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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 synovial response to exogenous phospholipid (synovial surfactant) injected into the equine radiocarpal joint compared with that to prilocaine, hyaluronan and propylene glycol. To determine the effects of the intra-articular injection of surface-active phospholipid in a propylene glycol carrier on synovial fluid composition and joint function of horses, and to compare these effects with those observed after the intra-articular administration of prilocaine, hyaluronan and propylene glycol alone. Methods: Twenty-four horses were randomly allocated to four treatment groups: Group 1 100 mg of surface-active phospholipid in 1 ml of propylene glycol; Group 2 1 ml of propylene glycol; Group 3 10 ml of prilocaine; Group 4 2 ml of hyaluronan. Left radiocarpal joints were inje...
Evaluation of xylazine and ketamine for total intravenous anesthesia in horses. To evaluate the use of xylazine and ketamine for total i.v. anesthesia in horses. Methods: 8 horses. Methods: Anesthetic induction was performed on 4 occasions in each horse with xylazine (0.75 mg/kg, i.v.), guaifenesin (75 mg/kg, i.v.), and ketamine (2 mg/kg, i.v.). Intravenous infusions of xylazine and ketamine were then started by use of 1 of 6 treatments as follows for which 35, 90, 120, and 150 represent infusion dosages (microg/kg/min) and X and K represent xylazine and ketamine, respectively: X35 + K90 with 100% inspired oxygen (O2), X35 + K120-(O2), X35 + K150-(O2), X70 + K90-(O2), K15...
In vitro evaluation of the contractile response to endothelin-1 of the circular and longitudinal myometrial layers of the uterine horn of nongravid mares. To characterize the in vitro response of circular and longitudinal myometrial layers of the uterine horn (CMLH and LMLH, respectively) of horses to endothelin (ET)-1 by use of specific ETA (BQ-123) and ETB (IRL-1038) receptor antagonists. Methods: Uteruses from 10 nongravid mares in anestrus. Methods: Muscle strips from the CMLH and LMLH were suspended in tissue baths and connected to force-displacement transducers interfaced with a polygraph. Strips were incubated for 45-minute intervals with no antagonist (control specimens), and 3 concentrations (10(-9), 10(-7), and 10(-5)M) of BQ-123, IRL-...
Investigation of the EEG effects of intravenous lidocaine during halothane anaesthesia in ponies. To record the electroencephalographic changes during castration in ponies anaesthetized with halothane and given intravenous (IV) lidocaine by infusion. The hypothesis tested was that in ponies, IV lidocaine is antinociceptive and would therefore obtund EEG changes during castration. Methods: Ten Welsh mountain ponies referred to the Department of Clinical Veterinary Medicine, Cambridge for castration under general anaesthesia. Methods: Following pre-anaesthetic medication with intramuscular acepromazine (0.02 mg kg(-1)) anaesthesia was induced with IV guaiphenesin (60 mg kg(-1)) and thiopenta...
The minimum infusion rate (MIR) of propofol for total intravenous anesthesia after premedication with xylazine in horses. To investigate an adequate infusion rate of propofol for total intravenous anesthesia (TIVA) in horses, the minimum infusion rate (MIR) comparable to the minimum alveolar anesthetic concentration (MAC) of inhalation anesthetic was determined under constant ventilation condition by intermittent positive pressure ventilation (IPPV). In addition, arterial propofol concentration was measured to determine the concentration corresponding to the MIR (concentration preventing reaction to stimulus in 50% of population, Cp(50)). Further, 95% effective dose (ED(95)) was estimated as infusion rate for acq...
Transient complete atrioventricular block following transvenous electrical cardioversion of atrial fibrillation in a horse. Transvenous electrical cardioversion was attempted in a horse with drug refractory atrial fibrillation. A temporary pacing catheter and two defibrillation catheters were inserted transvenously into the right ventricular apex, the right atrium and the pulmonary artery, respectively. Under general anaesthesia 100, 200, 300 and 360 J monophasic shocks were delivered between both defibrillation catheters but sinus rhythm could not be restored. Immediately after the 200, 300 and 360 J shock, transient third-degree atrioventricular block occurred for a period of, respectively, 15, 40 and 55 s. These...
Assessment of a platelet function analyser in horses: reference range and influence of a platelet aggregation inhibitor. The objective of this study was to assess whether a new human platelet function analyser (the PFA-100) could be used to evaluate platelet function in horses and detect acetylsalicylic acid (ASA)-induced platelet dysfunctions. Citrated blood samples from 40 healthy horses were processed to obtain reference values for closure time (CT) using cartridges with collagen-ADP (CT-ADP) and collagen-epinephrine (CT-EPI) as platelet agonists. In addition, CT-ADP and CT-EPI were also measured before and 24 h after oral ASA administration in another 12 healthy horses. The sensitivity and specificity of the...
Treatment strategies for mares with placentitis. Equine placentitis, and resultant preterm labor, are important sources of fetal and neonatal loss. The primary cause of equine placentitis is infection of the placenta with Streptococcus equi subspecies zooepidemicus, which ascends through the caudal reproductive tract. Current treatment protocols for mares affected with placentitis are empirical. This paper reviews treatment approaches for resolving placentitis and preterm labor in both equine and non-equine species. Specific therapies reviewed include antimicrobial, anti-inflammatory, tocolytic, and progestin agents.
Control of endoparasites in horses with a gel containing moxidectin and praziquantel. A gel formulation containing moxidectin (20 g/kg) and praziquantel (125 g/kg) reduced the geometric mean faecal strongyle egg count in horses to below 100 eggs per gram of faeces (epg) for at least 12 weeks despite their being exposed continuously to reinfection from pasture grazed by treated and untreated horses. The geometric mean egg count of horses treated with a proprietary paste containing abamectin (3.7 g/kg) and praziquantel (46.2 g/kg) increased steadily from six weeks after the treatment, peaking at over 820 epg after 12 weeks. Relative to the efficacy of the abamectin/praziquantel t...
Analysis of the strongylid nematodes (Nematoda: Strongylidae) community after deworming of brood horses in Ukraine. Communities of intestinal helminths in horses are commonly studied post mortem. The study objectives were here to examine the species composition of the strongylid community in brood horses in Ukraine after deworming with an aversectin drug Univerm. The site distribution of the strongylid species was analysed according to dynamics of their expulsion in faeces. Forty-four horses of different ages from Poltavska oblast (22 horses), Kyivska oblast (17 horses) and Sumska oblast (5 horses) of Ukraine were included in the study. Horses were treated with Univerm anthelmintic (0.2% aversectin) at a do...
The effects of halothane and isoflurane on cardiovascular function in laterally recumbent horses. Experimental studies in adult horses have shown that general anaesthesia maintained with isoflurane is associated with less depression of cardiovascular function compared with halothane anaesthesia. Adverse effects of intermittent positive-pressure ventilation (IPPV) have also been demonstrated. Nevertheless, the haemodynamic effects of these agents and the effects of differing modes of ventilation have not been assessed during clinical anaesthesia in horses undergoing surgery. Methods: The haemodynamic effects of isoflurane or halothane anaesthesia during spontaneous or IPPV were studied non-...
Role of endothelium and nitric oxide in modulating in vitro responses of colonic arterial and venous rings to vasodilatory neuropeptides in horses. The objective of this study was to determine and compare the in vitro responses of equine large colon arterial and venous rings to vasodilatory neuropeptides; calcitonin gene-related peptide (CGRP); substance P (SP); vasoactive intestinal polypeptide (VIP); and acetylcholine (ACh), a standard nonpeptide endothelium-dependent vasodilator. Responses of vessel rings to graded concentrations (10(-11) M to 10(-5) M) of each drug were determined in endothelium-intact, denuded, and Nomega-nitro-L-arginine methyl ester (L-NAME, 10(-5) M)-treated rings that were pre-contracted with norepinephrine. Perc...
L-Bupivacaine 0.5% vs. racemic 0.5% bupivacaine for caudal epidural analgesia in horses. Bupivacaine is available as a racemic mixture of its enantiomers, d-bupivacaine and l-bupivacaine (LB). The aim of this randomized, double-blind study was to investigate the clinical efficacy and safety of S(-)-bupivacaine compared with standard racemic bupivacaine (RB) in horses under caudal epidural analgesia. Two treatments were administered to each horse, with a 2-week interval between subsequent treatments. Treatment 1 consisted of 0.5% LB at a dose of 0.06 mg/kg of body weight, and treatment 2 consisted of 0.5% RB at a dose of 0.06 mg/kg of body weight. Epidural injections were given in ...
Influence of vedaprofen (Quadrisol) on quality and freezability of stallion semen. The objective of this study was to evaluate the effect of the non-steroidal anti-inflammatory drug (NSAID) vedaprofen (Quadrisol) on quality and freezability of stallion semen. Experiments were performed using 22 Franches Montagnes stallions from the National Stud in Avenches (Switzerland) randomly divided into a control and test group. Vedaprofen was given orally to all stallions of the test group at the recommended therapeutic dose (initial dose of 2mg/kg followed by 1mg/kg body weight every 12h) for 14 days. Control animals received the same amount of carrier substance. During treatment, bl...
COX-1 and COX-2 inhibition in horse blood by phenylbutazone, flunixin, carprofen and meloxicam: an in vitro analysis. We report on the inhibitory activity of the NSAIDs meloxicam, carprofen, phenylbutazone and flunixin, on blood cyclooxygenases in the horse using in vitro enzyme-linked assays. As expected, comparison of IC50 indicated that meloxicam and carprofen are more selective inhibitors of COX-2 than phenylbutazone and flunixin; meloxicam was the most advantageous for horses of four NSAIDs examined. However at IC80, phenylbutazone (+134.4%) and flunixin (+29.7%) had greater COX-2 selectivity than at IC50, and meloxicam (-41.2%) and carprofen (-12.9%) had lower COX-2 selectivity than at IC50. We therefor...
Changes in bacterial and fungal ocular flora of clinically normal horses following experimental application of topical antimicrobial or antimicrobial-corticosteroid ophthalmic preparations. To determine effects of topical antimicrobial and antimicrobial-corticosteroid preparations on the ocular flora of horses. animals: 40 horses. Methods: One eye was treated 3 times daily for 2 weeks with one of the following ointments: (1) neomycin-bacitracin-polymyxin B, (2) 0.6% prednisolone-0.3% gentamicin, (3) neomycin-polymyxin B-0.05% dexamethasone, or (4) treated (artificial tears) control. Contralateral eyes of treated control eyes served as untreated control eyes. Corneal and conjunctival specimens for bacterial and fungal cultures were collected prior to initiation of treatment, after...
Dermatological and parasitological evaluation of infestations with chewing lice (Werneckiella equi) on horses and treatment using imidacloprid. Lice infestations in horses caused by the chewing louse Werneckiella (Damalinia) equi are observed worldwide. In the present study, the efficacy of 10% imidacloprid was tested on horses naturally infested with lice. Two groups of animals received a double application of 4 ml and 8 ml Advantage 10% spot-on on day 0 and 28 either. Horses, presenting dermatological signs with negative lice counts, were also included in this investigation. 40.86% of the horses presented positive lice counts and 84.21% of these animals showed clinical dermatologic signs. 65.45% of the lice-negative horses also show...
Effect of prolonged use of altrenogest on behaviour in mares. Oral administration of altrenogest for oestrus suppression in competition horses is believed to be widespread in some equestrian disciplines, and can be administered continuously for several months during a competition season. To examine whether altrenogest has any anabolic or other potential performance enhancing properties that may give a horse an unfair advantage, we examined the effect of oral altrenogest (0.044 mg/kg), given daily for a period of eight weeks, on social hierarchy, activity budget, body-mass and body condition score of 12 sedentary mares. It was concluded that prolonged ora...
Effect of alpha-tocopherol and tocopherol succinate on lipid peroxidation in equine spermatozoa. The objective of this study was to compare the effect of alpha-tocopherol and its ester, alpha tocopherol succinate, on lipid peroxidation and motility of equine spermatozoa. In experiment one, spermatozoa were incubated with dl-alpha-tocopherol (5, 25, 100 or 500 microM), DL-alpha tocopherol succinate (5, 25, 100 or 500 microM) or vehicle (0.5% ethanol) at 38 degrees C, and sperm motility was determined at 30, 60 and 120 min. In experiment two, spermatozoa loaded with the lipophilic probe, C11BODIPY(581/591), were incubated with dl-alpha-tocopherol (50 and 100 microM), DL-alpha-tocopherol suc...
Efficacy of omeprazole paste for prevention of recurrence of gastric ulcers in horses in race training. To determine whether omeprazole oral paste administered at a dosage of 0.5 or 1 mg/kg (0.23 or 0.45 mg/lb), PO, every 24 hours would effectively prevent the recurrence of gastric ulcers in horses in race training. Methods: Prospective study. Methods: 135 horses. Methods: Horses with gastric ulcers were treated with omeprazole at a dosage of 4 mg/kg (1.8 mg/lb), PO, every 24 hours for 28 days. Horses in the dose selection portion of the study were sham dose treated or received 0.5 or 1 mg of omeprazole/kg, PO, every 24 hours for an additional 28 days. Horses in the dose confirmation portion of ...
Evaluation of the clinical efficacy of prokinetic drugs in the management of post-operative ileus: can retrospective data help us? The objectives of the study were to determine whether retrospective data can be used to answer questions about the efficacy of prokinetic agents when used to treat horses with post-operative ileus (POI). We describe prevalence and mortality of POI with reference to treatment with four prokinetic agents. By combining data from two Hospitals a study population of 55 horses with POI following pedunculated lipoma obstruction (PLO) was established. Univariable and multivariable associations were determined between short term survival and potential explanatory variables. With death as outcome in mul...
Intravenous amiodarone treatment in horses with chronic atrial fibrillation. Six horses without underlying cardiac disease were presented because of atrial fibrillation of between 5 and 12 months duration. These horses received an intravenous amiodarone treatment of 5mg/kg/h for 1 h followed by 0.83mg/kg/h for 23h and subsequently 1.9mg/kg/h for 30h. During treatment, clinical signs were monitored and a surface ECG and an intra-atrial electrogram were recorded. Infusion was discontinued when sinus rhythm or side effects occurred. Four horses successfully cardioverted, of which one showed symptoms of hind limb weakness and weight shifting. Two horses did not cardiovert ...
Clinical and clinicopathological changes in 6 healthy ponies following intramuscular administration of multiple doses of imidocarb dipropionate. Haematological variables and selected serum indices, particularly those affected by changes in renal and hepatic function, were examined in 6 healthy ponies following 4 intramuscular doses of 4 mg/kg imidocarb dipropionate administered every 72 hours. This treatment regime has been reported to sterilise experimental Babesia equi infections in horses and may have value in preventing the spread of this disease during exportation of possible carrier horses to non-endemic countries. Serum bile acids and serum gamma glutamyltransferase activity were measured to evaluate the effect of this treatment...
Effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and clinicopathologic variables in horses. To quantitate the effects of desflurane and mode of ventilation on cardiovascular and respiratory functions and identify changes in selected clinicopathologic variables and serum fluoride values associated with desflurane anesthesia in horses. Methods: 6 healthy adult horses. Methods: Horses were anesthetized on 2 occasions: first, to determine the minimum alveolar concentration (MAC) of desflurane in O2 and second, to characterize cardiopulmonary and clinicopathologic responses to 1X, 1.5X, and 1.75X desflurane MAC during both controlled and spontaneous ventilation. Results: Mean +/- SEM MAC ...
Effects of sevoflurane dose and mode of ventilation on cardiopulmonary function and blood biochemical variables in horses. To quantitate effects of dose of sevoflurane and mode of ventilation on cardiovascular and respiratory function in horses and identify changes in serum biochemical values associated with sevoflurane anesthesia. Methods: 6 healthy adult horses. Methods: Horses were anesthetized twice: first, to determine the minimum alveolar concentration (MAC) of sevoflurane and second, to characterize cardiopulmonary and serum biochemical responses of horses to 1.0, 1.5, and 1.75 MAC multiples of sevoflurane during controlled and spontaneous ventilation. Results-Mean (+/- SEM) MAC of sevoflurane was 2.84 +/- ...
Effects of caffeine on exercise performance of physically fit Thoroughbreds. To determine the effects of a dose of caffeine (2.5 mg/kg, IV) administered to physically fit Thoroughbreds during incremental exercise testing to fatigue on a treadmill. Methods: 10 conditioned Thoroughbreds. Methods: Horses were randomly assigned to receive caffeine or a control solution. Each horse received both treatments in a crossover design with a 3-week interval between treatments. Each horse was administered caffeine (2.5 mg/kg) or an equivalent amount of a control solution IV. One hour after injection, each horse performed an incremental exercise test to exhaustion. Hematologic value...
Endothelial mechanisms underlying responses to acetylcholine in the horse deep dorsal penile vein. This study evaluates the mechanisms underlying endothelium-dependent responses to acetylcholine in horse deep dorsal penile veins. Acetylcholine-induced relaxation was abolished by endothelium removal, the soluble guanylyl cyclase-inhibitor, and the nitric oxide (NO) synthase inhibitors. Acetylcholine-induced relaxation was inhibited by high K+ concentrations and blockade of large-conductance Ca(2+)-activated potassium (BK(Ca)) channels, and voltage-dependent potassium (K(v)) channels. Relaxations were unaffected by a small-conductance K(Ca) (SK(Ca)) channel blocker, or an ATP-sensitive potass...
