The topic of medication in horses encompasses the study and application of pharmaceutical substances used to treat, manage, or prevent diseases and conditions in equine patients. This field involves understanding the pharmacokinetics and pharmacodynamics of various drugs, including their absorption, distribution, metabolism, and excretion in horses. Medications commonly administered to horses include non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, anthelmintics, and sedatives. The appropriate use of these medications is critical for ensuring therapeutic efficacy and minimizing adverse effects. Research in this area focuses on dosage optimization, drug interactions, resistance development, and withdrawal times to ensure both the health of the horse and compliance with regulatory standards. This page aggregates peer-reviewed studies and scholarly articles that explore the pharmacological aspects, clinical applications, and regulatory considerations of equine medications.
Steel CM, Pannirselvam RR, Anderson GA.The aims of this study were to determine the risk of septic arthritis after intra-articular medication (IAM) and to identify potential risk factors for this complication. Methods: A retrospective and prospective descriptive study of prevalence, and matched case-control study for risk factors. Results: Of 16,624 joints injected in 1103 horses at 6695 horse-visits, septic arthritis occurred as a complication in 13 joints (13 horses). The risk of septic arthritis following IAM was 7.8 cases per 10,000 injections or 1 case per 1279 injections. Veterinarian and type of corticosteroid were identifie...
Love EJ, Taylor PM, Whay HR, Murrell J.Buprenorphine has recently obtained UK Marketing Authorisation for horses. The analgesic effects are long lasting, and have considerable potential for postoperative pain relief. This observer blinded, randomised study aimed to evaluate postsurgical analgesia in ponies premedicated with buprenorphine prior to castration under intravenous anaesthesia. Ponies received either 0.01 mg/kg bodyweight (BW) buprenorphine (group B) or an equivalent volume of 5 per cent glucose (group C) given intravenously before induction of anaesthesia. Pain was assessed and recorded using dynamic interactive visual a...
Zozaya H, Gutierrez L, Bernad MJ, Sumano H.Doxycyline (Dox) is a semisynthetic antibacterial drug with pharmacological advantages over its parent drug (tetracycline) in the treatment of various bacterial diseases in horses. Yet, at present a horse-customized pharmaceutical formulation is not available. Based on its pharmacokinetic/pharmacodynamic (PK/PD) ratio, Dox is considered a time-dependent antibacterial drug and ideally expected to achieve sustained plasma drug concentrations both at or slightly above the minimal inhibitory concentration (MIC) level for as long as possible between dosing intervals. Hence, the objective of this st...
Raidal SL, Edwards S, Pippia J, Boston R, Noble GK.The pharmacokinetics, efficacy, and safety of meloxicam have been evaluated in adult horses, but not foals. Physiologic differences between neonates and adults might alter drug pharmacokinetics and therapeutic index. Objective: The pharmacokinetics of meloxicam will be different in foals compared with adult horses, and foals could be at increased risk for adverse drug effects. Methods: Twenty lightbreed foals less than 6 weeks of age at commencement of the study. Methods: Single and repeated oral dose pharmacokinetics were determined for meloxicam (0.6 mg/kg) in 10 foals. The safety of the d...
Brosnan RJ.Inhaled agents represent an important and useful class of drugs for equine anesthesia. This article reviews the ether-type anesthetics in contemporary use, their uptake and elimination, their mechanisms of action, and their desirable and undesirable effects in horses.
Casbeer HC, Knych HK.Tolazoline is an α2-adrenergic receptor antagonist, used in veterinary medicine to antagonize the central nervous system depressant and cardiovascular effects of α2 receptor agonists. The pharmacokinetics and pharmacodynamic effects of tolazoline when administered subsequent to detomidine in the horse were recently reported, although the reversal of the sedative and cardiovascular effects following detomidine may not be complete. The current study therefore investigated the pharmacokinetics and pharmacodynamic effects of tolazoline when administered as a sole agent. Nine healthy adult horses...
Lerche P.Total intravenous anesthesia (TIVA) is the mainstay of short-term (up to 60 minutes) and field anesthesia in horses. This article discusses the pros and cons of TIVA, commonly used TIVA protocols, and their use, monitoring during, and recovery from, TIVA.
Brommer H, Schipper P, Barneveld A, van Weeren PR.Records of lame horses (2004-2007) with (peri-)synovial pain of the metacarpophalangeal joint (MCPJ, n = 53), digital flexor tendon sheath (DFTS, n = 20), and distal interphalangeal joint (DIPJ, n = 31) were evaluated (n = 104). Cases were grouped according to the following treatments: (1) systemic administration of NSAIDs (n = 40); (2) intrasynovial administration of glucocorticosteroids (n = 30); (3) combination treatment (n = 34). Outcome was defined as successful when the owner reported that the horse had returned to its previous level of performance within a period of up to six months aft...
Dulin JA, Drost WT, Phelps MA, Santschi EM, Menendez MI, Bertone AL.To determine the effects of exercise on the distribution and pharmacokinetics of technetium Tc 99m medronate ((99m)Tc-MDP) following intra-articular (IA) injection in horses. Methods: 5 horses. Methods: 1 antebrachiocarpal joint (ACJ)/horse was assigned to the exercised group (n = 5), and the contralateral ACJ was evaluated in the nonexercised group (5) after a minimum washout period of 7 days. Following IA injection of (99m)Tc-MDP (148 MBq), blood and scintigraphic images of the carpus were obtained at 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 240, 360, 480, 600, 720, and 1,440 minutes. Plasma ...
Klier J, Fuchs S, May A, Schillinger U, Plank C, Winter G, Coester C, Gehlen H.In the recent years, nanotechnology has boosted the development of potential drug delivery systems and material engineering on nanoscale basis in order to increase drug specificity and reduce side effects. A potential delivery system for immunostimulating agents such as cytosine-phosphate-guanine-oligodeoxynucleotides (CpG-ODN) needs to be developed to maximize the efficacy of immunotherapy against hypersensitivity. In this study, an aerosol formulation of biodegradable, biocompatible and nontoxic gelatin nanoparticle-bound CpG-ODN 2216 was used to treat equine recurrent airway obstruction in ...
Fleming K, Mueller PO.The objective of this study was to identify parameters that would assist in determining the probability of a successful outcome with medical management versus surgical intervention in horses with ileal impaction. Medical records of 245 horses admitted for ileal impaction were reviewed and placed into 2 groups: medical (med) and surgical (sx) treatment. Persistence of abdominal pain, gastric reflux, frequency of analgesic administration, and 1-year survival were evaluated. There were no differences in signalment, abdominal pain, or heart rate among groups; however, significantly more sx horses ...
Marais HJ, Page PC.Equine sarcoid has been diagnosed in endangered Cape mountain zebra (Equus zebra zebra) in at least two game reserves in South Africa, with prevalence as high as 53% in Bontebok National Park. Seven Cape mountain zebras with sarcoids were treated with either surgical excision, 5-fluorouracil, allogenous vaccine, or a combination of 5-fluorouracil and allogenous vaccine. One of the two sarcoids on one of the 5-fluorouracil-treated zebras was left untreated. The microscopic features of the tumors evaluated showed either all or most of the typical epidermal and dermal histologic features of equin...
Aljuffali IA, Brainard BM, Moore JN, Kwon S, Allen D, Robertson TP, Arnold RD.The purpose of this study was to determine the pharmacokinetics (PK) of the 5-HT(2A) receptor antagonist ketanserin in healthy adult horses, and to develop a computational model that could be used to optimize dosing. Plasma concentrations of ketanserin were determined using liquid chromatography with mass spectrometry after single and multiple intravenous administration in the horse. A two-compartment linear pharmacokinetic model described the plasma concentration-time profile of ketanserin after single and multiple doses in healthy horses; the terminal half-life was 11.5 h; steady-state volum...
Rumpler MJ, Sams RA, Colahan P.A rapid, sensitive, and specific ultra-high-performance liquid chromatography with heated electrospray ionization-tandem mass spectrometry (UHPLC-HESI-MS-MS) method to detect and quantify glycopyrrolate in horse plasma has been developed and validated. We also determined glycopyrrolate in plasma after oral and intravenous administration of clinically relevant doses to Thoroughbred horses. Calibration was accomplished by weighted, linear regression analysis using a deuterated analogue of glycopyrrolate as internal standard (IS). Glycopyrrolate (GLY) and the IS (GLY-d(3)) were isolated from plas...
Lyons ET, Tolliver SC.Macrocyclic lactones (MLs) revolutionized parasite control in horses and other animals. They are unique in that they are effective against arthropods and nematodes. The first of the widely used avermectins was ivermectin. In 1983, it was marketed for use in horses as an injectable formulation but was withdrawn in 1984 after about a year and half on the market because of adverse problems. It was replaced by a paste formulation and an oral/stomach tube liquid formulation. Ivermectin is highly active on bots, ascarids, large and small strongyles, pinworms, strongyloides, stomach worms, and some o...
Waguespack RW, Hanson RR.Navicular syndrome is a chronic, progressive condition affecting the navicular bone and bursa, deep digital flexor tendon (DDFT), and associated soft tissue structures composing the navicular apparatus. The treatment options for navicular syndrome are as varied as the proposed causes of the condition. The severity of clinical signs, intended use and workload of the horse, and owner compliance with therapy are important considerations in developing a treatment plan. Nonsurgical treatment of navicular syndrome consists of rest, hoof balance and corrective trimming/shoeing, and medical therapy, i...
Morton AJ, Varney CR, Ekiri AB, Grosche A.N-butylscopolammonium bromide (NBB) and xylazine are commonly used medications for the treatment of spasmodic colic and other forms of abdominal pain in horses. Both NBB and xylazine exert significant effects on the cardiovascular system and other vital systems of horses. Objective: To evaluate the effects of i.v. administration of NBB, xylazine, and the combination of NBB and xylazine on heart rate, other commonly measured physiological parameters, cardiac rhythm and blood pressure. Methods: Six mature horses of mixed breed were used. In a random cross-over design, each horse was given 0.3 mg...
Bizley SC, Dudhia J, Smith RKW, Williams AC.Oral and parenteral drug delivery in horses can be difficult. Equine-specific transdermal drug formulations offer improved ease of treatment; development of such formulations requires a deeper understanding of the structural and chemical tissue barrier of horse skin. Objective: To compare the structural composition and barrier properties of equine skin. Methods: Six warmblood horses (two males, four females) with no skin diseases. Methods: Routine histological and microscopic analyses were carried out with image analysis for skin from six different anatomical locations. In vitro drug permeatio...
Sykes BW, Underwood C, Mills PC.Esomeprazole warrants further investigation as a treatment for equine gastric ulcer syndrome. Objective: To investigate the duration of intraday acid suppression achieved with two doses of esomeprazole under two dietary conditions. Methods: A four way crossover design. Methods: Six adult Thoroughbreds instrumented with percutaneous gastrotomy tubes were used. Intragastric pH was measured for continuous 23 h periods (08.00-07.00 h) for 6 consecutive days (Days 0-5). Baseline data was recorded on Day 0 and esomeprazole was administered on Days 1-5. Two doses (0.5 and 2.0 mg/kg bwt/day per os onc...
Sanchez LC, Lester GD, Merritt AM.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...
Clode A, Davis J, Davidson G, Salmon J, Lafevers H, Gilger B.To determine the transcorneal penetration and systemic absorption of a compounded 0.2% terbinafine solution following repeated topical administration to normal equine eyes. Sample population Six healthy adult horses with normal ocular examinations. Methods: One eye of each horse received 0.2 mL of a compounded 0.2% terbinafine solution every 4 h for seven doses. During the 1 h following administration of the final dose, multiple peripheral blood samples were obtained, and a single aqueous humor (AH) sample was collected at the end of the hour. AH and plasma concentrations of terbinafine wer...
Owen JM.Thirty eight cases of Fasciola hepatica infection in horses with associated clinical signs are reported. A method of examining large amounts of faeces for fluke is described. A safe method of treatment for infected horses is given which involves oral medication with oxyclozanide at a dose rate of 15 ml/50 kg body weight.
Moore BR, Abood SK, Hinchcliff KW.The medical records from 9 consecutive miniature horses (n = 5) and miniature donkeys (n = 4) with hyperlipemia (serum triglyceride concentration > 500 mg/dL) were reviewed. In all cases, hyperlipemia was a secondary complication of a primary systemic disease including septicemia, colitis, parasitism, esophageal obstruction, gastric impaction and rupture, fecalith, and pituitary adenoma. Therapy consisted of specific treatment for the primary disease, supportive care, and nutritional support. The mean time for resolution of hyperlipemia in cases requiring nutritional support (n = 6) was 7 days...
Kornreich B, Enyeart M, Jesty SA, Nydam DV, Divers T.Pentoxifylline (PTX) possesses a number of vasomotor, immunomodulatory, and hemorheologic properties. Based upon the hypothesis that equine laminitis and navicular disease result from microthrombosis, the inhibitory effects of PTX on inflammatory cytokines, and its inhibitory effects on human platelet aggregation, PTX has been widely used to treat equine endotoxemia, navicular disease, and laminitis. Despite this, the effects of PTX on equine platelet aggregation have not been investigated previously. Objective: PTX decreases platelet aggregation in equine whole blood at concentrations approxi...
Wilcke JR, Crisman MV, Sams RA, Gerken DF.Single doses (2.2 mg/kg of body weight) of phenylbutazone (PBZ) were administered IV to 6 neonatal horses (5 to 17 hours old at time of dosing). Plasma concentrations of PBZ and its metabolite oxyphenbutazone were monitored serially for 120 hours after drug administration. Pharmacokinetic variables were calculated, using 1- and 2-compartment open models. Descriptive equations from the best model for each foal were then used to derive model-independent variables describing PBZ disposition. Median volume of distribution at steady-state was 0.274 L/kg (range, 0.190 to 0.401 L/kg). Median terminal...
Kuroda T, Minamijima Y, Nomura M, Yamashita S, Yamada M, Nagata S, Mita H, Tamura N, Fukuda K, Kuwano A, Kusano K, Toutain PL, Sato F.For medication control in several jurisdictions, withdrawal time is the period of refrain from racing after drug administration. It is set by adding a safety period to an experimental detection time. However, there are no reports of statistical analyses of detection time for the determination of withdrawal time in flunixin meglumine-treated horses. Objective: To analyse the population pharmacokinetics of flunixin in horses through the generation of a dataset for detection time statistical analysis and predictions via Monte Carlo simulation. Methods: Experimental study. Methods: Drug plasma and...
Marais HJ, Page PC.Equine sarcoid has been diagnosed in endangered Cape mountain zebra (Equus zebra zebra) in at least two game reserves in South Africa, with prevalence as high as 53% in Bontebok National Park. Seven Cape mountain zebras with sarcoids were treated with either surgical excision, 5-fluorouracil, allogenous vaccine, or a combination of 5-fluorouracil and allogenous vaccine. One of the two sarcoids on one of the 5-fluorouracil-treated zebras was left untreated. The microscopic features of the tumors evaluated showed either all or most of the typical epidermal and dermal histologic features of equin...
DiPietro JA, Todd KS.The common anthelmintics used to treat parasitic infections of horses are described. Dosage, anthelmintic spectrum, formulation and administration, mode of action, toxicity contraindications, and resistance of parasites to anthelmintics are included.
Rumpler MJ, Sams RA, Colahan P.A rapid, sensitive, and specific ultra-high-performance liquid chromatography with heated electrospray ionization-tandem mass spectrometry (UHPLC-HESI-MS-MS) method to detect and quantify glycopyrrolate in horse plasma has been developed and validated. We also determined glycopyrrolate in plasma after oral and intravenous administration of clinically relevant doses to Thoroughbred horses. Calibration was accomplished by weighted, linear regression analysis using a deuterated analogue of glycopyrrolate as internal standard (IS). Glycopyrrolate (GLY) and the IS (GLY-d(3)) were isolated from plas...
Knych HK, Arthur RM, Steinmetz S, McKemie DS.Ketoprofen (KTP) is currently only available as an injectable formulation for intravenous administration to horses. The primary goal of the study reported here was to characterize the pharmacokinetics of KTP, including determination of bioavailability following oral administration of the currently available injectable formulation as well as a paste formulation. KTP was administered intravenously and orally, and blood and urine samples were collected at various time points up to 96 h. KTP enantiomer concentrations were determined using LC–MS/MS, and pharmacokinetic analyses were performed. Me...
Jacks S, Giguère S, Gronwall RR, Brown MP, Merritt KA.Clarithromycin offers numerous advantages over erythromycin and thus, is an attractive alternative for the treatment of Rhodococcus equi infections in foals. The disposition of clarithromycin was investigated in 6 foals after intragastric administration at a dose of 10 mg/kg body weight. Detectable serum concentrations of clarithromycin were found in 3 of 6 foals at 10 minutes and in all foals by 20 minutes post-administration. Time to peak serum concentration (Tmax) was 1.5 hours and peak serum concentration (Cmax) was 0.92+/-0.17 microg/ml. Mean serum concentrations decreased to 0.03 microg/...
Pauwels FE, Schumacher J, Castro FA, Holder TE, Carroll RC, Sega GA, Rogers CW.To determine whether clinically effective concentrations of methylprednisolone or triamcinolone can be achieved in the navicular bursa after injection of methylprednisolone acetate (MPA) or triamcinolone acetonide (TA) into the distal interphalangeal joint (DIPJ) and whether clinically effective concentrations of these drugs can be achieved in the DIPJ after injecting the navicular bursa with the same doses of MPA or TA. Methods: 32 healthy horses. Methods: Horses in groups 1 through 4 received 40 mg of MPA in the DIPJ, 10 mg of TA in the DIPJ, 40 mg of MPA in the navicular bursa, and 10 mg of...
Sullins KE, Messer NT, Nelson L.Twenty-one adult horses were randomly assigned into 7 groups of 3 and were treated for 5 days with procaine penicillin G, benzathine penicillin , or phenylbutazone in various combinations and dosage schedules. Serum concentration of penicillin was measured serially over a 7-day period. The highest mean peak serum concentration was 2.06 micrograms/ml. Comparable peak values were seen 2 to 4 hours after administration of 22,000 IU of procaine penicillin G/kg of body weight given once or twice daily. A minimum serum concentration of 0.25 micrograms/ml was selected as adequate for efficacy against...
Driessen B, Zarucco L, Kalir B, Bertolotti L.Current use of acepromazine in the anaesthetic management of male horses and ponies and associated risks are largely unknown. Objective: To explore anaesthetic acepromazine use and related adverse effects in the male horse. Methods: Of 8533 anaesthetised horses and ponies medical records of male animals treated perianaesthetically with acepromazine were reviewed. Demographic data, time and dose of acepromazine administration, co-administered drugs, quality of induction and recovery from anaesthesia, arterial blood pressures, and occurrence of penile dysfunction were recorded. Practising ACVA a...
Shaw ML, Carpenter JW, Leith DE.Carfentanil citrate, the only opioid approved in the United States for immobilizing large exotic animals, increasingly has been used to chemically restrain exotic horses, such as Prezwalski's horses (Equus przewalskii) and wild horses (E caballus). Because carfentanil's duration of action is long and renarcotization may develop 2 to 24 hours after administration of antagonists, a study was designed to compare the physiologic effects of opioid antagonists, using domestic horses chemically restrained with xylazine hydrochloride and carfentanil. The study was terminated after the initial 3 horses...
Vogt NA, Vriezen E, Nwosu A, Sargeant JM.Honey has a history of medicinal use that predates written records. In recent decades, there has been renewed interest in the use of honey in human medicine, particularly for the treatment of burns and other wounds. Several recent systematic reviews in the human literature have demonstrated the efficacy of honey in the treatment of a number of conditions, including burns, wounds and oral mucositis. The goal of this scoping review was to describe the nature and extent of the current body of evidence addressing the medicinal use of natural honey and/or its derivatives in animals. Although the fo...
Bennet ED, Parkin TDH.To identify risk factors associated with race-related sudden death in Thoroughbred racehorses in the US and Canada. 4,198,073 race starts made by 284,387 Thoroughbred horses at 144 racetracks in the US and Canada between 2009 and 2021. Study data were extracted from the Equine Injury Database, which contains detailed records of 92.2% of all official race starts made in the US and Canada during the study period. Forty-nine potential risk factors were analyzed using univariable and multivariable logistic regression. Cases were defined as race starts that resulted in fatality within 3 days of rac...
Johansson AM, Gardner SY, Levine JF, Papich MG, Lafevers DH, Goldman RB, Sheets MK, Atkins CE.Furosemide is the most common diuretic drug used in horses. Furosemide is routinely administered as IV or IM bolus doses 3-4 times a day. Administration PO is often suggested as an alternative, even though documentation of absorption and efficacy in horses is lacking. This study was carried out in a randomized, crossover design and compared 8-hour urine volume among control horses that received placebo, horses that received furosemide at 1 mg/kg PO, and horses that received furosemide at 1 mg/kg IV. Blood samples for analysis of plasma furosemide concentrations, PCV, and total solids were obta...
Singh S, Chopra M, Dilbaghi N, Manuja BK, Kumar S, Kumar R, Rathore NS, Yadav SC, Manuja A.Isometamidium hydrochloride (ISMM) is an effective drug for the treatment of trypanosomosis, but it causes local and systemic toxicity. Isometamidium hydrochloride has limited therapeutic index and exhibit considerable variation in their prophylactic activities. We developed a trypanocidal nanoformulation using ISMM and polymers sodium alginate/gum acacia to enhance the efficacy of the drug at lower doses, while minimizing undesirable side effects. It was characterized by transmission electron microscopy and infrared spectroscopy for evaluation of size, morphology, functional groups, etc. In v...
