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.
Tydén E, Olsén L, Tallkvist J, Larsson P, Tjälve H.The intestinal enterocytes provide the initial site for cytochrome P450 (CYP)-mediated metabolism of orally absorbed xenobiotics. In man and some animal species, the CYP3A subfamily is highly expressed in the intestines and considered to be important in the first-pass metabolism of drugs and other xenobiotics. The aim of the present study was to investigate the mRNA expression, immunohistochemical localization and catalytic activity of CYP3A in the intestines of horse. Real-time RT-PCR analyses showed that the highest CYP3A mRNA expression was present in the duodenum with a decreasing level to...
Malinowski K, Kearns CF, Guirnalda PD, Roegner V, McKeever KH.Effects of longitudinal exercise training and acute intensive exercise (simulated race test) on immune function have not been reported in horses. Clenbuterol, a beta2-adrenergic agonist, is used to manage inflammatory airway disease in horses. This study investigated the interaction of 8 wk of exercise training with or without 12 wk of clenbuterol administration in horses. Twenty-three untrained standardbred mares (10 +/- 3 yr, Mean +/- SE) were used and divided into four experimental groups. Horses given clenbuterol plus exercise (CLENEX; n = 6) and clenbuterol alone (CLEN; n = 6) received 2....
Lizarraga I, Castillo F, Valderrama ME.Isoxsuprine is used clinically to treat navicular disease and laminitis in horses. Although it is thought to increase digital and laminar blood flow, isoxsuprine's mechanism of action remains controversial, and analgesia has been suggested recently as such possible mechanism. This research investigated the analgesic potential of isoxsuprine in healthy horses submitted to a mechanical nociceptive test. Isoxsuprine (1.2 mg/kg), xylazine (1.1 mg/kg), distilled water : ethanol 95% (2 : 1, v/v, 20 ml) and saline (0.9%, 20 ml) were injected intravenously, and nociceptive thresholds were measured ove...
Tomlinson JE, Blikslager AT.To determine whether ischemia and flunixin affect in vitro lipopolysaccharide (LPS) absorption in samples of the jejunum of horses. Methods: 12 horses. Methods: Horses were anesthetized, a midline celiotomy was performed, and the jejunum was located. Two 30-cm sections of jejunum (60 cm apart) were selected. One segment was designated as control tissue; ischemia was induced in the other segment for 120 minutes. Horses were then euthanatized. Mucosa from each jejunal segment was mounted on Ussing chambers and treated with or without flunixin. Tissues from 6 horses were used to assess permeabili...
Nuñez E, Steffey EP, Ocampo L, Rodriguez A, Garcia AA.To quantitate the dose- and time-related effects of IV administration of xylazine and detomidine on urine characteristics in horses deprived of feed and water. Methods: 6 horses. Methods: Feed and water were withheld for 24 hours followed by i.v. administration of saline (0.9% NaCI) solution, xylazine (0.5 or 1.0 mg/kg), or detomidine (0.03 mg/kg). Horses were treated 4 times, each time with a different protocol. Following treatment, urine and blood samples were obtained at 15, 30, 60, 120, and 180 minutes. Blood samples were analyzed for PCV and serum concentrations of total plasma solids, so...
MacEachern KE, Smith GL, Nolan AM.Hypoxaemia accompanies dorsal recumbency in the horse and frequently complicates general anaesthesia. The physiology associated with this phenomenon is poorly understood. One possible cause of poor tolerance to dorsal recumbency is an absent or reduced response to hypoxic pulmonary vasoconstriction (HPV). This study compared the HPV response in isolated pulmonary artery vessels from equivalent regions of equine and bovine lung. Methods: Equine and bovine, in vitro study. Methods: Equine and bovine pulmonary arteries were removed from the lungs of euthanased horses and cattle. Measurements of i...
Van Erck E, Votion D, Kirschvink N, Genicot B, Lindsey J, Art T, Lekeux P.The objective of this paper was to determine if changes in ventilation patterns could influence the outcome of respiratory function measurements performed with our impulse oscillometry system (IOS) in horses. In a first study, IOS tests were performed in vitro on six isolated equine lungs. Lung inflation levels were controlled by modifying depressurisation inside an artificial thorax and different ventilation patterns were imposed. In a second in vivo study, transient variations in breathing pattern were evaluated both with the IOS and a current reference technique (CRT) in five healthy mature...
Badino P, Odore R, Re G.Adrenergic receptors (ARs) are the cellular membrane binding sites through which natural catecholamines and sympathomimetic drugs exert their physiological and pharmacological effects. In recent decades, studies to clarify the distribution and function of ARs have been performed mostly on cultured cells, laboratory animals and human target tissues, but little is known about these aspects in domestic animals. This review focuses on AR structure, classification and signalling pathways and on AR subtype distribution in target tissues of some domestic animals, namely dogs, horses and bovines. In t...
Spoormakers TJ, Donker SH, Ensink JM.The anaesthetic potency, onset of action, duration of action, and side effects of lidocaine and lidocaine plus epinephrine for proximal metacarpal block of the lateral and medial palmar nerves were determined. Ten horses were used and legs were injected using a cross-over model with three test solutions: 1) solvent and lidocaine (2%) plus epinephrine (SLE); 2) solvent and lidocaine (2%) without epinephrine (SL); and 3) solvent only (S). The contra-lateral leg was injected with saline (placebo; P). In both the SL and SLE groups, the onset of anaesthesia occurred between 5 and 15 minutes after i...
Fitzgerald SD, Braselton WE.Diagnostic evaluation of a mildly ataxic young gelding Quarterhorse included a contrast myelogram. Unfortunately, sodium diatrizoate was inappropriately administered by intrathecal injection resulting in severe unrelenting seizure activity and necessitated the destruction of the animal. The contrast agent was identified by analyzing cerebrospinal fluid by high-performance liquid chromatography and confirmed with probe mass spectrometric analysis. This contrast agent is highly ionic, has high osmolarity, and also blocks neurotransmission at specific receptors; for these reasons it is contraindi...
Guan F, Uboh CE, Soma LR, Luo Y, Jahr JS, Driessen B.Oxyglobin (OXY) and Hemopure (HMP) are produced from bovine hemoglobin (Hb) and were developed for the treatment of anemia in animal and human patients, respectively. Hemolink (HML) is a blood substitute of human Hb origin under development. The ability of these agents to carry oxygen in circulating blood and their promise to improve oxygen delivery to tissues supports the potential for their abuse in equine and human athletes. To deter athletes from abuse of these agents, a method has been developed for the detection, confirmation and quantification of OXY, HMP, and HML in equine and human pl...
Sanchez LC, Murray MJ, Merritt AM.To evaluate the efficacy of omeprazole paste, a commonly used antiulcer drug, on intragastric pH in clinically normal neonatal foals. Methods: 6 clinically normal foals between 5 and 14 days of age. Methods: Intragastric pH was recorded in each foal by use of a disposable antimony pH electrode with internal reference. Values for intragastric pH were recorded every 4 seconds by use of an ambulatory pH monitor. There were two 24-hour recordings of intragastric pH for each foal, with 24 hours between recordings. Foals were not administered any drugs during the first recording. Foals were administ...
Drogemuller M, Failing K, Schnieder T, von Samson-Himmelstjerna G.This study was designed to investigate the effect of repeated treatments with increasingly high fenbendazole (FBZ) dosages on the phenotype and genotype of a benzimidazole (BZ)-resistant cyathostomin population. An experimentally infected horse was treated repeatedly with FBZ dose rates between 7.5 and 30.0 mg/kg body weight (bw) over approximately 2 years. Faecal egg counts (FECs) and larval cultures were performed weekly. A total of 45 faecal egg count reduction tests (FECRTs) were analysed, revealing a high variability during the course of experiment with a mean value in faecal egg count re...
Aleman M, Riehl J, Aldridge BM, Lecouteur RA, Stott JL, Pessah IN.Equine malignant hyperthermia MH has been suspected but never genetically confirmed. In this study, we investigated whether mutations in a candidate gene, RyR1, were associated with MH in two clinically affected horses. RyR1 gene sequences revealed polymorphisms in exons 15, 17, and 46 in WTRyR1 and MHRyR1 horses with one derived amino acid change in MHRyR1 exon 46, R2454G. The MHRyR1 horses were genetically heterozygous for this mutation, but presented an MH phenotype with halothane challenge. Skeletal sarcoplasmic reticulum from a R2454G heterozygote collected during a fulminant MH episode s...
Moore I, Horney B, Day K, Lofstedt J, Cribb AE.The effect of oral treatment with natural or recombinant human interferon alpha (HIA) on inflammatory airway disease in young standardbreds was assessed in a double-blind, randomized clinical trial. A total of 34 horses with nasal discharge, excess mucus in the trachea, and a persistent cough of at least 2 weeks' duration that interfered with training completed the trial. Horses were rested for 1 week and received oral treatment with either a saline placebo, recombinant human interferon alpha (rHIA; 90 U/horse/day), or natural human interferon alpha (nHIA: 50 U/horse/day) for 5 days. There was...
Bowen IM, Marr CM, Chester AH, Wheeler-Jones CP, Elliott J.The equine aortic valve is subject to non-inflammatory degenerative changes, associated with aortic valvular regurgitation (AR). This disease shares pathological and epidemiological features with AR in humans, and may serve as a useful model to study in-vitro functional responses associated with aging and disease. The study aim was to determine the contractile properties of the normal equine aortic valve. Methods: The contractile responses of equine aortic valves to angiotensin II, the thromboxane-mimetic U44069, endothelin-1, 5-hydroxytryptamine and the alpha-adrenoceptor agonists medetomidin...
Mamede FV, Laus JL, Cabral VP, Vicenti FA, Barbieri-Neto J.To possibly reduce postoperative adhesions that occur after ocular myoplasties, we investigated the topical effects of 0.04% mitomycin C on the repaired areas of the medial rectus muscle using an equine renal capsule preserved in 98% glycerin for reinforcement of the sutures. Twenty-four rabbits, divided into two groups of 12 animals each [untreated (control) and treated group (MMC)], were submitted to surgical rupture of the medial rectus muscle of one eye and repair of the defect 24 h later with sutures and an equine renal capsule. Post-operative prophylactic treatment of the two groups cons...
Westermann CM, Boerma S, van Nieuwstadt RA.Since the only registrated anti-ectoparasiticum for horses (foxim) is no longer available in The Netherlands, some cases of amitraz intoxication of the horse have occurred. In this article the literature concerning amitraz intoxications and experiments will be discussed and some cases will be described.
Stout TA, Colenbrander B.There are a number of situations in which it is desirable to suppress part or all of the reproductive endocrine system in a horse, notably the competing animal whose tractability during training, or performance during competition, is compromised by the expression of sexual or aggressive behavior. The current therapeutic approaches to reproductive endocrine suppression include gonadectomy and progestagen administration, where the former carries surgical risks and entails irreversible loss of breeding potential, and effective progestagen therapy requires frequent administration for extended peri...
Ho EN, Yiu KC, Tang FP, Dehennin L, Plou P, Bonnaire Y, Wan TS.Boldenone (1,2-dehydrotestosterone) is a common veterinary anabolic agent. Its structure is very similar to testosterone. Testosterone is endogenous in the horse, whereas there has been no report concerning the detection of endogenous boldenone. This paper reports the direct observation of sulphate conjugate of boldenone in equine urine from entires. The detection procedures involved solid-phase extraction, immunoaffinity column (IAC) purification, and then LC-MS-MS analysis on a Q-ToF instrument. The identification of boldenone sulphate has provided direct evidence for the endogenous nature o...
Schumacher J, Livesey L, DeGraves FJ, Schumacher J, Schramme MC, Hathcock J, Taintor J, Gomez J.Anaesthesia of the palmar digital nerves is claimed to attenuate lameness in some horses that are lame because of pain in the proximal interphalangeal (PIP) joint. Objective: To determine the response of horses with pain in the PIP joint to anaesthesia of the palmar digital nerves. Methods: Horses were video recorded trotting before and after induction of pain in the PIP joint and 10 mins after anaesthesia of the palmar digital nerves. The palmar digital nerves were anaesthetised 3 times at different sites, and the video recorded gaits were scored subjectively. Results: The median lameness sco...
Barton MH, Parviainen A, Norton N.A safe, affordable and effective treatment for endotoxaemia in horses is needed in order to reduce the incidence of this potentially fatal condition. Objective: To evaluate the effect of polymyxin B (PMB) on signs of experimentally-induced endotoxaemia. Objective: PMB ameliorates the adverse effects of endotoxaemia without causing nephrotoxicity. Methods: Four groups of 6 healthy mature horses each received 20 ng endotoxin/kg bwt i.v. over 30 mins. Additionally, each group received one of the following i.v.; 5000 u PMB/kg bwt 30 mins before endotoxin infusion; 5000 u PMB/kg bwt 30 mins after e...
Cornelisse CJ, Robinson NE, Berney CE, Kobe CA, Boruta DT, Derksen FJ.Although the efficacy of dexamethasone for the treatment of recurrent airway obstruction (RAO) has been documented, the speed of onset of effect and duration of action are unknown, as is the efficacy of orally administered dexamethasone with or without fasting. Objective: To document the time of onset of effect and duration of action of a dexamethasone solution i.v. or orally with and without fasting. Methods: Protocol 1 used 8 RAO-affected horses with airway obstruction in a crossover design experiment that compared the effect of i.v. saline and dexamethasone (0.1 mg/kg bwt) on pulmonary func...
Tomlinson JE, Wilder BO, Young KM, Blikslager AT.To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion. Methods: 24 horses. Methods: Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithel...
Rothschild CM, Hines MT, Breuhaus B, Gay J, Sellon DC.Trimethoprim-sulfadiazine was administered to horses in a randomized, placebo controlled study to determine the effects of potentiated sulfonamides on thyroid function in normal horses. The treatment group included eight horses that received trimethoprim-sulfadiazine mixed with molasses orally at 30 mg/kg once daily for eight weeks. The control group included 8 horses that received an oral placebo (flour mixed with molasses) once daily for the same period. Thyroid function was evaluated prior to initiation of treatment and after 8 weeks of treatment. Serum concentrations of total and free trii...
Lehner AF, Hughes CG, Harkins JD, Nickerson C, Mollett B, Dirikolu L, Bosken J, Camargo F, Boyles J, Troppmann A, Karpiesiuk WW, Woods WE, Tobin T.We have investigated the detection, confirmation, and metabolism of the beta-adrenergic agonist ractopamine administered as Paylean to the horse. A Testing Components Corporation enzyme-linked imunosorbent assay (ELISA) kit for ractopamine displayed linear response between 1.0 and 100 ng/mL with an I-50 of 10 ng/mL and an effective screening limit of detection of 50 ng/mL. The kit was readily able to detect ractopamine equivalents in unhydrolyzed urine up to 24 h following a 300-mg oral dose. Gas chromatography-mass spectrometry (GC-MS) confirmation comprised glucuronidase treatment, solid-pha...
Wijnberg ID, Ververs FF.Five adult horses with ventricular extra systoles (VES) and 2 with ventricular tachycardia (VT) refractory to treatment with rest, anti-inflammatory drugs, lidocaine, or procainamide were treated with phenytoin sodium p.o. q12h. The starting dosage of phenytoin was 20 or 22 mg/kg body weight (BW) q12h, and the maintenance dosage varied from 8 to 17 mg/kg BW q12h. The mean +/- standard deviation therapeutic blood concentration of total phenytoin was 8.8 +/- 2.1 mg/L, and the mean concentration of free phenytoin of 2.5 +/- 0.5 mg/L was relatively constant at a range of 24 to 29% of the total phe...
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...
Adams SB.Ileus may occur in horses of all ages secondarily to drug administration, colic, exhaustion, peritonitis, or metabolic disorders. Ileus most commonly occurs following abdominal surgery for colic and is a significant cause of postoperative mortality in these horses. The most common clinical signs of ileus are decreased or absent intestinal sounds and gastric reflux. Ileus is treated by eliminating the initiating causes, correcting metabolic imbalances, decompressing distended bowel, providing analgesia, stimulating motility with drugs, and regulating exercise and feed and water intake.
Manohar M, Goetz TE, Hassan AS.Because sensitivity of equine pulmonary vasculature to endogenous as well as exogenous nitric oxide (NO) has been demonstrated, we examined whether endogenous NO production plays a role in exercise-induced arterial hypoxemia. We hypothesized that inhibition of NO synthase may alter the distribution of ventilation-perfusion mismatching, which may affect the exercise-induced arterial hypoxemia. Arterial blood-gas variables were examined in seven healthy, sound Thoroughbred horses at rest and during incremental exercise protocol leading to galloping at maximal heart rate without (control; placebo...
Thomson JR, McPherson EA.When stabled in a controlled environment, horses effected with chronic obstructive pulmonary disease (COPD) became clinically asymptomatic in 4 to 32 days (mean [+/-sd] 9.1 +/- 4.9 days), the time being influenced most by the severity of the disease judged on maximum intrathoracic pressure change (Max delta Ppl) and the age of the animal. Sodium cromoglycate, a drug widely used for prophylaxis of allergic respiratory disease in man, was administered by inhalation to 56 COPD-affected horses. The results showed that a linear response existed between the number of successive days treatment with t...
Friebe M, Stahl J, Kietzmann M.Even though intra-articular injections play an important role in the treatment of joint-related lameness in horses, little is known about pharmacokinetic properties of substances used. Therefore, an ex vivo model for pharmacokinetic studies was developed using distal forelimbs of slaughtered horses. The extremity was perfused with gassed Tyrode solution for up to 8 h. Tissue viability was confirmed by measurements of glucose consumption, lactate production, and lactate dehydrogenase activity in the perfusate. Standard criteria for tissue viability had been determined in preliminary experiments...
Lyons ET, Tolliver SC, Stamper S, Drudge JH, Granstrom DE, Collins SS.Praziquantel injectable formulation was administered at 0.5 mg k-1 per os to 24 equids naturally infected with 1-183 (average 40) Anoplocephala perfoliata. Drug activity was evaluated by a modified critical test method with necropsy 24 h after treatment. There was variable efficacy of 0-100% (aggregate average 85%); for 18 equids, 93-100%, for three equids, 70-85%, and for three equids, 0-20%.
Doherty TJ, Geiser DR, Rohrbach BW.This study determined the effects of epidurally administered morphine, ketamine and butorphanol on halothane minimum alveolar concentration (MAC) in ponies. Seven ponies were anaesthetised with thiopentone and succinylcholine, intubated and anaesthesia maintained with halothane. Ventilation was controlled and blood pressure was maintained within normal limits. Following the determination of baseline halothane MAC for the pelvic and thoracic limbs the ponies were given morphine (0.1 mg/kg bwt), ketamine (0.8 or 1.2 mg/kg bwt), butorphanol (0.05 mg/kg bwt) or saline, epidurally, to a final volum...
Cox JH, DeBowes RM.Discomfort manifested by colic-like clinical signs in 2 young mares was presumed to be attributable to ovarian pain associated with follicular enlargement and ovulation. Diagnosis was based on the lack of detectable evidence of gastrointestinal disease, the finding of a large ovarian follicle or recent ovulation, the repetition of signs during several subsequent estrual periods, and the clinical response to pharmacologic suppression of estrus and ovulation. The similarity of the clinical signs in these 2 mares to cyclic intermenstrual pain in women was considered.
McClure SR, White GW, Sifferman RL, Bernard W, Hughes FE, Holste JE, Fleishman C, Alva R, Cramer LG.To determine whether omeprazole oral paste administered at a dosage of 0.5 or 1 mg/kg (0.23 or 0.45 mg/lb), PO, every 24 hours would effectively prevent the recurrence of gastric ulcers in horses in race training. Methods: Prospective study. Methods: 135 horses. Methods: Horses with gastric ulcers were treated with omeprazole at a dosage of 4 mg/kg (1.8 mg/lb), PO, every 24 hours for 28 days. Horses in the dose selection portion of the study were sham dose treated or received 0.5 or 1 mg of omeprazole/kg, PO, every 24 hours for an additional 28 days. Horses in the dose confirmation portion of ...
Golenz MR, Wilson WD, Carlson GP, Craychee TJ, Mihalyi JE, Knox L.The suitability of the intraosseous (i.o.) route for drug administration to equine neonates was evaluated in a study comparing the pharmacokinetics of amikacin administered by the i.o. and intravenous (i.v.) routes. Using a cross-over study design amikacin sulphate (7 mg/kg bwt) was administered i.o. or i.v. to 6 healthy foals at 3 and 5 days of age. Amikacin was instantaneously and completely absorbed after i.o. administration, achieving a mean +/- sd peak concentration (34.17 +/- 3.54 micrograms/ml) in the first sample collected 3 min after administration which was not significantly differen...
Gaffin SL, Wells M, Jordan JP.Death in humans from ionising radiation overexposure in the 3-8 Gy (300-800 rad) range is in part due to the toxaemia caused by the entry of gram-negative bacteria and/or their lipopolysaccharide toxin (LPS) into the blood circulation through the walls of partially denuded gut. Anti-LPS hyperimmune equine plasma was evaluated for its ability to lower irradiation-induced lethality. Mice were irradiated with 6.3 Gy (630 rad) and six days later received equine Anti-LPS hyperimmune plasma, control plasma or saline. Mortalities in the three groups were 58%, 92% and 79% (p less than 0.01) respective...
Becher AM, Pfister K.In recent years more and more cases of anthelmintic resistant equine strongyles were reported. The latest developments are cases of resistance against macrocyclic lactones. In order to delay this process less anthelmintics and only those which have been previously tested for their efficacy on each individual farm should be used. During the grazing season 2008 faecal samples of 281 horses and 5 donkeys from 26 farms were analysed in the area of Salzburg. To 164 of these horses selective anthelmintic treatment was implemented. Every four weeks faecal samples from the 164 horses were quantitative...
Crisman MV, Wilcke JR, Correll LS, Irby MH.The pharmacokinetics of pentoxifylline (P) and its alcohol metabolite I (MI) were determined after administration of intravenous pentoxifylline, sustained release pentoxifylline tablets (Trental), and crushed pentoxifylline tablets in corn syrup, to five healthy adult horses. Pharmacokinetics were evaluated in a model-independent manner. After intravenous administration, pentoxifylline was rapidly eliminated (mean residence time 1.09 +/- 0.67 h), had a large steady-state volume of distribution (2.81 +/- 1.16 l/kg), and high clearance (3.06 +/- 1.05 l/kg/h). Oral absorption of pentoxifylline fr...
Braim AE, Macdonald MH, Bruss ML, Stanley SD, Giri JK, Giri SN.To characterize the plasma pharmacokinetics and clinical effects of pirfenidone administered IV in healthy horses. Methods: 6 adult horses. Methods: A 15 mg/kg dose of pirfenidone was administered IV over 5 minutes. Physical variables were recorded and blood samples collected prior to infusion; 2.5 minutes after beginning infusion; at the end of infusion; and at 3, 6, 9, 12, 15, 20, 25, 30, 40, 50, 60, 75, and 90 minutes and 2, 2.5, 3, 4, 6, 8, 12, and 24 hours after completion of infusion. Plasma concentrations of pirfenidone and its metabolites were determined. Results: Mild clinical effects...
Carakostas MC, Moore WE, Smith JE, Johnson D.The functional capacity of the marrow granulocyte reserve (MGR) in 4 adult horses was studied, using 51Cr-labeled leukocytes. The mean increase in the peripheral granulocyte count following injections of etiocholanolone (0.3 mg/kg) was 870 granulocytes/mm3, and the mean increase following prednisolone administration (200 mg) was 5,880 granulocytes/mm3. Etiocholanolone failed to mobilize the MGR and decreased the rate of granulocyte egress from the blood. Prednisolone rapidly mobilized the MGR and markedly decreased the granulocyte specific activity during the first 3 hours after injection.
Ellerbrock RE, Canisso IF, Larsen RJ, Garrett KS, Stewart MC, Herzog KK, Kersh ME, Moshage SG, Podico G, Lima FS, Childs BA.Recent studies have shown that fluoroquinolones, specifically, enrofloxacin and its active metabolite (ciprofloxacin), cross the equine placenta without causing gross or histological lesions in the first and third trimester fetuses or resulting foal. However, it is possible that in utero exposure to fluoroquinolones may cause subtle lesions not detectable by standard means; thus, a more in-depth assessment of potential toxicity is warranted. Objective: To use quantitative magnetic resonance imaging (qMRI), biomechanical testing, and chondrocyte gene expression to evaluate the limbs of foals ex...
Madison JB, Garber JL, Rice B, Stumf AJ, Zimmer AE, Ott EA.Thirty-five newborn foals were assigned to 1 of 3 groups and treated with 0.9% NaCl solution (saline; group 1; n = 12), oxytetracycline (44 mg/kg of body weight; group 2; n = 12), or 2-pyrrolidone (oxytetracycline vehicle; group 3; n = 11) in saline solution during the first 36 hours after birth. Serum biochemical analyses were performed on samples obtained from group-1 and group-2 foals before treatment and 24 and 96 hours after treatment. Lateral to medial radiographic views of the forelimbs were obtained before treatment and 24 and 96 hours after treatment in all foals. Metacarpophalangeal ...
Kern JR, Cardellina JH.Anemonin, the dilactone of cyclobutane-1,2-diol-1,2-diacrylic acid derived from the cyclodimerization of protoanemonin, a known blistering agent, was isolated from Clematis hirsutissima, a plant used by the Nez Perce and Teton Sioux nations as a horse stimulant.
Sampaio CA, Prado ES.Ala-Phe-Lys-CH2-Cl is a chloromethylketone derivative which is able to promote the inhibition of several proteolytic enzymes. In this paper the inhibition of horse urinary and plasmatic kallikreins is described and this inhibition is compared to that produced in human plasma kallikrein. This compound was designed based upon the structure of bradykinin. This enzyme substrate system can provide a model for the study of the interactions between bradykinin and its receptor. The inhibition of the enzymes was achieved both for its esterase and kinin-releasing activities.
Sato K, Tokuhisa S, Inaba Y.The growth of group A human, bovine, equine and porcine rotaviruses were enhanced by pretreatment of virus with pancreatin, trypsin, protease, alkaline phosphatase or pepsin and incorporation of these enzymes in maintenance medium. In contrast, alpha-amylase or lipase inhibited the growth of equine and porcine rotaviruses. The other enzymes, adenosine deaminase, lactase, lysozyme, ribonuclease or triose-phosphate isomerase gave little or no change in the growth of all four rotaviruses.
May SA, Lees P, Higgins AJ, Sedgwick AD.The cardinal signs of acute inflammation have been recognised for almost 2000 years, but it is only in the last hundred years that significant progress has been made in understanding the underlying cellular response. Our knowledge of the chemical messengers which regulate and in some cases lead to persistence of the inflammatory process is, as yet, incomplete, but it is hoped that further research at this level will lead to the development of more effective therapeutic agents.
Schumacher J, Livesey L, DeGraves FJ, Schumacher J, Schramme MC, Hathcock J, Taintor J, Gomez J.Anaesthesia of the palmar digital nerves is claimed to attenuate lameness in some horses that are lame because of pain in the proximal interphalangeal (PIP) joint. Objective: To determine the response of horses with pain in the PIP joint to anaesthesia of the palmar digital nerves. Methods: Horses were video recorded trotting before and after induction of pain in the PIP joint and 10 mins after anaesthesia of the palmar digital nerves. The palmar digital nerves were anaesthetised 3 times at different sites, and the video recorded gaits were scored subjectively. Results: The median lameness sco...
Westermann CM, Boerma S, van Nieuwstadt RA.Since the only registrated anti-ectoparasiticum for horses (foxim) is no longer available in The Netherlands, some cases of amitraz intoxication of the horse have occurred. In this article the literature concerning amitraz intoxications and experiments will be discussed and some cases will be described.
Hess MB, Parker NA, Purswell BJ, Dascanio JD.Lufenuron, a benzoylphenyl urea derivative, was evaluated as a treatment for endometrial fungal infections in 4 mares. Intrauterine lavage was performed with lufenuron suspended in sterile saline (0.9% NaCl) solution. Cytologic evaluation and fungal culture of the endometrium, as well as subsequent reproductive performance, were used to monitor efficacy of this treatment. Fungal endometritis in mares is associated with infertility. Treatment is often ineffective and costly, and recurrence following treatment is not uncommon. Intrauterine infusions of lufenuron were effective in eliminating fun...
Olszewski MA, Robinson NE, Derksen FJ.In vitro responses of equine small peripheral airways (SA) and lung parenchyma (LP) were studied. We examined their contractile and relaxant responses and investigated effects of histamine, and endogenous prostanoids as these mediators may play a role in development or recurrent airway obstruction in horses (heaves). SA and LP electrical field stimulation (EFS) induced nearly maximal and partial frequency-dependent contractions, respectively. These contractions were virtually abolished in SA but only partially inhibited in LP by atropine (ATR) and tetrodotoxin (TTX). Methacholine (MCh) contrac...
Polyak MM, Morton AJ, Grosche A, Matyjaszek S, Freeman DE.Several therapeutic agents have been tested in models of ischaemia and reperfusion injury (IRI) in equine jejunum, with mixed results. This study was based on the use of an organ perfusion solution (OPS) designed to protect human allografts from IRI. Objective: A modified OPS can preserve the integrity of equine large colon during 12 h of isolated pulsatile perfusion, in the absence of oxygen and blood. Methods: Segments of large colon were removed from anaesthetised horses, the contents removed and the mucosa rinsed with 0.9% saline. Experimental segments were perfused for 12 h with one litre...
Watney GC, Jordan C, Hall LW.The effects of halothane, enflurane and isoflurane on bronchial calibre were investigated in five anaesthetized ponies using a computer-aided forced airflow oscillation technique to derive specific lower airways conductance (s.Glaw) and expiratory reserve volume (ERV). All the agents tended to increase s.Glaw (indicating bronchodilatation), but ERV was reduced by halothane and enflurane, and increased by isoflurane. It was concluded that the effects of these agents on bronchomotor tone were similar to those which occur in man. However, the reasons for the differences in their effects on ERV co...
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...
Kerr DD, Jones EW, Holbert D, Huggins K.A 3-way Latin square design was used to compare the sedative and preanesthetic effects of xylazine given intravenously (i.v.) (1.1 mg./kg.) and given intramuscularly (i.m.) (2.2 mg./kg.) and acetylpromazine maleate (0.66 mg./kg.) given i.v. in the horse. Physiologic responses were recorded and clinical observations were made. Intravenous administration of xylazine and atropine sulphate (0.011 mg./kg.) appeared to have superior sedative properties, without having adverse effects on cardiovascular and respiratory systems. Both the i.v. and the i.m. administrations of xylazine prior to induction ...
Manohar M, Goetz TE, Rothenbaum P, Humphrey S.The present study was carried out to ascertain whether beta2-adrenergic receptor stimulation with clenbuterol would attenuate the pulmonary arterial, capillary and venous hypertension in horses performing high-intensity exercise and, in turn, modify the occurrence of exercise-induced pulmonary haemorrhage (EIPH). Experiments were carried out on 6 healthy, sound, exercise-trained Thoroughbred horses. All horses were studied in the control (no medications) and the clenbuterol (0.8 pg/kg bwt, i.v.) treatments. The sequence of these treatments was randomised for every horse, and 7 days were allowe...
