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.
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...
Schatzmann U, Jossfck H, Stauffer JL, Goossens L.The effect of three alpha 2-agonistic sedatives, Detomidine (0.04 mg/kg), Romifidine (0.08 mg/kg) Xylazine (1.1 mg/kg) and placebo (NaCl), on intrauterine pressure was investigated with an intrauterine balloon model in four non-pregnant warmblood mares. Within 6.0 (+/- 2.2) min mean pressure increases of 9.80 (+/- 3.74), 6.88 (+/- 3.95) and 13.95 (+/- 5.19) mmHg were recorded for Detomidine, Romifidine and Xylazine, respectively. Placebo had no significant effect. The mean duration of pressure increase was 30.0 (+/- 5.10), 17.67 (+/- 9.87) and 19.50 (+/- 13.78) min for Detomidine, Romifidine a...
Manohar M.High-intensity exercise results in a dramatic increase in mean pulmonary capillary blood pressure of horses, and administration of furosemide 4 hours before exertion significantly attenuates this exercise-induced increment. To test whether this effect of furosemide is mediated via release of prostaglandins, right atrial and pulmonary vascular pressures were measured in 8 healthy, sound, exercise-trained Thoroughbreds at rest and during incremental-step exercise on a treadmill. Horses were studied on 3 separate occasions: after i.v. administration of saline (0.9% NaCl) solution, after administr...
Horspool LJ, Taylor DJ, McKellar QA.Amikacin was detectable (> 0.02 micrograms/ml) in plasma for 12 h in horses and donkeys and for 8 h in ponies following intravenous (i.v.) administration at a dose rate of 6 mg/kg bodyweight. The elimination half-life (harmonic mean) of amikacin was 2.8, 1.6 and 1.9 h in horses, ponies and donkeys, respectively, and the mean body clearance was relatively slow (45.2, 82.4 and 58.0 ml/h.kg, respectively). A suitable dosage interval for the i.v. administration of amikacin sulphate to horses, ponies and donkeys, at a dose rate of 6 mg/kg, would be every 8 h in horses, and every 6 h in ponies an...
Erichsen DF, Aviad AD, Schultz RH, Kennedy TJ.A field study of 239 horses was conducted to determine the efficacy and safety of clenbuterol HCl, a beta 2-adrenergic bronchodilator, when administered incrementally to effect in the treatment of chronic obstructive pulmonary disease (COPD). The severity of COPD (heaves) and response to treatment was determined by clinical evaluation; an overall 'heaveiness rating' (OHR) was assigned at each observation. The horses were treated orally b.i.d. with clenbuterol (as Ventipulmin Syrup), beginning with the lowest dosage of 0.8 micrograms/kg. On day 10 of treatment at the effective dose (0.8, 1.6, 2...
Zhang CH, Grünig G, Davis W, Antczak DF.The regulatory effects of phorbol myristate acetate (PMA) on the expression of the CD4 molecule on horse T cells were investigated. On both peripheral blood lymphocytes and thymocytes, PMA resulted in a rapid and transient down-regulation of equine CD4 expression, but had no such effect on the surface expression of equine CD5, CD8 or major histocompatibility complex (MHC) class I and class II molecules. Over 75% of the surface CD4 molecules per cell were lost after a 4 h exposure to PMA at 37 degrees C. The regulation of equine CD4 expression induced by PMA was temperature dependent and revers...
Horne MM, Pascoe PJ, Ducharme NG, Barker IK, Grovum WL.This study compared the severity of ischemic injury to the equine jejunal mucosa caused by arteriovenous obstruction (AVO) or venous obstruction (VO) with that caused by reperfusion after ischemia. The degree of mucosal damage and regeneration was scored according to a modified version of an established light microscopic classification for ischemic injury. Biopsy specimens taken after 3 and 4 hours of obstruction, and after 3 hours of obstruction and 1 hour of reperfusion, were compared. There were no changes in the severity of mucosal injury (characterized by epithelial sloughing, loss of vil...
LeBlanc M, Neuwirth L, Mauragis D, Klapstein E, Tran T.The effects of oxytocin on the percentage of technetium 99m albumin colloid (99mTc-microAA), cleared from the uterine lumen was measured in 13 mares. Scintigraphy was performed during 4 consecutive oestrous cycles, on Day 3 of oestrus during Cycles one and 3 and 48 h after ovulation during Cycles 2 and 4. Oxytocin (20 iu) was given i.v. after the initial scintigraphy image during Cycles 3 and 4. Seven multiparous mares (Group 1) were classified as 'susceptible' and 6 mares (2 nulliparous and 4 multiparous; Group 2) were classified as 'resistant' to endometritis. All mares cleared > 90% of 99mT...
Roger T, Bardon T, Ruckebusch Y.The electrical and mechanical activity of the large intestine and its response to administration of opiate mu and kappa agonists were assessed from electrodes and inductograph coils chronically implanted on the cecocolic segment in six ponies given a diet of hay and concentrates. Before the drugs were given, migrating complexes propagating from the cecum into the colon occurred at the rate of 1.5 to 16/hour. During this propulsive activity, the cecocolic sphincter opened and closed allowing the outflow of cecal contents and preventing the backflow of colic contents. Each pony was used as its o...
Durando MM, MacKay RJ, Linda S, Skelley LA.Polymyxin B and an antiserum against an Re mutant Salmonella typhimurium were evaluated for protective effect in an equine model endotoxemia. Six 3- to 5-month-old foals were given endotoxin (0.25 micrograms/kg of body weight) IV after no pretreatment, or pretreatment with polymyxin B (6,000 U/kg, IV) or S typhimurium antiserum (1.5 ml/kg, IV). When given without pretreatment, endotoxin caused transient recumbency and increases in rectal temperature, and heart and respiratory rates. In addition, leukopenia and increases in circulating tumor necrosis factor (TNF) and interleukin 6 (IL-6) activi...
Karges HE, Funk KA, Ronneberger H.Using diagnostics for the determination of clotting factors and fibrinolytic parameters in human plasma, samples from rat, guinea pig, rabbit, cat, dog, sheep, cattle, horse, pig, and monkey were analysed. The human system was employed even for standard curves and controls. Results obtained in this way are relative values in relation to pooled fresh human plasma of healthy donors which is defined to contain 100% of the norm or 1 unit of each factor per 1 ml. Under these conditions, marked differences between the human clotting system and those of different animal species appear. Thus, rabbits ...
Morais JF, de Freitas MC, Yamaguchi IK, dos Santos MC, da Silva WD.IgG and F(ab')2 fragments were prepared from horse plasma rich in specific antibodies against Brazilian Bothrops or Crotalus venoms. Both preparations, free of gross contamination with non-immunoglobulin proteins, were able to combine in vitro with their respective antigens, forming immune complexes at antigen excess, equivalence or antibody excess, and activating the C system, through either the classical or the alternative pathways. The IgG preparation was more effective in neutralizing the lethal factors in Bothrops or Crotalus venoms, compared with the F(ab')2 fragments. In contrast, IgG a...
Obi T, Kabeyama A, Nishio A.In coronary arterial rings isolated from horses, 10(-8)-10(-6) mol/l acetylcholine (ACh) induced concentration-dependent contractions which were potentiated by the removal of endothelium and by pretreatment with L-nitro-arginine (LNAG) or methylene blue (MB). Relatively lower concentrations of ACh (10(-14)-10(-8) mol/l) induced relaxation when the coronary rings were contracted by phenylephrine (PE). ACh-induced contractions in the coronary rings without endothelium were competitively inhibited by each muscarinic subtype selective antagonist in the following order of potency: 4-diphenylacetoxy...
Korenek NL, Legendre AM, Andrews FM, Blackford JT, Wan PY, Breider MA, Rinaldi MG.Itraconazole, a third-generation azole, was evaluated for treatment of resistant nasal mycotic infections in horses. Two horses with Aspergillus spp nasal granulomas and 1 horse with Conidiobolus coronatus nasal infection were treated with itraconazole (3 mg/kg PO bid). One of the horses with nasal aspergillosis was also treated by surgical resection of the nasal septum. The treatment time for the horses ranged from 3 to 4.5 months. No adverse effects were noted in any of the horses during the treatment period. Peak and trough serum itraconazole concentrations were < 0.5 micrograms/mL in al...
Hildebrand SV, Hill T.Evoked hind limb digital extensor tension (hoof twitch) was maintained at 40% of baseline for 1 h by atracurium infusion in 7 horses anaesthetised with halothane. After 1 h, atracurium was discontinued and hoof twitch allowed to recover to 75%. Atracurium was again given by infusion to maintain 40% twitch for a second hour, then 2 mg gentamycin/kg bwt were given i.v. Atracurium infusion was continued for a third hour, and then hoof twitch was again allowed to recover spontaneously to 75%. Gentamycin reduced twitch strength from 40 +/- 1% (mean +/- sem) to 29 +/- 4% within 7.0 +/- 1.5 min (P = ...
Hinchcliff KW, McKeever KH, Muir WW.The systemic haemodynamic and acid-base effects of the administration of phenylbutazone (4.4 mg kg-1 intravenously) to standing and running horses were investigated. Phenylbutazone, or a placebo, was administered to each of six mares either 15 minutes before, or after 30 minutes of a 60-minute submaximal exercise test which elicited heart rates approximately 55 per cent of maximal, and to the same horses at rest. The variables examined included the cardiac output, heart rate, systemic and pulmonary arterial pressures, right atrial and right ventricular pressures, and arterial and mixed venous ...
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...
Ko WH, O'Dowd JJ, Pediani JD, Bovell DL, Elder HY, Jenkinson DM, Wilson SM.Changes in intracellular free calcium concentration ([Ca2+]i) were monitored in a cell line that was derived from the equine sweat gland epithelium. ATP and closely related compounds could increase [Ca2+]i with a rank order of potency of UTP > or = ATP > ADP >> AMP = adenosine = alpha,beta-methylene-ATP. The responses to ATP and to UTP were initiated by the release of calcium from an internal store and subsequently sustained by calcium influx. The rise in [Ca2+]i thus seems to be mediated by P2U receptors that are coupled to phosphoinositidase C. Some desensitisation of this respon...
Prieto D, Simonsen U, Martín J, Hernández M, Rivera L, Lema L, García P, García-Sacristán A.The distribution of acetylcholinesterase (AChE)-positive nerve fibers and cells, as well as the effects of acetylcholine (ACh) on ureteral smooth muscle and small resistance arteries were investigated in the equine ureter by means of histochemical, classic organ baths and myograph techniques. AChE-positive nerve fibers were widely distributed throughout the ureteral wall forming muscular, subepithelial and perivascular nerve plexuses, whose density was highest at the intravesical ureter. AChE-positive nerve cells were also identified grouped as adventitial or intramural ganglia. ACh increased ...
Wilson DV, Patterson JS, Stick JA, Provost PJ.The role of platelet-activating factor (PAF) in mediating the colonic damage that develops after large-colon torsion was studied in 14 ponies. Morphologic changes in areas of the ascending colon and selected abdominal and thoracic viscera after 1 hour of large-colon torsion and 3 to 5 hours of reperfusion were determined, as well as the protective effects of systemic administration of a specific PAF antagonist (WEB 2086). Ponies were selected then allocated at random and in equal numbers to 2 groups that received 1 of 2 treatments prior to induction of large-colon torsion: group 1--control (sa...
Pompa G, Caloni F, Montana M, Pasqualucci C.1. Isoxsuprine [1-(4-hydroxyphenyl)-2-(1-methyl-2-phenoxyethylamino)-1- propanol] serum concentrations after single- and multiple-dose administration to horse were investigated using immunoenzymatic ELISA, HPLC-UV and thermospray HPLC-MS methods. 2. Using HPLC-MS, isoxsuprine was detected up to 72 h after a single administration (1.2 mg/kg by gastric probe) and up to 96 h after the end of serial administration (1.2 mg/kg every 12 h for 7 days). 3. ELISA detected the drug up to 96 h after a single dose and up to 6 days after the end of prolonged administration. 4. Isoxsuprine is present in hors...
Plumlee KH, Richardson ER, Gardner IA, Galey FD.Delays between time of sampling and time of testing are common; therefore, the length of time that blood can be stored at various temperatures was evaluated for effects on cholinesterase activity. Six horses were treated with 16 g of trichlorfon per os, 6 horses were treated with 15 g of dichlorvos per os, and 10 horses were untreated controls. The cholinesterase activity in whole blood from each horse was measured using an adaptation of the Ellman colorimetric method. The blood from each horse was then divided into 3 groups and stored at 5 C (refrigerated), 20 C (room temperature), or 38 C (i...
Singh B, Minhas KJ, Atwal OS.The pulmonary intravascular macrophages (PIMs) of the ponies possess all the characteristics of a fully differentiated resident macrophage, which forms adhesive plaques with the capillary-endothelial cells. In addition, it has a unique surface coat which does not conform to the concept of a carbohydrate rich membrane bound glycocalyx generally associated with macrophages. We studied the responses of these cells especially in the context of its globular surface coat to multiple doses of MB intravenously: 0.2 ml/kg body copper tracer substance. The ponies were treated with three doses of MB intr...
Dunlop CI.Physiologic similarities and differences between foals and adult horses, including response to pain, cardiopulmonary function, ability to compensate for dehydration and hemorrhage, and response to anesthetic drugs, are considered in this article. Preanesthetic evaluation, choice of anesthetic drugs, technique, and monitoring support requirements through to anesthetic recovery are based on these physiologic considerations. Anesthetic techniques discussed include drugs for premedication, parenteral or inhalational anesthetic induction, and maintenance using inhalational and parenteral anesthesia...
Sjostrom L, al-Abdulla IH, Rawat S, Smith DC, Landon J.Commercial antivenoms produced in horses were compared with monospecific antivenoms raised in sheep against Crotalus durissus terrificus, Crotalus atrox, Crotalus adamanteus, Micrurus fulvius fulvius, Naja naja, Naja kaouthia, Echis ocellatus, Vipera lebetina deserti, Vipera berus berus and Vipera ammodytes ammodytes venom. Antibodies raised by immunizing sheep with C. d. terrificus venom were more effective than their equine counterparts in preventing lethal toxicity in mice (ED50), in inhibiting the venom's pharmacological effects (haemolysis, platelet aggregation and coagulation), and in ne...
Slocombe JO, Cote JF.Twenty horses were treated with ivermectin either by nasogastric tube with a liquid formulation for sheep or per os with a paste formulation for horses at a dosage of 200 mug/kg of body weight. Fecal samples were collected from these horses and from ten untreated horses at the time of treatment and every 2 wk thereafter for up to 10 wk. The samples were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin Double Centrifugation procedures.There were no signs of toxicosis in horses treated with ivermectin. Strongyle eggs were found in the feces of all horses b...
Denham J, Hulme A.Sodium bicarbonate administration in the hours prior to exercise has been used as a performance-enhancing substance in horses since the late 1980s. Although sodium bicarbonate administration to racehorses 24 hours before racing is a banned practice in most racing industries, whether or not it improves running performance in racehorses is currently unclear. The aim of this systematic review and meta-analysis was to establish whether or not acute sodium bicarbonate administration improves running performance in trained Standardbred and Thoroughbred horses. Seven randomized controlled trials, in...
Engelking LR, Dodman NH, Hartman G, Valdez H, Spivak W.Effects of halothane anesthesia were investigated in ponies prepared surgically with chronic external biliary fistulas (T tubes) to determine the effects on liver function and biliary excretion during 2 hours of anesthesia. Four studies were performed on 2 ponies, 2 to 6 months after surgery with the enterohepatic circulation held intact between studies. Intravenous bile acid infusion was used to maintain steady-state bile flow, bilirubin, and bile acid excretion during each study. Compared with the immediate 2-hour preanesthesia values (base line), halothane caused a 138% increase in bilirubi...
Trenholme HN, Sakai DM, Berghaus LJ, Hanafi AL, Knych HK, Ryan CA, McHale B, Banovic F, Quandt JE, Barletta M, Reed RA. To evaluate changes in immunological parameters following subcutaneous (SC) and intramuscular (IM) administration of meperidine in horses through quantitative analysis of plasma tryptase, histamine, and IgE levels. Six adult horses were enrolled in a prospective randomized crossover design. Horses were administered one treatment per day, with a seven day washout period: (a) meperidine 1 mg/kg IM, saline 6 mL SC; (b) saline 6 mL IM, meperidine 1 mg/kg SC; (c) saline 6 mL SC, saline 6 mL IM. Blood samples were obtained for plasmatic histamine (baseline, 5, 10, 15, 30, and 60 min) via LC-MS/MS ...
López-Sanromán FJ, Freilich GM, Gomez-Cisneros D, Varela M, Santiago I, Manso-Díaz G.The objective of the present study was to compare, using accelerometry, the gait changes produced after administration of a dose of 0.2 mg/kg of morphine at the walk in healthy horses. Six mature horses were used, and all animals received two different treatments with, at least, two weeks interval in between. Treatments administered consisted of a single dose of 10 ml of saline solution or a total of 0.2 mg/kg of morphine diluted in 10 ml of saline solution. A three-dimensional accelerometric device was used to collect data continuously while horses were walking. The walking test was performed...
Dirikolu L, Karpiesiuk W, Lehner AF, Tobin T.Toltrazuril sulfone (ponazuril) is a triazine-based antiprotozoal agent with clinical application in the treatment of equine protozoal myeloencephalomyelitis (EPM). In this study, we synthesized and determined the bioavailability of a sodium salt formulation of toltrazuril sulfone that can be used for the treatment and prophylaxis of EPM in horses. Toltrazuril sulfone sodium salt was rapidly absorbed, with a mean peak plasma concentration of 2400 ± 169 (SEM) ng/mL occurring at 8 h after oral-mucosal dosing and was about 56% bioavailable compared with the i.v. administration of toltrazuril sul...
Bailly-Chouriberry L, Cormant F, Garcia P, Kind A, Popot MA, Bonnaire Y.Cobra venom (Naja kaouthia) contains a toxin called α-cobratoxin (α-Cbtx). This toxin is a natural protein containing 71 amino acids (MW 7821 Da) with a reported analgesic potency greater than morphine. In 2007, in USA, this substance was found in the barns of a thoroughbred trainer and since then till date, the lack of a detection of this molecule has remained a recurring problem for the horseracing industry worldwide. To solve this problem, the first method for the detection of α-cobratoxin in equine plasma has now been developed. Plasma sample (3 mL) was treated with ammonium sulfate at ...
DiPietro JA, Todd KS, Lock TF, Reuter-Dallman V.Fifty horses from a herd known to have benzimidazole-resistant small strongyles were treated with febantel (6 mg/kg), combinations of febantel (6 mg/kg) and piperazine citrate (25 or 55 mg base/kg), thiabendazole (44 mg/kg), or placebo (0.6 ml of water/kg). Pretreatment and 7-day posttreatment fecal examinations were done. Fecal cultures, strongyle egg per gram (epg) counts, sugar flotation fecal examinations, and in vitro testing for benzimidazole resistance were performed. Results of fecal examinations before treatment were similar in all horses, and results of testing were positive for benz...
Hackett RP, Ducharme NG, Ainsworth DM, Erickson BK, Erb HN, Soderholm LV, Thorson LM.To determine whether dorsal displacement of the soft palate (DDSP) results in pulmonary artery hypertension and leads to increases in transmural pulmonary artery pressure (TPAP); to determine whether pulmonary hypertension can be prevented by prior administration of furosemide; and to determine whether tracheostomy reduces pulmonary hypertension. Methods: 7 healthy horses. Methods: Horses were subjected to 3 conditions (control conditions, conditions after induction of DDSP, and conditions after tracheostomy). Horses were evaluated during exercise after being given saline (0.9% NaCl) solution ...
Kwok WH, Leung DK, Leung GN, Wan TS, Wong CH, Wong JK.A rapid liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed for the simultaneous screening of 19 drugs of different classes in equine plasma using automated on-line solid-phase extraction (SPE) coupled with a triple quadrupole mass spectrometer. Plasma samples were first protein precipitated using acetonitrile. After centrifugation, the supernatant was directly injected into the on-line SPE system and analysed by a triple quadrupole LC-MS-MS in positive electrospray ionisation (+ESI) mode with selected reaction monitoring (SRM) scan function. On-line extraction and c...
Harkins JD, Carney JM, Meier M, Leak SC, Tobin T.Lipopolysaccharide (LPS), or endotoxin, is a component of the cell wall of gram-negative bacteria and is toxic to humans and animals. The GI tract of horses contains large numbers of endotoxins which may cause disease if gut wall integrity is compromised. The objective of this study was to develop a unique therapeutic approach to the treatment of endotoxemia with a sulfonyl analog of the alpha-phenyl-N-tert-butyl-nitrone (PBN) spin-trap molecule which may prevent the LPS-induced cytokine cascade. Following challenge with 55 mg/kg LPS, the survivability of ICR Swiss mice was significantly impro...
Mitchell SM, Zajac AM, Davis WL, Lindsay DS.Toxoplasma gondii is an important apicomplexan parasite of humans and other warm-blooded animals. Ponazuril is a triazine anticoccidial recently approved for use in horses in the United States. We investigated the mode of action of ponazuril against developing RH strain T. gondii tachyzoites in African green monkey kidney cells. Host cells were infected with 2.0 x 10(5) tachyzoites and treated with 5 microg/ml ponazuril. Cultures were fixed and examined by transmission electron microscopy 3 days after treatment. Ponazuril interfered with normal parasite division. This led to the presence of mu...
Scarth JP, Spencer HA, Hudson SC, Teale P, Gray BP, Hillyer LL.In this study, the use of equine liver/lung microsomes and S9 tissue fractions were used to study the metabolism of the androgenic/anabolic steroid stanozolol as an example of the potential of in vitro technologies in sports drug surveillance. In vitro incubates were analysed qualitatively alongside urine samples originating from in vivo stanozolol administrations using LC-MS on a high-resolution accurate mass Thermo Orbitrap Discovery instrument, by LC-MS/MS on an Applied Biosystems Sciex 5500 Q Trap and by GC-MS/MS on an Agilent 7000A. Using high-resolution accurate mass full scan analysis o...
Gozalo-Marcilla M, Hopster K, Gasthuys F, Krajewski AE, Schwarz A, Schauvliege S.To compare the effects of a constant rate infusion (CRI) of dexmedetomidine and morphine to those of morphine alone on the minimum end-tidal sevoflurane concentration necessary to prevent movement (MACNM ) in ponies. Methods: Prospective, randomized, crossover, 'blinded', experimental study. Methods: Five healthy adult gelding ponies were anaesthetized twice with a 3-week washout period. Methods: After induction of anaesthesia with sevoflurane in oxygen (via nasotracheal tube), the ponies were positioned on a surgical table (T0), and anaesthesia was maintained with sevoflurane (Fe'SEVO 2.5%) i...
Yu M, Robinson NE, Wang Z, Derksen FJ.The effects of epithelial removal and cyclooxygenase inhibition on contractions induced by exogenous acetylcholine (ACh) and electrical field stimulation (EFS) were evaluated in horse tracheal strips and bronchial rings. Epithelial removal potentiated the response to ACh but had no influence on the response to EFS. The effect of epithelial removal was not altered by pretreating the tissues with meclofenamate, a cyclooxygenase inhibitor. In trachealis strips, meclofenamate augmented contractions induced by EFS but not by ACh. In bronchial rings, meclofenamate augmented EFS-induced contraction t...
Dyson DH, Pascoe PJ, McDonell WN.The purpose of this study was to determine the heart rate (HR) and blood pressure (BP) effect of glycopyrrolate in anesthetized horses with low HR ( 5 beats/min within 10 min), glycopyrrolate (same dose) was administered. Heart rate increased by > 5 beats/min in 3 out of 9 horses following the initial glycopyrrolate treatment. Overall changes in HR and mean BP were not significantly different, while systolic and diastolic BP increased significantly (P 5 beats/min, which was significant. A significant increase in BP was produced following treatment with 2.5 micrograms/kg BW, but not followi...
Cruz AM, Kerr CL, Bouré LP, Sears WC.To determine the cardiovascular effects of 60 minutes of abdominal insufflation with CO2 to an intra-abdominal pressure of 15 mm Hg in standing horses receiving a constant rate infusion of detomidine. Methods: 5 horses. Methods: Horses were randomly allocated into treatment or control groups. A washout period of a minimum of 7 days separated the 2 experimental periods of the crossover study. Catheters were placed into the right atrium, pulmonary artery, jugular vein, and right transverse facial artery after lidocaine infiltration. All horses were sedated with detomidine (8.54 microg/kg/h, i.v....
Boone LH, DeGraves FJ, Klein CE, Cole RC, Schumacher J.To assess onset of analgesia for 3% chloroprocaine hydrochloride and 2% mepivacaine hydrochloride when used for median and ulnar nerve blocks in lame horses. Methods: 6 naturally lame horses. Methods: A crossover experiment was conducted. Horses were assigned to 1 of 2 treatment groups (3% chloroprocaine or 2% mepivacaine first). Median and ulnar nerve blocks were performed in the lame limb with the assigned treatment. Lameness was objectively evaluated before treatment administration and at various points for 120 minutes after treatment with a wireless inertial sensor-based motion analysis sy...
Bailey J, Colahan P, Kubilis P, Pablo L.This study was designed to test the hypothesis that a specific beta 2 adrenergic receptor agonist, albuterol sulphate, when delivered by metered-dose inhaler (MDI) would affect the performance of Thoroughbred horses during incremental exercise testing. Six conditioned Thoroughbred horses were randomly assigned to one of 2 treatment groups: Group 1 horses received placebo and Group 2 received albuterol. Each horse received both treatments in a crossover design with a 3 week interval between trials. Horses inspired albuterol (900 micrograms) or placebo over a 5 min period followed by an incremen...
Boyd EH, Allen WE.Plasma concentrations of neomycin were measured following intrauterine infusion of 3.3 mg/kg bodyweight neomycin sulphate. Mares in oestrus absorbed approximately 6 per cent of neomycin infused whereas mares in a luteal phase absorbed 56 per cent. The volume of infusate also affected absorption as increased volume resulted in decreased absorption. The decreased absorption both during oestrus and when large volumes were used was probably due to reflux of antibiotic through the cervix.
Hilton HG, Magdesian KG, Groth AD, Knych H, Stanley SD, Hollingsworth SR.Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used systemically for the treatment of inflammatory ocular disease in horses. However, little information exists regarding the ocular penetration of this class of drugs in the horse. Objective: To determine the distribution of orally administered flunixin meglumine and firocoxib into the aqueous humor of horses. Methods: Fifteen healthy adult horses with no evidence of ophthalmic disease. Methods: Horses were randomly assigned to a control group and 2 treatment groups of equal sizes (n = 5). Horses assigned to the treatment groups rece...
Hinchcliff KW, McKeever KH, Muir WW, Sams RA.We theorized that furosemide-induced weight reduction would reduce the contribution of anaerobic metabolism to energy expenditure of horses during intense exertion. The effects of furosemide on accumulated O2 deficit and plasma lactate concentration of horses during high-intensity exercise were examined in a three-way balance randomized crossover study. Nine horses completed each of three trials: 1) a control (C) trial, 2) a furosemide-unloaded (FU) trial in which the horse received furosemide 4 h before running, and 3) a furosemide weight-loaded (FL) trial during which the horse received furo...
Kimball FA, Wyngarden LJ.Preliminary studies indicate the presence of PGF2alpha specific binding sites in membrane fractions prepared from equine corpora lutea. The equilibrium binding data indicate an apparent dissociation constant of 3.2 X 10(-9)M and the concentration of binding sites of -0.1 pmoles/mg membrane protein. Competition of several natural prostaglandins for equine luteal PGF2alpha specific binding sites indicates specificity for the 9alpha-hydroxyl moiety and the 5,6-cis doublebond. Significant increases in relative binding affinities were demonstrated for PGF2alpha analogs with a phenyl ring introduced...
Mason DE, Muir WW, Olson LE.Smooth muscle strips from the midcervical portion of the trachea and bronchial smooth muscle strips from third-generation airways of horses were placed in tissue baths, and isometric contractile force was measured. Active force was measured in response to electrical stimulation and exogenous acetylcholine. Square-wave electrical stimuli were applied at various voltages (10, 12, 15, 18, 20, 25 V), frequencies (3, 5, 10, 15, 20, 25, 30 Hz), and pulse durations (0.2, 0.5, 1.0, 1.5, 2.0 ms). Isometric contractile force increased as voltage, frequency, and pulse duration increased. Maximal contract...
Kim A, Sasaki N, Lee I, Seo JP.The purpose of this study was to assess the cardiorespiratory and behavioral responses to the combination of medetomidine and tramadol (M-T) or butorphanol (M-B) in standing laparoscopic ovariectomy in horses. One ovary was removed under M-T and the contralateral ovary was removed under M-B with at least 4 weeks between operations at random. Horses were sedated using intravenous medetomidine (5 µg/kg) followed by tramadol (1 mg/kg) or butorphanol (10 µg/kg) after 5 min. Sedation was maintained through the repeated injection of medetomidine (1 µg/kg) and tramadol (0.4 mg/kg) or medetomidine ...
Willette C, Aarnes TK, Lerche P, Ricco-Pereira C, Ballash GA, Bednarski RM.To assess anesthetic induction, recovery quality and cardiopulmonary variables after intramuscular (IM) injection of three drug combinations for immobilization of horses. Methods: Randomized, blinded, three-way crossover prospective design. Methods: A total of eight healthy adult horses weighing 470-575 kg. Methods: Horses were administered three treatments IM separated by ≥1 week. Combinations were tiletamine-zolazepam (1.2 mg kg), ketamine (1 mg kg) and detomidine (0.04 mg kg) (treatment TKD); ketamine (3 mg kg) and detomidine (0.04 mg kg) (treatment KD); and tiletamine-zolazepam (2.4 mg ...
Merritt AM, Burrow JA, Horbal MJ, Madison JB, Tran T.To better characterize the source of the large nonparietal secretory response to pentagastrin (PG) expressed in gastric contents of cannulated horses. Methods: Adult cross-bred horses: 4 geldings and 1 mare. Methods: Horses were prepared by surgical insertion of a silastic gastric cannula from which gastric contents after feed was withheld could be continuously collected by gravity drainage. During experiments, the horses were lightly restrained in stocks, the gastric cannula was opened, and a catheter was inserted into a jugular vein. Over the next 5 hours, gastric contents were collected in ...
Bessonnat A, Vanore M.Evaluate the effect of repeated doses of topical 1% cyclopentolate hydrochloride alone and in combination with topical 2.5% phenylephrine on pupil diameter (PD), tear production (STT-1), intraocular pressure (IOP), digestive function (gut motility and feces production), and heart rate (HR). Methods: Six healthy mares. Methods: In a prospective, randomized, controlled, and crossover design study, the left eye of six healthy mares was administered 0.2 mL of cyclopentolate alone and in combination with 0.2 mL of phenylephrine. The drugs were administered 3 times a day for 1 day, twice a day fo...
Hoffman AM, Couetil LL, Miller CJ.To describe the spectrum of nonspecific airway reactivity in a group of clinically normal foals. Methods: 12 clinically normal mixed-breed foals, 48 to 92 days old, without history of clinical lung disease. Methods: Nonspecific airway reactivity was determined by measuring the extent of changes in dynamic compliance during nebulization of incrementally increasing concentrations of histamine aerosol. Degree of airway reactivity was expressed as the dose of histamine that evoked a decrease in dynamic compliance (Cdyn) to 65% of the after saline nebulization value (PC65Cdyn) or increase in pulmon...
Boone L, Schumacher J, DeGraves F, Cole R.The objective of this study was to determine if buffering mepivacaine HCL (mepHCl) with sodium bicarbonate (NaHCO3) would significantly decrease the time to onset of analgesia when performing median and ulnar nerve blocks in naturally lame horses. Median and ulnar nerve blocks were performed on the naturally lame limb of nine horses during two separate study periods, with a minimum washout period of three days between study periods. Nerve blocks were performed by administering mepHCl alone or mepHCl mixed with NaHCO3 (nine parts 2 per cent mepHCl to one part 8.4 per cent NaHCO3). Lameness was ...
