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.
Slocombe RF, Covelli G, Bayly WM.Normal Standardbred horses were given an incremental exercise test on a horizontal treadmill to evaluate the influence of exercise on gas exchange, resistance, dynamic compliance and inertance of the respiratory system. The exercise test consisted of 2 min exercise steps at each of the following speeds: 2.4 m/sec (walk), 4.5 m/sec (slow trot), 7.0 m/sec (fast trot) and 10 m/sec (gallop). At rest and after 1 min of exercise at each step, airflow, tidal volume, respiratory frequency, pharyngeal, mid-oesophageal and transdiaphragmatic pressures and arterial blood gas tensions were measured. The s...
MacAllister CG, Sangiah S, Mauromoustakos A.Using video gastroscopy, the efficacy of a Histamine-H2 type receptor antagonist (WY 45, 727) was investigated in young ponies with spontaneous and experimentally induced gastric ulcers. Oral administration of WY 45, 727 at 2 mg/kg and 10 mg/kg of body weight every 12 hours for 14 days resulted in complete healing of spontaneous gastric ulcers in the non-glandular portion of the stomach in 2/5 (40%) and 3/4 (75%) of the ponies, respectively, compared (P < 0.05) to 0/5 (0%) placebo-treated ponies. After intramuscular administration of flunixin meglumine at 1.5 mg/kg body weight every 8 hours fo...
Lester GD, Bolton JR, Cullen LK, Thurgate SM.Myoelectric activity was monitored from the terminal ileum, cecum, and colonic pelvic flexure by use of AgpAgCl bipolar electrodes in 4 adult horses before, during, and after general anesthesia. Horses were anesthetized by way of 3 commonly used regimens, including xylazine (1.1 mg/kg of body weight) and ketamine hydrochloride (2.2 mg/kg); thiopental sodium (7.7 mg/kg), followed by halothane vaporized in oxygen; and thiopental sodium (2.5 g) in guaifenesin (100 mg/ml) solution given to effect, followed by halothane in oxygen. All 3 anesthetic regimens decreased intestinal spike-burst activity ...
Matthews NS, Miller SM, Hartsfield SM, Slater MR.Recovery from isoflurane anesthesia was shorter, with no difference in quality, compared with halothane anesthesia in 2 groups of horses. In 1 group, 12 horses scheduled for elective arthroscopy were randomly assigned to receive halothane or isoflurane for maintenance of anesthesia during surgery. In the other group, 6 horses received anesthesia only, on 2 occasions, with halothane on 1 occasion, and isoflurane on the other. Difference in the quality of recovery was not seen between isoflurane and halothane anesthesia in either group. In the group that had surgery, recovery to sternal position...
Uboh CE, Soma LR, Rudy JA, Morgan E, Mengeringhausen K, Sams R.This study was undertaken to determine the applicability of plasma concentration of furosemide and specific gravity (SG) of urine in regulating the use of furosemide administered 4 hours prior to race time in Exercise-Induced Pulmonary Hemorrhage (EIPH) race horses. Nonbleeders (CTL) and certified bleeders (FUR) actively racing in Illinois (IL) and Pennsylvania (PA) were used in the study. Various doses (less than 250, 250, 300, 350, 400 and 500 mg) were administered either as a single intravenous (IV) dose or as a combination (IV-IM) of IV and intramuscular (IM) administrations 4 hours before...
Ball BA, Wilker C, Daels PF, Burns PJ.Administration of progesterone in poly(d-,l-lactide) microspheres was used to maintain pregnancy in mares after luteolysis was induced by treatment with prostaglandin F2 alpha at day 14 of pregnancy. Mares were given vehicle only (control, n = 6) or 0.75 g (n = 7), 1.5 g (n = 8), or 2.25 g (n = 5) of microencapsulated progesterone at days 12 and 22 of pregnancy. Serum progesterone concentrations were determined daily, and pregnancy was evaluated by transrectal ultrasonography on alternate days. Significantly (P less than 0.05) more mares given 1.5 or 2.25 g of progesterone (6 of 8 and 4 of 5 m...
Muir WW.Mechanisms responsible for the positive inotropic effects of dopexamine were investigated in 8 halothane-anesthetized horses. The hemodynamic effects of increasing infusions of dopexamine (5, 10, 15 micrograms/kg of body weight/min) were determined before and after sequential administration of specific antagonists. Using glycopyrrolate and chlorisondamine, and atenolol and ICI 118,551, muscarinic and nicotinic ganglionic, and beta 1, and beta 2-adrenergic receptor blockade, respectively, was induced. Dopexamine infusions induced increase in heart rate, cardiac output, systolic and mean arteria...
Shoemaker RS, Bertone AL, Martin GS, McIlwraith CW, Roberts ED, Pechman R, Kearney MT.The effects of intra-articular administration of methylprednisolone acetate (MPA) on the healing of full-thickness osteochondral defects and on normal cartilage were evaluated in 8 horses. In group-1 horses (n = 4), a 1-cm-diameter, full-thickness defect was created bilaterally in the articular cartilage on the dorsal distal surface of the radial carpal bone. Cartilage defects were not created in group-2 horses (n = 4). One middle carpal joint was randomly selected in each horse (groups 1 and 2), and treated with an intra-articular injection of 100 mg of MPA, once a week for 4 treatments. Inje...
Beech J, Fletcher JE, Tripolitis L, Lindborgh S.The effects of phenytoin treatment were evaluated in 2 myotonic horses with hyperkalemic periodic paralysis (HPP). Phenytoin treatment abolished the clinical signs of muscle fasciculations following oral potassium challenge and decreased or abolished repetitive firing and myotonic discharges found on electromyographic examination. In both horses, an abnormally low threshold for calcium-induced calcium release was measured in heavy sarcoplasmic reticulum fractions from skeletal muscle, and this threshold increased with phenytoin treatment. Results suggest phenytoin is useful in modifying disord...
Zaugg JL, Lane VM.We evaluated the efficacy of buparvaquone in eliminating infection with Babesia equi of European origin in carrier horses and in splenectomized horses with experimentally induced acute infection. When administered at the rate of 5 mg/kg of body weight, IV, 4 times at 48-hour intervals, buparvaquone prompted rapid abatement of parasitemia. However, secondary and tertiary recrudescent parasitemias invariably returned with establishment of the carrier state. Buparvaquone, at the dosage evaluated, had transitory therapeutic efficacy against acute B equi infection in splenectomized horses, but was ...
Freeman DE, Ferrante PL, Palmer JE.A Latin square design was used to compare the effects of laxatives and a corresponding volume of water on gastrointestinal tract function in 4 healthy horses. Horses were intragastrically infused with each of the following: dioctyl sodium sulfosuccinate (DSS; 50 mg/kg of body weight); magnesium sulfate (0.5 g/kg--low dosage); magnesium sulfate (1.0 g/kg--high dosage); and an equal volume of water (6 L) given as a control infusion. From 5 to 33 hours after the high dosage of magnesium sulfate, feces were slightly softer than usual in all horses. In 1 horse, DSS caused mild colic, hyperpnea, and...
Luna SP, Massone F, Castro GB, Fantoni DT, Hussni CA, Aguiar AJ.A combination of 0.5 mg/kg of methotrimeprazine, 0.1 mg/kg of midazolam and 100 mg/kg of a 10 per cent guaiphenesin solution was investigated for the induction of recumbency in 15 horses; the addition of 1.6 mg/kg of ketamine was also evaluated in 15 horses and anaesthesia was maintained with halothane in oxygen. The horses became recumbent quickly and smoothly and they recovered quietly, with little ataxia. Tachycardia occurred after induction, but no other changes from pre-operative values were observed until halothane in oxygen had been given, when hypothermia, hypotension, bradypnoea, hype...
Staempfli HR, Prescott JF, Carman RJ, McCutcheon LJ.Ten healthy ponies from a single herd were found by repeated fecal culture to be free of Salmonella species and Clostridium cadaveris. In a preliminary study, four ponies administered a single oral dose of 10 mg/kg lincomycin did not develop idiopathic colitis when the drug was administered alone. Four other ponies were administered 10 mg/kg lincomycin by stomach tube together with 0.45 L of colonic content from a horse with idiopathic colitis induced earlier by lincomycin alone. Two of the four ponies were treated with 25 g oral zinc bacitracin premix (110 g/kg active ingredient) 24 h later. ...
Folz SD, Hanson BJ, Griffin AK, Dinvald LL, Swerczek TW, Walker RD, Foreman JH.Ceftiofur sodium was evaluated as a therapy for respiratory infections in horses. This cephalosporin antimicrobial was administered intramuscularly every 24 h and at a dose of 2.2 mg/kg (1.0 mg/lb) of body weight. The efficacy of ceftiofur sodium was compared with that of a positive control drug, ampicillin sodium (recommended dose of 6.6 mg/kg [3 mg/lb], given every 12 h). Both treatments were continued for 48 h after clinical symptoms were no longer evident (maximum of 10 days). Fifty-five (55) horses with naturally acquired respiratory infections were included in the study; 28 were treated ...
Gustafson SB, Trotter GW, Norrdin RW, Wrigley RH, Lamar C.Three doses of sodium monoiodoacetate (MIA) were used to induce degenerative changes in articular cartilage in middle carpal joints of horses. Twelve young (2- to 5-year-old) horses, free of lameness, were randomly allotted to 3 groups. One middle carpal joint of each horse was injected with 0.9% NaCl solution (control joint). The contralateral middle carpal joint was injected with 0.09 mg of MIA/kg of body weight (group 1); 0.12 mg/kg (group 2); or 0.16 mg/kg (group 3). After MIA administration, horses were allowed ad libitum exercise in a 2-acre paddock for 12 weeks. At the end of the study,...
Uhlinger C, Kristula M.Anthelmintic schedules that alternate between drug classes are widely used in horses. However, the results of investigations in which ovine nematode parasites were used have established that alternation of drug classes does not delay the development of drug resistance. This field study was designed to assess the effect of alternation of drug classes on the development of oxibendazole (OBZ) resistance in benzimidazole (BZD)-resistant equine small strongyles. A privately owned herd of horses was used for this study. These animals grazed the same pasture and had been treated with the same anthelm...
Wan PY, Trim CM, Mueller PO.Eight horses were anesthetized three times, by intravenous administration of xylazine (1.1 mg/kg) and ketamine (2.2 mg/kg), detomidine (0.02 mg/kg) and tiletamine-zolazepam (1.1 mg/kg), or detomidine (0.04 mg/kg) and tiletamine-zolazepam (1.4 mg/kg). The sequences were randomized. The duration of analgesia and the times to sternal and standing positions were recorded. Heart rate, arterial pressure, pHa, PaCO2, and PaO2 were measured before and during anesthesia. The duration of analgesia with the two doses of detomidine-tiletamine-zolazepam, 26 +/- 4 minutes and 39 +/- 11 minutes, respectively...
Whitehair KJ, Adams SB, Parker JE, Blevins WE, Fessler JF.Antibiotics were delivered to chronically infected tissues by regional limb perfusion in three horses with osteomyelitis associated with orthopedic implants. Two infections were resolved with implants in place; in one, a sequestrum was resorbed. In one horse, regional antibiotic perfusion was applied to treat progressively worsening bone infection after initial implants loosened and were removed.
Chapman CB, Courage P, Nielsen IL, Sitaram BR, Huntington PJ.Procaine penicillin is a commonly used antibiotic in equine medicine but its use is associated with a substantial incidence of adverse reactions. Soluble procaine concentrations were determined by HPLC in several commercially available procaine penicillin preparations, including some that were involved in adverse reactions. The mean (+/- SEM) soluble procaine concentrations in the veterinary preparations was 20.18 +/- 5.07 mg/ml, which was higher than the concentration in the only procaine penicillin preparation for use in humans in Australia of 7.3 mg/ml. Heating the veterinary procaine penic...
Burrows GE, MacAllister CG, Ewing P, Stair E, Tripp PW.The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The...
England GC, Clarke KW, Goossens L.The sedative effects of a new alpha 2-adrenoceptor agonist, romifidine, were compared with those of xylazine and detomidine. Five horses were treated with two doses of romifidine (40 micrograms/kg body weight and 80 micrograms/kg body weight), two doses of detomidine (10 micrograms/kg body weight and 20 micrograms/kg body weight) and one dose of xylazine (1 mg/kg body weight) given by intravenous injection using a Latin-square design. The dose of 80 micrograms/kg romifidine appeared equipotent to 1 mg/kg xylazine and 20 micrograms/kg detomidine, although at these doses both xylazine and detomi...
Lavoie JP, Pascoe JR, Kurpershoek CJ.The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P less than 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute a...
Clarke LL, Roberts MC, Grubb BR, Argenzio RA.In ponies fed concentrated (pelleted) meals, postprandial increases of plasma aldosterone have been temporally associated with a decrease in colonic fluid volume that parallels the conclusion of postfeeding fermentation. To determine the significance of short-term increases of plasma aldosterone on the rate of colonic Na absorption, in vitro transport studies were conducted on the mucosae of three morphologically distinct colonic segments (i.e., ventral, dorsal, and small colons) from ponies infused with a high physiological concentration of aldosterone for an 8-h period. In control ponies, ba...
Hoffman AM, Viel L, Muckle CA, Yager JS, Staempfli HR.Efficacy of sulbactam, a beta-lactamase inhibitor, in combination with ampicillin, was evaluated for treatment of experimentally induced pneumonia caused by beta-lactam-resistant Klebsiella pneumoniae. Infection was experimentally induced in 18 healthy weanling foals that were randomly allocated to 3 treatment groups: sulbactam plus ampicillin (S/A, 3.3 and 6.6 mg/kg of body weight, respectively), ampicillin (6.6 mg/kg), or vehicle only. Foals were treated daily for 7 days; the observer was unaware of treatment status. Compared with ampicillin and vehicle, treatment with S/A resulted in a stat...
Daniel GB, Tucker RL, Buckman T, Daniel SL.Isolated equine granulocytes (WBC), radiolabeled with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) or 111In-oxine, were evaluated in vitro for their labeling characteristics, viability, and phagocytic function over a 6-hour postlabeling period. Mean +/- SD labeling efficiency for 111In-oxine-WBC was 62.2 +/- 15.3%, which was significantly (P less than 0.001) higher than that for 99mTc-HMPAO-WBC (32.0 +/- 17.0%). In vitro elution of radiolabel from cells was significantly (P less than 0.02) greater for 99mTc-HMPAO-WBC at 0.5, 2, and 4 hours, but was not significantly different from elutio...
Hall LW, Young SS.Total respiratory resistance was measured rapidly and non-invasively in 6 conscious ponies before and after they inhaled approximately 25% of the minimal anaesthetic concentration (0.25 MAC) of either enflurane, halothane, or isoflurane, over a 10 min period. The forced random noise (FRN) method was used to measure the impedance over the frequency range of 5 to 40 Hz and its real part, the resistance, was extracted from these impedance measurements. At the concentrations used, halothane appeared to have no effect on the total respiratory resistance; enflurane and isoflurane seemed to increase ...
Hillyer MH, Mair TS.Equine multisystemic eosinophilic epitheliotropic disease is rare in horses. The clinical signs vary according to the organs affected, the skin and gastrointestinal tract being most commonly involved. This paper gives the first reported description of a horse with multisystemic eosinophilic epitheliotropic disease in the United Kingdom and the attempts to treat it. The horse showed dermatological, gastrointestinal, hepatic, pulmonary and pancreatic involvement. Some improvement was seen when the horse was treated with corticosteroid and hydroxyurea.
Eysker M, Boersema JH, Kooyman FN.A controlled and critical test on the efficacy of ivermectin against larval and adult stages of the cyathostomes was carried out in six yearling castrated male Shetland ponies. The ponies grazed together as one group from 3 May to 4 October 1990, after which they were housed. Three ponies were treated with ivermectin on 29 October while the others served as controls. The shedding of helminths in the faeces was followed in all ponies until necropsy on 14 November. Comparison of worm counts of both groups before and after necropsy showed no evidence for an effect of ivermectin against inhibited ...
Olsen SC, Coyne CP, Lowe BS, Pelletier N, Raub EM, Erickson HH.Four hours prior to exercise on a high-speed treadmill, 4 dosages of furosemide (0.25, 0.50, 1.0, and 2.0 mg/kg of body weight) and a control treatment (10 ml of 0.9% NaCl) were administered IV to 6 horses. Carotid arterial pressure (CAP), pulmonary arterial pressure (PAP), and heart rate were not different in resting horses before and 4 hours after furosemide administration. Furosemide at dosage of 2 mg/kg reduced resting right atrial pressure (RAP) 4 hours after furosemide injection. During exercise, increases in treadmill speed were associated with increases in RAP, CAP, PAP, and heart rate...
Coyne CP, Smith JE, DeBowes RM.Several pharmaceutical compounds were evaluated for their ability to selectively inhibit activated coagulation factor-XIII-like enzyme activity (eg, XIIIa*) in pooled equine plasma. Presence of coagulation factor-XIIIa*-like enzyme activity in plasma was established by assay procedures involving incorporation of the fluorescent amine compound, monodansylcadaverine, into purified casein, which served as a protein substrate. Pharmaceuticals inhibitory to coagulation factor-XIIIa*-like enzyme activity were recognized by plasma gel formation of high spectrophotometric transmittance (transparency),...
Lepage OM, Laverty S, Marcoux M, Dumas G.The effect of triamcinolone acetonide (0.09 mg/kg of body weight, IM) on serum osteocalcin concentration was studied. Two groups of horses were investigated and included clinically normal horses (group 1, n = 5) and horses with chronic obstructive pulmonary disease (group 2, n = 5). Before treatment, results of a t-test did not reveal any significant difference in serum osteocalcin concentration between the 2 groups. After treatment, a significant (P < 0.05) decrease in serum osteocalcin concentration was observed for both groups. Osteocalcin concentration in individual horses reached a min...
McKeever KH, Hinchcliff KW, Gerken DF, Sams RA.Four mature horses were used to test the effects of two doses (50 and 200 mg) of intravenously administered cocaine on hemodynamics and selected indexes of performance [maximal heart rate (HRmax), treadmill velocity at HRmax, treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l, maximal mixed venous blood lactate concentration, maximal treadmill work intensity, and test duration] measured during an incremental treadmill test. Both doses of cocaine increased HRmax approximately 7% (P < 0.05). Mean arterial pressure was 30 mmHg greater (P < 0.05) during the 4- to ...
Carter GK, Martens RJ, Brown SA, Martin MT.Pharmacokinetic values of sodium amoxicillin (22 mg/kg of body weight) in foals were determined after a single IM injection in 6 Quarter Horse foals at 3, 10, and 30 days of age. Serum amoxicillin concentrations were measured serially over a 24-hour period. The absorption of amoxicillin was rapid and followed a 1st-order elimination. Mean peak serum concentrations occurred 30 minutes after the injection in foals at all ages and were 17.31 +/- 9.59 micrograms/ml when the foals were 3 days old, 23.28 +/- 9.86 micrograms/ml when the foals were 10 days old, and 21.35 +/- 6.39 micrograms/ml when th...
Bijman J, Quinton PM.The effects of Ca2+, the cyclic nucleotides adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP), and other parameters of sweat secretion from single equine sweat glands were examined in vitro. Extracellular Ca2+, the Ca2+ ionophore A23187, and the Ca2+ channel antagonist verapamil were all without effect on sweat secretion. Prolonged rinsing of the glands in Ca2+-free Ringer solution with 5 mM ethylenediaminetetraacetic acid decreased the secretion to 30% of the control sweat rate in response to the beta-adrenergic agonist isoproterenol; the sweat respon...
Sojka JE, Johnson MA, Bottoms GD.This study was conducted to investigate the effect of starting time on dexamethasone suppression test results in horses. Eight adult horses were used throughout the trial. Baseline cortisol levels were established by collecting cortisol levels twice daily, at 8:00 A.M. and 8:00 P.M. for 4 consecutive days. Morning baseline cortisol levels were 46.3 +/- 5.94 ng/ml, and evening baseline cortisol levels were 32.8 +/- 5.59 ng/ml. Although lower, the evening cortisol levels were not statistically different (P = 0.154) from the morning levels. Dexamethasone suppression tests initiated at either 9:00...
Segabinazzi LGTM, Landers M, Kent A, Peterson E, Gilbert R, French H.Due to the limited literature available evaluating doses of Prostaglandin F2α in donkeys, doses for horses have been extrapolated and used as guidelines. This study aimed to assess the efficacy and side effects of four different cloprostenol sodium and dinoprost tromethamine doses to induce luteolysis in jennies. Sixty-three cycles of seven Jennies (nine cycles per jenny) were used in this study. Seven days after ovulation, jennies randomly received one of the treatments in a crossover design as follows: Control, no treatment was administered; C1, 250 µg of cloprostenol sodium (CS, Estrumate...
Gasthuys F, De Moor A, Parmentier D.The effects of calcium chloride administered at low infusion rates on the cardiovascular depression and the blood calcium balance were studied during a constant halothane anaesthesia in dorsally recumbent ventilated ponies. A pronounced cardiopulmonary depression characterized by decreases of all cardiac parameters and lowering of the mean arterial blood pressure was observed after the initial anaesthetic stabilization period of 30 minutes in the ponies. A significant decrease in the total calcium plasma concentration together with a constant ionized and complexed calcium fraction was present ...
Bianco AW, Moore GE, Cooper BR, Taylor SD.Flunixin meglumine (FM) is a commonly used Nonsteroidal anti-inflammatory drug (NSAID) in horses, but clinical efficacy is often unsatisfactory. Ketorolac tromethamine (KT) demonstrates superior efficacy compared to other NSAIDs in humans, but its anti-inflammatory effects have not been investigated in the horse. Safety of repeated dosing of KT has not been evaluated. The first objective was to conduct a dose determination study to verify that a previously described dosage of KT would inhibit Lipopolysaccharide (LPS)-induced eicosanoid production in vitro, and to compare KT effects of this inh...
Ansari Mood M, Rajaei SM, Faghihi H, Ghiadi A.This study was performed to evaluate the effect of topical 1% cyclopentolate hydrochloride on tear production (STT), intraocular pressure (IOP), and vertical pupil diameter (VPD) in healthy Turkman horses. Forty eyes of 20 clinically normal horses were used for this study, which were randomly assigned to two groups. Before instillation of 1% cyclopentolate, the baseline STT, IOP, and VPD of each group were recorded. Then, one drop of cyclopentolate was instilled randomly into one eye of each animal, and the contralateral eye served as control. Measurements were repeated at 20 minutes, 60 min...
Roberts CJ.Manual crushing of one blastocyst performed on 181 bicornuate twin pregnancies between Days 24 and 45 has shown that the uncrushed blastocyst can either survive and develop normally to full term or may be rejected and resorbed like its crushed twin, depending mainly on the stage of pregnancy. Crushing, which causes rupture of fetal membranes, results in a rapid fall in the survival rate of the uncrushed blastocyst when performed after Day 31. In some mares rupture is not possible after Day 35 even if extreme pressure is used. Crushed, but unruptured, blastocysts mainly between Days 35 and 45 m...
Bliss G.The Department of Pharmacology at the North Carolina State University College of Veterinary Medicine is currently conducting stability studies of oral suspensions of pergolide for the treatment of Cushing's disease. While those results are not available at this time, this paper summarizes the results of a literature search on possible clinical treatments for equine Cushing's and is intended to provide insight into the pathophysiology of the disease. Pharmacological options for treatment of equine Cushing's are discussed.
Aramaki S, Suzuki E, Ishidaka O, Momose A.The effects of exercise on the metabolism of caffeine (CA) were studied 3h after administration of the drug to race horses which then underwent exercise sets (1000-m gallop). Analysis was made of pharmacokinetics of CA, changes in its plasma concentrations, its metabolites, i.e., theophylline (TP), theobromine (TB) and paraxanthine (PX), and the molar concentration ratios of CA to these metabolites. After exercise, AUC and t1/2 tended to decrease, and the concentration of CA decreased, while the concentrations of TP and TB significantly increased. The TP/CA ratio and TB/CA ratio significantly ...
Kettner NU, Parker JE, Watrous BJ.A 2-week-old Morgan filly examined because of lameness of 5 days' duration was found, on the basis of clinical and radiographic findings, to have septic physitis of the distal end of the radius. The foal was treated by means of intraosseous regional perfusion with penicillin and amikacin and systemic administration of antimicrobials. Intraosseous regional perfusion was performed 3 times. The foal was anesthetized for the first episode of intraosseous regional perfusion, but was only sedated for the subsequent 2 episodes. Antimicrobials were administered systemically for 22 days. Foals with sep...
Sandbaumhüter FA, Gittel C, Larenza-Menzies MP, Theurillat R, Thormann W, Braun C.The enantioselectivity of the pharmacokinetics of methadone was investigated in anesthetized Shetland ponies after a single intravenous (0.5 mg/kg methadone hydrochloride; n = 6) or constant rate infusion (0.25 mg/kg bolus followed by 0.25 mg/kg/h methadone hydrochloride; n = 3) administration of racemic methadone. Plasma concentrations of l-methadone and d-methadone and their major metabolites, l- and d-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), respectively, were analyzed by CE with highly sulfated γ-cyclodextrin as chiral selector and electrokinetic analyte injection from...
Credille BC, Giguère S, Berghaus LJ, Burton AJ, Sturgill TL, Grover GS, Donecker JM, Brown SA.The objectives of this study were to determine the plasma and pulmonary disposition of ceftiofur crystalline free acid (CCFA) in weanling foals and to compare the plasma pharmacokinetic profile of weanling foals to that of adult horses. A single dose of CCFA was administered intramuscularly to six weanling foals and six adult horses at a dose of 6.6 mg/kg of body weight. Concentrations of desfuroylceftiofur acetamide (DCA) were determined in the plasma of all animals, and in pulmonary epithelial lining fluid (PELF) and bronchoalveolar lavage (BAL) cells of foals. After intramuscular (IM) admin...
de Haas GH, Dijkman R, Lugtigheid RB, Dekker N, Van den Berg L, Egmond MR, Verheij HM.The inhibitory power (Z) of a number of (R)-1-alkyl-2-acylamino phospholipid analogues was determined for three mammalian phospholipases A2 from pig, ox and horse pancreas. All three enzymes display a clear preference for anionic (phosphoglycol) inhibitors over the zwitterionic (phosphocholine) derivatives; this effect is most pronounced for the bovine enzyme. Upon variation of the 1-alkyl chain length, the bovine and equine phospholipases, like the porcine enzyme in previous studies, show an optimum in Z for a six-carbon alkyl group. The introduction of a double bond in the 2-acylamino group ...
Schauvliege S, Van den Eede A, Duchateau L, Pille F, Vlaminck L, Gasthuys F.To compare cardiac output () measurements using lithium dilution (LiDCO) and pulse contour analysis (PulseCO) techniques in isoflurane-anaesthetized ponies before and during the administration of different inotropic/vasoactive drugs. Methods: Prospective randomized experimental cross-over trial. Methods: Six ponies aged 5.0 +/- 1.6 (4-6.5) years and weighing 286 +/- 53 (212-368) kg. Methods: After sedation (romifidine) and induction (midazolam + ketamine), anaesthesia was maintained with isoflurane in oxygen. After 90 minutes (= T0), one of four treatments was administered: saline 0.1 mL kg(-1...
Douglas HF, Southwood LL, Meyer-Ficca ML, Hart SK, Meyer RG.To evaluate the poly (ADP-ribose) polymerase-1 (PARP1) enzyme and its inhibition in horses and explore its potential as a novel therapeutic target for equine intestinal ischemia-reperfusion injury by (1) identifying poly (ADP-ribose) (PAR) as an indication of PARP1 activation in equine cells using available immunoblot analytical techniques, (2) inducing PARP1 activation in an in vitro oxidative DNA damage model, (3) and demonstrating the inhibition of PARP1 in equine cells using commercially available PARP1 inhibitors. Methods: Experimental study. Methods: Blood samples were collected from sys...
Traub-Dargatz JL, Schlipf JW, Boon J, Ogilvie GK, Bennett DG, Wingfield WE, Hutchison JM.Ventricular tachycardia develops less frequently than supraventricular dysrhythmias and generally is more indicative of cardiac disease. The horse in this report had clinical signs of lethargy and hypophagia and was determined to have sustained ventricular tachycardia. Echocardiography was a valuable diagnostic tool and revealed an echodense area in the left ventricle that had subnormal ventricular performance. A primary heart problem of an inflammatory nature was suspected. The horse responded favorably to treatment with lidocaine, antimicrobials, and aspirin, as well as stall rest. The horse...
Gong L, Shi F, Su S, Xie Q, Xian R, Hang B, Zhao Y.In recent years, due to the shortage of donkey skin resources, the price of Asini Corii Colla has seen a rapid increase. Consequently, fake gelatin prepared from horse, mules, pig, and cow skin has appeared in the market, resulting in unreliable quality of Asini Corii Colla. Therefore, there is an urgent need to develop an efficient and accurate method for improving the quality of Asini Corii Colla. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used to determine the donkey skin components in Asini Corii Colla. Accordingly, 0. l g of the evenly mixed sa...
Beech J, Lindborg S.Horses with hyperkalaemic periodic paralysis were challenged with an oral dose of potassium chloride, and the prophylactic efficacy of phenytoin, acetazolamide and hydrochlorothiazide was evaluated, with at least three weeks separating the trials of each drug. After the administration of potassium chloride without prophylactic medication the horses' clinical signs ranged from generalised fine muscle fasciculations to gross tremors, and weakness with occassional prolapse of the nictitating membrane; plasma potassium concentration increased significantly (P < 0.01) from 4.0 +/- 0.2 to 6.0 +/-...
Fernandes I, Lima EX, Takehara HA, Moura-da-Silva AM, Tanjoni I, Gutiérrez JM.Horse IgG isotypes and cross-neutralization of two snake antivenoms produced in Brazil and Costa Rica. Toxicon 000-000. This work compared the specificity, ELISA titers and IgG subclass content of the polyvalent antivenom (anti-Bothrops asper, Crotalus durissus durissus and Lachesis muta stenophrys) of Instituto Clodomiro Picado (Costa Rica) and the bothropic antivenom (anti-Bothrops jararaca, B. jararacussu, B. moojeni, B. neuwiedi and B. alternatus) of Instituto Butantan (Brazil). The role of IgG(T) and IgGa subclasses in neutralization of some venom toxic activities and the cross neutraliza...
Snow DH, Summers RJ, Guy PS.The effects of two beta-adrenoceptor antagonists, propranolol (0.2 mg/kg) and metoprolol (0.2 mg/kg) on some physiological and metabolic changes produced by maximal exercise in the horse were investigated. Both drugs reduced the elevation in heart rate seen immediately following exercise and reduced performance as was seen by the increased time taken to perform each gallop. The rise in plasma glucose, glycerol and lactate, and the fall in blood pH seen following exercise were attenuated by both drugs. However, a greater increase in plasma free fatty acids occurred. Exercise produced a nine- to...
Gonzalez GA, Betbeze C, Wills R, Eddy A, Mochal-King C, Fontenot RL.To evaluate corneal sensitivity and adverse events following subconjunctival administration of three local anesthetics in horses. Methods: Randomized, masked, crossover study. Methods: Twelve healthy adult mares. Methods: The subconjunctival space of the treated eye was injected with 0.2 mL of liposomal bupivacaine (1.3%), ropivacaine (0.5%), or mepivacaine (2%). All horses received each medication once and the contralateral eye received saline (control). Corneal touch threshold (CTT) was measured using a Cochet-Bonnet esthesiometer before sedation, after sedation, and at specified intervals...
van der Woerdt A, Gilger BC, Wilkie DA, Strauch SM, Orczeck SM.To determine normal variation in, and effect of 2% pilocarpine hydrochloride on, intraocular pressure (IOP) and pupil size in female horses during a specified period. Methods: 10 female horses with normotensive eyes. Methods: IOP and horizontal and vertical pupil size were measured on a single day between 8 AM and 8 PM at hours 0, 0.5, 1, 2, 4, 6, 8, 10, and 12. Measurements were repeated after single- dose application of 2% pilocarpine to both eyes. IOP and pupil size were measured at 8 AM and noon in a 5-day experiment of twice-daily application of 2% pilocarpine. Results: Variation in IOP a...
Tessier GJ, Lackner PA, O'Grady SM, Kannan MS.The role of epithelium in the modulation of contractile responses to electrical field stimulation (EFS), acetylcholine (ACh), and KCl were studied in vitro in strips of equine tracheal smooth muscle (TSM). EFS with 0.5 ms pulses of voltage (70 V) resulted in frequency dependent contractions of equine TSM that were sensitive to tetrodotoxin (TTX) and atropine. In TSM without epithelium, preincubation with indomethacin significantly potentiated contractile responses to EFS. The potentiating effect of indomethacin on EFS contractions was abolished by the addition of 3 nM prostaglandin E2 (PGE2). ...
Clark-Price SC, Lascola KM, Auckburally A, Boone LH, Caldwell FJ, Weatherall KM, Hanson RR.Impairment of oxygen uptake can occur during general anesthesia in horses resulting in hypoxemia. Multiple treatments have been investigated for correction of hypoxemia with varying levels of success. In clinical trials, albuterol, a short-acting β2 adrenergic agonist, improved arterial oxygen partial pressure (PaO2) in anesthetized horses unresponsive to adjustments in mechanical ventilation and administration of positive inotropic drugs. However, controlled studies comparing the magnitude of change and duration of effect of albuterol on PaO2 in healthy, nonhypoxemic anesthetized horses are ...
Rakhit S, Murdoch R, Wilson SM.Adrenaline, forskolin and ATP all evoked accumulation of cyclic AMP in equine sweat gland epithelial cells, although the response to adrenaline was more transient than that to forskolin and ATP. Cells preincubated in adrenaline (10 micromol l-1, 32 min) showed essentially complete, homologous desensitisation, and this phenomenon reversed slowly (half-time 6.3+/-0.9 h). After 10 min of recovery from preincubation in adrenaline, isobutylmethylxanthine (IBMX, 5 mmol l-1) had no effect upon the desensitisation and the cells showed no loss of sensitivity to ATP and forskolin. After 10 h, however, t...
MacAllister CG, Sangiah S, Mauromoustakos A.Using video gastroscopy, the efficacy of a Histamine-H2 type receptor antagonist (WY 45, 727) was investigated in young ponies with spontaneous and experimentally induced gastric ulcers. Oral administration of WY 45, 727 at 2 mg/kg and 10 mg/kg of body weight every 12 hours for 14 days resulted in complete healing of spontaneous gastric ulcers in the non-glandular portion of the stomach in 2/5 (40%) and 3/4 (75%) of the ponies, respectively, compared (P < 0.05) to 0/5 (0%) placebo-treated ponies. After intramuscular administration of flunixin meglumine at 1.5 mg/kg body weight every 8 hours fo...
Engelking LR, Dodman NH, Hartman G, Valdez H.The acute 2-hour effects of isoflurane anesthesia on liver function and biliary excretion were examined in 2 ponies prepared surgically with chronic external biliary fistulas (T-tubes). Studies were conducted 2 to 8 months postoperatively with the enterohepatic circulation held intact between studies. Bile acid infusion IV (8.1 to 8.8 mumol/min) helped maintain bile flow and bile acid and bilirubin excretion during complete biliary diversion throughout each study. Following 3-hour control periods, anesthesia was induced and maintained at 1.3 to 1.5 minimal alveolar concentration plus O2 (spont...
