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.
Williams LA.Many skin disorders in horses share the same appearance-hair loss of various degrees, itchiness, lesions that may or may not be painful to the touch, oozing sores, or skin that is reddened, crusty, scaly, flaky, thickened or swollen- making diagnosis sometimes difficult. A horse owner's documentation of a horse's medical history, the history of the skin disorder, and the horse's environment assists veterinarians and compounding pharmacists in their diagnosis and treatment. This article discusses some of the common skin problems that affect horses, takes a look at causes, and provides a case re...
Brosnan RJ, Steffey EP.We hypothesized that propofol can produce rapidly-reversible, dose-dependent standing sedation in horses. Methods: Prospective randomized, blinded, experimental trial. Methods: Twelve healthy horses aged 12 +/- 6 years (mean +/- SD), weighing 565 +/- 20 kg, and with an equal distribution of mares and geldings. Methods: Propofol was administered as an intravenous bolus at one of three randomized doses (0.20, 0.35 and 0.50 mg kg(-1)). Cardiovascular and behavioral measurements were made by a single investigator, who was blinded to treatment dose, at 3 minute intervals until subjective behavior s...
de la Rebière de Pouyade G, Grulke S, Detilleux J, Salciccia A, Verwilghen DR, Caudron I, Gangl M, Serteyn DD.The aim of this study is to describe the prevalence of postoperative laminitis in colic cases and to determine if low-molecular-weight heparin (LMWH) is effective in preventing this complication. Methods: Retrospective clinical study. Methods: Client-owned horses. Interventions- SC administration of enoxaparin during the postoperative period. Results: Medical records of 360 horses undergoing surgery for colic and surviving at least 3 days were evaluated. Fifty-six horses admitted before 1995 did not receive LMWH (control group) and 304 admitted after 1995 received LMWH as a prophylaxis for lam...
Mitchell JD, Kuc RE, Maguire JJ, Davenport AP.The brain-gut peptide neuromedin U (NMU) is a ligand for the G-protein-coupled receptors, NMU1 and NMU2. In humans, an extended form of this peptide, NMU-25, and the structurally related peptide, neuromedin S (NMS), both produce potent vasoconstriction in isolated blood vessels. The aim of this study was to determine whether NMU fulfilled criteria for controlling vasoreactivity in the equine digital circulation. NMU receptors were characterised in the equine digital artery and vein based on the pharmacological criteria of specific, saturable and high affinity binding. Immunoreactive peptide wa...
Casasola A, Ramos-Cerrillo B, de Roodt AR, Carbajal Saucedo A, Chippaux JP, Alagón A, Stock RP.Venoms of snakes belonging to the same Genera tend to share biochemical, toxinological and antigenic characteristics. Accordingly, paraspecific neutralization of venom lethality by experimental antisera and commercial antivenoms has been reported. We studied the spectrum of neutralization of lethality of an experimental monovalent equine antiserum against the strongly neurotoxic African forest cobra (Naja melanoleuca) when tested against venoms of most species of African Naja, both neuro and cytotoxic as described by some authors. We report a comparison of the median lethal doses (LD50) of the...
Cuervo-Arango J, Newcombe JR.Prostaglandin F(2α) and its analogues (PGF) are widely used in equine reproductive practice. The interval from PGF treatment to ovulation (ITO) varies greatly with a range from 2 to 16 days. Clinical observation suggests that mares mated and ovulated soon after PGF treatment may have poor fertility. Reproductive records of 329 cyclic Thoroughbred mares were analysed retrospectively. The following parameters were analysed: (i) use of cloprostenol; (ii) ITO and (iii) number of ovulations per cycle. According to these parameters, mares were classified into four groups. (i) mares with spontaneous...
Schmitz A, Theurillat R, Lassahn PG, Mevissen M, Thormann W.CE with multiple isomer sulfated-CD as selector was used for the simultaneous analysis of the stereoisomers of ketamine, norketamine, 5,6-dehydronorketamine and hydroxylated metabolites of norketamine in liquid/liquid extracts of (i) in vitro incubations with ketamine or norketamine and equine liver microsomes and (ii) plasma and urine of ponies receiving a target-controlled infusion of ketamine under isoflurane anesthesia. Hydroxynorketamine metabolites with the hydroxy group at the cyclohexanone ring could be shown to be formed stereoselectively both in vitro and in vivo. Due to the lack of ...
Steffey EP, Mama KR, Brosnan RJ, Imai A, Maxwell LK, Cole CA, Stanley SD.To compare characteristics of horses recovering from 4 hours of desflurane anesthesia with and without immediate postanesthetic IV administration of propofol and xylazine. Animals-8 healthy horses (mean +/- SEM age, 6.6 +/- 1.0 years; mean body weight, 551 +/- 50 kg). Methods: Horses were anesthetized twice. Both times, anesthesia was induced with a combination of xylazine hydrochloride, diazepam, and ketamine hydrochloride and then maintained for 4 hours with desflurane in oxygen. Choice of postanesthetic treatment was randomly assigned via a crossover design such that each horse received an ...
Ueno D, Yabuki A, Obi T, Shiraishi M, Nishio A, Miyamoto A.We investigated the effect of bradykinin (BK) on isolated equine basilar arterial rings with and without endothelium. BK induced concentration-dependent contraction of resting arterial rings and no relaxation when the rings were precontracted by prostaglandin F(2alpha). The maximal response and pD(2) value were 161.2 +/- 28.1% (to 60 mm KCl-induced contraction) and 8.24 +/- 0.25 respectively. The cumulative concentration-response curve for BK was not shifted to the right by des-Arg(9)-[Leu(8)]-BK (a B(1)-receptor antagonist), HOE140 (a B(2)-receptor antagonist) or NPC567 (another B(2)-receptor...
Poulin Braim AE, MacDonald MH, Bruss ML, Grattendick KJ, Giri SN, Margolin SB.To characterize effects of IV administration of pirfenidone on clinical, biochemical, and hematologic variables and circulating tumor necrosis factor (TNF)-alpha concentrations in horses after infusion of a low dose of endotoxin. Methods: 18 healthy adult horses. Methods: Horses were randomly assigned to 3 groups (n = 6 horses/group) and administered an IV infusion of 30 ng of endotoxin/kg or saline (0.9% NaCl) solution during a 30-minute period. Lipopolysaccharide-pirfenidone horses received endotoxin followed by pirfenidone (loading dose of 11.6 mg/kg and then constant rate infusion [CRI] at...
de Vries A, Brearley JC, Taylor PM.Volatile agent-induced hypotension may contribute to anaesthetic-related morbidity and mortality in horses. Dobutamine is commonly used to support arterial blood pressure (ABP) but little is known about its cardiovascular effects under clinical conditions. The aim of this clinical study was to elucidate the relationship between cardiovascular function and dobutamine infusion in isoflurane-anaesthetized horses. Forty-four horses anaesthetized for a variety of surgical procedures were studied. Premedication with acepromazine, methadone and detomidine was followed by induction of anaesthesia with...
Abraham G, Allersmeier M, Gottschalk J, Schusser GF, Hoppen HO, Ungemach FR.There are no data available regarding the systemic (adverse) effects which might be induced by topical/dermal glucocorticoids (GCs) application in the horse. Besides their widespread use for the treatment of a variety of peripheral inflammatory disorders such as atopic dermatitis, eczemas or arthritis in the horse, their surreptitious application has become a concern in doping cases in competition/performance horses. Assessing both basal and ACTH-stimulated plasma cortisol as well as basal ACTH concentrations following application of dexamethsone-containing dermal ointment is necessary to dete...
Videla R, Andrews FM.Equine gastric ulcer syndrome (EGUS) is common in horses. A history of mild intermitted recurrent colic signs after eating is noted in many horses. Management of horses with abdominal pain caused by gastric ulcers is especially difficult, because non-steroidal anti-inflammatory agents, typically used to control abdominal pain, may exacerbate this condition. Effective pharmacologic agents are available to treat EGUS and eliminate abdominal pain, but more comprehensive measures of environmental and dietary management are needed to manage horses with EGUS and prevent recurrence. This article focu...
Doherty TJ.Surgical manipulation of the intestines activates intestinal macrophages that release cytokines and nitric oxide, which results in inhibition of intestinal motility. Subsequent infiltration of circulating leukocytes into the intestinal wall contributes to cytokine and nitric oxide release and exacerbates ileus. Other factors contributing to ileus are endotoxemia; edema of the intestine wall subsequent to excessive fluid therapy; hypocalcemia; and long abdominal incisions. Because treatment of ileus with prokinetic drugs has not proven to be very effective, efforts should be directed at reducin...
van Loon JP, Stienen PJ, Doornenbal A, Hellebrekers LJ.To determine whether epidurally derived evoked potentials (EPs) can be used to reliably assess nociception and antinociception in ponies. Methods: 7 ponies. Methods: EPs and electromyograms (EMGs) from the quadriceps femoris muscles were recorded simultaneously, following electrical stimulation applied to the distal portion of the hind limb. The effect of increasing stimulus intensity, conduction velocities of the stimulated nerves, effect of epidurally applied methadone, and effect of systemically administered propofol were evaluated. Results: In the EP and EMG waveforms, 2 distinct complexes...
Nagy A, Bodo G, Dyson SJ, Szabo F, Barr AR.Proximal diffusion of local anaesthetic solution after perineural anaesthesia may lead to the desensitisation of structures other than those intended. However, there is no evidence-based study demonstrating the potential distribution and diffusion of local anaesthetic solution after perineural analgesia in the distal limb. Objective: To document the potential diffusion of local anaesthetic solution using a radiopaque contrast model and to evaluate the influence of walking compared with confinement in a stable after injection. Methods: Radiopaque contrast medium was injected subcutaneously over...
Rohrbach H, Korpivaara T, Schatzmann U, Spadavecchia C.To evaluate and compare the antinociceptive effects of the three alpha-2 agonists, detomidine, romifidine and xylazine at doses considered equipotent for sedation, using the nociceptive withdrawal reflex (NWR) and temporal summation model in standing horses. Methods: Prospective, blinded, randomized cross-over study. Methods: Ten healthy adult horses weighing 527-645 kg and aged 11-21 years old. Methods: Electrical stimulation was applied to the digital nerves to evoke NWR and temporal summation in the left thoracic limb and pelvic limb of each horse. Electromyographic reflex activity was reco...
Schauvliege S, van Loon G, De Clercq D, Devisscher L, Deprez P, Gasthuys F.To examine the influence of direct current shock application in anaesthetized horses with atrial fibrillation (AF) and to study the effects of cardioversion to sinus rhythm (SR). Methods: Prospective clinical study. Methods: Eight horses successfully treated for AF (transvenous electrical cardioversion after amiodarone pre-treatment). Methods: Cardioversion catheters and a pacing catheter were placed under sedation [detomidine 10 microg kg(-1) intravenously (IV)]. After additional sedation (5-10 microg kg(-1) detomidine, 0.1 mg kg(-1) methadone IV), anaesthesia was induced with ketamine, 2.2 m...
Nourian AR, Mills PC, Pollitt CC.Intraosseous (i.o.) infusion of the distal phalanx (IOIDP) as a delivery route targeting hoof lamellar tissue of standing, conscious horses was evaluated. Following sedation and regional nerve blockade in six Standardbred horses, a microdialysis (MD) probe was implanted into the hoof lamellar tissue of one forelimb. A purpose designed cannulated bone screw was introduced into the body of the distal phalanx, approximately 6 cm from the MD probe. Gentamicin solution (25 mg/mL) was infused at 20 microL/min through the bone screw for 2 h without the application of a tourniquet. MD and blood sample...
Zhang N, Ding S, Kolbanovskiy A, Shastry A, Kuzmin VA, Bolton JL, Patel DJ, Broyde S, Geacintov NE.The equine estrogens equilin (EQ) and equilenin (EN) are the active components in the widely prescribed hormone replacement therapy formulation Premarin. Metabolic activation of EQ and EN generates the catechol 4-hydroxyequilenin (4-OHEN) that autoxidizes to the reactive o-quinone form in aerated aqueous solutions. The o-quinones react predominantly with C, and to a lesser extent with A and G, to form premutagenic cyclic covalent DNA adducts in vitro and in vivo. To obtain insights into the structural properties of these biologically important DNA lesions, we have synthesized site-specifically...
Enderle AK, Levionnois OL, Kuhn M, Schatzmann U.To compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses. Methods: Prospective, randomized, blinded clinical trial. Methods: Forty horses (ASA I-III) undergoing elective surgery. Methods: Horses were assigned to receive isoflurane anaesthesia alone (ISO) or with ketamine and lidocaine (LKI). After receiving romifidine, diazepam, and ketamine, the isoflurane end-tidal concentration was set at 1.3% and subsequently adjusted by the anaesthetist (unaware of treatments) to maintain a light plane of surgical anaesthesia. Animals in the LKI ...
Schauvliege S, Van den Eede A, Duchateau L, Gasthuys F.To evaluate the combined effects of enoximone and dobutamine on the cardiovascular system and respiratory gas exchange in isoflurane-anaesthetized ponies. Methods: Prospective, randomized, experimental study. Methods: Six ponies (286 +/- 52 kg), aged 5.0 +/- 1.6 years. Methods: After sedation (romifidine 80 microg kg(-1)), anaesthesia was induced with midazolam (0.06 mg kg(-1)) and ketamine (2.2 mg kg(-1)) and maintained with isoflurane in oxygen. The ponies were ventilated to maintain eucapnia. After 90 minutes (=T0), enoximone alone (0.5 mg kg(-1)) (E) or enoximone, followed by a constant ra...
You Y, Uboh CE, Soma LR, Guan F, Li X, Rudy JA, Liu Y, Chen J.An ultra-performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) method for fast-throughput analysis of eight anabolic and androgenic steroids (AAS) in equine plasma is reported. Analytes were recovered by liquid-liquid extraction using methyl tert-butyl ether, separated on a 1.9 microm C(18) reversed-phase column, and analyzed in positive electrospray ionization mode on a triple quadrupole mass spectrometer with selected reaction monitoring (SRM) and full product ion scans. Two SRM ion transitions were monitored for each AAS during screening to obtain highly selective screenin...
Nieto JE, Snyder JR, Vatistas NJ, Jones JH.To develop a protocol to induce and maintain gastric ulceration in horses and to determine whether gastric ulceration affects physiologic indices of performance during high-speed treadmill exercise. Methods: 20 healthy Thoroughbreds. Methods: Each horse was acclimatized to treadmill exercise during a 2-week period. Subsequently, baseline data were collected (day 0) and each horse began an incrementally increasing exercise training program (days 1 through 56). Beginning on day 14, horses were administered omeprazole (4 mg/kg, PO, q 24 h until day 56) or no drug (10 horses/group) and underwent a...
Capponi L, Schmitz A, Thormann W, Theurillat R, Mevissen M.To investigate cytochrome P450 (CYP) enzymes involved in metabolism of racemic and S-ketamine in various species and to evaluate metabolic interactions of other analgesics with ketamine. Methods: Human, equine, and canine liver microsomes. Methods: An analgesic was concurrently incubated with luminogenic substrates specific for CYP 3A4 or CYP 2C9 and liver microsomes. The luminescence signal was detected and compared with the signal for negative control samples. Ketamine and norketamine enantiomers were determined by use of capillary electrophoresis. Results: A concentration-dependent decrease...
Larenza MP, Ringer SK, Kutter AP, Conrot A, Theurillat R, Kummer M, Thormann W, Bettschart-Wolfensberger R.To compare anesthesia recovery quality after racemic (R-/S-) or S-ketamine infusions during isoflurane anesthesia in horses. Methods: 10 horses undergoing arthroscopy. Methods: After administration of xylazine for sedation, horses (n = 5/group) received R-/S-ketamine (2.2 mg/kg) or S-ketamine (1.1 mg/kg), IV, for anesthesia induction. Anesthesia was maintained with isoflurane in oxygen and R-/S-ketamine (1 mg/kg/h) or S-ketamine (0.5 mg/kg/h). Heart rate, invasive mean arterial pressure, and end-tidal isoflurane concentration were recorded before and during surgical stimulation. Arterial blood...
Ginther OJ, Siddiqui MA, Beg MA.The hypotheses were tested that prostaglandin F2alpha (PGF) travels from the uterus to the ovaries via a systemic route in mares, as opposed to a local route in ruminants, and that one pulse of PGF produces only partial luteolysis. Intravenous (i.v.) and intrauterine (i.u.) infusions of PGF were performed 8 days after ovulation at a constant rate for 2 h. Plasma concentrations of PGF were assessed by assay of 13,14-dihydro-15-keto-PGF2alpha (PGFM). Total doses administered were as follows: 0, 0.05, 0.1, 0.5 and 1.0 mg, i.v., PGF and 0 and 0.5 mg, i.u., PGF (n=4 mares per group). In addition, P...
Bonneau S, Maynard L, Tomczuk K, Kok D, Eun HM.In this blinded randomized and controlled study, the anthelmintic efficacy of a tablet formula of ivermectin-praziquantel was evaluated in horses experimentally infected with three species of Strongylus larvae. Eighteen previously dewormed horses were inoculated on study day 0 with third-stage larvae of Strongylus vulgaris, Strongylus equinus, and Strongylus edentatus. The horses were randomly allocated to three groups (n = 6): test-drug (tablet formula), positive-control (reference gel), and negative-control (placebo tablet). On day 56, the horses were treated once with the respective drugs. ...
Steiner A, Roussel AJ.Hypodynamic gastrointestinal disorders in horses and cattle that are thought to benefit from treatment with drugs restoring and coordinating gastrointestinal motility include postoperative ileus and large colon impaction in the horse and displacement of the abomasum and dilatation of the cecum in cattle. Important physiologic, pathophysiologic and pharmacologic mechanisms involved in the intrinsic control of gastrointestinal motility include cholinergic, adrenergic, dopaminergic, serotoninergic, and opioid-mediated pathways. Preliminary results suggest that cisapride, acting on 5-Hydroxytrypta...
Horspool LJ, Taylor DJ, McKellar QA.Amikacin was detectable (> 0.02 micrograms/ml) in plasma for 12 h in horses and donkeys and for 8 h in ponies following intravenous (i.v.) administration at a dose rate of 6 mg/kg bodyweight. The elimination half-life (harmonic mean) of amikacin was 2.8, 1.6 and 1.9 h in horses, ponies and donkeys, respectively, and the mean body clearance was relatively slow (45.2, 82.4 and 58.0 ml/h.kg, respectively). A suitable dosage interval for the i.v. administration of amikacin sulphate to horses, ponies and donkeys, at a dose rate of 6 mg/kg, would be every 8 h in horses, and every 6 h in ponies an...
Dowling BA, Dart AJ, Hodgson DR, Rose RJ, Walsh WR.To evaluate the effect of recombinant equine growth hormone (rEGH) on the in vitro biomechanical properties of healing superficial digital flexor tendon (SDFT) in horses. Methods: Completely randomized design. Methods: Twelve Standardbred horses, 3 to 7 years of age, with ultrasonographically normal forelimb SDFT. Methods: One week after induction of collagenase (2,000 U) induced superficial flexor tendonitis, horses were randomly divided into groups of 6. One group was administered intramuscular rEGH (10 microg/kg/day for 1 week, then 20 microg/kg/day for 5 weeks), whereas the other group (co...
Aleman MR, Kuesis B, Schott HC, Carlson GP.Renal tubular acidosis (RTA) is characterized by altered renal tubular function resulting in hyperchloremic metabolic acidosis. The purpose of the study was to describe RTA in 16 horses. No breed or sex predilection was found. The mean age at onset of the disease was 7 years of age. The type of diet had no apparent effect on development of RTA. The most common clinical signs were depression, poor performance, weight loss, and anorexia. Initial blood work revealed a marked hyperchloremic metabolic acidosis in all horses and a compensatory respiratory response in most horses. Sixty-three percent...
Endo Y, Tsuchiya T, Akiyama K, Takebe N, Nakai K, Korosue K, Ishimaru M, Tsuzuki N, Hobo S.In order to reveal the preventive effect of marbofloxacin (MRFX) administration just before transportation, we compared the occurrence of transportation-associated fever before and after introduction of MRFX administration. After the introduction of prophylactic MRFX administration, the rectal temperatures of horses after transportation were significantly lower than before the introduction of MRFX administration (P<0.01) and the number of febrile horses was significantly lower than before the introduction of MRFX administration (P<0.01). In conclusion, these results show that prophylacti...
Sarrafian TL, Garcia TC, Dienes EE, Murphy B, Stover SM, Galuppo LD.To develop a nonterminal large animal bone defect model for assessing the efficacy of regenerative and pharmacologic treatments designed to enhance bone healing. Methods: In vivo experimental. Methods: Adult gelding horses (n = 6). Methods: Under general anesthesia, using radiographic guidance, 13.5 mm diameter bilateral, full thickness mandibular defects were created in 6 horses using a custom surgical jig and coring bit. After 16 weeks, under general anesthesia, 23 mm diameter cores that encompassed the original healing defects and surrounding parent bone material were removed for evaluation...
Hood DM, Amoss MS, Grosenbaugh DA.Raynaud's phenomenon (RP) and equine laminitis in the horse are medical enigmas. Clinical and scientific data were compared to evaluate the degree of similarity that exists between these two peripheral vascular diseases. Data indicate that certain pathologic and pharmacologic aspects seem to have common features. Some of the correlations maybe due simply to both diseases having ischemia of the distal digits as a pathologic component. The exact etiology of the ischemia is not known for either disease. The results of this study suggest the hypothesis that RP and laminitis are the same disease in...
Freitas TV, Fortes-Dias CL, Diniz CR, Velarde DT, Freitas CF.1. A comparative study was carried out on horses immunized with Crotalus durissus terrificus venom using four different inoculation procedures, which included the use of Freund's adjuvant, A1(OH)3 and liposomes as adjuvants. The antibody titer was assessed by enzyme linked immunosorbent assay (ELISA) and the neutralizing potency by the neutralizing median effective dose (ED50). 2. The inoculation schedule used in horses to obtain antivenom serum consisted of sc injections of a 7.5 mg venom starting dose in 5.0 ml sterile saline emulsified with an equal volume of Freund's complete adjuvant. One...
Muir WW, Mason DE.The cardiorespiratory effects of thiamylal (10 mg/kg of body weight, IV) and the effects of preanesthetic medication with diazepam, acepromazine, detomidine, or xylazine administered prior to a thiamylal dosage of 6 mg/kg, IV, were evaluated in 6 adult horses. The quality of recovery from thiamylal anesthesia also was evaluated. Intravenous administration of thiamylal at a dosage of 10 mg/kg increased heart rate, systemic arterial, pulmonary artery, and central venous blood pressures, as well as cardiac output and arterial partial pressure of CO2 (PaCO2). The maximal rate of right ventricular ...
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)....
Black HE.Non-steroidal anti-inflammatory drugs represent the most heavily prescribed and used class of drugs in human medicine. Most are derivatives of either salicylates, propionic acid, indoleacetic acid, anthranilic acid, pyrazolone, or oxicams. They depress the synthesis of prostaglandins from arachidonic acid by reversible inhibition of the enzyme cyclooxygenase. In the kidney, prostaglandins PGE2 and PGI2 modulate the vasoconstrictor effects of angiotensin II, norepinephrine, and vasopressin. In the presence of volume contraction, anesthesia, or disease states associated with high levels of these...
Delesalle C, Deprez P, Schuurkes JA, Lefebvre RA.The use of human prokinetic drugs in colic horses leads to inconsistent results. This might be related to differences in gastrointestinal receptor populations. The motor effects of 5-hydroxytryptamine (5-HT; serotonin) on the equine mid-jejunum were therefore studied. Longitudinal muscle preparations were set up for isotonic measurement. 5-HT induced tonic contractions with superimposed phasic activity; these responses were not influenced by tetrodotoxin and atropine, suggesting a non-neurogenic, non-cholinergic pathway. The 5-HT receptor antagonists GR 127935 (5-HT(1B,D)), ketanserin (5-HT(2A...
Joyner RL, Liu CC, Cremer J, Carter RT, Lewin AC.Intravenous sedation is frequently necessary for ophthalmic examination in horses. Common sedation protocols have not been directly compared in terms of relative intraocular pressure (IOP) reduction, duration of IOP reduction and time to maximum IOP reduction. Objective: To compare the effects of standing sedation protocols on IOP. Methods: Randomised cross-over experiment. Methods: Twelve healthy horses received four intravenous sedation protocols with a 48 hours washout: 0.5 mg/kg xylazine and 0.01 mg/kg butorphanol (SED1); 10 µg/kg detomidine and 0.01 mg/kg of butorphanol (SED2); 10 ...
Clode A, Davis J, Davidson G, Salmon J, Lafevers H, Gilger B.To determine the transcorneal penetration and systemic absorption of a compounded 0.2% terbinafine solution following repeated topical administration to normal equine eyes. Sample population Six healthy adult horses with normal ocular examinations. Methods: One eye of each horse received 0.2 mL of a compounded 0.2% terbinafine solution every 4 h for seven doses. During the 1 h following administration of the final dose, multiple peripheral blood samples were obtained, and a single aqueous humor (AH) sample was collected at the end of the hour. AH and plasma concentrations of terbinafine wer...
Edlund O, Bowers L, Henion J, Covey TR.Urine samples were spiked with [17-methyl-2H3]methandrostenolone as internal standard and extracted with a mixture of dichloromethane and cyclohexane. The organic phase was concentrated and injected onto a short octyl-silica column (30 mm x 4.6 mm I.D.) for separation of methandrostenolone and 17-epimethandrostenolone. The effluent from the column was connected to a Sciex TAGA 6000E triple quadrupole mass spectrometer equipped with an atmospheric pressure ion source for sampling of ions generated by a heated pneumatic nebulizer with corona discharge ionization. This ion source produced abundan...
Lotz J, Içli S, Liu D, Caliskan S, Sieme H, Wolkers WF, Oldenhof H.Rational design of cryopreservation strategies for oocytes and ovarian cortex tissue requires insights in the rate at which cryoprotective agents (CPA) permeate and concomitant water transport takes place. The aim of the current study was to investigate possible differences in permeation kinetics of different CPAs (i.e., glycerol/GLY, ethylene glycol/EG, dimethyl sulfoxide/DMSO, and propylene glycol/PG), in equine oocytes as well as ovarian tissue. Membrane permeability of oocytes to water (Lp) and to CPAs (Ps) was inferred from video microscopic imaging of oocyte volume responses during perfu...
Okada CTC, Andrade VP, Freitas-Dell'Aqua CP, Nichi M, Fernandes CB, Papa FO, Alvarenga MA.Embryo mobility occurs as a result of prostaglandin production by the embryo and endometrium, promoting uterine smooth muscle contractions, which propels the embryonic vesicle through the lumen. Non-steroidal anti-inflammatory drugs (NSAIDs), as flunixin meglumine, are routinely used in equine medicine and can alter the conceptus mobility if applied in early pregnancy, which may impair maternal recognition of pregnancy. The objective of this study was to evaluate and compare the effect of flunixin meglumine (FM; 1.1 mg/kg IV), firocoxib (FIRO; 0.2 mg/kg PO), and meloxicam (ML; 0.6 mg/kg,...
Behrens C, Aurich JE, Klug E, Naumann H, Hoppen HO.Effects of the opioid antagonist naloxone on concentrations of LH and FSH in plasma were measured in mares during different stages of the oestrous cycle. During the follicular phase of the cycle, naloxone (300 mg i.v.) had no discernible effects on basal concentrations of LH and FSH. A significant increase in plasma LH (P < 0.01) and FSH (P < 0.05) concentrations was observed after naloxone in mares during the luteal phase. This response was not different between suckled and non-suckled mares. The gonadotrophin-releasing hormone analogue buserelin (0.02 mg i.v.) caused a significant (P < 0.05)...
Neuschaefer A, Bracher V, Allen WR.The effect of treating lactating mares with the dopamine agonist bromocriptine was investigated. Seven pony and 4 Thoroughbred lactating mares were given a single intramuscular (i.m.) injection of 100 mg bromocriptine between Days 18 and 28 after foaling when the secretion rate of prolactin was elevated. Prolactin and luteinizing hormone (LH) concentrations were measured in serial peripheral plasma samples taken before and after the treatment and, in 5 of the pony mares, levels of these hormones were also measured in pituitary venous effluent obtained by cannulation of the cavernous sinus. In ...
Stadler S, Dennler M, Hetzel U, Del Chicca F, Hoey S, Spiess BM, Voelter K, Pot SA.To compare the localization and distribution of two different anesthetic fluid volumes around equine cadaver eyes to determine an appropriate volume for a single sub-Tenon's injection in horses. Methods: A single sub-Tenon's injection of 2% lidocaine was performed in 10 equine cadaver heads (20 eyes) using two different volumes (7 mL on one side and 10 mL on the opposite side). The posterior circular distribution of the anesthetic was quantified in sagittal, dorsal, and transverse MRI (T2W-TSE) sequences and evaluated independently by three board-certified radiologists. The distribution of the...
Sasaki N, Mizuno Y, Yoshihara T.Electrogastrography (EGG), in which the electrical activity of the smooth muscular layer of the stomach is recorded percutaneously through the abdominal wall, has been applied in recent years to humans as a non-invasive method. In acute abdominal disease in horses, it is considered diagnostically useful to analyze digestive activity using EGG. Electrocecography (ECG) was examined to determine its effectiveness in evaluating equine digestive motility through comparison, after xylazine administration, between the results of the percutaneous ECG method and the results obtained using a strain-gaug...
Dória RG, Valadão CA, Duque JC, Farias A, Almeida RM, Netto AC.To evaluate the cardiorespiratory and behavioural effects of epidural xylazine (XYL) or clonidine (CLO) in horses. Methods: Blinded, randomized experimental study. Methods: Twelve healthy Arabian yearling horses weighing 117-204 kg were randomly allocated into two groups: XYL (n = 6) and CLO (n = 6). Methods: An epidural catheter was inserted and a facial arterial catheter was placed and the next day the horses were restrained in stocks. Baseline values for heart (HR) and respiratory (RR) rates, arterial pressure and behavioural responses were evaluated before (T0) and 10, 20, 30, 45, 60, 90 a...
Kamerling S, Wood T, DeQuick D, Weckman TJ, Tai C, Blake JW, Tobin T.Narcotic analgesics produce pharmacological effects by interacting with specific opiate receptors. At least five major types of opiate receptors have been recognised. These include mu (morphine) and kappa (ethylketazocine) receptor types. Narcotic analgesics which interact with mu receptors produce locomotor and autonomic stimulation at doses that produce little or no analgesia. Therefore, use of these drugs as analgesics in equine medicine has not been very satisfactory. Theoretical considerations suggested that the role of kappa agonists in equine analgesia be investigated. Using a pure kapp...
Lai SW, Lin JH, Lai SS, Wu YL.The characteristic ingredients of Ganoderma lucidum, such as polysaccharides, triterpenoids, nucleic acids and small proteins, have been found and proved to have many special pharmacological properties. Mice and rats have been extensively used to investigate the effects of G. lucidum. Experiments with horses as an animal model for investigating the effects of G. lucidum have never been reported. The purpose of this investigation was to understand the influence of G. lucidum feeding on blood biochemistry and immunocompetence in horses. Complete blood count (CBC) and blood biochemistry were surv...
Ensink JM, Bosch G, van Duijkeren E.Tissue chambers, implanted subcutaneously in the neck in six ponies, were inoculated with Streptococcus equi subsp. zooepidemicus in order to determine the clinical efficacy of prophylactic administration of trimethoprim/sulfadiazine (TMP/SDZ) against this infection. The TMP/SDZ treatment consisted of one intravenous (i.v.) injection of 5 mg/kg TMP and 25 mg/kg SDZ and the same dose of TMP/SDZ per os (p.o.), both given 3 h before inoculation. The oral dose was then repeated every 12 h for 5 days. TMP/SDZ concentrations in tissue chamber fluid (TCF) were above 10 times MIC at the moment of inoc...
Symonds KD, MacAllister CG, Erkert RS, Payton ME.To evaluate the musculoskeletal analgesic effect of etodolac administered PO every 12 or 24 hours in chronically lame horses by use of force plate analysis. Methods: 22 horses with navicular syndrome. Methods: Horses received etodolac (23 mg/kg, PO, q 12 h; n = 7), etodolac (23 mg/kg, PO, q 24 h; 8), or corn syrup (20 mL, PO, q 24 h; control treatment; 7) for 3 days. Combined forelimb peak vertical ground reaction force (PVF) was measured via force plate analysis before the first treatment (baseline) and at 6, 12, 24, and 36 hours after the last treatment. Differences in mean PVF (mPVF) betwee...
Mirbahar KB, McDonell WN, Bignell W, Eyre P.Pulmonary function tests were performed in seven conscious, standing horses. Changes in pulmonary mechanics and ventilation volumes were measured after inhalation challenge with saline (baseline), histamine (1% w/v solution for 5 min) and carbachol (0.5% w/v solution for 3 min). Comparisons between baseline and posthistamine values revealed a significant (P less than 0.05) increase in nonelastic work of breathing (Wb), maximum change in transpulmonary pressure (max delta Ppl), and pulmonary resistance (RL), while dynamic compliance (Cdyn) decreased (P less than 0.05). Tripelennamine completely...
Daniels SP, Proudman CJ.The ovicidal activity of benzimidazole (BZ) anthelmintics is unique and not seen in other drug classes. Such ovicidal efficacy is not widely reported for equine cyathostomins, nor has this activity been tested in the face of BZ resistance. Although the product label states that fenbendazole is for use against BZ-susceptible cyathostomins, susceptibility testing is rarely performed. In this field-based study, the ovicidal efficacy of fenbendazole in horses (n=39) harbouring BZ-resistant cyathostomins was compared when dosed at 7.5mg/kg body weight (BW) orally, as a single dose per os (n=21) or ...
Koivunen AL, Maisi P, Fang W, Sandholm M.To clarify the role of proteolytic enzymes in the pathogenesis of chronic obstructive pulmonary disease (COPD) in horses, and to investigate new possibilities for treatment of this disease by interfering in the proteolytic process. Methods: Effect of antiproteolytic activity of selected protease inhibitors on tracheal aspirates was studied in vitro, and the inhibition profiles were compared with those of purified proteases. Methods: Respiratory tract secretions with antiproteolytic activity from 9 horses with COPD. Methods: Caseinolytic agar-diffusion assay. Results: The protease-inhibition pr...
Yamanaka T, Tsujimura K, Kondo T, Hobo S, Matsumura T.We investigated the efficacy of the oral administration of oseltamivir phosphate (OP) in horses experimentally infected with equine influenza A virus (H3N8). Nine horses were divided into three horses each of control, treatment and prophylaxis groups. An administration protocol for the treatment group (2 mg/kg of body weight, twice a day for five days) was started immediately after the onset of pyrexia (above 38.9 degrees C). An administration protocol for the prophylaxis group (2 mg/kg of body weight, once a day for five days) was started on a day before viral inoculation. In the treatment gr...
