Blood samples from 30 healthy Thoroughbred horses were collected by via jugular venipuncture to assess platelet aggregation. Platelet-rich and platelet-poor plasma were prepared from all samples by centrifugation and divided into three different aliquots. In the first aliquot, platelet aggregation was measured after platelet activation with 1 µM and 0.5 µM ADP (Group A). In the other two aliquots, the effect of a 10 min prei...
Seo JP, Son WG, Gang S, Lee I.This study was performed to evaluate the sedative and analgesic effects of xylazine (X) and tramadol (T) intravenously (IV) administered to horses. Six thoroughbred saddle horses each received X (1.0 mg/kg), T (2.0 mg/kg), and a combination of XT (1.0 and 2.0 mg/kg, respectively) IV. Heart rate (HR), respiratory rate (RR), rectal temperature (RT), indirect arterial pressure (IAP), capillary refill time (CRT), sedation, and analgesia (using electrical stimulation and pinprick) were measured before and after drug administration. HR and RR significantly decreased from basal values with X and XT t...
Soma LR, Uboh CE, You Y, Guan F, Boston RC.To compare pharmacokinetics of triamcinolone acetonide (TA) following i.v., intra-articular (i.a.), and i.m. administration and determine its effect on plasma concentrations of hydrocortisone and cortisone. Methods: 6 Thoroughbreds. Methods: TA (0.04 mg/kg) was administered i.v., i.m., or i.a., and plasma TA, hydrocortisone, and cortisone concentrations were determined. Results: I.v. administration of TA was fitted to a 2-compartment model. Median distribution half-life was 0.50 hours (range, 0.24 to 0.67 hours); elimination half-life was 6.1 hours (range, 5.0 to 6.4 hours). Transfer half-life...
Parker RA, Clegg PD, Taylor SE.To investigate the effects of commonly used antibiotics on cell viability and gene expression of equine bone marrow-derived mesenchymal stromal cells (MSC) in vitro. Methods: Bone marrow-derived MSC were cultured in media containing gentamicin, amikacin, penicillin, enrofloxacin or ceftiofur at concentrations of 50, 100, 200 and 500 µg/ml. The alamarBlue fluorescence assay was used to assess cell viability over 48 h. After 5 days the cells were released and lysed prior to RNA extraction and reverse transcription. RNA levels were assessed using spectrophotometry and quantitative PCR was used...
Zhang J.Prion diseases (e.g. Creutzfeldt-Jakob disease (CJD), variant CJD (vCJD), Gerstmann-Straussler-Scheinker syndrome (GSS), Fatal Familial Insomnia (FFI) and Kuru in humans, scrapie in sheep, bovine spongiform encephalopathy (BSE or 'mad-cow' disease) and chronic wasting disease (CWD) in cattles) are invariably fatal and highly infectious neurodegenerative diseases affecting humans and animals. However, by now there have not been some effective therapeutic approaches or medications to treat all these prion diseases. Rabbits, dogs, and horses are the only mammalian species reported to be resistant...
Pease AP, Schott HC, Howey EB, Patterson JS.Pituitary pars intermedia dysfunction (PPID) is the most common endocrinologic disorder of aged horses. Objective: Pituitary glands of PPID-affected horses are larger than those of aged horses without signs of PPID, and the size difference can be detected using computed tomography (CT) imaging. Methods: Eight horses with clinical signs of PPID and supportive endocrinologic test results and 3 aged control (PPID-negative) horses. Methods: Computed tomography examination of the brain and pituitary gland was performed twice in 10 of the 11 horses, approximately 6 months apart. Six PPID-affected ho...
Menozzi A, Pozzoli C, Zullian C, Poli E, Serventi P, Bertini S.The effects of preferential µ (morphine), selective µ (fentanyl), selective κ (compound U69593) opioid receptor agonists, and nonselective (naloxone) and selective µ (naloxonazine) antagonists on equine small intestinal motility were evaluated in vitro. Samples of circular muscle from equine jejunum were placed in isolated organ baths and drug-induced modifications of both spontaneous and electrically evoked contractile activity were measured. None of the opioid agonists induced a significant change in spontaneous contractions. Fentanyl and U69593 reduced electrically induced contractions,...
Teixeira-Neto FJ, McDonell WN, Black WD, Harris W, Grovum L.This study investigated the effects of a muscarinic type 1 (M(1)), 2 (M(2)), and 3 (M(3)) antagonists (4-DAMP, pirenzepine, and methoctramine, respectively) on acetylcholine (Ach)-induced contractions of longitudinal jejunal muscle strips of horses. Strips were irrigated with Krebs-Henseleit solution gassed with 95% O(2) and 5% CO(2), and the developed tension in response to Ach was recorded before and after incubation with increasing concentrations of 4-DAMP (10(-8)-10(-6) M), pirenzepine (10(-6)-10(-4) M), and methoctramine (10(-5)-10(-3) M). When competitive antagonism was characterized, th...
Kruger K, Stegmann GF, Becker PJ.To characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine. Methods: Prospective four-period, four-treatment, blinded, randomized, crossover trial. Methods: Five, healthy, mixed breed horses. Methods: Prior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg(-1) ) romifidin...
Stahl J, Braun M, Siebert J, Kietzmann M.A water based combination of 0.1% octenidine dihydrochloride and 2% 2 - phenoxyethanol is registered in many European countries as an antiseptic solution (octenisept®) for topical treatment with high antimicrobial activity for human use, but octenidine based products have not been registered for veterinary use yet. The aim of the present study was to investigate whether octenidine dihydrochloride or 2 -phenoxyethanol, the two main components of this disinfectant, permeate through animal skin in vitro. Therefore, permeation studies were conducted using Franz-type diffusion cells. 2 ml of the t...
Iyer U, Kadambi VJ.Antibody drug conjugates (ADCs) consist of an antibody attached to a cytotoxic drug by means of a linker. ADCs provide a way to couple the specificity of a monoclonal antibody (mAb) to the cytotoxicity of a small-molecule drug and, therefore, are promising new therapies for cancer. ADCs are prodrugs that are inactive in circulation but exert their cytotoxicity upon binding to the target cancer cell. Earlier unsuccessful attempts to generate ADCs with therapeutic value have emphasized the important role each component plays in determining the efficacy and safety of the final ADC. Scientific adv...
Fintl C, Pearson GT, Mayhew IG, Hudson NP.The generation and maintenance of intestinal motility patterns involve the complex interactions of several components including the gastrointestinal pacemaker cells (interstitial cells of Cajal, ICC). Central to ICC function is the generation of rhythmic pacemaker currents, namely slow waves, which represent the rate limiting step for intestinal smooth muscle contractions. Currently, intracellular slow wave activity has not been demonstrated in the equine colon. Objective: To characterise the in vitro myoelectrical activity of the equine pelvic flexure using intracellular recording techniques....
Marshall JF, Bhatnagar AS, Bowman SG, Morris NN, Skorich DA, Redding CD, Blikslager AT.Flunixin meglumine is used for treatment of equine colic despite evidence of inhibited recovery of mucosal barrier function following small intestinal ischaemic injury. This study aimed to characterise an alternative treatment (AHI-805) for abdominal pain in the horse. Objective: To determine the effect of AHI-805, an aza-thia-benzoazulene derivative, on the cyclooxygenase enzymes and the recovery of mucosal barrier function following ischaemic injury. Methods: Effect of AHI-805 on in vitro COX-1 and COX-2 activity was determined by measuring coagulation-induced thromboxane B(2) (TXB(2)) and l...
Marshall JF, Blikslager AT.Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in the management of pain and endotoxaemia associated with colic in the horse. While NSAIDs effectively treat the symptoms of colic, there is evidence to suggest that their administration is associated with adverse gastrointestinal effects including right dorsal colitis and inhibition of mucosal barrier healing. Several studies have examined the pathophysiology of NSAID associated effects on the large and small intestine in an effort to avoid these complications and identify effective alternative medications. Differences in the re...
Miller SM, Short CE, Ekström PM.We compared the anesthetic combination of detomidine, ketamine, and halothane in control horses not undergoing apparently painful procedures with that in horses during arthroscopic surgery. The effectiveness of this regimen in suppressing neurologic response to surgery was, thus, evaluated. In this study, significant differences were not observed in electroencephalographic total amplitude, spectral edge, or beta-to-delta frequency ratio between surgically treated and nonsurgically treated (control) horses. On the basis of its attenuation of encephalographic responses, we conclude that detomidi...
Steel R, Timms M, Levina V, Vine J.The Dermorphins are a family of peptides that act as potent agonists of the opioid μ receptor. Originally identified as a seven amino acid peptide on the skin of the South American Phyllomedusa frog, peptide chemists have since developed a large number of Dermorphin variants, many with superior opioid activity to the original peptide. Dermorphins are unique among the peptide opioid agonists as they appear to have a limited ability to cross the blood brain barrier, producing effects on both the central and peripheral nervous systems. It is this ability of Dermorphins to provide central anaesth...
Gold JR, Grubb TL, Green S, Cox S, Villarino NF.In humans, gabapentin an analgesic, undergoes non-proportional pharmacokinetics which can alter efficacy. No information exists on the pharmacokinetics of dosages >20 mg/kg, escalating dosages or dose proportionality of gabapentin in horses. Objective: Gabapentin exposure in plasma would not increase proportionally relative to the dose in horses receiving dosages ≥20 mg/kg. To assess the plasma pharmacokinetics of gabapentin after nasogastric administration of gabapentin at dosages of 10 to 160 mg/kg in adult horses. Methods: Nine clinically healthy adult Arabian and Quarter Horses....
Malone ED, Brown DR, Trent AM, Turner TA.To characterize the response of equine jejunal smooth muscle to adrenergic and cholinergic mediators. Methods: Evaluation of myogenic responses, using an in vitro model. Methods: Intestinal tissues were obtained from horses without gastrointestinal tract disorders or systemic disease. Methods: Baseline myogenic tone and amplitude and frequency of contraction were determined for suspended jejunal muscle strips. The level of adrenergic and cholinergic regulation was assessed, using atropine and adrenoceptor antagonists. The response of the muscles to norepinephrine was characterized, using adren...
Steffey EP, Pascoe PJ.To quantitate the dose- and time-related magnitude of the anesthetic sparing effect of, and selected physiological responses to detomidine during isoflurane anesthesia in horses. Methods: Randomized cross-over study. Methods: Three, healthy, young adult horses weighing 485 ± 14 kg. Methods: Horses were anesthetized on two occasions to determine the minimum alveolar concentration (MAC) of isoflurane in O and then to measure the anesthetic sparing effect (time-related MAC reduction) following IV detomidine (0.03 and 0.06 mg kg). Selected common measures of cardiopulmonary function, blood glucos...
Pelletier N, Robinson NE, Kaiser L, Derksen FJ.We investigated regional differences of in vitro responses of pulmonary arteries (6-mm OD) from the dorsocaudal (top) and cranioventral (bottom) lung regions to endothelium-dependent vasodilators (methacholine, bradykinin, and calcium ionophore A-23187). Methacholine relaxed endothelium-intact top vessels; however, in bottom vessels, a small relaxation preceded a profound contraction. In top vessels, removal of endothelial cells converted relaxation to contraction, and in bottom vessels it abolished relaxation and enhanced contraction. Bradykinin and A-23187 were more potent and caused greater...
Bade D, Portis E, Keane C, Hallberg J, Bryson L, Sweeney M, Boner P.In vitro activity of ceftiofur and six other antimicrobial agents was evaluated against 79 Streptococcus equi subsp zooepidemicus isolates collected from horses with respiratory disease in Europe during 2007 and 2008. In addition, the in vitro activity of ceftiofur and other antimicrobial drugs was assessed against 59 S. equi subsp zooepidemicus and 49 S. equi subsp equi isolates collected by veterinary diagnostic laboratories in Europe from 2002 to 2006. The lowest concentration of ceftiofur that inhibited the growth of 90% of the isolates (MIC90) was 0.12 microg/ml, with the Clinical Laborat...
Erickson BK, Erickson HH, Coffman JR.Intravenous frusemide (1.0 mg/kg bwt) or phentolamine (0.33 mg/kg bwt) was given to 7 horses 1 h before exercise and their effects on pulmonary artery and aortic pressure changes during strenuous exercise were examined. Short-term near-maximal treadmill exercise (10 m/sec, 3 degrees incline) produced increases in heart rate, mean pulmonary artery pressure (PAP), mean aortic pressure (AP), and packed cell volume (PCV). Frusemide did not affect heart rate, PAP or PCV during exercise. Frusemide significantly decreased mean AP by 10 to 15 mmHg during exercise. Phentolamine produced an increase in ...
Sams RA, Ruoff WW.The pharmacokinetics and bioavailability of cefazolin given (IV, IM) to horses at the dosage of 11 mg/kg were investigated. The disposition of cefazolin given by IV route was characterized by a rapid disposition phase with a half-life of 5 to 10 minutes and a subsequent slower elimination phase with a half-life of 35 to 46 minutes. The total plasma clearance of cefazolin averaged 5.51 ml/min/kg and was due mainly to renal clearance (5.39 ml/min/kg) of unchanged drug. The volume of distribution at steady-state averaged 188 ml/kg. Plasma protein binding of cefazolin at a concentration of 10 micr...
Vengust M, Stämpfli H, De Moraes AN, Teixeiro-Neto F, Viel L, Heigenhauser G.Carbonic anhydrase (CA) catalyses the hydration/dehydration reaction of CO(2) and increases the rate of Cl(-) and HCO(3)(-) exchange between the erythrocytes and plasma. Therefore, chronic inhibition of CA has a potential to attenuate CO(2) output and induce greater metabolic and respiratory acidosis in exercising horses. Objective: To determine the effects of Carbonic anhydrase inhibition on CO(2) output and ionic exchange between erythrocytes and plasma and their influence on acid-base balance in the pulmonary circulation (across the lung) in exercising horses with and without CA inhibition....
Gerhards H.Low dose calcium heparin was administered subcutaneously at 12 hourly intervals to six healthy horses at an initial dose of 150 iu of heparin/kg bodyweight (bwt) and at a maintenance dose of 120 iu/kg bwt. All injections were given at 0900 and 2100 h. Blood samples for monitoring plasma heparin concentrations were obtained prior to, at 2 hourly intervals for 84 h (treatment period), and at Hours 24, 32, 48 and 96 of the control period. Blood samples for monitoring red blood cell (RBC) mass, plasma antithrombin III activity (AT III), activated partial thromboplastin time (APTT), and thrombin ti...
Muir WW, McGuirk SM.Hemodynamic measurements were obtained from 17 horses with atrial fibrillation or flutter. Eight horses had atrial fibrillation of unknown duration. In 7 horses, atrial fibrillation developed during anesthesia. Atrial flutter developed during recovery from anesthesia in 2 horses. Hemodynamic measurements were considered normal in 7 of 8 conscious horses with atrial fibrillation. Cardiac output was decreased and pulmonary arterial blood pressure and right atrial pressure were increased in 1 conscious horse which had signs of congestive heart failure. Arterial blood pressure decreased in 5 of 7 ...
Steffey EP, Dunlop CI, Farver TB, Woliner MJ, Schultz LJ.Circulatory and respiratory function was monitored in nonmedicated, spontaneously breathing horses (n = 7) immediately before, during, and 1 hour after 85 +/- 4.1 (X +/- SEM) minutes of constant 1.57% isoflurane in O2 anesthesia. Comparison of values during anesthesia with those obtained while horses were awake revealed a significant (P less than 0.05) decrease in arterial blood pressure that was related to a slight, but insignificant, decrease in cardiac output and peripheral vascular resistance. Although isoflurane anesthesia and recumbency resulted in a significant (P less than 0.05) decrea...
Johnson CB, Young SS, Taylor PM.The electroencephalogram (EEG) has been used in human clinical anaesthesia as an indicator of cortical activity and as an indicator of the depth of anaesthesia. It would be useful if it provided a reliable indication of the depth of anaesthesia of horses. In this study anaesthesia was induced with thiopentone and maintained with halothane in nine ponies. The end tidal halothane concentration (PE-Hal) was monitored and 20 seconds of EEG were recorded at 0.8 per cent, 1.0 per cent and 1.2 per cent halothane, equivalent to the minimum alveolar concentration (MAC), 1.25 MAC and 1.5 MAC. Each 20 se...
Glade MJ.Low molecular weight polysulfated glycosaminoglycan (PSGAG) stimulated net collagen and glycosaminoglycan synthesis by normal and arthritic equine fetlock cartilage tissues in organ culture. Arthritic tissues were more sensitive to PSGAG stimulation. The rates of cartilage-specific type-II collagen and chondroitin sulfate-rich glycosaminoglycan synthesis by confluent chondrocyte cell cultures obtained from normal and arthritic equine cartilage tissues were increased by 25 and 50 mg of PSGAG/ml. Cells from arthritic cartilage were also more sensitive to the presence of PSGAG. In addition, conce...
Fischer B, Clark-Price S.Anesthetizing the neonatal foal presents significant challenges as a result of physiologic differences from the adult equine. This article gives the reader an overview of these differences and the impact they have on anesthetic drug selection, monitoring, and support of the equine neonate. Special emphasis is directed to the sick neonate and appropriate preparation and maintenance of anesthesia in the face of commonly presented disease conditions.
Foster AP, Lees P, Andrews MJ, Cunningham FM.Platelet-activating factor (PAF) causes oedema and neutrophil accumulation when injected into the skin of normal horses. PAF is also known to induce aggregation of horse platelets in vitro. The selective PAF receptor antagonist WEB 2086 has now been used to determine whether these effects are mediated by PAF receptor activation. Addition of WEB 2086 to equine platelets in vitro inhibited PAF-induced aggregation in a competitive reversible manner (pA2 = 7.14). Inhibition of in vivo inflammatory responses to PAF occurred after local administration of WEB 2086: wheal formation induced by 0.1 micr...
Ibarra-Rubio ME, Pena JC, Pedraza-Chaverri J.1. Serum angiotensin-converting enzyme activities were obtained from nine mammalian species: rat, mouse, horse, sheep, guinea pig, hamster, rabbit, dog and man. 2. Kinetic constants (Km and Vmax) using hippuryl-L-histidyl-L-leucine as substrate and inhibitory constants (I50 and Ki) for captopril were determined for the serum ACE of each species. 3. There were important differences in the kinetic and inhibitory constants (Kms went from 6.6 mM to 1.21 mM for hamster and guinea pig; I50 ranged from 2100 nM to 3 nM for mouse and sheep) as well as differences in enzyme activity of the different spe...
Marzok MA, El-Khodery SA, Oheida AH.To evaluate the effect of intravenous administration of romifidine on the intraocular pressure (IOP) in horses. Methods: Twenty-four horses with no ocular abnormalities. Methods: Horses were randomly assigned into two equal groups (treatment and control). All horses in the treatment group received an intravenous (IV) injection of romifidine (40 μg/kg). The horses in the control group were administrated an intravenous injection of 0.9% saline (0.4 mL/100 kg). In both groups, the IOP values were measured immediately (T0 ) pre-administration and at 5 (T5 ), 15 (T15 ), 30 (T30 ), 45 (T45 ), 60 (T...
Gardner AK, Kelly CS, van Eps AW, Burns TA, Watts MR, Belknap JK.In sepsis models, mitogen-activated protein kinases (MAPKs) are reported to incite inflammatory injury to tissues and are purported to be a therapeutic target. Objective: To assess MAPK signalling in lamellae in sepsis-related laminitis (SRL) at different time points after induction of laminitis via carbohydrate overload, and to determine the effect of regional deep hypothermia (RDH) on MAPK signalling. Methods: In vitro study using archived tissue samples. Methods: Lamellar concentrations of MAPKs were assessed in archived lamellar samples from 2 studies: 1) the starch gruel model of SRL with...
Firth EC, Klein WR, Nouws JF, Wensing T.Single doses of sodium ampicillin (10 mg/kg) and kanamycin sulfate (5 mg/kg) were administered intramuscularly (i.m.) separately, and then together, to five pony mares. The plasma antibiotic concentration-time curves were constructed. The pharmacokinetic parameters of the antibiotics given separately were not altered by concurrent administration. Four of the five pony mares were then given the i.m. kanamycin/ampicillin combination 4 h after acute synovitis and fever had been induced by injection of lipopolysaccharide into the left intercarpal joint. The plasma concentration-time curves and the...
Durket E, Gillen A, Kottwitz J, Munsterman A.To determine the efficacy of lidocaine at reducing incidence of postoperative reflux (POR) in horses by using quantitative statistical analysis. Methods: Systematic meta-analytical review. Methods: Studies on horses undergoing gastrointestinal surgery for small intestinal lesions, identified by systematic search between 2001 and 2017. Methods: A search with PubMed/MEDLINE, Web of Science, and Google Scholar was performed, followed by secondary searches of veterinary trade journals and bibliographies of relevant articles. The primary outcome measure for this study was the effect of lidocaine th...
Ellerbrock RE, Canisso IF, Roady PJ, Rothrock LT, Zhong L, Wilkins P, Dirikolu L, Lima FS, Honoroto J.In selective cases, enrofloxacin may be an alternative antibacterial agent to treat unresponsive infections in pregnant mares. Supratherapeutic doses of enrofloxacin are toxic to adult horses and also to newborn foals, however, it is unknown if enrofloxacin crosses the equine placenta or if it is toxic to the fetus. Objective: To assess the diffusion of enrofloxacin and its metabolite to fetal fluids and its effects on fetal cartilage when administered to pregnant mares. Methods: In vivo and terminal controlled experiment. Methods: Healthy mares at 260 days of gestation were allocated into thr...
Vatistas NJ, Snyder JR, Hildebrand SV, Harmon FA, Woliner MJ, Barry SJ, Nieto J, Henry P, Enos LR, Magliano D, Brown SA, Drake C.To determine the effects of the 21-aminosteroid, U-74389G, on reperfusion of the equine jejunum, using total (TVO) and partial (PVO) vascular occlusion during the ischemic period. Methods: TVO: 16 healthy horses were randomly allotted to 3 groups-4 horses received the vehicle alone, 6 horses received a low dosage (3 mg/kg o body weight), and 6 horses a high dosage (10 mg/kg) of U-7438G. PVO: 10 healthy horses were randomly allotted to 2 groups--5 horses received the vehicle alone, and 5 horses received the low dosage (3 mg/kg) of U-74389G. Methods: TVO was induced for 1 hour followed by 2 hour...
Zhang N, Ding S, Kolbanovskiy A, Shastry A, Kuzmin VA, Bolton JL, Patel DJ, Broyde S, Geacintov NE.The equine estrogens equilin (EQ) and equilenin (EN) are the active components in the widely prescribed hormone replacement therapy formulation Premarin. Metabolic activation of EQ and EN generates the catechol 4-hydroxyequilenin (4-OHEN) that autoxidizes to the reactive o-quinone form in aerated aqueous solutions. The o-quinones react predominantly with C, and to a lesser extent with A and G, to form premutagenic cyclic covalent DNA adducts in vitro and in vivo. To obtain insights into the structural properties of these biologically important DNA lesions, we have synthesized site-specifically...
Gossett KA, French DD, Cleghorn B, Church GE.Hypertonic NaHCO3 infusion caused blood volume expansion, increased blood bicarbonate concentration, and delayed the onset of hypophosphatemia in ponies with endotoxemia. However, NaHCO3 infusion did not normalize blood pH, and it increased blood L-lactate concentration, and caused hypokalemia, hypernatremia, and hyperosmolality. The deleterious effects of NaHCO3 infusion in endotoxemia ponies outweighed the beneficial effects. The role of hypertonic NaHCO3 given IV for treatment of endotoxemia in equids must be reevaluated.
Stokol T, Serpa PBS, Zahid MN, Brooks MB.Equid herpes virus type-1 (EHV-1) is a major pathogen of horses, causing abortion storms and outbreaks of herpes virus myeloencephalopathy. These clinical syndromes are partly attributed to ischemic injury from thrombosis in placental and spinal vessels. The mechanism of thrombosis in affected horses is unknown. We have previously shown that EHV-1 activates platelets through virus-associated tissue factor-initiated thrombin generation. Activated platelets participate in thrombus formation by providing a surface to localize coagulation factor complexes that amplify and propagate thrombin genera...
Mainguy-Seers S, Bessonnat A, Picotte K, Lavoie JP.Inhaled corticosteroids are effective in the treatment of equine asthma. A recent study reported that nebulisation of injectable dexamethasone had low systemic bioavailability in healthy horses and could represent a cost-effective therapy for equine inflammatory lung diseases. Objective: To determine the effects of dexamethasone nebulisation on lung function in severe asthmatic horses. It was hypothesised that dexamethasone administered by nebulisation would be more effective than the same dose administered orally. Methods: Randomised blinded experimental study in severe asthmatic horses. Meth...
McMullen RJ, Davidson MG, Gilger BC.To determine the effects of tropicamide 1% on the refractive state of the adult equine globe and identify the most appropriate time period (in relation to mydriasis) to perform streak retinoscopy. Methods: Eight university-owned mares of various ages and breeds. Methods: Topical tropicamide 1% was applied to one randomly selected eye from each of the horses to induce mydriasis and cycloplegia. The contralateral eyes served as controls. Streak retinoscopy and pupillometry were performed prior to, and every 5 min after tropicamide 1% installation for 90 min. Results: All values are expressed as ...
Zielinski J, Mevissen M.Testosterone hydroxylation was investigated in human, canine and equine liver microsomes and in human and canine single CYPs. The contribution of the CYP families 1, 2 and 3 was studied using chemical inhibitors. Testosterone metabolites were analyzed by HPLC. The metabolites androstenedione, 6β- and 11β-hydroxytestosterone were found in microsomes of all species, but the pattern of metabolites varied within species. Androstenedione was more prominent in the animal species, and an increase over time was seen in equines. Testosterone hydroxylation was predominantly catalyzed by the CYP3A subf...
