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.
Phaneuf LP, Grivel ML, Ruckebusch Y.The electrical potentials were recorded from the antrum, the duodenum, the ileum and the first part of the colon of ponies under (a) normal resting conditions, (b) during nonpainful colic and (c) after intravenous morphine administration. The normal pony, at rest, had five contractions of the antrum per minute. On the small intestine, the basal electrical activity decreased from the duodenum (14-15/min) to the ileum (10-11/min). The small bowel also had three types of motility: peristaltic waves, rhythmic segmentations and random contractions. On the colon, bursts of potentials indicating inte...
Kerr DD, Jones EW, Holbert D, Huggins K.A 3-way Latin square design was used to compare the sedative and preanesthetic effects of xylazine given intravenously (i.v.) (1.1 mg./kg.) and given intramuscularly (i.m.) (2.2 mg./kg.) and acetylpromazine maleate (0.66 mg./kg.) given i.v. in the horse. Physiologic responses were recorded and clinical observations were made. Intravenous administration of xylazine and atropine sulphate (0.011 mg./kg.) appeared to have superior sedative properties, without having adverse effects on cardiovascular and respiratory systems. Both the i.v. and the i.m. administrations of xylazine prior to induction ...
Colahan PT, Bailey JE, Chou CC, Johnson M, Rice BL, Jones GL, Cheeks JP.Twelve clinically sound, healthy, athletically conditioned Thoroughbred horses were subjected to an incremental exercise stress test to determine the effects and period of detection of a single dose of flunixin meglumine (1.1 mg/kg by intravenous injection) in serum and urine by ELISA. Flunixin concentrations, performance, and hematologic and clinical chemical parameters were measured. All horses were rotated through four treatment groups of a Latin-square design providing for each horse to serve as its own control. Flunixin meglumine reduced prostaglandin F(1alpha) and thromboxane concentrati...
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...
Makhaeva GF, Shataeva GA, Iankovskaia VL, Fetisov VI, Loshadkin NA.The interaction of human erythrocyte acetylcholinesterase, horse serum butyrylcholinesterase and rat liver carboxylesterase with insecticides (RO)2P(O)SCH(COOEt)SP(O)(OR)2 (I) and (RO)2P(O)SCH(COOEt)OP(S)(OR)2 (II) was studied. The type I and II compounds were not hydrolyzed by carboxylesterase and inhibited the esterases irreversibly. A complex pattern of inhibition of acetylcholinesterase and butyrylcholinesterase by these compounds was caused by kinetically-manifested formation of an enzyme-inhibitor complex. The compounds I and II were more selective towards butyrylcholinesterase than towa...
Rakotoarisoa L, Mironneau C, Sayet I, Mironneau J.Specific binding of the Ca++ antagonist desmethoxyverapamil, (-)-[3H]D888, to cell membranes of equine portal vein smooth muscle was inhibited in a concentration-dependent manner by guanosine 5'-O-(gamma-thio)triphosphate and ATP but was little affected by guanosine 5'-O-(beta-thio)diphosphate, noradrenaline or phorbol 12-myristate 13-acetate ester. Inhibition constants for GTP and ATP were in the range of 0.1 to 0.3 mM. From Scatchard plots and dissociation kinetic experiments, it is proposed that D888 high affinity binding sites are transferred into low affinity sites. In intact strips of ra...
Hubbard CD, Shoupe TS.A transient phase for the hydrolysis of indophenyl acetate by the commercial preparation of horse serum cholinesterase was observed on a stopped-flow spectrophotometer. It was found that the transient process is a reaction of the ester with a major component of the preparation and is not caused by the serum cholinesterase enzyme. This noncholinesterase component was isolated and the dependence of its concentration and that of the ester upon the transient liberation of the indophenolate ion were determined. Studies with the isolated component and subsequent analyses have led to the tentative id...
Hesselkilde EZ, Carstensen H, Flethøj M, Fenner M, Kruse DD, Sattler SM, Tfelt-Hansen J, Pehrson S, Braunstein TH, Carlson J, Platonov PG....Large animal models are important in atrial fibrillation (AF) research, as they can be used to study the pathophysiology of AF and new therapeutic approaches. Unlike other animal models, horses spontaneously develop AF and could therefore serve as a bona fide model in AF research. We therefore aimed to study the electrical, functional and structural remodelling caused by chronic AF in a horse model. Nine female horses were included in the study, with six horses tachypaced into self-sustained AF and three that served as a time-matched sham-operated control group. Acceleration in atrial fibrilla...
Martin EM, Schirmer JM, Jones SL, Davis JL.Misoprostol is an E prostanoid (EP) 2, 3 and 4 receptor agonist that is anecdotally used to treat and prevent NSAID-induced GI injury in horses. Misoprostol elicits anti-inflammatory effects in vivo in men and rodents, and inhibits TNFα production in equine leucocytes in vitro. Objective: Define the pharmacokinetic parameters of oral misoprostol in horses, and determine the inhibitory effect of oral misoprostol administration on equine leucocyte TNFα production in an ex vivo inflammation model. Methods: Pharmacokinetic study, ex vivo experimental study. Methods: Six healthy adult horses ...
Sheldon SA, Aleman M, Costa LRR, Santoyo AC, Howey Q, Madigan JE.Trigeminal-mediated headshaking results from low-threshold firing of the trigeminal nerve resulting in apparent facial pain. Magnesium may have neuroprotective effects on nerve firing that potentially dampen signs of neuropathic pain. This hypothesis has not been investigated in horses with trigeminal-mediated headshaking. Objective: To investigate head-shaking behavior in affected horses after IV magnesium sulfate infusion. Methods: Six geldings with trigeminal-mediated headshaking. Methods: Prospective randomized crossover study. Horses were controlled for diet and infused IV with 5% dextros...
Ellison RS, Jacobs RM.This study was undertaken to ascertain if the isoelectric focusing pattern of serum alkaline phosphatase (AP) from sick horses with high activity is useful for determining its tissue origin. The effect of oral prednisolone and phenylbutazone therapy on this enzyme in healthy horses was also investigated. The sick horses were divided into three groups: hepatic, intestinal and miscellaneous. All sera had approximately thirteen bands of AP activity when focused on agarose gels with a pH gradient of 3.5 to 9.5. All the horses in the liver disease group had greater than 65% of enzyme activity in ba...
Sander K, Deegen E, Ohnesorge B.In a placebo-controlled drug study data were collected about flow, volume and expiratory CO2-concentration in 13 horses with chronic obstructive pulmonary disease before and until 2.5 h after intravenous injection of clenbuterol. An ultrasonic flow measuring unit and an infrared-CO2-analyser (Spiroson Scientific) were used. functional deadspace and expiratory mixed volume were calculated. In addition the effect on the partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2) in arterial blood was tested and the alveolo-arterial oxygen difference (AaDO2) determined. The volume of the functio...
Hammersley E, Duz M, Marshall JF.Triamcinolone is commonly used in equine practice for the treatment of orthopaedic conditions. A serious potential adverse effect of triamcinolone is laminitis. However, evidence for the risk of laminitis associated with triamcinolone use is limited. Objective: To determine the risk of laminitis within 90 days of triamcinolone administration and compare with the risk of laminitis in a veterinary-attended horse population. Methods: Retrospective study of clinical records. Methods: Text mining and data extraction was performed using content analysis software (SimStat-WordStat v.6) on a database ...
Brumbaugh GW, Thomas WP, Hodge TG.A 4-year-old Quarter Horse gelding with atrial fibrillation, mitral regurgitation, and signs of bilateral congestive heart failure was initially treated IV with digoxin and furosemide. After parenteral digitalization, a daily maintenance dose of digoxin was administered orally at a rate of 21.7 micrograms/kg of body weight. At this dosage, a steady-state serum digoxin concentration of 2.3 ng/ml was achieved without clinical signs of toxicosis. The furosemide dosage was decreased and eventually discontinued as clinical improvement occurred. Clinical signs of congestive heart failure were contro...
Geimer TR, Ekström PM, Ludders JW, Erichsen DF, Gleed RD.The haemodynamic effects of hyoscine-N-butylbromide (0.30 mg/kg, intravenously) were studied in eight adult ponies in a blinded two-period crossover experiment with repeated measures. Values for heart rate were 63%, 48% and 13% greater than control values at 1, 16 and 46 min, respectively, after administration of hyoscine-N-butylbromide. Cardiac output increased by 16% at 16 min after drug injection. Mean right atrial pressure was decreased by 79%, 63%, 45% and 52% at 1, 16, 46 and 61 min, respectively, after drug administration. Stroke volume was decreased by 32% at 1 min and pulmonary arteri...
Jacobs CC, Schnabel LV, McIlwraith CW, Blikslager AT.Orthopaedic disorders are commonly encountered in equine veterinary medicine, and non-steroidal anti-inflammatory drugs (NSAIDs) play an important role in the management of many equine orthopaedic disorders. There are multiple NSAIDs available for use in horses, including both non-selective and selective NSAIDS, and the body of literature evaluating the efficacy of these medications, their effects on normal and inflamed musculoskeletal tissues, and their side effects is broad. This review aims to summarise the current literature on the use of NSAIDs for equine orthopaedic disorders and examine...
Mischke R, Junker J, Deegen E.The sensitivity of commercial prothrombin time (PT) tests was assessed based on a dilution series of equine pooled plasma (EPP) (experiment 1) and on 40 equine plasma samples with reduced activity of coagulation factors II, V, VII and X (experiment 2). Two different PT reagents (reagent 1, human placental thromboplastin; reagent 2, recombinant human tissue factor) were used according to the manufacturers' instructions (standard test, PT([ST])) and compared to a modified test procedure (modified test, PT([MT])) using sample dilution and fibrinogen addition. In all samples, sensitivity was lower...
Shideler RK, Voss JL, Aufderheide WM, Hessemann CP, Squires EL.Twenty mares were assigned to 1 of 4 groups: no altrenogest; altrenogest at 0.044 mg/kg BW; altrenogest at 0.132 mg/kg BW; or altrenogest at 0.220 mg/kg BW. Treatment was administered daily for 86 days. No signs of illness attributable to feeding altrenogest were observed during the trial. Treatment had no effect (P greater than .05) on the following parameters: WBC, differential WBC, platelet number, creatinine, LDH, CPK, total bilirubin, cholesterol, globulin, BSP, and erythrocyte sedimentation rate. When comparing values over time with pretreatment means or among treatment groups, there wer...
Brumbaugh GW, Thomas WP, Enos LR, Kaneko JJ.Digoxin was administered orally and intravenously to seven healthy adult mares and geldings in two separate trials. At a dose of 44 microgram digoxin/kg body weight, the oral study was characterized by an absorption phase with a mean (+/- 1 standard deviation) peak serum digoxin concentration of 2.21 ng/ml (+/- 0.45) at a mean of 2.29 h (+/- 1.52) after administration. A second rise in serum digoxin concentration started about 6-8 h after administration and extended to about 20 h after administration. The mean bioavailability (F) was 23.38% (+/- 5.96). At a dose of 22 microgram digoxin/kg body...
Castilla-Castaño E, Vischi A, Navarro C, Lecru LA, Ribeiro C, Pradier S, Cadiergues MC.Two open-controlled studies evaluated the tolerance and the efficacy of a 10 mg/mL deltamethrin-based pour-on solution (Deltanil®; Virbac, France) in treating (study 1) and preventing (study 2) natural Damalinia equi infestations in horses. In study 1, seven adult horses received 10 mL of the solution from mane to tail head on day 0 (D0). Four adult horses, living separately, served as non-treated controls. All were naturally infected. Lice burden was recorded by counting the number of live parasites, bilaterally, over seven anatomic regions. Lesional score was based on alopecia, crusts, papu...
The objective of this study was to compare effects of butorphanol (BUT) or buprenorphine (BUP), in combination with detomidine and diazepam, on the sedation quality, surgical conditions, and postoperative pain control after cheek tooth extraction in horses, randomly allocated to 2 treatment groups (BUT: = 20; BUP: = 20). A bolus of detomidine (15 μg/kg, IV) was followed by either BUP (7.5 μg/kg, IV) or BUT (0.05 mg/kg, IV). After 20 min, diazepam (0.01 mg/kg, IV) was administered and sedation was maintained with a detomidine IV infusion (20 μg/kg/h), with rate adjusted based on scores to ...
Schnuelle ML, Hopster K, Toribio RE, Hurcombe SD.To compare the effects of 7.2% hypertonic and 0.9% isotonic saline (sodium chloride) solutions on cardiovascular parameters and plasma arginine vasopressin (AVP) concentrations in healthy, isoflurane-anesthetized horses. Methods: 8 healthy horses. Methods: In a prospective, randomized, crossover study, horses were anesthetized with isoflurane twice with a 14-day washout period between anesthetic episodes. While anesthetized, horses received a bolus (4 mL/kg) of 7.2% hypertonic saline solution (HS) or 0.9% isotonic saline solution (IS). Heart rate; systolic, mean, and diastolic arterial blood p...
El-Sherif MA, Nabil G, Ibrahim R, Mohamed N, Mohamed M, Jaheen AH.Based on the growing attention to the Arabian horses with a lack of records regarding their normal physiological parameters, which are critically vital for disease diagnosis &convenient drug administration, we give great attention to their thyroid gland normalcy. The thyroid gland is one of the key players in regulating many physiological processes. Therefore, we tackled thyroid biology & morphology in 14 Arabian stallions & 18 Arabian mares from the beginning of March to the middle of April on animals from 4 to 19 years old. First, the blood samples taken from their jugular vein ...
Andrews FM, Doherty TJ, Blackford JT, Nadeau JA, Saxton AM.To determine the effects of orally administered omeprazole, as enteric-coated capsules, on baseline and stimulated gastric acid secretion in horses. Methods: 5 healthy 8-year-old mixed-breed horses fitted with gastric cannulas. Methods: Enteric-coated granules of omeprazole were mixed with corn syrup and administered orally once daily for 5 consecutive days. On days 1 and 5 beginning 5 hours after omeprazole administration, 4 gastric fluid samples were collected, each for 15 minutes, via the gastric cannula (baseline samples). Pentagastrin was administered IV as a constant infusion for the sub...
Lind EO, Uggla A, Waller P, Höglund J.The aim of this study was to investigate the suitability of a larval development assay (LDA) for the determination of anthelmintic resistance in cyathostomin nematode populations of the horse. In addition, comparison of results between geographic regions, types of horse establishment, and the use of anthelmintics in Sweden, was established. Seventy horse herds from different parts of Sweden were sampled, and strongyle eggs from the faeces of 54 of those were investigated by an LDA (DrenchRite). The following anthelmintics were tested: thiabendazole (TBZ), levamisole (LEV), ivermectin monosacch...
Bollwein H, Kolberg B, Stolla R.In recent years, a positive relationship between genital perfusion and fertility has been established; in species other than horses, uterine and ovarian perfusion was improved by exogenous estrogen but impaired by exogenous progestin. The goal of the present study was to investigate the effect of exogenous estrogen and progestin on uterine and ovarian blood flow in cycling mares. Five Trotter mares were examined daily during three estrous cycles. Mares were given no treatment, altrenogest (0.044 mg/kg BW) orally from Day 0 (ovulation) to Day 14 and estradiol benzoate (5mg i.m.) on Days 0, 5, a...
Landoni MF, Foot R, Frean S, Lees P.The objective of this study was to analyse the effects of 4 nonsteroidal anti-inflammatory drugs (NSAIDs) on the production of beta-glucuronidase (beta-glu), tumour necrosis factor alpha (TNF alpha), interleukin-6 (IL-6), interleukin-1 (IL-1) and prostaglandin E2 (PGE2) by lipopolysaccharide (LPS)-stimulated equine synoviocytes. The agents studied were flunixin, tolfenamic acid, S(+)ketoprofen (KTP) and R(-)ketoprofen. LPS-induced release of beta-glu from synoviocytes was inhibited in a concentration dependent manner by all 4 compounds, tolfenamic acid being the most potent. Of the 2 KTP enant...
Hagedorn HW, Schulz R, Jaeschke G.An enzyme linked immunosorbent assay (ELISA) was developed to detect the anabolic steroid boldenone in equine blood and urine. The polyclonal antiserum was raised in rabbits, employing boldenone-17-hemisuccinate-bovine serum albumin as antigen. Boldenone-17-hemisuccinate-horseradish peroxidase served as enzyme conjugate. Sensitivity of the assay was 26.0 +/- 3.0 pg/well. Among the endogenous steroids tested only progesterone and testosterone exhibited moderate cross-reactivities, 3.4 and 2.5%, respectively. These cross-reactivities are of no importance for the boldenone assay. For the reductio...
Henion JD, Maylin GA.A sensitive, quantitative method has been developed for the determination of hydrochlorothiazide in equine plasma and urine. Thin-layer chromatography is used to screen for the presence of the drug in unknown samples. The TLC screening methods described provide minimum detection limits of 50 ng/mL in plasma and 25 ng/mL in urine. A silica micro chromatography column is used to clean up ethyl acetate extracts for HPLC analysis and mass spectral confirmation. An internal standard, trichloromethiazide, is used to derive quantitative data at concentrations as low as 25 ng/mL for plasma disappearan...
Corley KT, Axon JE.Early intervention can dramatically alter outcome in foals. Cardio-pulmonary cerebral resuscitation can be successful and clinically worthwhile when applied to foals that arrest as part of the birthing process. Readily available equipment and an ordered plan starting with addressing the respiratory system (airway and breathing) followed by the circulatory system (circulation and drugs) are the keys to success. Hypoglycemia is common in foals that are not nursing and in septic foals. Support of serum glucose can be an important emergency treatment. Respiratory support with oxygen therapy should...
Warnken T, Brehm R, Feige K, Huber K.The aim of the study was to analyze key proteins of the equine insulin signaling cascade and their extent of phosphorylation in biopsies from muscle tissue (MT), liver tissue (LT), and nuchal AT, subcutaneous AT, and retroperitoneal adipose tissues. This was investigated under unstimulated (B1) and intravenously insulin stimulated (B2) conditions, which were achieved by injection of insulin (0.1 IU/kg bodyweight) and glucose (150 mg/kg bodyweight). Twelve warmblood horses aged 15 ± 6.8 yr (yr), weighing 559 ± 79 kg, and with a mean body condition score of 4.7 ± 1.5 were included in the s...
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...
