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Topic:Pharmacokinetics
Pharmacokinetics in horses involves the study of how drugs are absorbed, distributed, metabolized, and excreted in equine species. This field of study provides insights into the time course of drug concentrations within the horse's body and helps in understanding the effects of various pharmaceuticals. Key parameters in equine pharmacokinetics include absorption rates, bioavailability, half-life, and clearance. These parameters can vary significantly due to factors such as age, breed, and health status of the horse. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetic profiles of different drugs in horses, aiming to optimize dosing regimens and improve therapeutic outcomes in equine medicine.
Diffusion of fluoroquinolones into equine fetal fluids did not induce fetal lesions after enrofloxacin treatment in early gestation. While recent work demonstrated that enrofloxacin and ciprofloxacin reach the fetoplacental unit without causing obvious lesions in the 9-month-old equine fetus or resulting foal, many practitioners still hesitate to prescribe a fluoroquinolone during pregnancy. Since early gestation is a critical time for fetal skeletal development, if fluoroquinolones are chondrotoxic to the fetus at any point during gestation, this period would be important. The aim of this study was to assess the effects of 2 weeks' exposure to enrofloxacin on the equine fetus between 46 and 60 days gestation. Twelve pregna...
Pharmacokinetics of hydroxyzine and cetirizine following oral administration of hydroxyzine to exercised Thoroughbred horses. Hydroxyzine is a first-generation antihistamine and cetirizine, a second-generation antihistamine and active metabolite of hydroxyzine. Hydroxyzine is commonly used in performance horses and as such its use in closely regulated; however, there are no published studies suitable for establishing appropriate regulatory recommendations. In the current study, 12 exercised Thoroughbred research horses received a single oral administration of 500ย mg of hydroxyzine. Blood and urine samples were collected prior to and up to 96ย hr postdrug administration and concentrations of hydroxyzine and cetirizin...
Behavioural and cardiovascular effects of medetomidine constant rate infusion compared with detomidine for standing sedation in horses. To compare the efficacy of a medetomidine constant rate infusion (CRI) with a detomidine CRI for standing sedation in horses undergoing high dose rate brachytherapy. Methods: Randomized, controlled, crossover, blinded clinical trial. Methods: A total of 50 horses with owner consent, excluding stallions. Methods: Each horse was sedated with intravenous acepromazine (0.02 mg kg-1), followed by an ฮฑ2-adrenoceptor agonist 30 minutes later and then by butorphanol (0.1 mg kg-1) 5 minutes later. A CRI of the same ฮฑ2-adrenoceptor agonist was started 10 minutes after butorphanol administration and ma...
Retrospective evaluation of clinical use of cis-atracurium in horses. To the authors' knowledge, there are no reports describing the use of cis-atracurium in the horse. To describe the onset time and the duration of the neuromuscular blockade (NMB) of three different doses of cis-atracurium in horses and to determine the appropriate dose needed maintain a NMB. Retrospective study. Horses which received cis-atracurium as part of a balanced anaesthetic protocol at the Equine Teaching Hospital of the University of Liรจge between March 2014 and June 2017 were included in this study. A train-of-four (TOF) stimulation pattern was used to assess the NMB. The cis-atracu...
Systematic analysis to assess the scientific validity of the international residue limits for caffeine and theophylline in horse-racing. Based on their performance-enhancing potential, caffeine and theophylline are prohibited substances in equine sports. Residues in horses can be caused by wilful application or by unintended uptake of contaminated feed. The International Federation of Horseracing Authorities recently introduced international residue limits (IRLs) to facilitate the discrimination between pharmacological relevant and irrelevant concentrations in doping samples. The objective of this study was to investigate the scientific validity of these IRLs. A systematic analysis was performed to assess the IRLs by different ...
Pharmacokinetics of furosemide in thoroughbred horses subjected to supramaximal treadmill exercise with and without controlled access to water. The primary objective of this study was to assess the disposition of furosemide in Thoroughbred horses treated intravenously with 1โmg/kg of furosemide 4 and 24โh before supramaximal treadmill exercise without and with controlled access to water, respectively. Another objective was to determine whether furosemide was detectable in the plasma of horses after exposure to supramaximal treadmill exercise. Thoroughbred horses (nย =โ4-6) were administered single intravenous doses of 1โmg/kg of furosemide at 4 and 24โh before supramaximal exercise on a high-speed treadmill, with controlled ...
Detection, pharmacokinetics, and selected pharmacodynamic effects of methamphetamine following a single transmucosal and intravenous administration to exercised Thoroughbred horses. Methamphetamine is a central and peripheral nervous system stimulant. There is only a single study that describes exposure to and disposition of this compound in horses. The potential for abuse and inadvertent exposure in equine athletes along with the limited data available necessitates further study. The objectives of the current study were to describe drug and metabolite concentrations, develop an analytical method that could be used to regulate its use, and describe selected pharmacodynamic effects. In phase 1, six horses were randomized into three transmucosal dose groups (nย =ย 2/group; ...
Characterization of the in vitro CYP450 mediated metabolism of the polymorphic CYP2D6 probe drug codeine in horses. Despite their widespread popularity as sport and companion animals and published and anecdotal reports of vast difference in drug disposition and pharmacokinetics between individuals, studies describing equine drug metabolism are limited. It has been theorized that similar to humans, members of the CYP2D family in horses may be polymorphic in nature leading to differences in metabolism of substrates. This study aims to build on the limited current knowledge regarding P450 mediated metabolism in horses by describing the metabolism of the polymorphic CYP2D6 probe drug codeine in vitro. Codeine, ...
Pharmacokinetics and pharmacodynamics of olopatadine following administration via nasogastric tube to healthy horses. To investigate the pharmacokinetics and antihistaminic effects (pharmacodynamics) of olopatadine in a small population of healthy horses after administration via nasogastric tube. Methods: 4 healthy adult Thoroughbreds. Methods: Olopatadine (0.1 mg/kg, once) was administered via nasogastric tube. Blood samples were collected at predetermined time points for pharmacokinetic analyses of the drug in plasma. Olopatadine effects were investigated by measurement of cutaneous wheals induced by ID histamine injection (0.1 mL [10 ฮผg]/injection) at predetermined time points. Inhibition effect ratios we...
Tamoxifen in horses: pharmacokinetics and safety study. Tamoxifen (TAM), a selective modulator of estrogen receptors (SERMs) has been recently explored as a therapeutic option for the oral treatment of airway inflammation in the horse. The objective of this work was to establish pharmacokinetic parameters of TAM and its main metabolites in equines, as well as to determine its clinical safety in short-term treatments. Results: We determined TAM and its three main metabolites (4-OH tamoxifen, endoxifen, and N-desmethyl tamoxifen) in plasma after single administration of 0.25โmg/kg in healthy adult horses (ย =โ12). A maximum concentration of TAM w...
Plasma and synovial fluid pharmacokinetics of a single intravenous dose of meropenem in adult horses. The objective of this study was to determine the pharmacokinetics of meropenem in horses after intravenous (IV) administration. A single IV dose of meropenem was administered to six adult horses at 10ย mg/kg. Plasma and synovial fluid samples were collected for 6ย hr following administration. Meropenem concentrations were determined by bioassay. Plasma and synovial fluid data were analyzed by compartmental and noncompartmental pharmacokinetic methods. Meanย ยฑย SD values for elimination half-life, volume of distribution at steady-state, and clearance after IV administration for plasma samples ...
Disposition and effect of intra-articularly administered dexamethasone on lipopolysaccharide induced equine synovitis. Dexamethasone is used for the intra-articular route of administration in management of aseptic arthritis in horses. Despite its widespread use there is very little quantitative data of the disposition and response to dexamethasone. The aim of this study was to investigate and describe the synovial fluid and plasma dexamethasone concentration over time and to explore the relation between synovial fluid concentration and response using clinical endpoints as response biomarkers after IA injection of dexamethasone disodium salt solution in an equine model of synovitis. Results: Inflammation was in...
Evaluation of the sedative effects and pharmacokinetics of detomidine gel administered intravaginally to horses. To determine the sedative effects and pharmacokinetic profile of detomidine when administered intravaginally as a gel formulation to horses. Methods: Randomized, crossover, masked experimental design. Methods: A group of six healthy adult mares (494 ยฑ 56 kg). Methods: Mares were studied on two occasions and were administered either detomidine hydrochloride (10 ฮผg kg) intravenously (treatment IV) or detomidine gel (40 ฮผg kg) intravaginally (treatment IVG), separated by 1 week. Sedation, ataxia, muzzle-floor distance and heart rate (HR) were evaluated every 15 minutes for 240 minutes. Venous ...
Perspectives on the utility of moxidectin for the control of parasitic nematodes in the face of developing anthelmintic resistance. Macrocyclic lactone (ML) anthelmintics are the most important class of anthelmintics because of our high dependence on them for the control of nematode parasites and some ectoparasites in livestock, companion animals and in humans. However, resistance to MLs is of increasing concern. Resistance is commonplace throughout the world in nematode parasites of small ruminants and is of increasing concern in horses, cattle, dogs and other animals. It is suspected in Onchocerca volvulus in humans. In most animals, resistance first arose to the avermectins, such as ivermectin (IVM), and subsequently to...
Pharmacokinetics of single doses of maropitant citrate in adult horses. The neurokinin-1 (NK) receptor antagonist, maropitant citrate, mitigates nausea and vomiting in dogs and cats. Nausea is poorly understood and likely under-recognized in horses. Use of NK-1 receptor antagonists in horses has not been reported. The purpose of this study was to determine the pharmacokinetic profile of maropitant in seven adult horses after single intravenous (IV; 1ย mg/kg) and intragastric (IG; 2ย mg/kg) doses. A randomized, crossover design was performed. Serial blood samples were collected after dosing; maropitant concentrations were measured using LC-MS/MS. Pharmacokinetic pa...
Plasma concentrations at two dexmedetomidine constant rate infusions in isoflurane anaesthetized horses: a clinical study. To determine dexmedetomidine plasma concentrations at two infusion rates in isoflurane anaesthetized horses and compare cardiovascular effects and anaesthetic recovery between treatments. Methods: Prospective, randomized, masked clinical study. Methods: Healthy, adult, client-owned, non-food producing horses presented for castration. Methods: Premedication consisted of acepromazine, romifidine and morphine, and anaesthesia was induced with ketamine and midazolam. The horses were randomized to receive dexmedetomidine 0.5 ฮผg kg hour (treatment DL, nย = 7) or 1.75 ฮผg kg hour (treatment DH, nย =...
Pharmacokinetics of chloramphenicol base in horses and comparison to compounded formulations. Chloramphenicol is commonly used in horses; however, there are no studies evaluating the pharmacokinetics of veterinary canine-approved tablets. Studies using different formulations and earlier analytical techniques led to concerns over low bioavailability in horses. Safety concerns about human health have led many veterinarians to prescribe compounded formulations that are already in suspension or paste form. The objective of this study was to evaluate the pharmacokinetics of approved chloramphenicol tablets in horses, along with compounded preparations. The hypothesis was that chloramphenico...
Effect of fentanyl on thermal and mechanical nociceptive thresholds in horses and estimation of anti-nociceptive plasma concentration. There are few investigations relating anti-nociception to plasma concentrations of fentanyl in horses. The study objective was to evaluate analgesic efficacy and duration in horses and determine the minimum anti-nociceptive plasma concentrations. Eight horses were treated with saline (P) and fentanyl (F=2.5ฮผg/kg; F=5ฮผg/kg; F=10ฮผg/kg) given IV over 5min, with a wash-out period of 10 days. To evaluate thermal (ยฐC) and mechanical (N) nociceptive threshold single stimulations were applied prior to (baseline) and 10, 30, 60, 90, 120, 180, 240, 300, 360, 420, 540min and 22.5h after treatment. Pl...
Effects of high doses of levothyroxine sodium on serum concentrations of triiodothyronine and thyroxine in horses. To investigate the effect of high doses of orally administered levothyroxine sodium (LT) on serum concentrations of triiodothyronine (T) and thyroxine (T) in euthyroid horses. Methods: 12 healthy adult horses. Methods: 10 horses initially received water (vehicle) or 240 mg (5X treatment) or 480 mg (10ร treatment) of LT, and blood samples were collected at baseline (0 hours) and 0.5, 1, 2, 4, 6, 8, 10, 12, 18, 24, 48, 72, 96, and 120 hours after treatment to measure serum T and T concentrations. Three horses then received 480 mg of LT for 14 days, and T concentration was measured on days 0, 14...
Paper spray high-resolution accurate mass spectrometry for quantitation of voriconazole in equine tears. Paper spray high-resolution accurate mass spectrometry is a fast and versatile analysis method. This ambient ionization technique enables the quantitation of xenobiotics in complex biological matrices without chromatography or conventional sample extraction. The simplicity, rapidity, and affordability of the paper spray mass spectrometry (PS-MS) method make the technique especially attractive for clinical investigations where fast and affordable sample analysis is crucial. A new PS-MS method for the quantitation of voriconazole in equine tears was developed and validated. For a concentration r...
Intra-articular triamcinolone acetonide improves lung function in horses with severe asthma. Locally administered corticosteroids are commonly used to treat joint diseases in sport and racehorses. As they are also the most potent drugs for the treatment of equine asthma, we hypothesised that the intra-articular corticosteroids used to treat joint diseases also improve the lung function in horses with severe asthma, thus potentially delaying the diagnosis of this common lung condition. Objective: To compare the effects of intra-articular (IA) and intramuscular (IM) triamcinolone acetonide (TA) on lung function in horses with severe asthma. Methods: Randomised and controlled experiment ...
In silico and in vitro analysis of genetic variants of the equine CYP3A94, CYP3A95 and CYP3A97 isoenzymes. Cytochrome P450 enzymes (CYPs) of the equine CYP3A subfamily are predominantly involved in drug metabolism. In this study, genetic variants of the equine CYP3A94, CYP3A95, and CYP3A97 were identified and characterized using in silico modeling and in vitro enzyme kinetics. The genomes of 81 horses were sequenced to obtain the genetic variants. Structural CYP modifications of the most frequent variants were analyzed in silico using the 3D-structures predicted by homology modeling. Enzyme kinetic analyses were performed using testosterone as substrate. Twenty genetic variants were found including...
A retrospective study of fecal output and postprocedure colic in 246 horses undergoing standing sedation with detomidine, or general anesthesia with or without detomidine. To determine time to first passage of feces, total fecal piles and incidence of colic in the first 24 hours postprocedure in horses undergoing standing sedation with detomidine, or general anesthesia with or without detomidine. Methods: Retrospective cohort study. Methods: A total of 246 horses. Methods: Records of all horses that underwent standing sedation or general anesthesia between December 2012 and March 2016 were reviewed. Horses aged <6 months, admitted for colic or cesarean section, with inadequate data, and those not administered xylazine and/or detomidine were excluded. Records ...
Effects of continuous positive airway pressure on respiratory function in sedated foals. To characterize the effects of continuous positive airway pressure (CPAP) delivered by a commercial human CPAP device on respiratory function in foals with pharmacologically induced respiratory suppression. Methods: Prospective randomized, cross-over study comparing CPAP with spontaneous respiration and oxygen insufflation. Methods: University veterinary teaching hospital. Methods: Twelve foals born in consecutive seasons from a university teaching herd. Methods: Foals were randomized to receive 10 minutes of respiratory support by mask oxygen supplementation or CPAP as a first treatment after...
Pharmacokinetics and competitive pharmacodynamics of ADP-induced platelet activation after oral administration of clopidogrel to horses. To determine pharmacokinetics and pharmacodynamics after oral administration of a single dose of clopidogrel to horses. Methods: 6 healthy adult horses. Methods: Blood samples were collected before and at various times up to 24 hours after oral administration of clopidogrel (2 mg/kg). Reactivity of platelets from each blood sample was determined by optical aggregometry and phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Concentrations of clopidogrel and the clopidogrel active metabolite derivative (CAMD) were measured in each blood sample by use of liquid chromatography-tandem...
Pilot study to quantify the time to clear dexamethasone from plasma and urine of adult horses following a single nebulisation. To quantify the time to clear dexamethasone from plasma and urine of horses following a single nebulisation. Methods: Experimental using six Standardbred mares. Methods: Dexamethasone sodium phosphate (0.04โmg/kg) diluted in 0.9% sodium chloride was administered as an aerosol using a Flexineb E2ยฎ nebuliser. Blood samples (0, 2, 4, 6, 8, 10, 12, 24, 32, 48, 72 and 96โh) and urine samples (0, 1, 4, 8, 24, 32, 48, 72 and 96โh) were collected for analysis using liquid chromatography mass spectrometry. Results: Maximum plasma concentrations (t ) were reached by the earliest detection point (...
Pharmacokinetics and safety of repeated oral dosing of acetaminophen in adult horses. There are no published studies on the pharmacokinetics of acetaminophen at the dosage used clinically (20ย mg/kg), nor has the safety of multiple doses in horses been investigated. Objective: Define the pharmacokinetic parameters of oral acetaminophen at 20ย mg/kg in adult horses as a single dose, and twice daily for 14ย days to assess the safety of multiple dosing. Methods: Pharmacokinetic study, multiple dose safety study. Methods: Eight healthy Thoroughbred geldings were given acetaminophen (20ย mg/kg; 500ย mg tablets) orally as a single dose followed by doses every 12ย h for 14ย days. Seri...
Continuous fluid infusion per rectum compared with intravenous and nasogastric fluid administration in horses. Rectal fluid administration may offer a simple, safe and inexpensive alternative to intravenous or nasogastric fluid therapy in equine clinical cases. Objective: To evaluate the tolerance and effects of rectally administered fluid and compare the measurements of haemodilution and intravascular volume with those during nasogastric and intravenous fluid administration. Methods: Randomised controlled experimental trial. Methods: Six clinically normal Standardbred geldings were used in a 4-way crossover study: each received three different fluid treatments (intravenous, nasogastric and rectal) at ...
Endogenous and exogenous effects of PGF2ฮฑ during luteolysis in mares. An inhibitor of PGF2ฮฑ biosynthesis (flunixin meglumine, FM) was used to study the role of endogenous PGF2ฮฑ on the luteolytic effect of exogenous PGF2ฮฑ in mares. A 2-h infusion of PGF2ฮฑ at a constant rate (total dose, 0.1ย mg) on Day 10 (ovulationย =ย Day 0) was used to mimic the maximal concentrations of a spontaneous pulse of a PGF2ฮฑ metabolite (PGFM). Treatment with FM (1.7ย mg/kg) was done 1ย h before and 5ย h after the start of PGF2ฮฑ infusion. In hourly blood samples beginning 1ย h before the start of PGF2ฮฑ infusion, progesterone decreased (Pย <ย 0.05) similarly by 5ย h in each o...
Clinical pharmacokinetics and pharmacodynamics of intravenous alfaxalone in young Thoroughbred horses premedicated with medetomidine and midazolam. To investigate the clinical pharmacokinetics and pharmacodynamics of intravenous alfaxalone in young Thoroughbred horses, seven Thoroughbred horses were randomly anaesthetised twice with either 1 or 2โmg/kg of intravenous alfaxalone after premedication with medetomidine (6โยตg/kg intravenous) and midazolam (20โยตg/kg intravenous). Blood samples were collected at predetermined time points up to twoโhours after administration. Plasma alfaxalone concentrations were quantified by a liquid chromatography tandem-mass spectrometry method and analysed by non-compartmental pharmacokinetic analy...
