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.
Turner GA, Taylor DM.The interactions between tetravalent plutonium and horse serum proteins were studied in vitro by electrophoresis on cellulose acetate and by gel filtration. The results show that in horse serum, as in other mammalian sera, the plutonium is associated principally with the transferrin component of the beta1-globulins. The formation of the plutonium-transferrin complex requires the presence of HCO3-, and plutonium is displaced from the complex by excess iron, thus indicating that similar binding sites may be involved in the complexing of iron and plutonium. The plutonium complex is considered to ...
Babel I, Stella RC, Prado ES.Previous experiments indicated that horse urinary kallikrein (UK) hydrolyzes salminei- e and polyarginine, a but not polylysine. This paper reports the action of UK on bradykinyl-serine, methionyllysyl-bradykinin and lysyllysyl-bradykinin.
Oishi S.The author has already reported on the time course of blood level of sulfonamides in horses at various dose schedules3). The present paper is concerned with the tissue distri-bution of sulfadimethoxine and sulfamonomethoxine in horses. The distribution of sulfonamides has been reported by KoNDol) in experimental animals, in which the concentrations of these drugs in the kidney, liver, lung and spleen were found to be close to the blood level. Many investigators ascribed the low concen-tration of sulfonamides in the spinal fluid to the existence of a blood-brain barrier, and also observed that ...
Harkins JD, Tobin T.Fentanyl and other opioid drugs have their effect in the central nervous system; however, activity at peripheral sites has also been demonstrated. Pain-suppression activity at peripheral sites raises the possibility of skilled individuals producing local anaesthetic effects with small doses of opioid drugs that would be difficult to detect forensically and could be used to affect the outcome of a race. Therefore, the local pain-suppression effect (peripheral nerve inhibition) of fentanyl was tested using an abaxial sesamoid block/hoof withdrawal model. With this model, fentanyl did not produce...
McCarthy HE, Singer ER, Davies Morel MC.This study compared the effect of sodium heparin and gentamicin sulphate on equine articular cartilage (AC) explants in order to investigate the possible use of sodium heparin in the treatment of infectious arthritis. Six concentrations of sodium heparin and gentamicin sulphate were tested. The supernatant and explant digest were assayed for glycosaminoglycan (GAG) content with the dimethyl-methylene blue assay and the per cent loss of GAG was calculated. A significant (P< 0.001) increase in percentage GAG loss was noted for the sodium heparin groups when compared to the control, whilst no ...
Houghton E, Ginn A, Teale P, Dumasia MC, Copsey J.The stereochemistry of an isomer of 5-estrane-3,17 alpha-diol, the major metabolite of 19-nortestosterone in horse urine has been established by the use of methylene unit (MU) values. The empirical MU values of the bis-trimethylsilyl (TMS) derivatives of the eight available isomers of 5-androstane-3,17-diol and four isomers of 5-estrane-3,17 beta-diol were determined by capillary gas chromatography using three different columns. From this data the theoretical MU values for the bis-TMS derivatives of the four 5-estrane-3,17 alpha-diol isomers were predicted. Comparison of the experimentally det...
Monclin SJ, Farnir F, Grauwels M.Tetracaine hydrochloride (THCl) has been reported to cause irritation in dogs. In man, some topical anaesthetics have been shown to disrupt the tear film. Tear break-up time (TBUT) is a useful test allowing an assessment of the quality of the precorneal tear film. Only one TBUT value has been reported in horses with no information on the technique used. Objective: To provide a method for performing the TBUT in horses and to report any side effects of a single application of THCl in clinically normal horses, particularly on the stability of the tear film. Methods: In Study 1, one drop of 0.5 or...
McDonnell AM, Watson ED.Four pony mares were used in a cross-over study to investigate the effect of different treatments on experimentally-induced endometritis. The mares were treated with progesterone to facilitate establishment of uterine infections. They received an intrauterine infusion of Streptococcus zooepidemicus 5 days after the start of progesterone therapy. Five days later, they were treated by intrauterine infusions of 2 g ampicillin in 50 ml sterile water or by sterile water without antibiotic for 3 consecutive days. Prior to infusion of Strep. zooepidemicus, no bacteria were cultured from the uteri of ...
Ellis JS, Mama KR, Rao S, Sadler RA, Marinkovich M, Clancy MM, Howard LL, Lamberski N, Kinney ME.Przewalski's horses () are an endangered equid species. Anesthesia administered by remote delivery is often needed to provide medical care. Behavioral and physiologic parameters were prospectively compared in 14 horses (8 females and 6 males, 3-18 yr) after a single-dart or staged two-dart anesthesia induction protocol with intramuscular medetomidine (0.06 mg/kg), butorphanol (0.05 mg/kg), thiafentanil (0.02 mg/kg), and ketamine (1 mg/kg). Seven horses were randomly assigned to receive all drugs in a single dart, and the other seven to receive medetomidine and butorphanol 10 min prior to thiaf...
Inaba M, Goto I, Sato K, Maede Y.This report describes a unique response of the anion transporter in equine erythrocytes to the fluorescent substrate N-(2-aminoethyl sulfonate)-7-nitrobenz-2-oxa-3-diazole (NBD-taurine). Equine erythrocytes showed fluxes of NBD-taurine both inward and outward at rates considerably slower than those in human cells. These fluxes were completely abolished by a typical anion transport inhibitor, 4,4'-diisothiocyanostilbene-2,2'-disulfonate. Furthermore, NBD-taurine competitively inhibited the uptake of phosphate in equine red cells with an inhibition constant of phosphate that was slightly higher ...
Rumpler MJ, Sams RA, Colahan P.We describe a validated, rapid, sensitive, and specific UHPLC-MS/MS method to detect and quantify glycopyrrolate in 0.5 mL of horse urine. Further, we investigated the elimination of glycopyrrolate in urine after both intravenous and oral administration of clinically relevant doses to Thoroughbred horses. Quantification was performed by weighted, linear regression analysis using a deuterated analogue of glycopyrrolate as internal standard (IS). The method was characterized by a linear range of 5-2500 pg/mL, a lower limit of quantification of 5 pg/mL and a limit of detection of 1 pg/mL. The int...
Bowen JM.Characteristics of minature end-plate potentials (MEPP) of isolated external intercostal muscle preparations of 7 mammalian species (dog, cat, pig, horse, cow, and goat) including 1 marsupial (opossum, Didelphis marsupialis) were determined with intracellular microelectrodes. Mean amplitude (+/- standard error of MEPP for all species was 0.60 +/- 0.06 mV, and the range was 0.28 mV (opossum) to 1.07 mV (pig). Amplitude was inversely correlated (P less than 0.01) with muscle fiber diameter which ranged from 93 mum (opossum) to 51 mum (pig). Mean values for rise time, half-decay time, and frequen...
Aurich C, Aurich JE, Klug E.Clinical effects of the opioid antagonist naloxone were investigated in healthy horses. Naloxone caused a transient increase in the frequency of defecations, a softening of the faeces and alterations in the intensity of abdominal borborygmi. Total serum protein concentrations decreased. Behavioural changes like frequent yawning and flehmen occurred, heart rate decreased and respiratory rate tended to increase but no clinical signs of distress or pain were observed. It can be concluded that in healthy animals naloxone had only minor side-effects and could be used to investigate the physiologica...
Baxter GM, Moore JN, Tackett RL.The in vitro responses of isolated vascular preparations of digital arteries and veins obtained from healthy anaesthetised horses were determined for dopamine and fenoldopam. The digital vessels were harvested, cut into 4 mm vascular segments, suspended in tissue baths and attached to force-displacement transducers. Dose-response studies between 10(-8) and 10(-4)M concentrations were performed for all drugs. The change in tension of each vascular ring was measured in grams of force. The reactivity between palmar and plantar digital vessels and baseline vascular responses were determined for do...
Gehlen H, Vieht JC, Stadler P.Twenty horses with mitral valve insufficiency, but without signs of congestive heart failure, and five horses without signs of heart disease were examined before and after medication with an angiotensin-converting enzyme (ACE) inhibitor. The examination included echocardiography assessment as well as heart catheterization. The echocardiographic examination included B-mode, M-mode, conventional and colour Doppler techniques. For 8 weeks, all horses were treated with Accupro 20 (active substance: Quinapril) at an oral dose rate of 120 mg/horse/day. A follow-up of the horses with mitral valve ins...
Weidolf LO, Chichila TM, Henion JD.Methods for screening by thin-layer chromatography, quantification by high-performance liquid chromatography with ultraviolet detection and confirmation by gas chromatography-mass spectrometry of boldenone sulfate in equine urine after administration of boldenone undecylenate (Equipoise) are presented. Sample work-up was done with C18 liquid-solid extraction followed by solvolytic cleavage of the sulfate ester. Confirmatory evidence of boldenone sulfate in equine urine was obtained from 2 h to 42 days following a therapeutic intramuscular dose of Equipoise. The use of 19-nortestosterone sulfat...
Müntener C, Kupper J, Naegeli H, Gassner B.A total of 306 reports of adverse reactions to veterinary medicinal products were received during the year 2017 representing an increase of 21% compared to the previous year. The majority of these reports described reactions concerning companion animals (180 dogs and 59 cats) as well as cattle (38 reports) and horses (14 reports). Most of the reported reactions were linked to the use of antiparasitics (158 reports), hormone products (30 reports) and anti-inflammatory products (25 reports). 40 reports were generated from consultations with Tox Info Suisse in Zürich and mainly involved the ex...
Bochsler PN, Slauson DO, Neilsen NR.The essential role of the CD11/CD18 family of leukocyte adhesion molecules (LeuCams) in neutrophil-substrate adhesion is well documented. We have found that a monoclonal antibody designated 60.3 (MoAb 60.3) that recognizes the common beta-subunit (CD18) on human neutrophils (PMN) also recognizes a surface antigen on equine PMN. Antigen expression as assessed by immunofluorescence flow cytometry was enhanced by zymosan-activated serum (ZAS) or phorbol 12-myristate 13-acetate (PMA) stimulation. Pretreatment of equine PMN with MoAb 60.3 inhibited ZAS-stimulated aggregation, indicating that the mo...
Goodrich LR, Furr MO, Robertson JL, Warnick LD.A double-blind study was performed, in horses, to determine the potential toxic effects of the nonsteroidal anti-inflammatory drug, eltenac(4-[(2,6-dichlorophenyl) amino]-3-thiopheneacetic acid). Four treatment groups of six horses were formed. The drug was injected intravenously, once daily, at a dose level of 0.5 mg/kg, 1.5 mg/kg or 2.5 mg/kg for 15 days. A control group was injected with sterile saline solution. Horses were monitored for changes in appetite, physical examinations, biochemical evaluations and gastroscopic examinations. Complete post-mortem examinations were also performed. A...
Carlson A, Johnson PJ, Lei Z, Keegan KG.Soluble epoxide hydrolase (sEH) inhibitors are novel anti-inflammatory and analgesic agents that could improve pain management in horses. The objective of the present study was to evaluate the anti-nociceptive effect of a single-dose intravenous administration of the sEH inhibitor trans-4-{4-[3-(4-trifluro-methoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB) using an adjustable heart bar shoe (a-HBS) model of lameness. We hypothesized that t-TUCB would improve objective and subjective lameness measures compared to the control. Methods: Reversible lameness was induced in 8 horses for 24...
Ritschel WA, Agrawala P, Kraeling M, Sathyan G, Berger K.In a preceding in vivo study in horses, wide interindividual variation was found in the extent of bioavailability and time to reach peak concentration after peroral administration of one specific theophylline sustained-release dosage form. The purpose of the present study was to investigate the factors of potency, the pH of dissolution medium, the enzymes in the dissolution medium, and the crushing of the pellets on in vitro performance. The results show a wide variation in potency for the individual units, an increase in release rate with increasing pH, and an increase in release rate if the ...
Rousselle JC, Gillet G, Fillion G.The solubilization of the serotonergic 5HT1 and 5HT3 sites was performed with digitonin and sodium cholate at 1% (final concentration). Two binding sites for [3H]5HT were observed on rat or horse brain synaptosomal membranes solubilized with these detergents. The corresponding dissociation constants (KD) were 1-3 nM and 13-30 nM respectively. These values were closely similar to those corresponding to 5HT1 and 5HT3 sites located in intact membranes. The solubilized sites specifically bound 5HT. The effect of GTP decreasing the binding to 5HT1 sites was lost on solubilized 5HT1 sites; it was re...
Hildebrand SV, Howitt GA.Efficacy of neostigmine (0.04 mg/kg of body weight) and edrophonium (1 mg/kg), as antagonists for pancuronium neuromuscular blockade in halothane-anesthetized ponies, was evaluated. Neostigmine and edrophonium were satisfactory antagonists, with edrophonium having a significantly (P less than 0.01) more rapid onset of action than did neostigmine. Muscarinic activity of neostigmine and edrophonium was also evaluated. Neither antagonist was administered with atropine. Gastrointestinal effects, increased salivation, and increased airway secretions were minimal with edrophonium, but were marked af...
Sundra T, Gough S, Rossi G, Kelty E, Rendle D.Oral omeprazole is the accepted treatment for equine squamous gastric disease (ESGD); however, it is not universally effective. Esomeprazole results in more consistent and pronounced acid suppression in men and is more effective than omeprazole in the treatment of oesophageal and gastric disease. Pharmacodynamic and pilot clinical studies have indicated esomeprazole might also be more effective than omeprazole in horses. Objective: To compare the efficacy and safety of oral esomeprazole and omeprazole pastes in the treatment of ESGD and, where present, concurrent equine glandular gastric disea...
Komori M, Higami A, Imai Y, Imaoka S, Funae Y.A form of P450 [termed P450(h-1)] was purified from the liver microsomes of a male horse to electrophoretic homogeneity. The specific content of the final P450(h-1) preparation was 14.8 nmol/mg of protein and the recovery was 0.38% of the microsomal P450. The apparent molecular weight of P450(h-1) was 52,000 Da. The absorption spectra of P450(h-1) indicated that P450(h-1) was a low- and high-spin mixed type P450 in the oxidized form. The reconstituted system containing P450(h-1) could catalyze benzphetamine N-demethylation, 7-ethoxycoumarin O-deethylation, and testosterone 16 alpha-hydroxylati...
Milam SB, Mackay RJ, Skelley LA.Secretion of tumor necrosis factor (TNF) by equine mammary exudate macrophages (MEM phi) exposed to bacterial lipopolysaccharide (LPS) was dose-dependent and was maximal (216.5 +/- 51.9 U/ml) at 100 micrograms LPS/ml, the highest concentration tested. All concentrations of dexamethasone tested (10(-8) to 10(-4) M) significantly (P less than or equal to 0.05) inhibited TNF production by MEM phi when the agent was added 1 hour before LPS. Pretreatment with pentoxifylline at concentrations greater than 3 micrograms/ml also significantly (P less than or equal to 0.05) reduced secretion of TNF by M...
Kapustian VA, Matokhina AG, Perelygina OV.Comparative assessment of efficacy of homologous and heterologous diphtheria antitoxins on the example of diphtheria intoxication. Methods: Homologous hyperimmune sera were obtained through immunization of rabbits and guinea-pigs with diphtheria toxoid according to schedule. Immune rabbit sera contained 70 - 100 IU/mL of antitoxin antibodies and guinea-pig sera contained 60 - 80 IU/mL. Equine diphtheria antitoxin was used as a heterologous one. Measurement of antitoxin level using experimental animals is based on quantitative assessment of ability of studied sera to neutralize specific dermone...
Solti L, Eulenberger K, Kurth D, Schöne L.Anoestrous mares were treated with prostaglandin (n = 43) and those that did not respond to prostaglandin (n = 29) with a synthetic progestagen, allyloestrenol, at a dose of 0.05 mg/kg body mass for 12 days. After the cessation of the long-term per os gestagen blockade the animals were checked for heat and, if a preovulatory follicle could be palpated, 2000 IU hCG was administered to induce ovulation. In some animals the plasma 17 beta-oestradiol (E2) and progesterone (P4) levels were also followed up throughout the gestagen treatment and for 10-14 days thereafter. As the favourable oestrus ra...
McDonald J, Gall R, Wiedenbach P, Bass VD, DeLeon B, Brockus C, Stobert D, Wie S, Prange CA, Ozog FJ.A one step enzyme-linked immunosorbent assay (ELISA) test for morphine was evaluated as part of a panel of pre- and post-race tests for narcotic analgesics in racing horses. This ELISA test is very sensitive to morphine with an I-50 for morphine of about 400 pg/ml. The test is also rapid, and ten samples, a normal pre-race complement, can be analyzed in about thirty minutes. The test can be read with an inexpensive spectrophotometer, or even by eye. The test readily detects the presence of morphine or its metabolites in equine blood for up to six hours after administration of sub-therapeutic d...
Kowalczyk DF, Beech J.The pharmacokinetics of the anti-convulsant phenytoin were investigated in clinically healthy horses after oral (p.o.) and intravenous (i.v.) administration. A single dose of phenytoin (8.8 mg/kg body weight) was given i.v. as a bolus to nine horses and one horse received 13.2 mg/kg. A two-compartment open model was used to describe the disposition of phenytoin. Four of the horses that received an i.v. dose (three at 8.8 mg/kg and one at 13.2 mg/kg) were then given the same dose 3 days later by the oral route. Phenytoin achieved a peak concentration in serum within 1-4 h after p.o. administrat...
Knych HK, Stanley SD.To describe the effects of alpha2 -adrenergic receptor antagonists on the pharmacodynamics of sublingual (SL) detomidine in the horse. Methods: Randomized crossover design. Methods: Nine healthy adult horses with an average age of 7.6 ± 6.5 years. Methods: Four treatment groups were studied: 1) 0.04 mg kg(-1) detomidine SL; 2) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 0.075 mg kg(-1) yohimbine intravenously (IV); 3) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 4 mg kg(-1) tolazoline IV; and 4) 0.04 mg kg(-1) detomidine SL followed 1 hour later by 0.12 m...
Azimpour S, Emami Alagha H, Faghihi H, Rajaei SM, Shokoohimand A.The purpose of this study was to determine the effects and potential side effects of topical preservative-free (PF) tafluprost 0.0015% in ophthalmologically normal horses. Methods: Five adult grade horses. Methods: One of the eyes of each horse was randomly chosen as the "treatment" eye, and consequently, the contralateral eye served as the "control." A single dose of PF tafluprost 0.0015% (0.2 mL) was instilled in the treated eye of each horse. Intraocular pressure (IOP), Schirmer's tear test (STT) levels of each eye, and an ophthalmic examination were performed at T0 (baseline), T30, T120, ...
Midon M, Yamada DI, Zangirolami Filho D, Natalini CC, Escobar A, Clark-Price SC.This randomized double-blinded study evaluated the recovery from isoflurane anesthesia in horses receiving doxapram and xylazine. 6 horses were anesthetized 4 times (minimum of 2-week washout period). Anesthesia was performed with xylazine (0.6 mg/kg), ketamine (2.2 mg/kg), midazolam (0.1 mg/kg), and maintained with isoflurane for 90 minutes. At recovery, horses received one of the following randomized treatments: RX: xylazine (0.2 mg/kg), RXD1: xylazine (0.2 mg/kg) and doxapram (0.1 mg/kg), RXD2: xylazine (0.2 mg/kg) and doxapram (0.2 mg/kg), or RS: saline. Recoveries were rope-assisted and e...
