Plasma is the liquid component of blood in horses, consisting primarily of water, electrolytes, proteins, and waste products. It serves as a transport medium for nutrients, hormones, and waste products throughout the body. Plasma also plays a role in maintaining blood pressure and volume, as well as serving as a reservoir for critical proteins involved in clotting and immune responses. Research on equine plasma often focuses on its composition, functions, and applications in veterinary medicine, such as transfusions and diagnostic testing. This page compiles peer-reviewed research studies and scholarly articles that explore the properties, functions, and clinical applications of plasma in equine health.
McKeever KH, Antas LA, Kearns CF.The objective of the present study was to measure plasma endothelin-1 (ET-1) at rest and during exercise in the horse. Six healthy, Standardbred and Thoroughbred mares (5.3+/-0.8 years; 445.2+/-13.1 kg) which were unfit, but otherwise accustomed to running on the treadmill, were used in the study. Plasma ET-1 concentrations were measured using a commercially available radioimmunoassay kit. Horses performed three trials: a standing control (CON) trial where blood was collected from the jugular vein every minute for 5 min; a graded exercise test (GXT) where blood samples were collected at the en...
Hubbell JA, Hinchcliff KW, Grosenbaugh DA, Beard WL, Beard LA.Frusemide reduces pulmonary vascular pressures in resting horses and attenuates exercise-induced increases in these pressures in exercising horses. The mechanism underlying these effects of frusemide is unclear. We tested the hypothesis that the haemodynamic effects of frusemide are dependent on diuresis by examining the effect of frusemide in anaesthetised horses in which diuresis was prevented by ligation of ureters. Twenty four horses were assigned randomly to one of 4 treatments: 1) frusemide (1 mg/kg bwt i.v.) and intact ureters; 2) frusemide and ligated ureters; 3) saline placebo and lig...
Belloli C, Crescenzo G, Lai O, Carofiglio V, Marang O, Ormas P.The objective of this study was to determine the pharmacokinetic behaviour of imidocarb in horses following a single i.m. injection at the dose commonly administered to treat Babesia caballi infections or to prevent babesiosis. Eight horses were injected i.m. with a single dose of 2.4 mg imidocarb dipropionate/kg bwt and blood, faecal, urine and milk samples were collected. For imidocarb determination, a high-performance liquid chromatographic method (HPLC) was used after weak cation-exchange solid phase, or liquid-liquid, extraction procedures. Twelve hours after treatment, no detectable plas...
van Duijkeren E, Ensink JM, Meijer LA.The distribution of trimethoprim (TMP) and sulfadiazine (SDZ) into subcutaneously implanted noninfected tissue chambers was studied in healthy adult ponies. Six ponies were given an oral TMP/SDZ paste formulation at a dose of 5 mg/kg TMP and 25 mg/kg SDZ at 12 h intervals for 2 days in order to reach steady-state concentrations. Plasma concentrations and tissue chamber fluid (TCF) concentrations of both drugs were measured at regular intervals during a period commencing 24 h after the last oral administration. The peak concentration of TMP (mean +/- SD) was 2.92 +/- 0.86 microg/mL for plasma a...
Fumuso E, Checura C, Losinno L, Soto P, Sánchez S.Endometritis in mares is a common cause of infertility. Conventional treatments of the disease have mostly been unsuccessful, so new therapeutic alternatives need to be investigated. This study evaluated the uterine disposition and plasma pharmacokinetic behaviour of a commercial formulation of enrofloxacin (EFX) given by the intrauterine (i.u.) route (2.5 mg/kg) in healthy mares. In order to evaluate the uterine inflammatory response, an initial histopathological study assessing polymorphonuclear cell infiltration was carried out in 20 mares over a 14-day period after treatment. In a second s...
Guan F, Uboh CE, Soma LR, Luo Y, Li R, Birks EK, Teleis D, Rudy JA, Tsang DS.Clenbuterol (CBL) is a potent beta(2)-adrenoceptor agonist used for the management of respiratory disorders in the horse. The detection and quantification of CBL can pose a problem due to its potency, the relatively low dose administered to the horse, its slow clearance and low plasma concentrations. Thus, a sensitive method for the quantification and confirmation of CBL in racehorses is required to study its distribution and elimination. A sensitive and fast method was developed for quantification and confirmation of the presence of CBL in equine plasma, urine and tissue samples. The method i...
Hansen RA, Savage CJ, Reidlinger K, Traub-Dargatz JL, Ogilvie GK, Mitchell D, Fettman MJ.An 18-week feeding trial was performed to investigate the effects of an omega-3 (n-3) fatty acid-enriched ration on plasma fatty acid concentrations and platelet aggregation in healthy horses. Flaxseed oil served as the source of the n-3 fatty acid alpha-linolenic acid (ALA). Twelve horses were fed dietary maintenance requirements using a complete pelleted ration (80%) and timothy grass hay (20%) for a 2-week acclimation period before being randomly assigned either to a treatment (group 1) or control (group 2) group. Group 2 horses (n = 6) were fed the diet described in the acclimation period,...
Lazar A, Epstein E, Lustig S, Barnea A, Silberstein L, Reuveny S.Peptic cleavage of horse plasma IgG is a common procedure for the preparation of F(ab)(2) products for human use, such as antivenin and antitoxin. The removal of the Fc fragment from the IgG molecule by enzymatic cleavage at low pH, ensures fewer side-effects of the F(ab)(2) product for passive immunotherapy compared with the whole IgG molecule. Since the starting material may be contaminated by zoonotic horse viruses, it is necessary to demonstrate the removal or inactivation of possible viral contaminants. Guidelines for performing such studies were published by the Commission for Plasma-Der...
Du J, Eddington N.A sensitive and selective HPLC method for the determination of the disaccharides of chondroitin sulfate in horse and dog plasma was validated. Chondroitin sulfate is degraded by chondroitinase ABC to three primary unsaturated disaccharides, (1) 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-D-galactose, (2) 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose, and (3) 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D-galactose, when treated with chondroitinase. Plasma samples (0.5 ml) were treated with 50 mU of chon...
McKenzie EC, Valberg SJ, Godden SM, Pagan JD, Carlson GP, MacLeay JM, DeLaCorte FD.To determine whether plasma, urine, and fecal electrolyte and mineral concentrations differ between clinically normal horses and Thoroughbreds with recurrent exertional rhabdomyolysis (RER) after consumption of diets varying in cation-anion balance. Methods: 5 Thoroughbred mares with RER and 6 clinically normal mixed-breed mares. Methods: Each of 3 isocaloric diets designated as low, medium, and high on the basis of dietary cation-anion balance (DCAB) values of 85, 190, and 380, respectively, were fed to horses for 14 days. During the last 72 hours, 3 horses with RER and 3 control horses had d...
Frank N, Sojka JE, Latour MA.To measure and compare the concentration and composition of very low-density lipoprotein (VLDL) in plasma and selected lipids in serum of horses fed mixed grass hay ad libitum or denied feed for 36 hours. Methods: 4 healthy adult mares. Methods: Mares were either fed mixed grass hay ad libitum or denied feed for 36 hours beginning at 8:00 AM. Blood samples were collected every 2 hours during the study period and analyzed for nonesterified fatty acid (NEFA), triglyceride (TG), VLDL, and glucose concentrations and composition of VLDL. Results: Withholding feed significantly increased mean serum ...
Hamlin MJ, Shearman JP, Hopkins WG.Various changes in physiological parameters are associated with overtraining, which can be a serious problem for human and equine athletes. A 34 week longitudinal study was conducted to investigate the effects of an acute training overload on physiological parameters in 10 Standardbred racehorses. After 24 weeks of training, horses received 8 weeks of increased workload, followed by 2 weeks recovery. Horses performed a 2400 m time trial and a progressive submaximal exercise test on alternate weeks. By the end of the heavy training period, the average time for the final 1200 m of the time trial...
Carretero M, Rodríguez C, San Andrés MI, Forés P, de Lucas JJ, Nieto J, Waxman S, San Andrés MD, González F.The pharmacokinetic behaviour of marbofloxacin, a new fluoroquinolone antimicrobial agent developed exclusively for veterinary use, was studied in mature horses (n = 5) after single-dose i.v. and i.m. administrations of 2 mg/kg bwt. Drug concentrations in plasma were determined by high performance liquid chromatography (HPLC) and data obtained were subjected to compartmental and noncompartmental kinetic analysis. This compound presents a relatively high volume of distribution (V(SS) = 1.17 +/- 0.18 l/kg), which suggests good tissue penetration, and a total body clearance (Cl) of 0.19 +/- 0.042...
Toutain PL, Lassourd V.The current performance of analytical techniques used for drug control in horses lead the Regulatory Authorities to decide whether trace levels of drugs legitimately used for therapeutic medication should or should not be reported. Here, we propose a well-ordered and nonexperimental pharmacokinetic/pharmacodynamic approach for the determination of irrelevant drug plasma (IPC) and urine concentrations (IUC). The published plasma clearance is used to transform an effective (marketed) dose into an effective concentration (EPC). EPC is transformed into an IPC by applying a safety factor (SF). This...
Geelen SN, Sloet van Oldruitenborgh-Oosterbaan MM, Beynen AC.The hypothesis tested was that the feeding of extra fat to horses would raise the production of plasma triacylglycerols (TAG). To measure TAG secretion, the indirect Triton method was used. Six adult horses were given a low-fat control or a high-fat diet according to a crossover design. In keeping with our earlier work, the high-fat diet lowered fasting plasma TAG concentrations by an average of 42% and raised post-heparin total lipoprotein lipase activity by 79%. The rate of increase in plasma TAG concentration after Triton administration was 49% lower when the horses were fed the high-fat di...
Pérez R, Cabezas I, Godoy C, Rubilar L, Muñoz L, Arboix M, Castells G, Alvinerie M.A study was undertaken in order to compare plasma disposition kinetic parameters of doramectin (DRM) and ivermectin (IVM) in horses after oral administration. Ten crossbreed adult horses, clinically healthy, weighing 380-470 kg body weight (bw) were selected for study. Faecal examinations were performed to determine faecal parasite egg counts. Horses were allocated to two groups of five animals to provide an even distribution considering the variables sex, body weight and faecal egg count. Group I, were treated with an oral paste formulation of IVM at 0.2 mg/kg b/w and Group II, were treated w...
Grulke S, Gangl M, Deby-Dupont G, Caudron I, Deby C, Serteyn D.Gastrointestinal disorders in horses leading to endotoxic shock could have further consequences on other splanchnic organs such as the pancreas, as can be seen in humans suffering from septic shock. In this study, the range of enzymatically active trypsin (EAT) in healthy horses was established and is similar to the range observed in healthy humans. EAT values were determined in horses with acute abdominal crises on admission as well as during anaesthesia and in the postoperative phase. A significant increase in plasma EAT was found in 59% of the horses with surgical colic when compared to our...
Lakritz J, Wilson WD, Marsh AE, Mihalyi JE.Plasma concentrations and pharmacokinetics of erythromycin and related compounds were determined after administration of erythromycin ethylsuccinate to six healthy male foals 3 to 5 months of age. Hay was withheld from the foals overnight and erythromycin ethylsuccinate (25 mg/kg of body weight) was administered intragastrically. Plasma erythromycin concentrations were determined at specific times after drug administration by high-performance liquid chromatography assay. Maximum peak plasma concentrations, time to maximum concentrations, area under plasma concentration versus time curves, elim...
Allen AL, Myers SL, Searcy GP, Fretz PB.The Hematologic values of 19 equine fetuses between 202 and 238 days gestation were compared with those of their dams. The red blood cell (RBC) count, hemoglobin concentration, hematocrit, and mean corpuscular hemoglobin concentration were significantly lower in fetal blood, while the mean corpuscular volume, mean corpuscular hemoglobin, and red cell distribution width were significantly higher. Mares had a significantly higher nucleated blood cell count than fetuses, and all nucleated cells were leukocytes (WBC). Most WBC in mare blood were segmented neutrophils and lymphocytes. In contrast, ...
Hallebeek JM, Beynen AC.In a Latin square design, six horses were fed hay and concentrates with isoenergetic amounts of either starch, cellulose or medium chain triacylglycerols (MCT). The dietary variables provided on average 22% of total dietary net energy. Plasma triacylglycerols and other variables of lipid metabolism were determined. The experimental periods lasted 21 days. Blood samples were taken just before the morning meal and three and six hours later. The diet rich in MCT significantly raised the plasma level of triacylglycerols when compared to either the starch- or cellulose-rich diet. The plasma concent...
Schwarzwald CC, Feige K, Wunderli-Allenspach H, Braun U.To determine pharmacokinetic variables and to evaluate the influence on clotting times after SC administration of single doses of dalteparin and enoxaparin to horses. Methods: 5 healthy adult horses. Methods: The study was designed as a 4-period crossover study. Each horse received a single SC injection of dalteparin (50 and 100 anti-Xa U/kg) and enoxaparin (40 and 80 anti-Xa U/kg). Plasma anti-Xa activities and clotting times were measured, and pharmacokinetic variables were determined. Absolute and relative maximal prolongation of clotting times was calculated, and correlation between plasma...
The Journal of nutritionJune 4, 2002
Volume 132, Issue 6 Suppl 2 1628S-31S doi: 10.1093/jn/132.6.1628S
Williams CA, Hoffman RM, Kronfeld DS, Hess TM, Saker KE, Harris PA.alpha-Lipoic acid (LA) has demonstrated antioxidant effects in humans and laboratory animals. The objective of this study was to determine whether the effects of LA are similar in horses. Five Thoroughbred geldings were supplemented with 10 mg/kg/d DL-alpha-lipoic acid in a molasses and sweet feed carrier and five received only the carrier as a placebo (CON). Blood samples were obtained at baseline (0 d), after 7 and 14 d of supplementation, and 48 h postsupplementation (16 d). Blood fractions of red and white blood cells (RBC and WBC, respectively) and plasma were analyzed for glutathione (GS...
The Journal of nutritionJune 4, 2002
Volume 132, Issue 6 Suppl 2 1622S-7S doi: 10.1093/jn/132.6.1622S
Marlin DJ, Fenn K, Smith N, Deaton CD, Roberts CA, Harris PA, Dunster C, Kelly FJ.Prolonged low-medium intensity exercise is associated with increased oxidative stress in humans. We hypothesized that competitive equine endurance racing would induce changes in circulatory antioxidants and produce systemic oxidative stress. Forty horses competing in a 140-km endurance race in warm conditions [shade temperature 15-19 degrees C; 62-88% relative humidity (%RH)] were sampled before (Pre), immediately after exercise (End) and at approximately 16 h into recovery (+16 h). Plasma ascorbic acid concentration was not different between Pre [11.1 (median); 4.6-20.3 micromol/L (range)] an...
Balogh N, Gaál T, Ribiczeyné PS, Petri A.Physical exercise in the horse induces a series of normal physiological and biochemical adaptations. Increasing metabolism and oxygen uptake may induce oxidative stress in various organs. The aim of this study was to examine exercise-induced changes in some plasma and RBC biochemical and antioxidant variables in pentathlon horses. Blood samples were taken from 14 horses before, immediately after, and 24 hours after competing in two 1-minute runs of intense exercise over jumps. The peak intensity periods were preceded by a 20-minute warm-up and separated by a 20-minute break. The following plas...
Gokbulut C, Nolan AM, McKellar QA.Oxibendazole (OBZ) was administered to eight horses at an oral dose of 10 mg kg(-1) bodyweight each. Parent OBZ could only be detected in plasma at the 0.5 and 1.0 hours post administration sampling times and the mean maximum plasma concentration was 0.008 microg ml(-1). Parent OBZ was detected in faeces between 12 and 72 hours after administration and the highest dry faecal concentration was detected at 24 hours. An unidentified metabolite was detected in plasma between 0.5 and 72 hours. The unidentified metabolite in the plasma of treated horses corresponded to the second eluted metabolite i...
Donadeu FX, Thompson DL.Sixteen seasonally anovulatory mares were randomly allotted to two groups and injected daily with either sulpiride (1 mg/kg body weight) or vehicle from 14 January to 14 February. Sulpiride administration increased daily plasma prolactin concentrations (P < 0.05), although the prolactin response during the 6 h following sulpiride injections decreased markedly from the 1st to the 6th day of treatment (treatment by day, P < 0.0001). Plasma concentrations of LH and FSH were not affected by treatment (P > 0.1). Injection of GnRH and TRH on 15 February showed that the response of plasma prolactin t...
Davis JL, Gardner SY, Jones SL, Schwabenton BA, Papich MG.The properties of azithromycin suggest that it may be an alternative to erythromycin for treatment of Rhodococcus equi pneumonia in foals. To investigate this possibility, the disposition of azithromycin in plasma, polymorphonuclear leukocytes (PMN), and alveolar cells was examined after a single administration in foals. Azithromycin suspension was administered orally (p.o.) at a dose of 10 mg/kg to five healthy 2-3-month-old foals. Two weeks later, azithromycin for injection was administered by intravenous (i.v.) infusion at a dose of 5 mg/kg to the same foals. Plasma samples were collected a...
Knoll U, Strauhs P, Schusser G, Ungemach FR.Olsalazine sodium (Dipentum*) has been used therapeutically against inflammatory bowel disease in human medicine as an alternative to sulphasalazine over the past 20 years. Bacteria in the colon split this prodrug into two molecules of the locally effective 5-aminosalicylic acid (5-ASA). Considering the potential therapeutic use in equine colitis, the pharmacokinetics of olsalazine (OLZ) after single oral administration to six horses at a dosage of 30 mg/kg was investigated. Plasma concentrations of OLZ, 5-ASA, and its main metabolite N-acetyl-5-aminosalicylic acid (Ac-5-ASA) were analysed by ...
Erkert RS, Macallister CG.Isoxsuprine hydrochloride has been suggested for use in horses for treatment of navicular syndrome and laminitis. The drug has been shown to be a beta-adrenoreceptor antagonist with beta-adrenoreceptor agonistic properties, with both characteristics contributing to vasodilation and uterine relaxation. In addition, the drug is capable of decreasing blood viscosity and platelet aggregation. Studies have shown i.v. isoxsuprine to have a plasma half-life of <3 h with a large apparent volume of distribution. Cardiovascular effects resolve rapidly following i.v. administration, but are absent wit...
Hallebeek JM, Beynen AC.The influence of dietary soybean oil versus palm oil on the plasma level of triacylglycerols was determined in a crossover experiment with four horses. Based on published data for humans and laboratory animals it was expected that a diet rich in unsaturated fatty acids in the form of soybean oil compared to saturated fatty acids in the form of palm oil would lower the plasma triacylglycerol level. The feeding of soybean oil versus palm oil for a period of four weeks did not change the level of plasma triacylglycerols in horses. Mean levels of triacylglycerol, free fatty acids and 3-hydroxybuty...
Valencia NA, Thompson DL, Mitcham PB.Six insulin-sensitive and 6 insulin-insensitive mares were used in a replicated 3 by 3 Latin square design to determine the pituitary hormonal responses (compared with vehicle) to sulpiride and thyrotropin-releasing hormone (TRH), 2 compounds commonly used to diagnose pituitary pars intermedia dysfunction (PPID) in horses. Mares were classified as insulin sensitive or insensitive by their previous glucose responses to direct injection of human recombinant insulin. Treatment days were February 25, 2012, and March 10 and 24, 2012. Treatments were sulpiride (racemic mixture, 0.01 mg/kg BW), TRH (...
Hallowell GD, Corley KT.Hypertonic saline and hydroxyethyl starches have been proposed as alternatives to isotonic crystalloids for reversal of hypovolemia in horses with colic. However, no direct comparison of these fluids has been performed in a clinical setting. Objective: Preoperative administration of hypertonic saline or pentastarch would produce similar effects on intra operative hemodynamics in horses with colic. Methods: Thirty horses requiring colic surgery were enrolled in this prospective, randomized, open-label clinical trial. Inclusion criteria were owner consent, and at least 2 of 3 clinicopathologic a...
Worthy K, Colquhoun K, Escreet R, Dunlop M, Renton JP, Douglas TA.Plasma prolactin concentrations were measured in mares using an homologous radioimmunoassay. An annual rhythm in plasma prolactin was found, with concentrations higher during the summer than during the winter. In addition to this seasonal pattern, occasional high concentrations of prolactin were seen when concentrations were otherwise basal. Blood samples taken from mares during an oestrous cycle in October-November showed that prolactin values were basal for most of the cycle, with a marked rise in prolactin shortly before the onset of oestrus. This prolactin peak was associated with an incre...
van der Kolk JH, Rijnen KE, Rey F, de Graaf-Roelfsema E, Grinwis GC, Wijnberg ID.To determine whether increased glucose metabolism is the potential cause of the decreased plasma glucose curve determined after oral glucose tolerance testing in horses with lower motor neuron degeneration. Methods: 3 horses with signs suggestive of lower motor neuron degeneration, 1 horse with malignant melanoma with multiple metastases, and an obese but otherwise healthy horse. Procedures-Glucose metabolism was assessed by use of the hyperglycemic clamp and euglycemic hyperinsulinemic clamp techniques. Results: Mean rate of glucose metabolism of horses with lower motor neuron degeneration wa...
Hamamoto-Hardman BD, Steffey EP, McKemie DS, Kass PH, Knych HK.Meperidine is a synthetic opioid that belongs to the phenylpiperidine class and is a weak mu receptor agonist. In horses there are a limited number of published studies describing the analgesic effects of systemically administered meperidine in horses. The objective of this study was to describe the pharmacokinetics, behavioral and physiologic effects and effect on thermal threshold of three doses of intravenously administered meperidine to horses. Eight University owned horses (four mares and four geldings, aged 3-8 years were studied using a randomized balanced 4-way cross-over design. Hors...
Mateus L, da Costa LL, Cardos JJ, Silva JR.The efficiency of treatments for unobserved oestrus and their effect on the reproductive performance of a dairy cattle herd with low oestrous detection rate till 60 days post-partum (dpp), attributed to the declivous and slippery concrete floor were investigated. The herdsman requested advice in order to improve the mean days open of the herd, but no investments were allowed because a new unit was about to be built. Due to the low oestrus detection rate of the herd, the breeding policy was to inseminate at the first detected post-partum oestrus. Cows were examined at 20-30 dpp to assess uterin...
Sosa Leon L, Hodgson DR, Evans DL, Ray SP, Carlson GP, Rose RJ.The second day of a 3-day event is the most physically demanding of the 3 days. If this is performed under hot and humid environmental conditions, detrimental effects on cardiovascular and thermoregulatory function and, therefore, on exercise capacity, may occur due to exercise-induced dehydration. We hypothesised that the administration of fluid equivalent to 6% of the horse's bodyweight prior to a simulated second day of a 3-day event would increase plasma volume and limit increases in core temperature. Seven Standardbred geldings underwent a training protocol prior to the study. A standardi...
Nogueira BCF, Orozco AMO, Argumedo AK, de Oliveira Faustino A, de Oliveira LL, da Fonseca LA, Campos AK.Ticks have saliva rich in immunoregulatory molecules that interfere with the host's physiology in order to feed. This study aimed to evaluate the concentration of acute phase proteins and circulating oxidative stress in response to infestation by Amblyomma sculptum and Dermacentor nitens in two breed horses, Mangalarga Marchador and Breton Postier, to define resistance or susceptibility to ticks. Among the oxidative stress markers, we observed lower malondialdehyde and nitric oxide in horses with tick infestation, consequently not altering the antioxidant enzymes. Breton Postier with tick infe...
Gretler SR, Finno CJ, McKemie DS, Kass PH, Knych HK.To describe the pharmacokinetics and selected pharmacodynamic variables of codeine and its metabolites in Thoroughbred horses following a single oral administration. Methods: Prospective experimental study. Methods: A total of 12 Thoroughbred horses, nine geldings and three mares, aged 4-8 years. Methods: Horses were administered codeine (0.6 mg kg) orally and blood was collected before administration and at various times until 120 hours post administration. Plasma and urine samples were collected and analyzed for codeine and its metabolites by liquid chromatography-mass spectrometry, and plas...
Nerenberg C, Runkel RA, Matin SB.A simple radioimmunoassay was developed for the determination of oxfendazole in plasma. Oxfendazole N-1(3)-valerate was coupled to polylysine via a carbodiimide reaction, and antiserum was developed in rabbits after inoculation with oxfendazole--polylysine conjugate. The assay was developed so that oxfendazole could be measured directly in a 0.1-ml aliquot of diluted or undiluted plasma. With the developed procedure, 200 pg of oxfendazole/ml of plasma can be determined quantitatively. Cross-reactivity was determined for closely related compounds and metabolites. The method was used to determin...
Hoffmann SL, Seminoff K, McKemie DS, Kass PH, Knych HK.Grapiprant is a prostaglandin E2 receptor antagonist that has been found to be an effective anti-inflammatory in dogs and that is devoid of some of the adverse effects associated with traditional NSAIDs that elicit their effects through inhibition of PGE2 production. Previously published reports have described the pharmacokinetics of this drug in horses when administered at 2 mg/kg; however, pharmacodynamic effects in this species have yet to be described. The objective of the current study was to describe the pharmacokinetics and pharmacodynamics of grapiprant at a higher dose. Eight horses...
Wilson KE, Bogers SH, Council-Troche RM, Davis JL.To determine the effects of general anesthesia on the safety and efficacy of co-administered potassium penicillin G (PEN) and gentamicin (GENT) in horses. Methods: Nonrandomized crossover. Methods: Six adult, Thoroughbred horses. Methods: Horses were administered PEN (22 000 IU/kg IV) and GENT (6.6 mg/kg IV). Plasma samples were collected over a 6 h period and synovial fluid was collected at 30 min and 6 h respectively. Drug administration and sample collection protocols were repeated after at least a 48 hour washout period and induction of anesthesia using xylazine/ketamine and main...
Lees P, Taylor JB, Higgins AJ, Sharma SC.The clinically recommended dose rate of phenylbutazone (4.4 mg/kg) was administered intravenously as a single dose to five Welsh Mountain ponies. Distribution of phenylbutazone and its active metabolite oxyphenbutazone into body fluids was studied by measuring concentrations in plasma, tissue-cage fluid, peritoneal fluid and acute inflammatory exudate harvested from a polyester sponge model of inflammation. The ready penetration of phenylbutazone into inflammatory exudate was demonstrated by the relatively high mean value for Cmax of 12.4 micrograms/ml occurring at a time of 4.6 h and a mean A...
Knowles EJ, Menzies-Gow NJ, Mair TS.Plasma fructosamine concentration ([fructosamine]) is believed to reflect medium term, average blood glucose concentration and in a previous study was higher in horses with active laminitis than in normal horses. Pituitary pars intermedia dysfunction (PPID) is associated with hyperglycaemia and laminitis. Objective: To test the hypotheses that: [fructosamine] is higher in PPID cases than normal animals; furthermore, that within cases of PPID [fructosamine] is higher in those with active laminitis than nonlaminitic cases and in cases that have been affected by active laminitis in the preceding ...
Abu-Basha EA, Bani Ismail Z, Ababneh MM, Hamzeh E, Gehring R.This study was designed to investigate the safety and pharmacokinetic (PK) profile of tildipirosin in horses after intravenous (i.v.) and subcutaneous (s.c.) injection of a single dose at 4 mg/kg of body weight (b.w.). A total of 12 healthy mixed breed horses were used in the study. Horses were monitored for systemic and local adverse effects, and whole blood samples were collected for hematology and plasma biochemistry analysis at time (0) and at 6, 24, and 72 h after drug administration. For PK analysis, blood samples were collected at pre-determined times before and after tildipirosin adm...
Olsén L, Ingvast-Larsson C, Bondesson U, Broström H, Tjälve H, Larsson P.The pharmacokinetics of the histamine H(1)-antagonist cetirizine and the effects of pretreatment with the antiparasitic macrocyclic lactone ivermectin on the pharmacokinetics of cetirizine were studied in horses. After oral administration of cetirizine at 0.2 mg/kg bw, the mean terminal half-life was 3.4 h (range 2.9-3.7 h) and the maximal plasma concentration 132 ng/mL (101-196 ng/mL). The time to reach maximal plasma concentration was 0.7 h (0.5-0.8 h). Ivermectin (0.2 mg/kg bw) given orally 1.5 h before cetirizine did not affect its pharmacokinetics. However, ivermectin pretreatment 12 h be...
Harris P, Snow DH.To investigate the effect of moderate to high intensity exercise of up to 6 min duration on plasma potassium and lactate concentrations, 6 Thoroughbred horses were studied using a treadmill at a 5 degree incline. Each test consisted of an 8-min standardised warm-up followed by an exercise bout at 8, 9, 10 or 12 m/sec. The horses were galloped at each speed for up to a maximum of 6 min or until signs of fatigue were present. The horses were then walked at 0 degree incline. Carotid arterial blood samples were taken during and after the exercise. At 8, 9 and 10 m/sec there was a general pattern o...
Bettschart-Wolfensberger R, Taylor PM, Sear JW, Bloomfield MR, Rentsch K, Dawling S.To examine the physiologic and pharmacokinetic effects of a technique of total intravenous anesthesia in ponies. Methods: 6 healthy ponies. Methods: Ponies were premedicated with acepromazine (0.03 mg/kg of body weight, IV) and xylazine (1.0 mg/kg, IV). Two minutes later, anesthesia was induced with ketamine (2.0 mg/kg, IV) followed by climazolam (0.2 mg/kg, IV). Anesthesia was maintained for 120 minutes by an infusion of climazolam (0.4 mg/kg/h) and ketamine (6.0 mg/kg/h). Oxygen (5 L/min) was supplemented. 20 minutes after the infusion was stopped sarmazenil (0.04 mg/kg, IV) was administered...
Asami K.Horse erythrocytes, murine lymphoblasts (L5178Y) and lipid vesicles that were treated with dipicrylamine (DPA) as a lipophilic ion were studied by dielectric spectroscopy over a frequency range of 10 Hz to 10 MHz. The DPA-treated cells and lipid vesicles showed low-frequency (LF) dielectric dispersion around 1-10 kHz in addition to β-dispersion due to the Maxwell-Wagner effect. The LF dispersion corresponds to that found in previous electrorotation (ROT) studies on DPA-treated cells, being due to the translocation of mobile ions in the plasma membranes. Analysis of the LF dispersion based on ...
Robertson SA, Green SL, Carter SW, Bolon BN, Brown MP, Shields RP.Anesthesia and surgery in a Quarter Horse affected with hyperkalemic periodic paralysis resulted in euthanasia after 7 days of postoperative recumbency. Initial recovery was uneventful after extensive sinus surgery, but within 2 hours, the horse had severe muscle weakness. Plasma electrolyte concentrations were within the normal range during the period of recumbency. There was no clinical or laboratory evidence of severe muscle damage. Despite treatment with acetazolamide, isoproterenol, and intensive nursing, the horse was unable to stand for more than a few seconds and developed severe decub...
Shaba JJ, Behan Braman A, Robinson NE.In many inflammatory diseases plasma cortisol concentration (CORT) increases at the onset of acute inflammation, but the situation in recurrent airway obstruction (RAO) of horses is unknown. Methods: Split-plot repeated measures design with one grouping factor (disease) and two repeated factors (day and 3-hour intervals). Objective: To test the hypothesis that CORT increases as acute exacerbations of RAO develop. Methods: Four RAO-susceptible and 4 control horses were placed in a low dust environment (LDEnv) for 2 days followed by 2 days in a high dust environment (HDEnv). Exacerbations of RAO...
Baker SJ, Gerring EL.We investigated the effects of a range of IV administered doses of omeprazole (0.125 to 2.0 mg/kg of body weight) on gastric pH (monitored by indwelling electrode) and plasma gastrin concentration, compared with those of IV administered ranitidine (1.0 mg/kg) in 4 Welsh mountain-type ponies. Pharmacokinetic variables of IV administered omeprazole also were examined. Episodes of high gastric pH in the basal state obscured the effect of acid suppression on intragastric pH; however, omeprazole induced dose-dependent increase in mean gastric pH (P < 0.01) during the 11 hours after its administr...
Southwood LL, Gassert T, Lindborg S.It is the impression of some surgeons that geriatric horses have a lower survival rate compared to mature nongeriatric horses following colic surgery. One possible reason for this is that geriatric horses may be more critically ill at admission and have more severe disease than mature nongeriatric horses. Objective: To compare admission historical, physical examination and laboratory data for geriatric and mature nongeriatric horses referred for signs of colic. Methods: Medical records of horses admitted with a presenting complaint of colic between 2000 and 2006 were reviewed. Geriatric horses...
Gozalo-Marcilla M, Moreira da Silva R, Pacca Loureiro Luna S, Rodrigues de Oliveira A, Werneck Fonseca M, Peporine Lopes N, Taylor PM, Pelligand L.The alpha(α) -agonist detomidine is used for equine sedation with opioids such as methadone. We retrieved the data from two randomized, crossover studies where detomidine and methadone were given intravenously alone or combined as boli (STUDY 1) (Gozalo-Marcilla et al., 2017, Veterinary Anaesthesia and Analgesia, 2017, 44, 1116) or as 2-hr constant rate infusions (STUDY 2) (Gozalo-Marcilla et al., 2019, Equine Veterinary Journal, 51, 530). Plasma drug concentrations were measured with a validated tandem Mass Spectrometry assay. We used nonlinear mixed effect modelling and took pharmacokinetic...
Schnuelle ML, Hopster K, Toribio RE, Hurcombe SD.To compare the effects of 7.2% hypertonic and 0.9% isotonic saline (sodium chloride) solutions on cardiovascular parameters and plasma arginine vasopressin (AVP) concentrations in healthy, isoflurane-anesthetized horses. Methods: 8 healthy horses. Methods: In a prospective, randomized, crossover study, horses were anesthetized with isoflurane twice with a 14-day washout period between anesthetic episodes. While anesthetized, horses received a bolus (4 mL/kg) of 7.2% hypertonic saline solution (HS) or 0.9% isotonic saline solution (IS). Heart rate; systolic, mean, and diastolic arterial blood p...
Karakka Kal AK, Nalakath J, Kunhamu Karatt T, Perwad Z, Mathew B, Subhahar M.The detection and separation of medetomidine enantiomers from the complex biological matrices poses a great analytical challenge, especially in the field of forensic toxicology and pharmacology. Couple of researchers reported resolution of medetomidine using protein-based chiral columns, but the reported method is quiet challenging and tedious to be employed for routine analysis. This research paper reported a method that enables the enantio-separation of medetomidine by using polysaccharide cellulose chiral column. The use of chiralcel OJ-3R column was found to have the highest potential for ...
Villani M, Cairoli F, Kindahl H, Galeati G, Faustini M, Carluccio A, Veronesi MC.Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the j...
Ginther OJ, Beg MA.The temporal associations of cortisol, estradiol-17β, and oxytocin with pulses of PGFM at the common hour of transition between preluteolysis and luteolysis was studied in plasma from hourly blood samples in mares (n=8). The transitional hour was determined from progesterone concentrations and occurred between 2PM and 2AM in all mares. Pulses of PGFM were grouped into those occurring at the last pulse of preluteolysis (preluteolytic pulse), at the hour of transition (transitional), and during luteolysis (luteolytic). The preluteolytic PGFM pulse (45±16pg/ml at peak) and transitional pulse (4...
Guan F, Uboh CE, Soma LR, Birks EK, Teleis D, Rudy JA, Watson AO, Tsang DS.A reliable and sensitive method for the extraction and quantification of phenytoin (5,5'-diphenylhydantoin), its major metabolite, 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) and minor metabolite, 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) in horse urine and plasma is described. The method involves the use of solid-phase extraction (SPE), liquid-liquid extraction (LLE), enzyme hydrolysis (EH) and high-performance liquid chromatography (HPLC). The minor metabolite, 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) was not present in a reliably quantifiable concentration in all samples. The ...
Muir WW, Milne DW, Skarda RT.Intravenous administration of furosemide in the horse resulted in an immediate and significant decrease in right atrial pressure, pulmonary arterial pressure, pulmonary arterial wedge pressure, cardiac output, and stroke volume (P less than 0.05). There was a significant increase in total systemic vascular resistance and heart rate (P less than 0.05). There were no significant alterations in mean arterial pressure. Coincidental with these hemodynamic changes were increased urine production and associated increase in packed cell volume and total serum protein. All variables except cardiac outpu...
