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.
Daels PF, Mohammed HO, Odensvik K, Kindahl H.To determine the relative role of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion in cloprostenol-induced abortion in mares that no longer require luteal progesterone secretion for maintenance of pregnancy, and to evaluate the ability of a prostaglandin cyclooxygenase inhibitor (flunixin meglumine) to prevent cloprostenol-induced abortion. Methods: The effect of flunixin meglumine on PGF2 alpha secretion and outcome of pregnancy was compared between mares treated with cloprostenol only and mares treated with cloprostenol plus flunixin meglumine. Methods: Five pregnant mares, aged 4 to...
Jolly WT, Whittem T, Jolly AC, Firth EC.The dose-related effects of phenylbutazone and Depo-Medrol on chondrocyte viability and chondrocyte-mediated synthesis and depletion of proteoglycans were investigated using cultured explants of equine middle carpal joint articular cartilage. Explants from 12 horses (941 x 3 mm diameter) were cultured for a total of 5 days, which included 3 days' exposure to either phenylbutazone (0, 2, 20, 200 or 2000 micrograms/mL) or Depo-Medrol (0, 20, 200 or 2000 micrograms/mL). For each explant, amino sugar content was used as a measure of proteoglycan content, 35S incorporation as a measure of the rate ...
Cogswell AM, Johnson PJ, Adams HR.To test the hypothesis that endothelium-derived nitric oxide modulates vasomotor reactivity in equine digital arteries. Methods: Digital arteries were isolated from adult horses, and their vasodilator properties were examined in an in vitro controlled environment. Methods: Five adult horses (1 gelding, 4 mares) without evidence of hoof or vascular disease were studied. Methods: Arterial rings with or without endothelium were exposed to endothelium-dependent vasodilator drugs in the presence or absence of a pharmacologic inhibitor of the enzyme nitric oxide synthase. Results: Vasodilator effect...
Landoni MF, Lees P.The bioavailability of S(+) and R(-) ketoprofen (KTP) in six horses was investigated after oral administration of the racemic (rac) mixture. Two oral formulations were studied, an oil-based paste containing micronised rac-KTP and powder from the same source in hard gelatin capsules, each at a dose rate of 2.2 mg/kg. For the oil-based paste two feeding schedules were used; horses were either allowed free access to food or access to food was restricted for 4 h before and 5 h after dosing. The drug in hard gelatin capsules was administered to horses with restricted access to food. After intraveno...
van der Kolk JH, Wisse H, van Dijk S.A 20-year-old Arab crossbred gelding was examined because it had apparently suffered an overstimulation of the parasympathetic nervous system for three hours. The clinical signs consisted of hypersalivation, profuse sweating, maximal miosis, fasciculation of the muscles and lateral recumbency in combination with continuous convulsions without diarrhoea. The horse's plasma pseudocholinesterase activity was approximately 10 per cent of normal. It responded well to 10 mg atropine and 50 mg diazepam administered intravenously.
Alexander SL, Irvine CH.We used our nonsurgical method for collecting equine pituitary venous blood to study the role of endogenous opioids in the basal regulation of the hypothalamo-pituitary-adrenal axis. We gave mares the opioid antagonist, naloxone (NAL), at either a high (0.5 mg/kg i.v. bolus, followed by infusion of 0.25 mg/kg.h; n = 4) or low (0.2 mg/kg i.v. bolus; n = 6) dose rate. Pituitary venous blood was collected continuously, divided into 0.5- or 1-min segments for 15-30 min before and 1 h after the NAL bolus, and assayed for CRH, arginine vasopressin (AVP), and ACTH. The mares tolerated NAL administrat...
Valdez RA, DiPietro JA, Paul AJ, Lock TF, Hungerford LL, Todd KS.The bioequivalence of Strongid C and generic pyrantel tartrate was determined in a controlled study using 30 horses with naturally acquired endoparasitic infections. Three horses were randomly allocated to each of ten replicates based on quantitative nematode and ascarid egg counts and fecal larvae culture results. Horses within each replicate were randomly assigned to one of three treatment groups. Horses in Treatment Group 1 received only oats; horses in Treatment Group 2 received generic pyrantel tartrate pellets (2.65 mg pyrantel tartrate kg-1) mixed with oats; horses in Treatment Group 3 ...
Olszewski MA, Robinson NE, Yu MF, Derksen FJ.During acute bouts of recurrent airway obstruction (heaves) in horses, neutrophils that are capable of increased production of reactive oxygen species accumulate in the airways. In the study reported here, the effect of hydrogen peroxide (H2O2; 1 microM to 0.1M), one of these reactive oxygen species products, on the responses of isolated trachealis muscle of horses was determined. Before and after incubation with H2O2, contractile responses to acetylcholine, electrical field stimulation (EFS), 127 mM KCl, and relaxation responses to isoproterenol and activation of the nonadrenergic noncholiner...
Dillon AM, Heath MF.Protein tyrosine phosphorylation (PTP) in thrombin- and platelet-activating factor (PAF)-stimulated equine platelet activation was investigated in the absence and presence of 2 protein tyrosine kinase inhibitors (PTKIs), methyl 2,5-dihydroxycinnamate (MDHC) and genistein. Washed equine platelets aggregated irreversibly in response to thrombin or PAF in an agonist concentration dependent fashion. MDHC produced an MDHC concentration and time dependent inhibitory effect on rate and extent of thrombin- and PAF-induced aggregations, whereas the effect of genistein on the same parameters was only ge...
Cargile JL, MacKay RJ, Dankert JR, Skelley L.Tumor necrosis factor-alpha (TNF) is an important mediator of endotoxin-induced pathologic changes. To help define the role of TNF in equids with endotoxemia, the effects of pretreatment with a murine monoclonal antibody (MAB) against equine TNF were evaluated in Miniature Horses given endotoxin. Five horses were given TNF MAB at a dosage of 1.86 mg/kg of body weight, IV, and 5 were given control MAB. Five minutes later, lipopolysaccharide (LPS; Escherichia coli O55:B5), 0.25 microgram/kg, was given to all horses by bolus IV infusion. Clinical signs of disease were monitored at intervals up to...
Aramaki S, Suzuki E, Ishidaka O, Momose A.The effects of exercise on the metabolism of caffeine (CA) were studied 3h after administration of the drug to race horses which then underwent exercise sets (1000-m gallop). Analysis was made of pharmacokinetics of CA, changes in its plasma concentrations, its metabolites, i.e., theophylline (TP), theobromine (TB) and paraxanthine (PX), and the molar concentration ratios of CA to these metabolites. After exercise, AUC and t1/2 tended to decrease, and the concentration of CA decreased, while the concentrations of TP and TB significantly increased. The TP/CA ratio and TB/CA ratio significantly ...
Monahan CM, Chapman MR, Taylor HW, French DD, Klei TR.Moxidectin was tested for efficacy in ponies against experimental infections of 56 day Strongylus vulgaris larvae and 11 day Parascaris equorum larvae. Three dosages of moxidectin were tested: 300 micrograms per kg live body weight, 400 micrograms per kg, and 500 micrograms per kg, and the vehicle served as control. Ponies were first infected with 600 S. vulgaris third-stage larvae (L3) on Experiment Day 0 and then with 3000 embryonated P. equorum eggs on Day 45. Moxidectin treatments were administered on Day 56 and necropsy examinations were performed on Day 91. Strongylus vulgaris fourth-sta...
Monreal L, Villatoro AJ, Monreal M, Espada Y, Anglés AM, Ruiz-Gopegui R.Thirty healthy male horses were allotted to 3 groups and treated blindly during 4 days. Group-1 horses received unfractioned calcium heparin (100 IU/kg of body weight, SC, q 12 h). Group-2 horses received a single dose of a low-molecular-weight heparin (50 anti-Xa IU/kg, SC) every morning, and a similar volume of saline solution every evening. Group-3 horses received the vehicle (saline solution), SC, every 12 hours. Citrated and EDTA-anticoagulated blood samples were collected before starting the medication (T-0) and once daily 3 hours after each morning injection (T-3, T-27, T-51, and T-75)....
Cuvelliez S, Rosseel G, Blais D, Salmon Y, Troncy E, Larivière N.Intravenous anesthesia in the horse: Comparison of xylazine-ketamine and xylaxine-tiletamine-zolazepam combinations. Six healthy adult horses were anesthetized twice at random with following intravenous combinations: 1.1 mg/kg of body weight (BW) of xylazine followed by 2.2 mg/kg BW of ketamine (X-K) and 1.1 mg/kg BW of xylazine followed by 1.65 mg/kg BW of tiletamine-zolazepam (X-TZ). The modifications of some cardiorespiratory parameters and the duration of anesthesia were evaluated and compared for the 2 protocols used. Few significant differences were observed between the 2 protocols in re...
Hawkins DL, Cargile JL, MacKay RJ, Broome TA, Skelley LA.Six horses received intra-articular injections of a mixture of 1 micrograms of endotoxin/5 mg of equine tumor necrosis factor (eqTNF) monoclonal antibody in 1 antebrachiocarpal joint and an equal volume (2 ml) of 1 micrograms of endotoxin/5 mg of control antibody in the opposite joint. Synovial fluid sample collection (1 ml) was accomplished by use of an indwelling, intra-articular catheter at postinjection hours (PIH) 0, 1, 1.5, 2, 5, and 8, and by arthrocentesis at PIH 24. Joint fluid samples were analyzed for nucleated cell count, protein concentration, and TNF, interleukin 6 (IL-6), IL-1, ...
Eaton SA, Allen D, Eades SC, Schneider DA.Starling forces and hemodynamics in the digits of 5 horses were studied during early laminitis induced by oral administration of an aqueous extract of black walnut (Juglans nigra). The black walnut extract was prepared from heartwood shavings and was administered by nasogastric tube. Heart and respiratory rates, rectal temperature, central venous and arterial pressures, digital pulses, and signs of lameness were monitored. Blood samples were collected for determination of WBC count, hemoglobin concentration, and PCV and for endotoxin and tumor necrosis factor assays. Total WBC count and centra...
Theodorakis JL, Armes LG, Margoliash E.beta-Thiopropionyl derivatives of horse cytochrome c singly modified at each of 18 different lysine epsilon-amino groups have been prepared using sulfosuccinimidyl-2-(biotinamido)ethyl-1,3-dithiopropionate and purified to homogeneity by high-pressure liquid chromatography. These derivatives were characterized by determination of: (i) the location of the modification; (ii) reduction potentials; (iii) visible and NMR spectra: and by (iv) measurement of electron transfer activity with cytochrome-c oxidase. No significant changes in structure were indicated, except for the ferric forms of the deri...
Geor R, Hope E, Lauper L, Piela S, Klassen J, King V, Murphy M.The effects of dexamethasone (0.2 mg/kg of body weight; IV, IM, and PO) and methylprednisolone acetate (120 mg given intra-articularly) on serum osteocalcin and cortisol concentrations were studied in 6 horses. Serum osteocalcin and cortisol concentrations were serially monitored after each treatment. A significant (P < 0.05) decrease in serum osteocalcin and cortisol concentrations was observed from 12 to 24 and 2 to 48 hours, respectively, after IV and IM administrations of dexamethasone. Serum osteocalcin and cortisol concentrations were significantly decreased from 6 to 48 and 3 to 72 h...
Gratzek AT, Kaswan RL, Martin CL, Champagne ES, White SL.Topical cyclosporine A was safely used in a series of 11 cases of equine keratitis and keratouveitis and appeared to be an effective anti-inflammatory agent in 9 cases. The clinical diagnoses included interstitial keratouveitis, endotheliitis, multifocal punctate keratopathy and a melting stromal ulcer. In most cases, the presence or absence of insidious bacterial infection was not conclusively determined. Topical cyclosporine A had no deleterious effects in this series of cases. The authors suggest that topical cyclosporine in both aqueous and lipid base vehicles should be investigated and ev...
Parraga ME, Kittleson MD, Drake CM.The aim of this study was to determine if quinidine administration increases steady state serum digoxin concentration in horses. Digoxin (0.01 mg/kg q. 12 h per os) was administered to 6 horses for 7 days. Steady state was confirmed by identifying statistically indistinguishable peak and trough serum digoxin concentrations on Days 4, 5, and 6. On Day 6, serum digoxin concentration was measured at baseline and 0.25, 0.5, 1, 2, 4, 6, 8 and 12 h after digoxin administration. On Day 7, quinidine (20 g at baseline and 10 g at 2, 4 and 6 h) was administered per os and serum digoxin concentration was...
Muir WW.The haemodynamic effects of milrinone hydrochloride were determined in halothane-anaesthetised horses. Six healthy adult horses were anaesthetised with guaifenesin and thiamylal and maintained with halothane in oxygen (end-tidal halothane concentration of 1.15%). Baseline haemodynamic data were recorded after a 45 min stabilisation period. All 6 horses received a single loading dose of milrinone HCl, 0.2 microgram/kg i.v., followed by progressively increasing infusions of 2.5, 5, 10 and 20 micrograms/kg bwt/min. Each infusion lasted for 15 min and produced dose related increases in heart rate,...
Patteson MW, Gibbs C, Wotton PR, Cripps PJ.Twenty-six horses were sedated with detomidine hydrochloride (Domosedan, SmithKline Beecham Animal Health, Tadworth, Surrey, UK) at a dose of 10 micrograms/kg bwt, administered i.v. Echocardiograms were recorded before and after sedation, measurements of cardiac dimensions were made and functional indices were calculated. The pre- and post sedation values were compared. No significant change was detected following sedation in the ejection time (ET), left ventricular dimension, left atrial diameter at the sinotubular junction at end-systole or end-diastole or at the sinus of Valsalva at end-dia...
Uboh CE, Rudy JA, Railing FA, Enright JM, Shoemaker JM, Kahler MC, Shellenberger JM, Kemecsei Z, Das DN.Although urine is the sample of choice for drug tests in racehorses, it is rarely obtained following the sudden death of a racehorse on the track while racing. The purpose of this study was to demonstrate the significance of postmortem tissue samples as an alternative to urine and blood samples in equine drug analysis following the sudden death of a racehorse on the track while participating in a competitive race. Postmortem tissue samples were frozen (-80 degrees C) until analyzed. A 30-40-g portion of each organ was homogenized in a 0.1 M phosphate buffer (pH 7.4), deproteinized, hydrolyzed ...
Lloyd DR, Rose RJ.Sodium bicarbonate given by nasogastric tube has been used by some trainers as the key ingredient in a 'milkshake'. It has been suggested that such treatment given 3-5 h prior to racing may enhance a horse's racing performance by increasing the blood buffering capacity and enhancing lactate clearance from skeletal muscle, thereby delaying the onset of fatigue. Several experiments were conducted to examine the effects on fluid, electrolyte and acid-base values of 0.5 g kg-1 dose of sodium bicarbonate, were examined. The effects of fasting, the simultaneous administration of glucose (0.5 g kg-1)...
Burrows GE, MacAllister CG, Ewing P, Stair E, Tripp PW.The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The...
Menzies-Gow NJ, Sepulveda MF, Bailey SR, Cunningham FM, Elliott J.To evaluate the roles of 5-hydroxytryptamine (5-HT), thromboxane A2 (TxA2), and platelet-activating factor (PAF) in endotoxin-induced digital hypoperfusion in horses. Methods: 6 healthy adult Thoroughbreds. Methods: Horses were treated with IV administration of saline (0.9% NaCl) solution (control treatment) or the 5-HT 1B/D selective antagonist, GR55562 (0.3 mg/kg), prior to tryptamine infusion (1.6 microg/kg/min for 30 minutes) to establish an effective GR55562 dose. In a crossover study, horses were treated with IV administration of saline solution (control treatment), aspirin (4 mg/kg, 2 h...
Daels PF, Besognet B, Hansen B, Mohammed H, Odensvik K, Kindahl H.To determine the role of progesterone in the regulation of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion during cloprostenol-induced abortion and to investigate use of progestins to prevent prostaglandin-associated abortion. Methods: 16 pregnant mares. Methods: To induce abortion, cloprostenol (250 micrograms/d) was administered daily until fetal expulsion or for up to 5 days. In experiment 1, 8 mares, 98 to 153 days' pregnant, received progesterone (300 mg/d) at 24-hour intervals for 5 days, starting 18 hours after the first cloprostenol administration. In experiment 2, 8 mares, 93...
Votion D, Ghafir Y, Munsters K, Duvivier DH, Art T, Lekeux P.Therapeutic aerosols pay an increasing role in the treatment of equine respiratory disorders. This route of delivery permits concentration of significant amounts of drugs at the site of action without unwanted high systemic concentration and resultant side effects. The efficiency of such a topical therapy depends on the quantity of inhaled drugs deposited in the lungs and, for some drugs, on the proportion retained in specific parts of the lungs. The objective of this study was to define and to compare quantitative (dose deposited) and qualitative (regional distribution) deposition of an aeros...
Hamm D, Willeford KO, White G, Reed SM, Hamm J.Suppurative lower airway disease is a common debilitating disease in performance horses and, while rarely fatal, is often recalcitrant to conventional therapy. A variety of treatments have been used to combat this condition and we conducted two types of studies to determine if caprine serum fraction--immunomodulator (CSFI), a nonspecific immunomodulator, improved recovery from lower respiratory disease. Two dose response studies were performed to ascertain the efficacy of CSFI. Horses were maintained daily on conventional antibiotic therapy. Respiratory tract exudate, nasal discharge, dyspnoea...
Ohta M, Kurimoto S, Tokushige H, Kuroda T, Ishikawa Y.To determine hemodynamic effects of hydroxyethyl starch (HES) infusion during anesthesia in horses, incremental doses of 6% HES were administered to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and administered 3 intravenous dose of 6% HES (5 ml/kg) over 15 min with 15-min intervals in addition to constant infusion of lactated Ringer's solution at 10 ml/kg/hr. Hemodynamic parameters were measured before and e...
Hubbell JA, Muir WW.The rate of rise of arterial partial pressure of carbon dioxide (PaCO2) was determined in 49 apneic halothane-anesthetized horses following controlled ventilation. Drugs given for induction of anesthesia did not affect the rapid rate of rise of PaCO2 during the first minute after controlled ventilation, the PaCO2 at 1 minute after controlled ventilation, or the PaCO2 at which spontaneous ventilation began. Horses given xylazine-ketamine for induction of anesthesia had a significantly (P less than 0.05) faster rate of rise of PaCO2 after 1 minute following controlled ventilation than did horses...
Wasfi IA, Zorob OM, Boni NS, Hadi AA, Agha BA, Elghazali M.The activity of hepatic mixed function oxidases was compared in horses and camels (Camelus dromedarius) by studying the pharmacokinetics of antipyrine in seven camels and five horses following intravenous administration of a single dose of antipyrine (25 mg/kg). The data obtained (mean +/- SEM and median in brackets) in camels and horses, respectively, were as follows: the elimination half-lives were 3.25 +/- 0.23 (3.19) and 3.09 +/- 0.25 (2.90) hr; the apparent volumes of distribution (area method) were 0.691 +/- 0.045 (0.648) and 0.642 +/- 0.034 (0.676) l/kg; the volumes of distribution at s...
Donnelly CG, Burns E, Easton-Jones CA, Katzman S, Stuart R, Cook SE, Finno CJ.Vitamin E is essential for neuromuscular function. The primary treatment, oral supplementation with natural ('RRR') α-tocopherol, is not effective in all horses. The objectives of this pilot study were to evaluate the safety and efficacy of a subcutaneously administered RRR-α-tocopherol preparation. Horses were randomly assigned in a cross-over design to initially receive RRR-α-tocopherol (5000 IU/450 kg of 600 IU/mL) subcutaneously (n = 3) or orally (n = 3) or were untreated sentinels (n = 2). Tissue reactions following injection in Phase I of the study necessitated adjustment of the prepa...
Doyle AJ, MacDonald VS, Bourque A.A 12-year-old gelding was diagnosed with recurrent lymphoma in multiple cutaneous sites. A highly invasive preputial mass caused urethral obstruction. The horse was treated with surgery and chemotherapy consisting of lomustine (CCNU) and prednisolone. The treatment was well-tolerated and effective. This is the first reported use of lomustine (CCNU) in a horse for the treatment of equine lymphoma. Utilisation de lomustine (CCNU) dans un cas de lymphone cutané équin. Un hongre âgé de 12 ans a été diagnostiqué avec un lymphome récurrent sur plusieurs sites cutanés. Une masse préputiale ...
Marlin DJ, Roberts CA, Schroter RC, Lekeux P.The respiratory stimulant lobeline has been used in equine clinical practice to increase inspiratory and expiratory airflow rates at rest in order to facilitate investigation of both lower and upper airway function. Some of the responses to lobeline in the pony have been reported, but the detailed time course, effect of dose, possible side effects and reproducibility associated with lobeline administration have not been described in the horse. Respiratory airflow rates and oesophageal pressure were measured with a Fleisch No. 5 pneumotachometer and lightweight facemask and a microtip pressure ...
Rötting AK, Freeman DE, Eurell JA, Constable PD, Wallig M.To evaluate the in vitro protective effects of acetylcysteine and response of resident mucosal eosinophils in oxidant-induced injury to tissues of right dorsal colon of horses. Methods: 9 adult horses. Methods: Gastrointestinal mucosa was damaged in vitro with 3 mM hypochlorous acid (HOCl), with and without prior exposure to 6mM acetylcysteine. Control tissues were not exposed to HOCl or acetylcysteine. Control and damaged tissues were incubated in Krebs-Ringer-bicarbonate solution and tissue resistance measured during 240 minutes. Tissue permeability to radiolabeled mannitol was also used to ...
Chen CL, Goldberg J, Gronwall RR.A radioimmunoassay was developed for prednisolone using IgG purified from rabbit antiserum. The assay was employed to determine the pharmacokinetics of prednisolone following intravenous administration of 450 mg of prednisolone sodium succinate (Solu Delta Cortef) to five adult Thoroughbred horses. The RIA had a sensitivity of 2 ng/ml and was relatively specific. It had cross-reactivity with 21-deoxycortisol (83.3%) cortisol (27.8%), 11-beta-hydroxyprogesterone (39.2%) and 17-hydroxyprogesterone (50%). However, it did not cross-react with naturally occurring steroids (cholesterol, testosterone...
Clemmons RM, Lee MR, Bliss EL, Asbury AC, Cook D, Brown V.Superoxide dismutase (SOD), a free radical scavenger with anti-inflammatory activity, was administered IM to horses. Ex vivo platelet aggregation in response to arachidonic acid was monitored to determine whether exogenous SOD altered equine platelet prostaglandin metabolism. Preparations of platelet-rich plasma obtained before SOD administration were incubated with different concentrations of SOD and were aggregated with arachidonic acid. Superoxide dismutase did not exert a demonstrable effect, either ex vivo or in vitro. Aspirin abolished arachidonic acid-induced platelet aggregation in vit...
Oberhaus EL, Wilson KM, Camp CM, Sones JL.Sulpiride in vegetable shortening (VS) stimulates prolactin in horses for up to 10 days. Although effective, a pharmaceutical grade vehicle is needed for clinical application of sulpiride in horses. Sucrose acetate isobutyrate (SAIB), a hydrophobic polymer, may be an alternative to VS. Four in vivo experiments assessed the efficacy of SAIB for delivery of sulpiride, estradiol cypionate (ECP), and estradiol benzoate (EB). The first three studies utilized geldings to compare prolactin and luteinizing hormone (LH) concentrations between sulpiride delivered in VS and SAIB, and ECP or EB delivered ...
Caron JP, Peters TL, Hauptman JG, Eberhart SW, Orth MW.To determine the effects of orally administered glucosamine on concentrations of markers of bone and cartilage metabolism in Standardbred horses during race training. Methods: Twenty 16- to 20-month-old Standardbreds beginning race training. Methods: Horses were randomly assigned to 2 groups. One group received glucosamine hydrochloride (4 g, PO, q 12 h), and the second (control) group received glucose (4 g, PO, q 12 h). Serum samples were obtained prior to onset of the study (baseline) and at regular intervals for 48 weeks for determination of concentrations of keratan sulfate (KS), osteocalc...
Young LE, Blissitt KJ, Clutton RE, Molony V.To evaluate the hemodynamic effects of a 60-minute infusion of dopexamine in horses anesthetized with halothane. Methods: 7 adult Thoroughbreds. Methods: Measurements of left ventricular function obtained by transesophageal Doppler echocardiography and cardiac catheterization. Results: Infusion of dopexamine (4 micrograms/kg of body weight/min) significantly increased heart rate, cardiac output, maximal rates of increase and decrease of left ventricular pressure, and maximal acceleration and maximal velocity of aortic blood flow. Left ventricular ejection time significantly increased, and pre-...
Allen WR, Sanderson MW, Greenwood RE, Ellis DR, Crowhurst JS, Simpson DJ, Rossdale PD.A total of 18 experimental pony and 136 commercial maiden, barren and foaling Thoroughbred mares in seasonal or lactation-related anoestrus were injected subcutaneously with 1 or 2 slow-release D,L-lactide-glycolide co-polymer implants impregnated with 0.9 or 1.8 mg of the potent GnRH analogue, ICI 118 630, to give a daily release of, respectively, 30 or 60 micrograms analogue for 28 days; 32 of the Thoroughbred mares were also given a daily oral dose of 27.5 mg allyl trenbolone for 5 days after injection of the implant. Thirteen pony (76%) and 120 Thoroughbred (88%) mares ovulated 3-18 days a...
Skrabalak DS, Covey TR, Henion JD.Several important corticosteroids were qualitatively determined in the plasma and urine of horses by micro-liquid chromatography-mass spectrometry (micro-LC-MS). The sensitivity and specificity of micro-LC-MS are demonstrated as is the ability of micro-LC-MS to deal with endogenous interferences. In turn, the relative amount of dexamethasone and its major unconjugated metabolite were determined in equine urine by micro-LC-MS; the conclusions drawn are reported.
Snow DH, Frigg M.The bioavailability of ascorbic acid administered to thoroughbreds by intramuscular injection was investigated. For intramuscular injection two preparations were studied, and the percentage bioavailability up to 24 h of 10 g of ascorbic acid was 95% +/- 22 in four horses and 60% in two horses with preparations A and B, respectively. Bioavailability at 24 h in three horses injected subcutaneously with 10 g of preparation B was 82%. Intramuscular injection of both preparations was apparently well tolerated while subcutaneous injection of preparation B (pH 6.0) was associated with marked irritanc...
Weisrock KU, Winkelsett S, Martin-Rosset W, Forssmann WG, Parvizi N, Coenen M, Vervuert I.Intermittent administration of parathyroid hormone (PTH) is an anabolic therapy for osteoporotic conditions in humans. This study evaluated the effects of equine PTH fragment (ePTH-1-37) administration on bone metabolism in 12 healthy horses. Six horses each were treated once daily for 120days with subcutaneous injections of 0.5μg/kg ePTH-1-37 or placebo. Blood was collected to determine ionized calcium (Ca(++)), total Ca (Ca(T)), inorganic phosphorus, serum equine osteocalcin (eOC), carboxy-terminal telopeptide of type I collagen (ICTP), bone-specific alkaline phosphatase, and carboxy-termin...
Neuhauser S, Palm F, Ambuehl F, Aurich C.In this study, effects of altrenogest treatment (0.088 mg/kg daily) given to mares during late gestation until parturition on the time and the process of foaling, neonatal adaptation and postnatal development were analysed. The number of animals was 6 in the treatment group and 7 in the control group. Gestational length tended to be shorter in mares given altrenogest. Birth weight of the foals and weight of the placenta did not differ between groups. The second stage of parturition was prolonged in the altrenogest-treated mares (p<0.05). Foals born to altrenogest-treated mares had a significan...
Wasfi IA, Abdel Hadi AA, Elghazali M, Alkateeri NA, Hussain MM, Hamid AM.The pharmacokinetics of diphenhydramine (DPHM) was compared in camels (n = 8) and horses (n = 6) following intravenous (i.v.) administration of a dose of 0.625 mg/kg body weight. In addition, the metabolism and urinary detection time of DPHM was evaluated in camels. The data obtained (median and range in brackets) in camels and horses, respectively, were as follows. The terminal elimination half lives (h) were 1.58 (1.13-2.58) and 6.11 (4.80-14.1), and the total body clearances (L/h per kg) were 1.42 (1.13-1.74) and 0.79 (0.66-0.90). The volumes of distribution at steady state (L/kg) were 2.38...
Foster AP, Cunningham FM, Andrews MJ, Lees P.The effects of the selective platelet activating factor (PAF) receptor antagonist WEB 2170 on PAF-induced responses in equine cells and tissues have been examined and compared with those of WEB 2086. In initial experiments WEB 2170 was shown to inhibit in vitro platelet aggregation in a dose-dependent, competitive reversible manner (pA2 = 7.21). Co-administration of the antagonists with either PAF or histamine also inhibited PAF, but not histamine, induced wheal formation and PAF-induced neutrophil accumulation in vivo in equine skin. Intravenous (i.v.) administration of both drugs at a dose o...
Silva GB, De La Côrte FD, Brass KE, Palma HE, Gallio M, Cantarelli C, Bertolin K, Krause A, Wergutz J, Fontanari Krause LM, Antoniazzi AQ.Chondrocyte health is altered when exposed to local anesthetics, raising concerns as to the long-term effects of local anesthetics intra-articularly for diagnosis and analgesia. To investigate the drug with the lowest toxic potential, the effect of ropivacaine and mepivacaine on chondrocytes was evaluated. Articular cartilage from normal metacarpophalangeal joints of five equine cadaver specimens was used to establish chondrocyte cultures. Following seven days, chondrocytes were exposed to standard culture medium (DMEM), ropivacaine 7.5 mg/ml (ROP7.5), ropivacaine 10 mg/ml (ROP10), mepivacaine...
Stewart AJ, Wright JC, Behrend EN, Martin LG, Kemppainen RJ, Busch KA.To determine the lowest ACTH dose that would induce a significant increase in serum cortisol concentration and identify the time to peak cortisol concentration in healthy neonatal foals. Methods: Prospective randomized crossover study. Methods: 11 healthy neonatal foals. 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) was administered IV. Serum cortisol concentrations were measured before and 10, 20, 30, 60, 90, 120, 180, and 240 minutes after administration of cosyntropin or saline s...
Buss DD, Bisgard GE.Hemodynamics and myocardial contractility were evaluated in 6 unanesthetized ponies during hypocapnic and isocapnic hypoxia and during hypocapnic hypoxia after beta adrenergic blockade with propranolol. Hypocapnic hypoxia, with a mean arterial oxygen pressure (PaO2) of 41.9 mm of Hg, produced a decrease in stroke index and an increase in heart rate, with no change of cardiac index. A moderate increase in left ventricular contractility occurred during hypocapnic hypoxia. Beta adrenergic blockade abolished changes in nearly all indices of left ventricular contractility during hypocapnic hypoxia,...
Vudathala D, Murphy L.A simple and highly sensitive LC/MS method was developed for the simultaneous determination of six ionophores--lasalocid, monensin, laidlomycin, maduramycin, salinomycin, and narasin--in feed. The procedure involved extraction of 1 g of feed with 4 mL of methanol-water (9 + 1, v/v) by shaking on a platform shaker for 45 min. After centrifugation, the extracts were diluted with methanol-water (75 + 25, v/v) and analyzed without any cleanup. The analysis was performed on a Betasil C18 column (150 x 4.6 mm id, 5 pm particle size) connected to an LC/MS system operated in the atmospheric pressure c...
Mackenzie CJ, Carslake HB, Robin M, Kent RJ, Malalana F.An 8-year-old mare was presented for investigation of a 1-month history of blepharospasm, eyelid swelling, corneal edema, and ocular discharge of the right eye (OD). Ophthalmic examination confirmed mucopurulent ocular discharge, conjunctival hyperemia, and a dry, dull appearance to the cornea OD. Schirmer tear test results confirmed an absence of tear production OD (0 mm/min) consistent with keratoconjunctivitis sicca. Treatment with topical 0.2% cyclosporine A resulted in an improvement in clinical signs. An episcleral cyclosporine A implant was placed under standing sedation 5 days after in...
Arden WA, Stick JA, Parks AH, Chou CC, Slocombe RF.Physiologic effects of 1 hour of ischemia and 1 hour of reperfusion on equine jejunum and protective effects of systemic administration of dimethyl sulfoxide (DMSO, 1 g/kg of body weight) were investigated in 18 ponies, using neurally intact segments of jejunum perfused at constant flow with heparinized blood. Ponies were allotted to 4 groups: group 1, saline solution administered (control, n = 3); group 2, DMSO administered (DMSO, n = 3); group 3, ischemia induced and saline solution administered (ischemia, n = 6); and group 4, ischemia induced and DMSO administered (ischemia-DMSO, n = 6). In...
