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Topic:Pharmacology
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.
The effects of equivalent doses of tromethamine or sodium bicarbonate in healthy horses. To describe the effects of tromethamine, a putative treatment for metabolic acidosis, and to compare its biochemical effects with those of sodium bicarbonate. Methods: Randomized intervention study with repeated measures. Methods: 16 healthy horses, 3 to 17 years old, weighing 391 to 684 kg. Methods: Ten horses received 3 mEq/kg tromethamine and six received 3 mEq/kg sodium bicarbonate. Samples of venous blood and cerebrospinal fluid (CSF) were collected at intervals before and after drug administration. Heart rate and breathing rate were also recorded at intervals. Results: Median standard ba...
HPLC on Chiralcel OJ-R for enantiomer separation and analysis of ketoprofen, from horse plasma, as the 9-aminophenanthrene derivative. Racemic ketoprofen is a non-steroidal anti-inflammatory drug used to treat musculoskeletal and colic conditions in horses. The enantioselective chiral inversion of ketoprofen administered to horses has been studied by use of cellulose tris(4-methylbenzoate), also known as Chiralcel OJ-R, as chiral stationary phase; acetonitrile - 0.02 M perchlorate buffer (pH 2.0)-methanol, 60:15:25 (v/v/v) was used as mobile phase. Before chromatography, to effect adequate chiral interaction with the chiral stationary phase ketoprofen was derivatized with 9-aminophenanthrene, under acid conditions, after soli...
Effect of ranitidine on intragastric pH in clinically normal neonatal foals. To determine intragastric pH in newborn foals and to examine the effect of i.v. or oral administration of an H2-receptor antagonist on intragastric pH. Methods: Prospective controlled study. Methods: 6 healthy mixed-breed neonatal foals. Methods: Intragastric pH was measured, using an antimony electrode. Foals were monitored on days 2, 4, and 6 after birth, and each received 3 treatments. The pH was recorded for 4 hours before treatment and for 10 hours after ranitidine administration (2 mg/kg [0.91 mg/lb] of body weight, i.v.; 6.6 mg/kg [3 mg/lb], PO) or 20 hours after corn syrup administrati...
Development and use of an enzyme-linked immunosorbent assay to monitor serum and urine acepromazine concentrations in thoroghbreds, and possible changes associated with exercise. To develop an ELISA that is sensitive and suitable for measurement of immunoreactive acepromazine (ACP) in horse serum and urine and to determine the acute effects of exercise on immunoreactive ACP values in Thoroughbreds. Methods: 12 healthy Thoroughbreds (5 mares, 5 geldings, 2 stallions), aged 2 to 8 years. Methods: A commercially available antibody and a horseradish peroxidase-conjugated oxime derivative of immunoreactive ACP were used to develop a one-step ELISA. Horses were used in a crossover design study to evaluate possible effects of treadmill exercise on serum and urine ACP concentr...
Effect of xylazine, detomidine, and a combination of xylazine and butorphanol on equine duodenal motility. To evaluate the effect on equine duodenal motility of some analgesic agents commonly used to treat colic. Methods: 4 healthy adult healthy horses--2 mares and 2 geldings--which were carrying an indwelling gastric cannula made of silastic rubber. One horse also carried 2 long-term indwelling bipolar electrodes that had been sutured onto the duodenum and jejunum. Methods: To ensure an empty stomach, solid food was withheld from horses for around 20 hours prior to an experiment. Using videoendoscopic guidance, an 8-F catheter with 3 small, discrete pressure sensors was passed through the gastric ...
Role of prokinetic drugs for treatment of postoperative ileus in the horse. All horses undergoing coeliotomy for an acute abdominal crisis are at risk of developing ileus and should receive therapy aimed at promoting gastrointestinal function by restoring fluid and electrolyte balance. Adequate analgesia and prevention against peritonitis, bacteraemia and endotoxaemia should be provided. Horses that at the time of surgery have a strangulating or non-strangulating small intestinal obstruction should be considered to be at greater risk of developing a persistent ileus that is refractory to treatment than those horses with lesions involving the large intestine. In horses...
Effects of inflammation-associated acute-phase response on hepatic and renal indices in the horse. To determine the effect of an acute soft tissue inflammatory response on biochemical and haematological indices of hepatic and renal function in the Thoroughbred horse. Methods: Soft tissue inflammation was induced in four Thoroughbred horses by intramuscular injections of Freund's complete adjuvant. The horses were clinically examined and blood and urine samples were collected before and after the adjuvant injections. Biochemical and haematological indices were measured in samples collected and used to determine the onset of the acute-phase response and to assess hepatic and renal function at...
Intracardiac overdrive pacing as a treatment of atrial flutter in a horse. A five-year-old warmblood mare with atrial fibrillation was treated with quinidine sulphate. The atrial rhythm changed to atrial flutter and, because there were toxic effects, the treatment was discontinued. Seven months after the occurrence of the atrial flutter, treatment with a rapid atrial pacing technique restored a normal sinus rhythm. One year after the pacing therapy the horse was still in sinus rhythm and had been brought back into training.
Elimination of mucosal cyathostome larvae by five daily treatments with fenbendazole. The efficacy of five daily treatments with 7.5 mg fenbendazole/kg bodyweight against mucosal cyathostome larvae was evaluated in 20 12- and 24-month-old ponies with naturally acquired cyathostome infections. After three weeks communal grazing on infected pasture and six weeks indoors, one group of 10 ponies were treated. Six weeks later, both groups of ponies were humanely destroyed and their burdens of large intestinal cyathostome worms, including luminal parasites and mucosal larvae, were assessed. In the control animals approximately 7 per cent of the total worm burden was present in the gu...
Influence of atipamezole on effects of midsacral subarachnoidally administered detomidine in mares. To examine effects of atipamezole on detomidine midsacral subarachnoidally-induced analgesia, cardiovascular and respiratory activity, head ptosis, and position of pelvic limbs in healthy mares. Methods: 10 healthy mares. Methods: Using a randomized, blinded, crossover study design, mares received detomidine (0.03 mg/kg of body weight, diluted in 3 ml of CSF) midsacral subarachnoidally, followed by atipamezole (0.1 mg/kg [test]) or sterile saline (0.9% NaCl) solution (control), i.v. 61 minutes later and saline solution (3 ml, midsacral subarachnoidally) on a separate occasion, at least 2 weeks...
Plasma 5-hydroxytryptamine constricts equine digital blood vessels in vitro: implications for pathogenesis of acute laminitis. Cumulative concentration response curves to 5-hydroxytryptamine (5-HT; 10(-10)-10(-4) mol/l) were constructed using isolated rings of equine digital, facial, tail and coronary arteries (endothelium intact). 5-HT was 17.7 and 41 times more potent as a vasoconstrictor of digital arteries than facial and tail arteries respectively. Removal of the endothelium increased the vasoconstrictor potency of 5-HT in the facial artery by 3.7-fold (P<0.05) but did not alter the sensitivity of digital arteries to 5-HT. Coronary arteries failed to contract to 5-HT. Coronary arteries pre-contracted with U440...
Effects of inhaled beclomethasone dipropionate on respiratory function in horses with chronic obstructive pulmonary disease (COPD). The effects of beclomethasone dipropionate on pulmonary function and arterial blood gas values were investigated in horses with chronic obstructive pulmonary disease (COPD). Six mature mares, diagnosed as having COPD based on clinical signs, cytological examination of bronchoalveolar lavage and pulmonary function testing, were used. Beclomethasone dipropionate (3750 microg) was administered b.i.d. for a 2 week period with a metered dose inhaler using a mask. Pulmonary function tests and arterial blood gas analyses were performed at weekly intervals, starting before beclomethasone administratio...
Pulmonary vascular pressures of strenuously exercising Thoroughbred horses after administration of phenylbutazone and frusemide. The present study was carried out to examine the effects of phenylbutazone treatment on the pulmonary haemodynamic effects of frusemide in strenuously exercising horses. Using catheter mounted manometers, whose in vivo signals were referenced at the point of the shoulder, heart rate, right atrial, right ventricular and pulmonary vascular pressures were measured in 3 different sets of experiments. Seven Thoroughbreds were subjected to 1) control (no medications), 2) frusemide control and 3) phenylbutazone + frusemide. The experiments were carried out in random order and were separated by 7 days...
Behavioural changes in stabled horses given nontherapeutic levels of virginiamycin. Abnormal behaviour commonly develops in intensively managed horses. A possible cause is the change in diet occurring when the horse is stabled. An experiment was performed to examine this possibility by manipulating the diet with the feed supplement virginiamycin, as Founderguard. During 4 weeks, 18 horses were fed diets ranging from hay alone to concentrate plus hay in the ratio of 3:1. The rations of half the horses given concentrate were supplemented with Founderguard. Horses eating high concentrate rations displayed abnormal oral behaviours at a higher frequency than those eating only hay....
Influence of tidal volume and positive end-expiratory pressure on inspiratory gas distribution and gas exchange during mechanical ventilation in horses positioned in lateral recumbency. To study effects of intermittent positive-pressure ventilation (IPPV) with large tidal volumes and addition of positive end-expiratory pressure (PEEP) on maldistribution of ventilation in anesthetized horses positioned in lateral recumbency. Methods: 6 healthy adult horses. Methods: Anesthesia was induced by i.v. infusion of thiopental sodium and guiafenesin and was maintained with supplemental doses of thiopental and i.v. infusion of chloral hydrate. Functional separation of the lungs was achieved, using a tube-in-tube intubation technique. Intermittent positive-pressure ventilation of both l...
Effect of alpha 2-adrenergic, cholinergic, and nonsteroidal anti-inflammatory drugs on myoelectric activity of ileum, cecum, and right ventral colon and on cecal emptying of radiolabeled markers in clinically normal ponies. To determine effect of xylazine hydrochloride (XYL), yohimbine hydrochloride (YOH), bethanechol chloride (BET), neostigmine methyl sulfate (NEO), or flunixin meglumine (FLU) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Methods: 6 healthy adult ponies. Methods: A cecal cannula was surgically implanted, and 12 were sutured to the ileum, cecum, and right ventral colon. After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were...
Effect of erythromycin lactobionate on myoelectric activity of ileum, cecum, and right ventral colon, and cecal emptying of radiolabeled markers in clinically normal ponies. To determine the effect of erythromycin lactobionate (ERY) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Methods: 6 healthy adult ponies. Methods: After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were administered directly into the cecal apex. The following drug concentrations were tested: ERY, 0.01, 0.10, 1.0, and 10.0 mg/kg of body weight; ERY, 0.10 mg/kg bolus; and saline (0.9% NaCl) solution, 10 ml. All treatments, ...
Determination of butorphanol in horse race urine by immunoassay and gas chromatography-mass spectrometry. An analytical procedure to screen butorphanol in horse race urine using ELISA kits and its confirmation by GC-MS is described. Urine samples (5 ml) were subjected to enzymatic hydrolysis and extracted by solid-phase extraction. The residues were then evaporated, derivatized and injected into the GC-MS system. The ELISA test (20 microl of sample) was able to detect butorphanol up to 104 h after the intramuscular administration of 8 mg of Torbugesic, and the GC-MS method detected the drug up to 24 h in FULL SCAN or 31 h in the SIM mode. Validation of the GC-MS method in the SIM mode using nalbup...
Persistent desensitisation of the beta 2 adrenoceptors expressed by cultured equine sweat gland epithelial cells. 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...
Inhibition and inactivation of equine aromatase by steroidal and non-steroidal compounds. A comparison with human aromatase inhibition. In order to approach the detailed structure-function relationships of aromatase, we studied the inhibitory and inactivatory potencies of several steroidal androstenedione analogues (1: 4-hydroxyandrostenedione, 2: 4-acetoxyandrostenedione and 3: 7 alpha-(4'-amino)phenylthio-4-androstene-3, 17-dione) and non-steroidal imidazole derivatives (4: ketoconazole, 5: miconazole and 6: fadrozole) on equine aromatase in placental microsomes, a well established mammalian model. Human placental microsomes and the purified enzyme from equine testis were also used to compare inhibition by 1 and 2. In equine...
A toxicity study of eltenac, a nonsteroidal anti-inflammatory drug, in horses. 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...
Efficacy of moxidectin 2% equine gel against natural nematode infections in ponies. The efficacy of moxidectin 2% oral gel (Equest, Fort-Dodge) against European worm strains was studied through post-mortem worm counts and feacal egg counts (FECs) in 12 young ponies naturally infected. The animals were allocated in two groups of six ponies each: the first one was treated at 0.4 mg/kg b.w. and the second one received a placebo and served as control. All the ponies were necropsied 14 days post-treatment. The efficacy of moxidectin in reducing strongyle FECs ranged from 99.8% to 100% from 3 to 14 days after treatment. Moxidectin efficacy was 100% against Trichostrongylus axei and...
The reappearance of strongyle eggs in the faeces of horses after treatment with moxidectin. The reappearance of strongyle eggs in the faeces of horses treated with moxidectin (0.4 mg/kg of body weight) was compared with that in the faeces of horses treated with ivermectin (0.2 mg/kg of body weight). The study was performed from December 1995 till June 1996. Horses were infected naturally in the preceding grazing period. Two groups of 24 horses each were treated with moxidectin and ivermectin respectively at week 0. No side effects were seen after treatment. Horses were housed from week -1 till week 17. From week 17 onwards the horses were on pasture. Faecal samples were taken from ea...
Duration of effects of phenylbutazone on serum total thyroxine and free thyroxine concentrations in horses. The objectives of this study were to determine if phenylbutazone decreased serum thyroxine (TT4) and free thyroxine (FT4) concentrations using radioimmunoassay and equilibrium dialysis techniques in horses, and, if so, an additional objective was to determine the duration of this decreased concentration once phenylbutazone administration was discontinued. Serum TT4 and FT4 concentrations were determined before and after administration of 4.4 mg/kg of phenylbutazone i.v. bid for 5 days. Treatment with phenylbutazone caused a significant decrease in TT4 and FT4 concentrations (P < .05). Serum...
Effects of enantiomers of beta 2-agonists on ACh release and smooth muscle contraction in the trachea. The beta 2-agonists currently used as bronchodilators are racemic mixtures of R- and S-enantiomers. In the present study, we examined the effects of enantiomers of the beta 2-agonists albuterol and formoterol on acetylcholine (ACh) release from equine trachealis parasympathetic nerves. ACh release was evoked by electrical field stimulation (20 V, 0.5 ms, 0.5 Hz) and measured by high-performance liquid chromatography coupled with electrochemical detection. We also tested the effects of enantiomers of albuterol and formoterol on equine tracheal smooth muscle (TSM) contraction in response to exog...
Plasma pharmacokinetics of ranitidine HCl in foals. Plasma pharmacokinetics of ranitidine HCl were investigated after intravenous (i.v.) and oral (p.o.) administration of drug to six healthy foals. Twelve- to sixteen-week-old foals received 2.2 mg ranitidine/kg i.v. and 4.4 mg ranitidine/kg p.o. Concentrations of ranitidine were determined using normal phase high performance liquid chromatography. Plasma concentrations of ranitidine HCl declined from a mean of 3266 ng/mL at 5 min to 11 ng/mL at 720 min after administration. The profile of the plot of concentrations of ranitidine HCl vs. time was best described by a two-exponent equation for two...
