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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.
Analgesic use, safety and pharmacokinetics of acetaminophen in equids: A structured scoping review. Despite its frequent use in equine clinical practice, scientific data on the use of acetaminophen in horses remain limited. Objective: To map and critically appraise the available evidence on the analgesic use, safety and pharmacokinetics of acetaminophen in horses. Methods: Structured scoping review. Methods: A comprehensive search was performed in accordance with the PRISMA Extension for Scoping Reviews using the terms '(paracetamol OR acetaminophen) AND (pain OR safety OR toxicosis OR pharmacokinetics) AND (horse OR pony OR donkey OR mule)' across Web of Science, Scopus, and PubMed from dat...
Challenges for interpreting results of antimicrobial susceptibility testing for treating infections of foals with Rhodococcus equi. Rhodococcus equi is a facultative intracellular pathogen and a major cause of pneumonia in foals worldwide. The standard treatment for affected foals is a combination of a macrolide with rifampicin. The widespread use of this combination has led to the emergence of multidrug-resistant (MDR) strains of R. equi. Consequently, antimicrobial susceptibility testing is essential for guiding treatment of rhodococcal pneumonia. Unfortunately, clinical breakpoints for macrolides and other antimicrobials against R. equi for foals are lacking, thereby complicating clinical interpretation of in vitro resu...
Pharmacokinetic/Pharmacodynamic Analysis of Quinidine-Induced Dominant Frequency Reduction in Thoroughbred Horses With Atrial Fibrillation. Quinidine has long been used for the pharmacological treatment of atrial fibrillation (AF) in horses; however, the plasma concentration required for conversion to sinus rhythm remains unclear. Dominant frequency (DF), derived from surface electrocardiograms, reflects atrial activation rate during AF. This study aimed to quantify the relationship between plasma quinidine concentration and DF using a pharmacokinetic/pharmacodynamic (PK/PD) approach. Ten Thoroughbred horses with naturally occurring AF received quinidine sulfate via a nasogastric tube. Plasma quinidine concentrations and DF values...
Detection of Cyclosporine in Horse Hair After Ocular Implant Administration. This study describes the detection and temporal distribution of cyclosporine in equine hair following ocular implant administration in a Thoroughbred gelding. Mane hair samples were collected at 172- and 217-day post-implantation and analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after alkaline hydrolysis and liquid-liquid extraction. The method achieved an estimated limit of detection of 0.1 pg/mg. Cyclosporine was detected in hair at both sampling time points, with segmental analysis revealing distribution patterns consistent with systemic exposure and incorporation ...
Plasma and Urinary Concentrations of Synephrine in Horses Following Controlled Oral Administration. Synephrine is a sympathomimetic alkaloid of regulatory interest in both horse racing and equestrian sports, where feed‑related exposure may lead to its detection in equine blood and urine. This study characterized plasma and urinary concentrations of synephrine in horses following controlled oral administration. Six Thoroughbred horses received single oral doses of 100 mg or 800 mg synephrine, and blood and urine samples were collected sequentially. Each sample was analyzed both before and after β‑glucuronidase hydrolysis, demonstrating that synephrine was present predominantly as conjuga...
Canagliflozin treatment of a horse with hyperinsulinemia, including pharmacokinetic analysis of different dosing protocols: a case report. Laminitis is a complex and painful disease of the equine foot. Insulin dysregulation (ID) resulting in hyperinsulinemia is responsible for more than 90% of cases in the general horse and pony population. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a relatively new class of drug that has gained considerable popularity as an off-label treatment of hyperinsulinemia-associated laminitis (HAL) in horses when traditional management changes and treatments are unsuccessful. In Canada, canagliflozin is the SGLT2i most available to equine veterinarians; although no dosing protocols have been ...
Administration Study of Bedinvetmab, an Antinerve Growth Factor Monoclonal Antibody, in Horses for Doping Control Purposes. Monoclonal antibodies (mAbs) targeting nerve growth factor (NGF) represent a novel therapeutic approach for managing acute and chronic pain in humans and animals. However, their potential misuse as pain-masking agents in competitive equine sports raises significant welfare and integrity concerns. To enhance understanding of the elimination profile of anti-NGF mAb if misused in horses, this study describes the first administration of bedinvetmab (a canine anti-NGF mAb) in three geldings, establishing its plasma elimination profile following subcutaneous administration. Bedinvetmab plasma concen...
Correction: Phenylbutazone concentrations in synovial fluid following administration via intravenous regional limb perfusion in the forelimbs of six adult horses. [This corrects the article DOI: 10.3389/fmed.2026.1810077.].
Assessment of pharmacokinetic parameters, oral bioavailability, and physiological effects of amantadine in horses. Without adequate pain management, central nervous system plasticity can result in acute or adaptive pain developing into chronic or maladaptive pain. This is difficult to manage and often unresponsive to traditional analgesics. An important mechanism associated with maladaptive pain is central sensitization which results in part from increased NMDA (N-methyl-D-aspartate) receptor activation. Amantadine is an NMDA receptor antagonist that has been used in combination with opioids and NSAIDs in humans and dogs for the treatment of conditions associated with central sensitization. The goal of the...
Characterization of the Pharmacokinetics and Physiological Effects of Tapentadol in Horses. Tapentadol is a dual mechanism analgesic utilizing both μ-opioid receptor (MOR) agonism and norepinephrine reuptake inhibition (NRI). This study evaluated the pharmacokinetics and pharmacodynamics of tapentadol as a potential analgesic with the goal of treating pain in horses. Pharmacokinetics of both tapentadol and tapentadol-O-glucuronide were elucidated. Six horses received three separate escalating single oral doses (1, 3, and 5 mg/kg) and a single intravenous (0.32 mg/kg) dose of tapentadol in a four-period sequential design. Concentrations of tapentadol and tapentadol-O-glucuronide ...
Meta-Analysis and Physiologically-Based Modeling of the Pharmacokinetics and Pharmacodynamics of Dexamethasone in Horses. Dexamethasone (DEX) is widely used in equine practice for its potent anti-inflammatory effects and diverse studies have examined its pharmacology in horses. We integrated all available pharmacokinetic (PK) and pharmacodynamic (PD) data from 12 studies to quantify DEX disposition and endocrine effects in horses. Methods: DEX concentrations in blood, urine and synovial fluid, plus cortisol (CTS) and glucose (GLU) in plasma, following various administration routes (intravenous (IV), intramuscular (IM), intra-articular, oral) were available from original studies or digitized from literature. A mi...
Comparative Pharmacokinetics of Gentamicin in Healthy Young-Adult and Geriatric Horses. Aging may modify the pharmacokinetic disposition and excretion of gentamicin, although drug dose adjustments in aged horses are uncommon in clinical practice. Since high-dose, once daily dosing of gentamicin is considered therapeutically most effective, a comparative single-dose study was conducted to evaluate the differences in pharmacokinetics between healthy young-adult (5-10 years) and geriatric (≥ 25 years) horses receiving 6.6 mg/kg gentamicin intravenously. Blood samples were collected at designated time-points following drug administration and frozen at -80°C until assayed b...
Pharmaceutical and Nutraceutical Therapies for Liver Disease. Liver dysfunction may reduce the metabolism of drugs that undergo extensive hepatic processing. This will lead to reduced clearance and elimination, and can cause accumulation of the drug, increasing the risk of toxicity. Pentoxifylline and ursodeoxycholic acid are 2 pharmaceuticals that can provide benefits for a variety of equine hepatic diseases. Nutraceuticals are frequently used in horses with hepatopathy, targeting oxidative stress, inflammation, and hepatocellular injury. Neutraceuticals such as S-adenosylmethionine, silymarin and vitamin E are most commonly used although extensive rese...
Plasma and urinary exposure of cannabidiol and cannabidiolic acid in horses following consumption of contaminated feed. Cannabidiol (CBD) and cannabidiolic acid (CBDA) are non-psychoactive cannabinoids naturally present in hemp-derived products. While these compounds are prohibited during equine competition, horses may be inadvertently exposed through contaminated feed. Data describing systemic and urinary exposure to CBD and CBDA following such low-dose, involuntary intake are limited. This study aimed to describe plasma and urine concentration-time profiles of CBD and CBDA in horses after consumption of experimentally contaminated feed. Results: Twelve Standardbred horses received feed containing low doses (1...
A Genetic Algorithm-Based Approach for Quantitative Prediction of Drug-Drug Interactions Caused by Cytochrome P450 3A Inhibition or Induction in Horses. A genetic algorithm (GA)-based approach was designed to predict drug-drug interactions (DDIs) triggered by cytochrome P450 3A (CYP3A) inhibition or induction in horses. Area under the concentration-time curve ratios (AUCRs), obtained from published in vivo DDI studies in horses, were used to compute the following parameters: (1) the contribution ratio (CR), i.e., the fraction of the substrate dose metabolized via the CYP3A pathway, and (2) the interacting drug's inhibitory potency or inducing efficacy (IR or IC, respectively). AUCRs for 9 substrates, 12 inhibitors, and 1 inducer of equine C...
Investigation of Metformin Contamination in Horses: Implications for Environmental Exposure and Doping Control. Metformin is a diabetes medication with minimal therapeutic efficacy in veterinary medicine. However, recently there have been several adverse analytical findings in regulatory samples collected from racehorses. Metformin is commonly prescribed to humans, is excreted unchanged in urine, and is resistant to environmental degradation, raising concerns with respect to environmental contamination. In this study, six horses were exposed to shavings contaminated with metformin-positive urine at concentrations of 10, 135, and 270 μg/mL. Blood (plasma, serum, whole blood, and red blood cells) and u...
Pharmacokinetics of Diclazuril in the Plasma and Cerebrospinal Fluid of Healthy Adult Horses After a Single Oral Dose Administered as a Pelleted Topdressing. Equine protozoal myeloencephalitis can cause acute infections with rapid onset of neurologic signs, necessitating immediate empiric therapy with antiprotozoal medication. The objective of the study was to identify when concentrations of diclazuril reached the MIC of Sarcocystis neurona in CSF (1 ng/mL) of healthy adult horses after a single oral dose. Six healthy adult horses were used. Blood and CSF were collected from indwelling intravenous jugular catheters and intrathecal catheters in the lumbosacral space prior to drug administration and then at 1-, 4-, 8-, 12-, 16-, 24-, 48-, 72-, 96-,...
Metabolic effects and pharmacokinetics of oral cannabidiol (CBD) in Connemara ponies following 21 days of treatment. Cannabidiol (CBD) has gained interest in equine medicine due to its potential therapeutic effects. Preclinical studies suggest that CBD may influence metabolic pathways relevant to metabolic syndrome, which present in both human and equine populations. The aim of this study was to evaluate the effects of oral CBD on metabolic parameters in Connemara ponies and to characterize its pharmacokinetics. Unassigned: A total of 13 Connemara ponies [seven with equine metabolic syndrome (EMS)] were stratified by EMS status and age and randomly assigned to a CBD-treated group (2 mg/kg orally, twice dai...
LC-HRMS detection of three ionizable lipids in equine plasma: surrogate markers for long-term LNP-mediated gene-doping surveillance. Lipid nanoparticles (LNPs) are essential delivery vehicles for messenger ribonucleic acid (mRNA)-based therapies. However, their potential misuse as gene-doping agents in horse racing and equestrian sports necessitates robust analytical surveillance. This study presents a highly sensitive, Orbitrap technology-driven liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method for the simultaneous detection of three clinically relevant ionizable lipids: ALC-0315, SM-102, and DLin-MC3-DMA (MC3), which are critical components of approved RNA therapeutics and vaccines. Following a modi...
Sensitive and selective quantification of elcatonin in equine plasma and urine using LC-FAIMS-MS/MS. The use of drugs for enhancing bone strength is prohibited under international regulations governing horse racing and equestrian sports. Elcatonin, a synthetic peptide with analgesic and bone-strengthening properties, is routinely monitored for compliance. However, its cyclic structure and high molecular weight hinder reliable detection. In this study, we developed and validated a sensitive liquid chromatography-high-field asymmetric waveform ion mobility spectrometry-tandem mass spectrometry method for quantifying elcatonin in equine plasma and urine. Sample preparation was optimised via weak...
Pharmacokinetics of Ertugliflozin, a Sodium-Glucose Co-Transporter-2 Inhibitor (SGLT2i) in Horses After Enteral Administration. Ertugliflozin is a sodium-glucose co-transporter-2 inhibitor that has demonstrated promise as a treatment for hyperinsulinaemia in horses. Despite the frequent use of ertugliflozin in equine clinical practice, the pharmacokinetics of this drug in horses has not been established. The aim of the present study was to determine the pharmacokinetics of one supratherapeutic dose (0.25 mg/kg) of ertugliflozin in eight horses. Horses were defined as being healthy by physical examination, haematological, blood biochemical and oral sugar test (OST) results. Plasma concentrations of ertugliflozin were qu...
An in vitro collagen gel contraction assay to assess the relaxing effect of potential pharmacological alternatives to oxytetracycline on foals’ tendons. Oxytetracycline has been successfully used to treat flexural limb deformities in foals. However, its antimicrobial properties and potential adverse side effects warrant the investigation of alternatives. Inhibition of matrix metalloproteinases (MMPs) or collagen cross-linking have been suggested as possible mechanisms of action. This study assessed the influence of potential alternative substances lacking antimicrobial properties on collagen gel contraction by juvenile equine myofibroblasts in vitro. Myofibroblasts were isolated from forelimb SDFTs and inferior check ligaments from foals eutha...
Efficacy of an iron absorption test on assessing iron status in horses. Iron absorption tests (IATs) are used to evaluate iron absorption in humans. However, this testing has not been conducted in horses. Objective: The objective was to assess how a large dose of iron affects blood iron parameters during an IAT. Methods: Mixed-breed geldings (n=12) were offered 2% of their bodyweight (BW) in mixed-grass hay and an iron-free vitamin-mineral supplement. A baseline IAT (Baseline IAT) was performed, where horses received 25 milligrams per kilogram (mg/kg) of BW of iron (ferrous sulfate) orally. Jugular venous samples were taken before the iron dose, and 3-, 6-, 12-, a...
Erythrocyte sequestration of metformin in horses: impact on matrix-specific pharmacokinetics and detection windows. BACKGROUND: Metformin is used for the treatment of type 2 diabetes and is one of the most prescribed medications in human medicine. It is less commonly prescribed in equine medicine, and its use is tightly regulated in several performance horse disciplines. In horseracing, it is considered a banned substance. A previous pharmacokinetic study of metformin in horses demonstrated a prolonged, unpredictable elimination phase. In the current study it was hypothesized that this was due to sequestration of metformin in a “deep” compartment, specifically red blood cells. This could result in pharm...
A single pneumatic tourniquet is superior to wide rubber tourniquets for saphenous intravenous regional limb perfusion with amikacin in standing, sedated horses. To establish whether tourniquet type and number influence synovial fluid amikacin concentrations of the tarsocrural joint (TCJ) or metatarsophalangeal joint (MTPJ) after standing saphenous IV regional limb perfusion (IVRLP) with 2 g of amikacin. Unassigned: 8 healthy adult horses underwent 4 saphenous IVRLP protocols with amikacin, differing in tourniquet type (pneumatic vs wide rubber) and number (1 placed mid-gaskin vs 1 placed mid-gaskin and 1 mid-metatarsus) in a randomized, crossover design. Amikacin concentrations were measured in serum and synovial fluid of the TCJ and MTPJ at 15 and 30...
Analytical Challenges and Emerging Detection Strategies of Synthetic Cannabinoids in Horse Doping Control. Synthetic cannabinoids (SCs) were originally synthesized to advance the understanding of the endocannabinoid system, facilitate disease research, and support the development of novel therapeutic agents. Compared with tetrahydrocannabinol, these compounds exhibit substantially higher psychoactive potency and enhanced receptor-binding affinity. The rapid and continuous evolution of SC derivatives presents significant challenges for analytical laboratories and increases the risk of misuse. Furthermore, SCs may be exploited to alter performance in both human and animal sports. The scarcity of comp...
Pharmacokinetics of 2 mg/kg Bupivacaine in a Rectus Abdominis Sheath Block in Horses. Administering large volumes of bupivacaine in the rectus abdominis sheath (RAS) block in horses could cause local anesthetic toxicity. This study aimed to evaluate the pharmacokinetics of 2 mg/kg bupivacaine in RAS blocks and the associated toxicity risk. Six healthy adult horses were sedated with xylazine and received an ultrasound-guided bilateral 2-point RAS block. Plasma samples were collected at baseline and from 5 min to 24 h after the block and analyzed using liquid chromatography-tandem mass spectrometry. A noncompartmental analysis was performed to determine the maximum concentr...
Pharmacokinetics of Intramuscularly Administered Ketamine at Subanaesthetic Dosage in Horses. Subanaesthetic doses of ketamine (0.5 mg kg) provide analgesia in several species, but there is limited information on the pharmacokinetics and clinical effects of intramuscularly administered ketamine in horses. This study investigated the pharmacokinetics of ketamine and norketamine, and evaluated clinical effects, ataxia, and vital parameters, following intramuscular and intravenous administration of 0.5 mg kg ketamine in nine healthy horses, using a randomized two-period crossover design with a 1-week washout period. Plasma concentrations were analyzed using Ultra-High Performance ...
Plasma Concentrations Following Oral Administration of Two Different Forms of Resveratrol in Horses. Resveratrol is a compound found in multiple plants and there is evidence for its use as a supplement in horses, particularly through protection of chondrocytes. Previous studies on the clinical efficacy of resveratrol supplementation in horses have reported limited benefits. To date, there is no pharmacokinetic data of resveratrol in horses but the bioavailability of resveratrol in other species is poor. In this crossover study, the plasma concentrations of two forms of resveratrol were examined. Each horse received via nasogastric tube, either a single dose of resveratrol phospholipid or a st...
Plasma and Urinary Elimination Profiles of Medetomidine Metabolites in Horses for the Purpose of Doping and Medication Control. Medetomidine, an α₂-adrenergic agonist, is widely used as a sedative in horses. While its pharmacological effects are established, limited data exist on elimination of its metabolites, 3'-hydroxy medetomidine (HMD) and 3'-carboxy medetomidine (CMD), which are of regulatory interest. HMD is currently targeted in plasma and urine under International Screening Limits (ISLs) established by the International Federation of Horseracing Authorities (IFHA). In this study, seven Thoroughbreds received 6.3 μg/kg of medetomidine intravenously. Blood and urine were collected for 96 h and analyzed b...
