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.
Colborn DR, Thompson DL, Rahmanian MS, Roth TL.Ten lighthorse stallions were used to determine 1) whether prolactin (PRL) and cortisol responses previously observed after acute exercise in summer would occur in winter when PRL secretion is normally low, 2) whether subsequent treatment with a dopamine receptor antagonist, sulpiride, for 14 d would increase PRL secretion and response to thyrotropin-releasing hormone (TRH) and exercise, and 3) whether secretion of LH, FSH, and cortisol would be affected by sulpiride treatment. On January 11, blood samples were drawn from all stallions before and after a 5-min period of strenuous running. On J...
Humber KA, Beech J, Cudd TA, Palmer JE, Gardner SY, Sommer MM.Azathioprine, a thiopurine antimetabolite used in the treatment of immune-mediated thrombocytopenia in human beings and dogs, was used in 2 cases of immune-mediated thrombocytopenia in horses that failed to respond to corticosteroid therapy alone. Platelet counts were increased to acceptable values in both horses. One horse returned to a successful racing career, and the other was euthanatized after developing renal disease and mild laminitis.
Kallings P, Ingvast-Larsson C, Persson S, Appelgren LE, Förster HJ, Rominger KL.To evaluate the effects of clenbuterol on cardio-respiratory parameters and blood lactate relation to exercise tolerance, experimental horses performed standardized exercise tests on a high-speed treadmill before and after administration of the drug. Clenbuterol was administered in feed to six healthy Standardbreds at a dose rate of 0.8 micrograms/kg b.wt twice daily for 5.5 days. Each horse was tested twice, without and with a respiratory mask, during two consecutive days. One week elapsed between the baseline tests without drug and the tests with clenbuterol treatment (each horse served as i...
Steffey EP, Willits N, Wong P, Hildebrand SV, Wheat JD, Meagher DM, Hodgson D, Pascoe JR, Heath RB, Dunlop C.Fifty-eight foals were divided into two groups for study of aspects of the clinical anesthetic management of foals and to characterize effects of halothane (n = 30) and isoflurane (n = 28) in foals. There were no significant differences (P greater than 0.05) in the demographics of the two groups. Results of hemograms and biochemical analysis of venous blood samples before and after anesthesia were either not influenced or only mildly (clinically unimportant) affected by either agent. Like adult horses, foals have an increased PaCO2 when anesthetized with inhaled anesthetics. We could detect no...
Redding WR, Booth LC.Equine fibroblasts and Staphylococcus aureus were exposed for 30 minutes to six dilutions of chlorhexidine gluconate, a chlorous acid-chlorine dioxide irrigation solution, a chlorous acid-chlorine dioxide disinfectant, and phosphate buffered saline controls. Cell viability was determined by trypsinizing the cells, staining them with trypan blue, and counting cells that did not take the stain. All fibroblasts were killed when exposed to 1.0% and 0.5% chlorhexidine. The survival rate of fibroblasts increased linearly with decreasing concentrations of chlorhexidine gluconate, with a peak survival...
Horspool LJ, McKellar QA.A high performance liquid chromatography (HPLC) method was developed for the determination of seven short-chain fatty acids in equine caecal liquor. Samples were cleaned up on a Sep-pak (C18) cartridge, and the analyte was eluted from the extraction cartridge and filtered through a 0.45 micron cellulose nitrate filter. The analyte was chromatographed by ion exchange HPLC. Detection was by UV at 210 nm. Recovery from phosphate buffer (0.05 M, pH 7.0) and equine caecal liquor was 76.95% (lactic), 76.76% (valeric). The limit of (propionic), 89.35% (isobutyric), 88.73% (butyric), 80.33% (isovaleri...
Ingvast-Larsson C.A comparison between the relaxant effects of clenbuterol and theophylline on horse tracheal smooth muscle has been made in vitro. Rat tracheal smooth muscle was also investigated as a reference. The tracheal preparations were initially contracted with carbachol since the smooth muscle did not spontaneously develop tone. The response of the carbachol-contracted preparations to theophylline was the same in the two species. The response to clenbuterol varied. In only five out of eleven horses were the tracheal smooth muscles sensitive to clenbuterol (mean pD2 = 7.92 M). In the remaining six horse...
Timofeev BA, Bolotin IM, Stepanova LP, Bogdanov AA, Georgiu Kh, Malyshev SN, Petrovskiĭ , Klibanov AL, Torchilin VP.The cultures of Nuttalia eque mainly develop in the reticuloendothelial organs and so in treatment of nuttaliosis in horses and the Nuttalia carriers diamidine, an analog of imidocarb or imidozoline, was used encapsulated in liposomes. The liposomes were prepared with a modification of the phase inversion method (the lipids were dissolved in a mixture of freon-11 and chloroform). The content of the organic solvents in the preparation, as evidenced by gas liquid chromatography, was less than 0.2 per cent. The main fraction consisted of particles 1.5 to 2.5 microns in diameter. The tests on anim...
Scott JS, Berney CE, Derksen FJ, Robinson NE.Pulmonary function measurements were made in control ponies and in ponies with recurrent obstructive pulmonary disease (principals) during clinical remission and during an attack of acute airway obstruction. The ponies were given beta-adrenergic antagonists and agonists to determine the role of beta receptors in recurrent obstructive pulmonary disease, and to determine the subtypes of beta receptors mediating bronchodilation in ponies. Aerosol administration of the beta antagonists, propranolol (beta 1 and beta 2), atenolol (beta 1), and butoxamine (beta 2) decreased dynamic compliance (Cdyn) ...
Drudge JH, Lyons ET, Tolliver SC.Critical tests were completed on foals (n = 15) naturally infected with benzimidazole (BZ)-resistant population-B strongyles during the period between 1981 and 1987. Thiabendazole at a dosage of 44 mg/kg was tested in 8 foals, oxfendazole at 10 mg/kg was tested in 4 foals, and phenothiazine at 55 mg/kg, cambendazole at 20 mg/kg, and fenbendazole at 5 mg/kg were tested in 1 foal each. Efficacies of thiabendazole, cambendazole, and fenbendazole against the 5 species of BZ-resistant small strongyles (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocylus nassatus, Cylicostephanus goldi, and ...
Chapman MR, Klei TR, French DD.A critical trial was performed with five ponies 6-9 months of age and raised on a horse farm with demonstrated benzimidazole-resistant cyathostomes. Eleven species of cyathostomes were recovered, seven of which had resistance to thiabendazole. Degrees of resistance varied among ponies and from species to species. Resistant species were Cyathostomum coronatum, Cyathostomum catinatum, Cylicostephanus minutus, Cylicostephanus calicatus, Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicocylus nassatus. This is the first study identifying resistant cyathostome species in the Gulf Coast...
Gasthuys F, de Moor A, Parmentier D.The influence of different rates of dopamine and dobutamine on the cardiovascular depression during a standard halothane anesthesia was studied in dorsally recumbent ventilated ponies. Haemodynamic and respiratory responses were investigated by means of cardiac output (CO) determination (thermodilution technique), mean systemic (MAP) and pulmonary artery pressure (MPAP) (direct intravascular method) and arterial blood analysis (blood gases and packed cell volume). An important cardiopulmonary depression characterized by decreases (55% of the standing values) in CO, cardiac index (CI), MAP, MPA...
Dieckmann M, Deegen E.Twelve horses with clinical symptoms of a gastric disorder were studied by gastroscopy. Symptoms of gastric disorders were periprandial colic, bruxism, ructus and reflux. Preliminary to gastroscopy the horses were fasted for 24 h. Access to water was not restricted. The gastroscopy could be conducted easily using a fiberscope 2.5 m in length and 11 mm in outer diameter. While ulcers were present in the squamous fundus of all horses only one horse showed ulceration of the glandular fundus. Solitary ulcers near the margo plicatus were found in horses with mild clinical symptoms. In contrast, dif...
Watson TD, Sullivan M.The effects of sedation with detomidine on oesophageal function were assessed by contrast radiography in 10 healthy adult thoroughbred horses. Barium swallows were monitored by means of image intensification, first without sedation and then after the intravenous administration of detomidine at doses of 10 and 20 micrograms/kg bodyweight. The transit time of contrast agent to the oesophageal hiatus was recorded and each swallow was scored for markers of oesophageal dysfunction. Analysis of the data indicated that there were highly significant dose dependent increases in the transit time, the re...
Rutkowski JA, Eades SC, Moore JN.A chronic model with an ultrasonic transit time blood flow probe and strain gauge force transducers implanted on the cecum was used to evaluate cecal mechanical activity and cecal arterial blood flow in 4 conscious adult horses. Intravenous administration of xylazine (1.1 mg/kg of body weight) significantly decreased heart rate and cardiac output, but significantly increased diastolic pulmonary arterial pressure, mean pulmonary arterial pressure, carotid arterial pressure, and central venous pressure. Lateral cecal arterial blood flow after xylazine administration was decreased substantially m...
Hinchcliff KW, Muir WW.Furosemide, a diuretic, is frequently administered to horses for the prophylaxis of exercise-induced pulmonary hemorrhage and the treatment of a number of clinical conditions, including acute renal failure and congestive heart failure. Furosemide increases the rate of urinary sodium, chloride, and hydrogen ion excretion. Plasma potassium concentration decreases after furosemide administration but urinary potassium excretion in horses is minimally affected. Renal blood flow increases after furosemide administration. Systemically, furosemide increases venous compliance and decreases right atrial...
Huntington PJ, Seneque S, Slocombe RF, Jeffcott LB, McLean A, Luff AR.Five horses with Australian stringhalt were treated with 15 mg/kg phenytoin orally for 2 weeks. During the second week of the trial, 3 of the horses were given an additional dose of 10 mg/kg phenytoin. The response to treatment was clinically assessed by grading the severity of the gait abnormality at the walk, trot, turning and backing twice daily. There was a significant (P less than 0.05) improvement in the gait abnormality when pre-treatment values were compared with the mean of the last 3 assessments before treatment stopped. When reassessed 2 weeks after treatment ceased, there remained ...
Martin GR, Sutherland RJ, Robertson ID, Kirkpatrick WE, King DR, Hood PJ.The toxicity of pindone, a rabbit poison, to horses, cattle, goats, chickens, dogs and cats was investigated, using extension of prothrombin time (PT) as an index of poisoning. The daily dose of pindone, administered for 5 days, ranged from 0.3 mg/kg for dogs to 2.5 mg/kg for chickens. This range of dose rates was considered to be indicative of the worst possible case that could arise following a campaign of baiting for rabbits. Although significant elevations in PT (more than double baseline values) were noted in all species other than horses, clinical signs of anticoagulant poisoning were no...
LeBlanc PH, Broadstone RV, Derksen FJ, Robinson NE.Distal airway segments (ID, 3 to 4 mm; length, 5 mm) from 2 groups of horses were isolated and suspended in tissue baths filled with Krebs solution, aerated with 5% CO2 in oxygen and maintained at 37 degrees C. Responses to exogenous acetylcholine, isoproterenol, or electrical field stimulation were compared. Control horses (n = 30) had no history of recurrent airway obstruction, whereas principal horses (n = 15) had recurrent airway obstruction and were studied during an acute episode of airway obstruction. Although the distal airways contracted in response to the cumulative half-logarithmic ...
Matthews NS, Hartsfield SM, Cornick JL, Williams JD, Beasley A.Six combinations of injectable anesthetic agents were administered to six adult horses in a Latin square design. The drug combinations were xylazine-ketamine, xylazine-butorphanol-ketamine, xylazine-tiletamine-zolazepam, xylazine-butorphanol-tiletamine-zolazepam, detomidine-ketamine, and detomidine-butorphanol-ketamine. Measured variables were heart rate, respiratory rate, systolic blood pressure, arterial pH (pHa), PaCO2, PaO2, recumbency time, and number of attempts necessary to stand. Quality of induction and recovery, muscle relaxation, and response to stimulus were evaluated subjectively....
Field HJ, Awan AR, de la Fuente R.The compound (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) had been previously shown to be highly effective in treatment of EHV-1 in a murine model for the equine disease. This paper describes the isolation of a series of mutants resistant to the drug. Resistance was demonstrated in cell culture and one mutant was tested in a murine model. The resistant mutant was pathogenic for mice; infectious virus was recovered from respiratory tissues and blood at levels similar to the parental virus. However, the mutant showed a significant degree of resistance in vivo, thus proving the viru...
Welch RD, Watkins JP, DeBowes RM, Leipold HW.The effects of intra-articular administration of dimethylsulfoxide (DMSO) on chemically induced synovitis in the middle carpal joint of 6 weanling horses were evaluated. Following aseptic collection of synovial fluid, the middle carpal joint of each forelimb was injected with 50 mg of Na-monoiodoacetate to induce synovitis. Eight days after injection, synovial fluid was obtained and the right middle carpal joints were injected with 2 ml of 40% DMSO in lactated Ringer solution. The corresponding joints of the left limb (control) were injected with 2 ml of lactated Ringer solution. Sampling and ...
Craig AM, Blythe LL, Rowe KE, Lassen ED, Walker LL.An oral vitamin E absorption test used in human beings was modified for use in horses. The most appropriate techniques with which to measure gastrointestinal tract absorption of vitamin E (alpha-tocopherol) in horses were developed. Vitamin E was administered orally, and serum values of alpha-tocopherol were measured by use of high-performance liquid chromatography at 0, 3, 6, 9, 12, and 24 hours after vitamin E administration. Variables included comparison of 2 dosages (45 and 90 IU/kg of body weight), routes of administration, and absorption dynamics of 3 preparations of dl-alpha-tocopherol....
Gaughan EM, Nixon AJ, Krook LP, Yeager AE, Mann KA, Mohammed H, Bartel DL.Sodium hyaluronate reduces adhesions after tendon repair in rodents and dogs, and has been used in limited clinical trials in people. To evaluate its effect on tendon healing and adhesion formation in horses and to compare these effects with those of a compound of similar visco-elastic properties, a study was performed in horses, using a model of collagenase injection in the flexor tendons within the digital sheath. Eight clinically normal horses were randomly allotted to 2 groups. Adhesion formation between the deep digital flexor tendon and the tendon sheath at the pastern region was induced...
Paradis MR, Breeze RG, Laegreid WW, Bayly WM, Counts DF.Eight ponies were allotted to 2 groups of 4. Group-1 ponies (1-4) were given 0.2 g of indole/kg of body weight orally and group-2 ponies (5 to 8) were given 0.1 g of indole/kg. Various physical, hematologic, and physiologic measurements were obtained after administration of indole. Intravascular hemolysis and hemoglobinuria were detected in both groups within 24 hours of dosing. Hemolysis was reflected by decreases in PCV, hemoglobin concentration, and RBC count, and an increase in indirect bilirubin. Erythrocyte fragility appeared to increase in both groups at 8 hours after dosing and peaked ...
Wagner AE, Muir WW, Hinchcliff KW.The cardiovascular effects of xylazine and detomidine in horses were studied. Six horses were given each of the following 5 treatments, at 1-week intervals: xylazine, 1.1 mg/kg, IV; xylazine, 2.2 mg/kg, IM; detomidine, 0.01 mg/kg, IV; detomidine, 0.02 mg/kg, IV; and detomidine, 0.04 mg/kg, IM. All treatments resulted in significantly decreased heart rate, increased incidence of atrioventricular block, and decreased cardiac output and cardiac index; cardiac output and cardiac index were lowest following IV administration of 0.02 mg of detomidine/kg. Mean arterial pressure was significantly redu...
Dumasia MC, Houghton E.A method for the screening and confirmatory analysis of beta-agonists and -antagonists in equine urine is described. Following initial enzymic hydrolysis, the basic drugs and metabolites are extracted using Clean Screen DAU or Bond Elut Certify cartridges, and analysed as their trimethylsilyl ether or 2-(dimethyl) silamorpholine derivatives by capillary gas chromatography-mass spectrometry. The method proved to be very sensitive and selective for basic drugs. After administration of therapeutic doses of propranolol, metoprolol, timolol, isoxsuprine and clenbuterol to thoroughbred horses, the p...
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...
Vieitez V, Gómez de Segura IÁ, Martin-Cuervo M, Gracia LA, Ezquerra LJ.Lipid emulsion has been reported to be effective for the treatment of local anaesthetic overdoses in rats, dogs and man. Objective: To describe the successful treatment of cardiovascular lidocaine toxicity in a foal with intravenous lipid administration. Methods: Observational study: case report. Methods: An 8-month-old Arabian cross foal was anaesthetised for removal of the right alar fold and nasal plate. Anaesthesia was maintained with isoflurane in oxygen and lidocaine administered with a loading dose followed by a continuous rate infusion (CRI). The anaesthetic period was uneventful and 3...
Ellison RS, Jacobs RM.This study was undertaken to ascertain if the isoelectric focusing pattern of serum alkaline phosphatase (AP) from sick horses with high activity is useful for determining its tissue origin. The effect of oral prednisolone and phenylbutazone therapy on this enzyme in healthy horses was also investigated. The sick horses were divided into three groups: hepatic, intestinal and miscellaneous. All sera had approximately thirteen bands of AP activity when focused on agarose gels with a pH gradient of 3.5 to 9.5. All the horses in the liver disease group had greater than 65% of enzyme activity in ba...
Minguet G, de la Rebière G, Franck T, Joris J, Serteyn D, Sandersen C.To investigate the effects of the volatile anaesthetic sevoflurane on the release of total and active myeloperoxidase (MPO) by non-stimulated and stimulated polymorphonuclear neutrophils (PMNs) in whole blood from healthy horses. Methods: In vitro experimental study. Methods: Adult healthy horses. Methods: Samples of whole venous blood were collected and incubated in air or in air plus 2.3% or 4.6% sevoflurane for 1 hour. PMNs were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP), with a combination of cytochalasin B (CB) and fMLP or with phorbol myristate acetate (PMA). Total an...
Weiss DJ, Geor RJ, Burger K.To determine whether furosemide treatment altered the blood flow properties and serum and RBC electrolyte concentrations of Thoroughbreds during submaximal treadmill exercise. Methods: Thoroughbreds were subjected to submaximal treadmill exercise with and without treatment with furosemide (1 mg/kg of body weight, IV). Methods: 5 healthy Throughbreds that had raced within the past year and had no history of exercise-induced pulmonary hemorrhage. Methods: Venous blood samples were obtained before exercise, at treadmill speeds of 9 and 13 m/s, and 10 minutes after exercise, and hemorheologic and ...
Castilla-Castaño E, Vischi A, Navarro C, Lecru LA, Ribeiro C, Pradier S, Cadiergues MC.Two open-controlled studies evaluated the tolerance and the efficacy of a 10 mg/mL deltamethrin-based pour-on solution (Deltanil®; Virbac, France) in treating (study 1) and preventing (study 2) natural Damalinia equi infestations in horses. In study 1, seven adult horses received 10 mL of the solution from mane to tail head on day 0 (D0). Four adult horses, living separately, served as non-treated controls. All were naturally infected. Lice burden was recorded by counting the number of live parasites, bilaterally, over seven anatomic regions. Lesional score was based on alopecia, crusts, papu...
Pucket JD, Allbaugh RA, Rankin AJ, Ou Z, Bello NM.To compare efficacy and duration of effect on corneal sensitivity of 0.5% proparacaine hydrochloride, 0.5% bupivacaine hydrochloride, 2% lidocaine hydrochloride, and 2% mepivacaine hydrochloride solutions following ocular administration in clinically normal horses. Methods: 68 clinically normal horses. Methods: 60 horses were assigned to receive 1 anesthetic agent in 1 eye. For each of another 8 horses, 1 eye was treated with each of the anesthetic agents in random order with a 1-week washout period between treatments. Corneal sensitivity was assessed via corneal touch threshold (CTT) measurem...
Yokota S, Hikasa Y, Shimura I, Kusunose S.To investigate effects of various imidazoline and nonimidazoline α-adrenergic agents on aggregation and antiaggregation of bovine and equine platelets. Methods: Blood samples obtained from 8 healthy adult cattle and 16 healthy adult Thoroughbreds. Methods: Aggregation and antiaggregation effects of various imidazoline and nonimidazoline α-adrenergic agents on bovine and equine platelets were determined via a turbidimetric method. Collagen and ADP were used to initiate aggregation. Results: Adrenaline, noradrenaline, or α-adrenoceptor agents alone did not induce changes in aggregation of bov...
Andrews FM, Doherty TJ, Blackford JT, Nadeau JA, Saxton AM.To determine the effects of orally administered omeprazole, as enteric-coated capsules, on baseline and stimulated gastric acid secretion in horses. Methods: 5 healthy 8-year-old mixed-breed horses fitted with gastric cannulas. Methods: Enteric-coated granules of omeprazole were mixed with corn syrup and administered orally once daily for 5 consecutive days. On days 1 and 5 beginning 5 hours after omeprazole administration, 4 gastric fluid samples were collected, each for 15 minutes, via the gastric cannula (baseline samples). Pentagastrin was administered IV as a constant infusion for the sub...
Her GR, Watson JT.Sensitive and specific methodology based on capillary column gas chromatography-electron capture-negative chemical ionization-mass spectrometry has been developed for the quantitative analysis of corticosteroids from biological fluids. The feasibility of this method is demonstrated in the quantitative analysis of dexamethasone in horse urine following administration of the drug. A structurally similar compound, 6 alpha-methylprednisolone, is added to the urine as an internal standard. The free dexamethasone and the internal standard are extracted and oxidized to high-electron-affinity 1,4-andr...
Barsan WG, Hedges JR, Syverud SA, Dalsey WC.The treatment of cardiovascular collapse and anaphylactic shock is largely empiric. A simple animal model was developed to evaluate the hemodynamic alterations in anaphylaxis. Eight adult New Zealand white rabbits of both sexes were studied. All animals weighed 3.8 kg to 5.3 kg. Sensitization was accomplished with a 2-mL subcutaneous dose of horse serum followed in two days with a 2-mL intravenous (IV) dose. At least 14 days elapsed after the IV dose before a 1-mL challenge dose of horse serum was given. On the day of the challenge dose, a femoral arterial catheter, arterial temperature probe,...
Robinson NE, Dabney JM, Weidner WJ, Jones GA, Scott JB.The digital circulation was isolated in 12 ponies under pentobarbital anesthesia. Blood flow was either controlled by a pump or measured under natural perfusion. The responses to rapid changes and stoppages of blood flow indicated no evidence of autoregulation or reactive hyperemia. Local administration of acetylcholine, histamine, and prostaglandins E1 and E2 decreased prevenous resistance, whereas epinephrine and serotonin caused prevenous constriction. Large doses of epinephrine and serotonin decreased venous caliber. The effects of prostaglandins A1 and F2alpha were variable. The equine di...
Panitz E.Ethyl-6-ethoxybenzothiazole-2-carbamate (Sch 18099) was evaluated for efficacy against natural helminth infections in ponies, pigs, lambs and chickens. Sixteen critical trials were conducted in ponies at dosages of 15 to 150 mg/kg. At 15 mg/kg, efficacy against adult and larval Oxyuris equi was 100% and 91% and against small strongyles it was 98%. Efficacy levels were 95% against Strongylus vulgaris and S. edentatus at the 20 mg/kg dosage. In two trials at 100 mg/kg efficacy against Parascaris equorum was 77%. No efficacy was observed against Gastrophilus spp. or Anoplocephala spp. In swine si...
Queiroz-Neto A, Zamur G, Carregaro AB, Mataqueiro MI, Salvadori MC, Azevedo CP, Harkins JD, Tobin T.Caffeine is the legal stimulant consumed most extensively by the human world population and may be found eventually in the urine and/or blood of race horses. The fact that caffeine is in foods led us to determine the highest no-effect dose (HNED) of caffeine on the spontaneous locomotor activity of horses and then to quantify this substance in urine until it disappeared. We built two behavioural stalls equipped with juxtaposed photoelectric sensors that emit infrared beams that divide the stall into nine sectors in a 'tic-tac-toe' fashion. Each time a beam was interrupted by a leg of the horse...
Vermeer C, Ulrich M.The presence of vitamin K-dependent carboxylase is demonstrated in the microsomal fraction of horse liver, spleen and kidney. The carboxylating enzyme systems in the spleen and in the kidney are susceptible to warfarin in a similar way as is carboxylase from the liver. It is concluded, that during the administration of vitamin K-antagonists (anticoagulation therapy) carboxylase in all these tissues is inhibited. Since most probably the majority of the reaction products of spleen and kidney carboxylase are no clotting factors, the inhibition of their production is a side-effect of the anticoagu...
Aarnes TK, Bednarski RM, Bertone AL, Hubbell JA, Lerche P.The objective of this study was to compare recovery from desflurane anesthesia in horses with or without post-anesthetic xylazine. Six adult horses were anesthetized on 2 occasions, 14 d apart using a prospective, randomized crossover design. Horses were sedated with xylazine, induced to lateral recumbency with ketamine and diazepam, and anesthesia was maintained with desflurane. One of 2 treatments was administered intravenously at the end of anesthesia: xylazine [0.2 mg/kg body weight (BW)] or an equivalent volume of saline. Recovery parameters were recorded and assessed by 2 blinded observe...
Pozor MA, Zambrano G, Roser J, Hess R, Runyon S, Runcan E, Thomas BF, Dymock D, Macpherson ML, Troedsson MH, Kelleman A.The objective of this study was to evaluate acute endocrine effects as well as histological changes in testicular parenchyma induced by the contraceptive compound RTI-4587-073(l). Six miniature stallions were used in this experiment. The treatment group (n = 3) received one oral dose of 12.5 mg/kg of RTI-4587-073(l), and the control group (n = 3) received placebo only. The stallions' baseline parameters (semen, testicular dimensions, endocrine values) were collected and recorded for 5 weeks before treatment and for 6 weeks after treatment. Multiple blood samples were collected for endoc...
Dobler D, Gerber M, Schmidts TM, Runkel F, Schlupp P.Human nail diseases, mostly caused by fungal infections, are common and difficult to treat. The development and testing of new drugs and drug delivery systems for the treatment of nail diseases is often limited by the lack of human nail material for permeation studies. Animal material is frequently used, but there are only few comparative data on the human nail plate, and there is neither a standardized test design nor a nail bed analogue to study drug uptake into the nail. In this study, a new permeation device was developed for permeation studies, and the permeation behavior of three model s...
Fowden AL, Silver M.Epostane, a competitive inhibitor of 3 beta-HSD was administered intravenously to a pregnant mare between 292 and 330 days of gestation at doses of 1-3 mg/kg/min. Plasma progesterone concentrations fell rapidly during epostane infusion in both the artery and uterine vein and remained significantly depressed for 4-5 h after the start of infusion. The venous arterial (V-A) plasma concentration difference in progesterone across the uterus also decreased significantly in response to epostane infusion. There were no significant changes in plasma progesterone or in the V-A concentration difference i...
Roberts MC, Seawright AA.Colic was induced in horses and ponies following topical or intravenous (iv) administration of amitraz, a formamidine acaricide. The condition was characterised by rapid cessation of intestinal sounds, stasis, extensive impaction and tympany throughout the large colon. Three animals that were necropsied had a faecalith obstructing the proximal small colon aboral to marked colonic impaction. A reproducible and reversible impaction colic syndrome could be induced by an iv injection of 1 mg amitraz/kg body weight in solvent. There were immediate central nervous system and intestinal signs. Large ...
Jondorf WR, Moss MS.1. Cross-bred and thoroughbred geldings were injected with veterinary doses of various synthetic anabolic steroids. Urines collected sequentially from treated animals were analysed, following solvent extraction, by radioimmunoassay using 19-[3H]nortestosterone and an antibody raised against a 19-nortestosterone immunogen. 2. Urinary excretion of 19-nortestosterone and/or its cross-reacting metabolites was detectable for various times after administration of different nortestosterone esters, as follows: phenylpropionate (400 mg), greater than 14 days; cyclohexylpropionate (100 mg), greather tha...
Boeckh S, Buchanan C, Boeckh A, Wilkie S, Davis C, Buchanan T, Boothe D.Following approval of a concentrated injectable formulation of enrofloxacin for cattle (Baytril 100 Injectable, Bayer Corp. Agricultural Division, Shawnee Mission, KS), equine practitioners have started administering this preparation both parenterally and orally to horses, despite the lack of pharmacokinetic data in this species. Six healthy horses received enrofloxacin at 7.5 mg/kg both orally and intravenously, with the sequence being randomly assigned and at least 1 week of washout allowed between administrations. Blood samples were collected from each horse at various intervals after drug ...
Harkins JD, Hackett RP, Ducharme NG.Twelve horses (6 Standardbreds and 6 Thoroughbreds) received IM injections of furosemide (250 mg) or physiologic saline solution and performed standard exercise tests, to assess the effects of furosemide and breed on blood gas values, PCV, plasma lactate concentration, and heart rate during exercise. After furosemide administration, arterial and venous blood pH values were significantly (P < 0.05) increased. Partial pressures of O2 and CO2 in arterial blood and of CO2 in venous blood (PaO2, PaCO2, and PVCO2, respectively) were unaffected by furosemide treatment, whereas venous partial press...
Airway obstruction is the main trait of severe equine asthma that affects respiratory function and elicits detrimental effects on clinical presentation. Only few and underpowered clinical studies have investigated the impact of improvement in lung function induced by bronchodilators on the clinical signs of asthma-affected horses. Objective: To identify the minimal important difference (MID) in lung function elicited by bronchodilator leading to a meaningful improvement in clinical signs. Methods: Pairwise meta-analysis and meta-regression analysis. Methods: Literature searches were performed ...
Colas C, Popot MA, Garcia P, Bonnaire Y, Bouchonnet S.LC/ESI-MS n methods have been previously set up to detect the administration of (i) Harpagophytum and (ii) preparations containing a plant capable of anti-stress properties: Eleutherococcus senticosus. Harpagoside has been found to be the main indicator of Harpagophytum administration in the horse. These methods have been applied to a large number of horse urine samples of various origins. Regarding the detection of Harpagophytum administration, harpagoside, harpagide and 8-para-coumaroyl harpagide were detected together in only one sample out of 317. Eleutheroside E was found to be the main i...
Tendillo FJ, Mascías A, Santos M, López-Sanromán J, De Rossi R, San Román F, Gómez de Segura IA.To determine the minimum alveolar concentration (MAC) of desflurane (DES) in the horse. Methods: Prospective study. Methods: Six healthy adult horses (three males and three females) weighing 370 +/- 16 kg and aged 9 +/- 2 years old. Methods: Anesthesia was induced with DES vaporized in oxygen via a face mask connected to a large-animal, semiclosed anesthetic circle system. The horses were endotracheally intubated and positioned in right lateral recumbency. Inspired and end-tidal DES were monitored using a calibrated Ohmeda RGM 5250 multigas analyzer (Ohmeda-BOC, Spain). The MAC of desflurane t...
Abutarbush SM, Naylor JM.To compare the outcome of horses with nephrosplenic entrapment of the large colon (NSELC) treated surgically or medically by rolling, administration of phenylephrine hydrochloride (or both), and exercise. Methods: Retrospective study. Methods: 11 medically treated horses and 8 surgically treated horses with NSELC. Methods: Medical records of horses with nephrosplenic entrapment between 1992 and 2002 were reviewed. Medically treated horses were included if diagnosis and outcome of treatment of nephrosplenic entrapment were confirmed via transrectal examination and ultrasonographic examination. ...
Klohnen A, Wilson DG, Hendrickson DA, Cooley AJ, MacWilliams PS.To evaluate the bactericidal properties of chlorhexidine diacetate (CHD) after potentiation with EDTA and Tris buffer (EDTA-Tris), and to find a potentiated CHD concentration that would achieve 90 to 100% killing for all bacteria tested. Methods: 6 adult ponies. Methods: Serial dilutions of CHD, CHD in EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal activity against Staphylococcus aureus, Escherichia coli, and Streptococcus zooepidemicus. The tarsocrural joints of 6 ponies were lavaged with either 1 L phosphate-buffered saline solution (control) or 1 L of 0.0005% CHD in EDTA-Tris...
Manohar M, Goetz TE, Rothenbaum P, Humphrey S.The present study was carried out to examine whether pentoxifylline administration to horses premedicated with frusemide would attenuate the exercise-induced pulmonary arterial, capillary and venous hypertension to a greater extent than frusemide alone, thereby affecting the occurrence of exercise-induced pulmonary haemorrhage (EIPH). Using established techniques, we determined right heart and pulmonary vascular pressures in 6 healthy, sound Thoroughbred horses at rest and during exercise performed at maximal heart rate at a workload of 14 m/s on 3.5% uphill grade in the control (no medication...
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...
