The topic of drugs and horses encompasses the study of various pharmacological agents used in equine medicine for therapeutic purposes. This includes the administration of medications for pain management, disease treatment, and performance enhancement. The pharmacokinetics and pharmacodynamics of drugs in horses are key areas of research, as they determine the absorption, distribution, metabolism, and excretion of these substances. Additionally, the topic covers the detection and regulation of substances in competitive equestrian sports to ensure fair play and animal welfare. This page compiles peer-reviewed research studies and scholarly articles that explore the effects, safety, and regulatory aspects of drug use in equine health and performance.
McKenzie HC, Murray MJ.To assess gentamicin concentrations in serum and bronchial lavage fluid (BLF) of horses during a 24-hour period after once-daily aerosol administration of gentamicin (GAER) for 7 days and the pattern and degree of bronchial tree inflammation associated with repeated GAER. Methods: 13 healthy adult horses (9 geldings and 4 mares). Methods: The treatment group comprised 8 horses, and 5 horses were untreated control animals. Gentamicin (20 mL of gentamicin [50 mg/mL]) was administered via aerosol once daily for 7 days. Samples of serum and BLF were obtained from all horses before GAER and 0.5, 4,...
van den Hoven R, Hierweck B, Dobretsberger M, Ensink JM, Meijer LA.The Pharmacokinetics (PK) and distribution into tissue chamber fluid (TCF) of intramuscularly (i.m.) administered ampicillin sodium were examined in horses in order to design adequate dosing strategies. Concentration-time curves of ampicillin in plasma and TCF were determined in six horses following administration of 15 mg/kg ampicillin sodium, before and after the induction of local inflammation with 0.5% carrageenan. The calculated parameters were used to simulate various dosage-dosing interval combinations. Ampicillin was absorbed very rapidly following i.m. administration. Plasma concentra...
Kollias-Baker C, Maxwell L, Stanley S, Boone T.Cocaine is a naturally occurring alkaloid that is commonly abused by human-beings for its psychostimulatory effects. Occasionally, very small concentrations (i.e. <100 ng/mL) of the primary cocaine metabolite, benzoylecgonine (BZE) have been detected in urine collected from horses competing in athletic events. In this study urine samples, collected from four horses following the administration of 2.5 and 20 mg of cocaine sublingually and 50 mg of cocaine intravenously, were analyzed for the presence of cocaine and/or its metabolites by enzyme-linked immunosorbent assay (ELISA) and gas chrom...
Johnston GM, Eastment JK, Taylor PM, Wood JL.Approximately 1 in 100 horses suffer unexpectedly from anaesthetic-related death. Identification and use of the safest anaesthetic drugs should support this aim. Experimental evidence has suggested that isoflurane should be a safer maintenance agent in equine anaesthesia than halothane. Objective: The death rate would be reduced in horses being maintained with isoflurane compared to halothane. Methods: A multicentre randomised controlled trial was undertaken to compare the effects of isoflurane and halothane for maintenance of equine anaesthesia for all types of operation. Data were analysed f...
Luo Y, Rudy JA, Uboh CE, Soma LR, Guan F, Enright JM, Tsang DS.The method describes quantification and confirmation of flunixin in equine plasma by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC/Q-TOF/MS/MS). Samples were screened by enzyme-linked immunosorbent assay (ELISA) and only those samples presumptively declared positive were subjected to quantification and confirmation for the presence of flunixin by this method. The method is also readily adaptable to instrumental screening for the analyte. Flunixin was recovered from plasma by liquid-liquid extraction (LLE). The sample was diluted with 2 ml saturated phosphate buffer (pH ...
Papich MG.Antibiotics will always be needed in horses for many types of infections, but the adverse consequences also must be considered. For the conditions described in this article, there is justification for antibiotic therapy. The intestinal problems that antibiotics can induce are among the risks from their administration to horses. Disruption of the endogenous bacterial population, colitis, and diarrhea are the most common complications from antibiotic therapy.
Nebbia C, Dacasto M, Carletti M.Little is known about the effects of aging on the hepatic drug metabolizing capacity of horses despite the relatively long lifespan characterizing this species. A wide array of cytochrome P450 (CYP)-dependent monooxygenases, carboxylesterases and transferases were assayed in liver microsomes from 50 female horses in an age range between less than 1 year to over 12 years. Rather unexpectedly, both the CYP content and the activity of NADPH cytochrome c reductase rose as a function of age. Accordingly, a general increasing trend was recorded in the rate of the in vitro metabolism of the substrate...
O'Conner MS, Steiner JM, Roussel AJ, Williams DA, Meddings JB, Pipers F, Cohen ND.To evaluate the use of sucrose permeability testing to detect ulcers in the gastric squamous mucosa of horses. Methods: 13 adult horses ranging from 5 to 19 years of age. Methods: Following induction of gastric ulcers by intermittent feed deprivation, horses underwent sucrose permeability testing (administration of sucrose by nasogastric intubation followed by collection of urine at 2 and 4 hours after intubation) and gastric endoscopy. Squamous ulcers were assigned a severity score (range, 0 to 3) by use of an established scoring system. Horses were subsequently administered omeprazole for 21...
Monreal L, Sabaté D, Segura D, Mayós I, Homedes J.The objective was to compare the gastrointestinal and general toxicity of suxibuzone (SBZ) to that of phenylbutazone (PBZ) when administered orally in horses. Fifteen healthy horses were allocated to three treatment groups. One group received a high dose of PBZ for two weeks; the second group was given an equimolecular dosage of SBZ; and a third group received placebo. Horses were daily monitored, and blood samples were collected before and during the study. On day 18, complete post-mortem examinations were performed. One horse treated with PBZ showed clinical signs of NSAID toxicosis. Small o...
Thevis M, Opfermann G, Schänzer W.Electrospray ionization (ESI) mass spectra of 19 common beta(2)-agonists were investigated in terms of fragmentation pattern and dissociation behavior of the analytes, proving the origin of fragment ions and indicating mechanisms of charge-driven and charge-remote fragmentation. Based on these data, liquid chromatographic/ESI tandem mass spectrometric (LC/ESI-MS/MS) screening and confirmation methods were developed for doping control purposes. These procedures employ established sample preparation steps including either acidic or enzymatic hydrolysis, alkaline extraction and, in the case of eq...
Edwards JG, Newtont JR, Ramzan PH, Pilsworth RC, Shepherd MC.Dantrolene sodium (Dantrium) has been used extensively for the treatment of myopathies in man and anecdotal evidence suggests it is of clinical benefit in the control of exercise-induced rhabdomyolysis (ER) in racehorses, although data to support this are currently lacking. Objective: To investigate the efficacy of oral dantrolene sodium in controlling ER in a randomised, double-blind, placebo-controlled crossover trial involving 77 Thoroughbred racehorses in Newmarket, UK. Methods: Horses were treated on 2 occasions 1 week apart, with treatment days coinciding with a return to exercise follow...
Ikeda T.Ivermectin is an oral semi-synthetic lactone anthelmintic agent derived from avermectins isolated from fermentation products of Streptomyces avermitilis. Ivermectin showed a concentration-dependent inhibitory effect on motility of a free-living nematode, Caenorhabditis elegans (C. elegans). There exist specific binding sites having a high affinity for ivermectin in the membrane fraction of C. elegans, and a strong positive correlation was detected between the affinity for these binding sites and the suppressive effect on motility of C. elegans in several ivermectin-related substances. These re...
Broome TA, Brown MP, Gronwall RR, Casey MF, Meritt KA.Six healthy adult horses (5 mares and 1 stallion) were given a single dose of acetylsalicylic acid (ASA), 20 mg/kg of body weight, by intravenous (IV), rectal, and intragastric (IG) routes. Serial blood samples were collected via jugular venipuncture over a 36-h period, and plasma ASA and salicylic acid (SA) concentrations were determined by high-performance liquid chromatography. After IV administration, the mean elimination rate constant of ASA (+/- the standard error of the mean) was 1.32 +/- 0.09 h(-1), the mean elimination half-life was 0.53 +/- 0.04 h, the area under the plasma concentra...
Kaminsky R.The purpose of this review is to illustrate where drug resistance in parasitic nematodes has become a major problem. The mechanisms underlying anthelmintic resistance, the possible reasons for the development of anthelmintic resistance, and recommendations to minimize the further development of anthelmintic resistance in humans will be addressed. Results: Resistance has developed to all drugs of the few anthelmintic classes currently available. Drug resistance has become a major threat to sheep production in Australia, New Zealand, Great Britain and South Africa. In addition, the treatment of ...
Wasfi IA, Abdel Hadi AA, Elghazali M, Alkateeri NA, Hussain MM, Hamid AM.The pharmacokinetics of diphenhydramine (DPHM) was compared in camels (n = 8) and horses (n = 6) following intravenous (i.v.) administration of a dose of 0.625 mg/kg body weight. In addition, the metabolism and urinary detection time of DPHM was evaluated in camels. The data obtained (median and range in brackets) in camels and horses, respectively, were as follows. The terminal elimination half lives (h) were 1.58 (1.13-2.58) and 6.11 (4.80-14.1), and the total body clearances (L/h per kg) were 1.42 (1.13-1.74) and 0.79 (0.66-0.90). The volumes of distribution at steady state (L/kg) were 2.38...
Lyons E.Population-S small strongyles have been studied since 1974 in central Kentucky in a closed Shetland pony breeding herd. The ponies were treated approximately every 8 weeks with cambendazole (1974-1978), oxibendazole (OBZ) (1978-1992), or pyrantel pamoate (PRT) (1992-1999). Small strongyles in the ponies have shown resistance to these compounds in field and critical tests. One purpose of this presentation was to compare different parameters for determination of effects on the small strongyle species in ponies after treatment, mainly with OBZ or PRT, from data in critical tests (n=112). Also, th...
Stanley SD, McKemie D, Skinner W.A rapid, sensitive, and rugged method for detecting drugs and drug metabolites in extracts of horse urine is described. The use of large-volume injection (LVI) gas chromatography-mass spectrometry (GC-MS) for analysis of horse urine extracts allowed automation of the derivatization procedure and reduction of the sample volume from 5 mL to 1 mL of urine. An autosampler and temperature-programmable inlet were used to automatically dissolve the sample extract and form trimethylsilyl derivatives of over 200 analytes. The suitability of this procedure for routine GC-MS detection of approximately 80...
McKenzie HC.A study was conducted to characterize the aerosols produced by a medical ultrasonic nebulizer using solutions containing antimicrobials appropriate for therapy of equine lower respiratory bacterial infections (gentamicin sulfate and ceftiofur sodium). Test aerosols were generated using an ultrasonic nebulizer and were analyzed using a laser diffraction aerosol particle analyzer. The aerosol was described in terms of the particle size distribution (volume median diameter), span (sample dispersion), and aerosol density (% volume). The particle size distribution and aerosol density of gentamicin ...
Harkins JD, Dirikolu L, Lehner AF, Hughes C, Schroedter D, Mayer B, Bratton C, Fisher MV, Tobin T.Guanabenz (2,6-dichlorobenzylidene-amino-guanidine) is a centrally acting antihypertensive drug whose mechanism of action is via alpha2 adrenoceptors or, more likely, imidazoline receptors. Guanabenz is marketed as an antihypertensive agent in human medicine (Wytensin tablets, Wyeth Pharmaceuticals). Guanabenz has reportedly been administered to racing horses and is classified by the Association of Racing Commissioners International as a class 3 foreign substance. As such, its identification in a postrace sample may result in significant sanctions against the trainer of the horse. The present ...
Moens Y, Lanz F, Doherr MG, Schatzmann U.To study the analgesic potency of the alpha2-agonist romifidine in the horse using both an electrical current and a mechanical pressure model for nociceptive threshold testing. In addition, a comparison was made with doses of detomidine and xylazine that produce equivalent degrees of sedation. Methods: Randomized, placebo-controlled, blinded cross-over study. Methods: Six adult Swiss warmblood horses, one mare and five geldings, weighing from 530 to 650 kg and aged 6-15 years. Methods: Nociceptive thresholds were measured using an electrical stimulus applied to the coronary band and using a pn...
Olbrich VH, Mosing M.To evaluate and compare the effects of caudal epidural administration of methadone (METH) and lidocaine (LIDO) on tolerance to thermal stimulation over the dermatomes of the perineal, sacral, lumbar and thoracic regions in the horse. Methods: A blinded, randomized, prospective, experimental cross-over study. Methods: Seven healthy horses, 15.7 +/- 4.9 years (mean +/- SD) of age, weighing 536 +/- 37 kg. Methods: The horses were randomly assigned to receive two treatments (group M: METH, 0.1 mg kg-1 or group L: LIDO, 0.35 mg kg-1) at intervals of at least 28 days. An 18-gauge 80-mm Tuohy epidura...
Pascoe PJ, Taylor PM.To determine whether specific dopamine receptor antagonists block alfentanil-induced locomotor stimulation in horses. Methods: Randomized, prospective, crossover experiment. Methods: Eight adult horses (462-604 kg). Methods: Doses of dopamine-1 (D1) (NNC 01-0756) and dopamine-2 (D2) antagonists (eticlopride) were selected in a pilot study prior to a three part, blinded, cross-over study. In part 1, horses received 7.5 micro g kg-1 eticlopride, 5 micro g kg-1 NNC 01-0756 or an equal volume of saline. In part 2, they received both antagonists and in part 3, acepromazine at 0.05 mg kg-1. Locomoto...
Harder A, Schmitt-Wrede HP, Krücken J, Marinovski P, Wunderlich F, Willson J, Amliwala K, Holden-Dye L, Walker R.There are three major classes of anthelmintics for veterinary use: the benzimidazoles/prebenzimidazoles, the tetrahydropyrimidines/imidazothiazoles, and the macrocyclic lactones. In nematodes, there are five targets for the existing anthelmintics: the nicotinergic acetylcholine receptor which is the target of tetrahydropyrimidines/imidazothiazoles and indirectly that of the acetylcholineesterase inhibitors; the GABA receptor which is the target of piperazine, the glutamate-gated chloride channel as the target of the macrocyclic lactones, and beta-tubulin as the target of prebenzimidazoles/benz...
Massoco C, Palermo-Neto J.Benzodiazepines (BDZ) are among the most frequently used class of psychotropic drugs employed in veterinary medicine in Brazil and worldwide due to their anxiolytic, muscle relaxant and anticonvulsant effects [J. Clin. Pharmacol. 33 (1993) 124]. Peripheral benzodiazepine receptor (PBR) sites were described in peripheral organs, endocrine steroidogenic tissues and immune organs and cells. Midazolam is a mixed-type agonist of PBRs. The present study is focused on the effects of midazolam on equine peripheral blood neutrophils, peritoneal macrophages and cortisol levels in plasma. Adult horses we...
Matthee S.Anthelmintic products form the basis of helminth control practices on horse stud farms at present. Regular evaluation of the efficacy of these products is advisable, as it will provide information on the worm egg reappearance period and the resistance status in the worm population. The aim of this study was to evaluate the efficacy of doramectin, pyrantel pamoate, ivermectin and moxidectin on a Thoroughbred stud farm in the Western Cape Province, South Africa. The study also compared the anthelmintic efficacy of two moxidectin formulations administered at their recommended dosages (an injectab...
Abo El Sooud K.The pharmacokinetics of gentamicin was studied in lambs, calves and foals, respectively after single intravenous (i.v.) injections of 5 mg kg(-1) body weight. The plasma concentration-time curves of gentamicin sulphate were best fitted to follow a two-compartment open model in calves and foals and a three-compartment open model in lambs. Gentamicin showed high plasma level at 5 min post-injection. Then its concentration decreased gradually until its minimum detectable level at 10 and 12 h post-injection in foals and calves, respectively, was reached. In contrast, the plasma concentrations were...
Lyons ET, Tolliver SC.Fenbendazole (FBZ) suspension was administered intraorally at the dose rate of 7.0-10.3 mg/kg once a day for 5 consecutive days to 58 thoroughbred yearlings on two farms in central Kentucky in April, 2002. The average dose rates of drug given to groups of colts and fillies on each farm were 7.8-8.5 mg/kg. Only 3 of the yearlings had negative counts of strongyle eggs per gram of feces (EPGs) after treatment which was at 8.4, 8.7, or 9.4 mg/kg; the pretreatment EPG counts were low (10-30). Reduction of EPG values at the highest dose rates was 0% (at 9.5 mg/kg) and 78% (at 10.3 mg/kg). This study...
Hearn FP, Peregrine AS.During September 2002, routine fecal examinations performed on 16 Thoroughbred foals residing on a farm outside Toronto, Ontario, Canada, revealed low to moderate numbers of Parascaris equorum eggs in feces from 9 of the 16. All foals were then treated with ivermectin at a dose of 220 to 280 microg/kg (100 to 127 microg/lb), p.o., and fecal egg counts were repeated 12 days later. Fecal P. equorum egg counts increased between the first and second fecal examination in 7 foals, were unchanged in 1, and decreased in 5. Fecal samples were collected 13 days after treatment from 21 additional foals t...
Pérez R, Godoy C, Palma C, Cabezas I, Muñoz L, Rubilar L, Arboix M, Alvinerie M.A study was undertaken in order to evaluate and compare ivermectin's (IVM) plasma disposition kinetic parameters after oral or intramuscular (IM) administration in horses. Ten clinically healthy adult horses, weighing 380-496 kg body weight (BW), were allocated to two experimental groups of five horses. Group I, was treated with an oral paste formulation of IVM at the manufacturer's recommended dose of 0.2 mg/kg BW. Group II, was treated IM with an injectable 1% formulation of IVM at a dose of 0.2 mg/kg BW. Blood samples were collected by jugular puncture at different times between 0.5 h and 7...
Göktaş EF, Kabil E, Arıöz F.Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used in therapeutic doses in human and veterinary medicine for the treatment of inflammation, pain, and fever. A method for the simultaneous determination of nine NSAIDs, known as therapeutic prohibited substances, in equine urine was developed and fully validated according to the European Commission Decision 2002/657/EC and Association of Official Racing Chemists criteria. The validation was performed for naproxen, flunixin, ketoprofen, diclofenac, eltenac, meclofenamic acid, phenylbutazone, vedaprofen, and carprofen in equine urine i...
Sigel CW, Byars TD, Divers TJ, Murch O, DeAngelis D.Two fasted and 2 fed horses were dosed orally with a combined trimethoprim and sulfadiazine paste formulation at a dose of 35 mg (1:5 combined active ingredients)/kg. Serum concentrations of each drug were determined periodically for 3 consecutive days for the 4 horses. The extent and rate of absorption for trimethoprim were variable, but peak serum concentrations occurred generally within 3 hours; sulfadiazine absorption was slower, reaching peak concentrations by 6 hours. Fasting did not have a consistent effect on the serum concentration profiles for either drug. Both drugs achieved serum c...
Orsini JA, Dreyfuss DJ, Vecchione J, Spencer PA, Uhlman R.The effects of a potent new histamine-2 (H2) receptor antagonist, BMY-25368, were studied on gastric acid secretion in 5 foals from which food was withheld. Doses of 0.02, 0.11, 0.22, and 1.10 mg/kg of body weight were administered IM in a randomly assigned treatment sequence. Following BMY-25368 administration, hydrogen ion concentration was decreased and mean pH was higher than baseline values in a dose-response pattern. At the 0.22 and 1.10 mg/kg doses, the high pH was sustained for greater than 4 hours. The BMY-25368 thus may be useful for treating gastric ulcer disease in horses.
Short CR, Beadle RE, Aranas T, Pawlusiow J, Clarke CR.The pharmacokinetics of cephapirin sodium and its distribution into a tissue chamber implanted subcutaneously in the neck of mature horses are described. Cephapirin was administered as an intravenous bolus dose of 20 mg/kg. The serum concentration vs time curve was best described by a two-compartment open model. Cephapirin disappeared from serum rapidly (t1/2 beta = 18.8 min), and had only a modest volume of distribution (Vd(area) approximately equal to 346 mg/kg, Vd(ss) approximately equal to 204 ml/kg). Total clearance was also rapid (approximately equal to 13 ml/min.kg). Concentrations of t...
Natalini CC, Polydoro Ada S, Linardi RL.To evaluate the effects of subarachnoidally administered hyperbaric morphine, buprenorphine, and methadone on avoidance threshold to noxious electrical stimulation of the perineal, sacral, lumbar, and thoracic regions in horses. Methods: 6 healthy adult horses. Methods: Horses were assigned to receive subarachnoid administration of hyperbaric morphine (0.01 mg/kg), buprenorphine (0.001 mg/kg), methadone (0.01 mg/kg), or 10% dextrose solution in equal volumes (5 mL). Electrical stimulation was applied every 10 minutes for 60 minutes and every 30 minutes for 120 minutes after subarachnoid inject...
Weiss DJ, Geor RJ, Burris SM, Smith CM.Pentoxifylline has been reported to improve peripheral vascular circulation by altering the flow properties of blood. To determine if the hemorrheological effects of pentoxifylline were mediated by alterations in neutrophil function and/or flow properties, we evaluated the drug's effects on equine neutrophils in vitro. Pentoxifylline, at a concentration of 1 x 10(-1) M, but not at concentrations of 1 x 10(-6) M to 1 x 10(-2) M, markedly suppressed neutrophil superoxide production, zymosan phagocytosis and adherence to nylon wool. Pentoxifylline failed to improve neutrophil filterability throug...
Court MH, Engelking LR, Dodman NH, Anwer MS, Seeler DC, Clark M.The pharmacokinetics of dantrolene sodium were investigated in horses following both intravenous (2 mg/kg) and intragastric (4 mg/kg) administration. Two ponies also received dantrolene sodium intravenously (2 mg/kg) in a pilot study to obtain preliminary kinetic data and to determine urinary and biliary excretion of the intact drug. Distribution and elimination of dantrolene was rapid, resulting in an elimination half-life of 129 +/- 8 (SEM) min and a whole body clearance of 4.16 +/- 0.52 ml/min/kg. Following intragastric administration, dantrolene rapidly acheived peak concentrations within ...
Clarke CR, Burrows GE, MacAllister CG, Spillers DK, Ewing P, Lauer AK.Single-dose pharmacokinetic variables of pyrimethamine were studied in horses. Pyrimethamine (1 mg/kg of body weight) was administered IV and orally to 6 adult horses, and plasma samples were obtained at frequent intervals thereafter. Plasma pyrimethamine concentration was assayed by gas chromatography, and concentration-time data were analyzed, using a pharmacokinetic computer program. The IV and oral administration data were best described by 3-compartment and 1-compartment models, respectively. The median volume of distribution at steady state after IV administration was 1,521 ml/kg and the...
Mills PC, Cross SE.An increasing number of formulations are applied to equine skin, yet variable penetration can affect efficacy, or the incidence of adverse effects, or both. To investigate the effects of common methods of skin preparation on transdermal drug penetration in vitro, we clipped, harvested, and froze skin samples from 5 Thoroughbred geldings. Thawed samples were prepared as follows: control (no preparation); cleaned with aqueous chlorhexidine (Aq-C, 0.1% w/v); cleaned with alcoholic chlorhexidine (Al-C, 0.5% w/v); shaved (Sh); or tape-stripped (Ta) with the use of adhesive tape. The samples were th...
Frincke JM, Henderson GL.Fentanyl, a potent, synthetic narcotic analgesic, has reportedly been used to "dope" racehorses. Urine was collected from a horse dosed with 70 mg of [3H]fentanyl, and the primary metabolite, a water-soluble, amphoteric compound, was isolated by high-pressure liquid chromatography and identified by spectroscopic analysis. This metabolite was found to be N-[1-(2-phenethyl-4-piperidinyl)] malonanilinic acid.
Pearson W.Standardbred trainers from 1 racetrack and 7 off-track training facilities were surveyed to determine the most common drugs, and prevalence of concurrent herb administration. Furosemide (on-track) and anti-inflammatory drugs (off-track) were the most common drugs administered. Among horses on-track, 9.8% received herbs compared with 13.8% off-track horses; 67% and 58% of these horses, respectively, received concurrent drugs. Les soigneurs de Standardbreds de 1 piste de course et de 7 installations d’entraînement hors piste ont été interrogés afin de déterminer les médicaments les plus...
Stucki M, Voegel CD, Binz TM, Kraemer T, Lavaud A, Voelter K.Equine sport agencies list steroids as prohibited substances for competing horses. Objective: The objective of this study was to investigate if the controlled substances dexamethasone and prednisolone are detectable in equine serum and urine samples during and after treatment with eye drops and if this can generate a positive doping test. Methods: Prospective cohort study. Methods: The study cohort included 11 horses. One eye of the horses was treated with either dexamethasone (Maxitrol 0.1%, n = 5 eyes) or prednisolone (Pred forte 1%, n = 6 eyes) eye drops 3 times daily for 14 days. Dexa...
Knych HK, Stanley SD, Arthur RM, McKemie DS.The use of anti-ulcer medications, such as cimetidine, ranitidine, and omeprazole, is common in performance horses. The use of these drugs is regulated in performance horses, and as such a withdrawal time is necessary prior to competition to avoid a medication violation. To the authors' knowledge, there are no reports in the literature describing repeated oral administrations of these drugs in the horse to determine a regulatory threshold and related withdrawal time recommendations. Therefore, the objective of the current study was to describe the disposition and elimination pharmacokinetics o...
Maxson AD, Soma LR, May LL, Martini JA.Effects of furosemide, exercise, and atropine on tracheal mucus transport rate (TMTR) in horses were investigated. Atropine (0.02 mg/kg of body weight) administered IV or by aerosolization significantly (P < 0.05) decreased TMTR at 60, but not at 30 minutes after its administration in standing horses. Furosemide (1.10 mg/kg, IV) did not have any significant effect on TMTR when measured at 2 or 4 hours after its administration in standing horses. Exercise alone or furosemide (1.10 mg/kg, IV) administration followed 4 hours later by exercise did not alter TMTR, compared with values for standi...
Orsini JA, Spencer PA.A dose-response study was undertaken of the effects of a newly developed histamine type 2 receptor antagonist, BMY-26539-01, on gastric acid secretion in 4 fasted horses. Doses of 0.1 mg/kg, 0.3 mg/kg, 0.5 mg/kg, or placebo were administered in a randomly assigned treatment sequence. Hydrogen ion concentration and pH were variable during baseline measurements in all 4 animals; however, following BMY-26539-01 administration, mean pH increased and hydrogen ion concentration decreased in a dose-related pattern. At the 0.3 mg/kg and 0.5 mg/kg dose levels, pH remained elevated for > 4 h and >...
Knych HK.Pharmacokinetics is the study of the movement of drug in the body and includes the processes of absorption, distribution, metabolism, and excretion. Pharmacodynamics is the pharmacologic effect of the drug on the body. The pharmacokinetics of a drug determines its pharmacologic effect. Pharmacokinetic studies describe drug concentrations while pharmacodynamics allow for assessment of drug effects. Combined pharmacokinetic/pharmacodynamic studies allow for integration of drug concentrations with pharmacologic effect. Data generated from pharmacokinetic studies can be especially useful in establ...
Yi R, Zhao S, Lam G, Sandhu J, Loganathan D, Morrissey B.Cathinone is the principal psychostimulant present in the leaves of khat shrub, which are widely used in East Africa and the Arab peninsula as an amphetamine-like stimulant. Cathinone readily undergoes metabolism in vivo to form less potent cathine and norephedrine as the metabolites. However, the presence of cathine and norephedrine in biological fluids cannot be used as an indicator of cathinone administration. The metabolism of pseudoephedrine and ephedrine, commonly used in cold and allergy medications, also produces cathine and norephedrine, respectively, as the metabolites. Besides, cath...
Lee S, Hector RC, Hess AM, Wotman KL.To determine whether dexmedetomidine prolongs corneal anesthesia following subconjunctival ropivacaine injection in healthy equine eyes. Methods: Ten horses with normal ophthalmic exams were enrolled in a randomized, blinded, crossover experiment with a minimum 4-week washout between treatments. Baseline corneal touch thresholds (CTT, cm) were measured via esthesiometry and a subconjunctival injection was performed in the treatment eye with ropivacaine (R, 0.3 mL 0.5%) or dexmedetomidine-ropivacaine (DR, 0.1 mL 0.5 mg/mL + 0.2 mL 0.5%) and saline (control, 0.3 mL) in the contrala...
Dumasia MC, Houghton E, Sinkins S.A gas chromatographic-mass spectrometric (GC-MS) method using three analytes to detect and confirm the administration to equine male castrates of veterinary pro-drugs based upon esters of testosterone is described. The method involves extraction of steroid conjugates from horse urine by C18-bonded cartridges and fractionation into glucuronic acid and sulpho-conjugates by Sephadex LH-20 column chromatography. After deconjugation, the free neutral steroids were partially purified by thin-layer chromatography and following derivatization (methyloxime-trimethylsilyl ether) were analysed by capilla...
Hunter BG, Parker JE, Wehrman R, Stang B, Cebra CK.To determine synovial concentrations of morphine after intravenous regional limb perfusion (IVRLP) with morphine or morphine in combination with gentamicin in clinically healthy, standing sedated horses. Methods: Experimental. Methods: Adult horses (n = 6). Methods: IVRLP was performed using 0.1 mg/kg morphine (M) in standing sedated horses. After a 3-week washout period, IVRLP was performed on the same forelimb with a combination of 0.1 mg/kg morphine and 1 g gentamicin (M/G). Synovial fluid from the middle carpal joint of the perfused limb and jugular blood samples were collected i...
Robinson MA, Guan F, McDonnell S, Uboh CE, Soma LR.Dermorphin is a μ-opioid receptor-binding peptide that causes both central and peripheral effects following intravenous administration to rats, dogs, and humans and has been identified in postrace horse samples. Ten horses were intravenously and/or intramuscularly administered dermorphin (9.3 ± 1.0 μg/kg), and plasma concentration vs. time data were evaluated using compartmental and noncompartmental analyses. Data from intravenous administrations fit a 2-compartment model best with distribution and elimination half-lives (harmonic mean ± pseudo SD) of 0.09 ± 0.02 and 0.76 ± 0.22 h, respe...
Kollias-Baker C, Sams R.The objective of this study was to determine if the administration of poppy seeds to horses would result in detectable concentrations of morphine in urine and blood samples, as has been shown to occur in humans. In this study blood and urine samples were collected following administration of poppy seeds and morphine sulfate orally to four horses. Urine samples were subjected to enzyme-linked immunosorbent assay (ELISA) for the presence of morphine. All urine samples testing positive by ELISA, as well as plasma samples collected after administration of the 10-g doses of poppy seeds, were analyz...
Afonso T, Giguère S, Brown SA, Barton MH, Rapoport G, Barba M, Dembek KA, Toribio RE, Coleman AE.Despite the paucity of data available, orally administered angiotensin-converting enzyme (ACE) inhibitors are empirically used in horses with valvular regurgitation. Objective: Evaluate the echocardiographic and hormonal changes in response to oral benazepril in horses with left-sided valvular regurgitation. Methods: Prospective, randomised double-blind, placebo-controlled trial. Methods: Horses with mitral valve (MR) and/or aortic valve regurgitation (AR) received oral benazepril (n = 6) at a dosage of 1 mg/kg q 12 h or a placebo (n = 5) for 28 days. Echocardiography was performed before drug...
Stick JA, Arden WA, Chou CC, Parks AH, Wagner MA, Johnston CC.Using isolated autoperfused intestinal segments, the effects of flunixin meglumine administration on systemic arterial blood pressure, jejunal blood flow, vascular resistance, motility, arteriovenous oxygen difference, and oxygen consumption were determined in 10 anesthetized ponies ventilated with a mixture of halothane and oxygen. Saline solution or flunixin meglumine (1.1 mg/kg of body weight) was infused as a single bolus into the left jugular vein. By 10 minutes, flunixin meglumine increased systemic arterial blood pressure and increased intestinal vascular resistance. The jejunal blood f...
Nagata S, Yamashita S, Kurosawa M, Kuwajima M, Hobo S, Katayama Y, Anzai T.To determine the pharmacokinetics and tissue distribution of minocycline in horses. Methods: 5 healthy Thoroughbred mares for the pharmacokinetic experiment and 6 healthy Thoroughbred mares for the tissue distribution experiment. Methods: Each mare was given 2.2 mg of minocycline hydrochloride/kg, IV. Blood samples were collected once before minocycline administration (0 hours) and 10 times within 48 hours after administration in the pharmacokinetics study, and 24 tissue samples were obtained at 0.5 and 3 hours in the distribution study. Results: No adverse effects were observed in any of the ...
Machin J, Childers T, Kudrimoti S, Eisenberg R, Fenger C, Hartmann P, Maylin G, Shults T, Tobin T.Aminorex is a US DEA Schedule 1 controlled substance occasionally detected in racing horses. A number of aminorex identifications in sport horses were thought to have been caused by exposure to plant sources of aminorex. Glucobarbarin, found in plants of the Brassicaceae family, has been suggested as a potential proximate chemical source by being metabolized in the plant or the horse to aminorex. In Brassicaceae, glucobarbarin is hydrolyzed by myrosinase to yield barbarin, which serves as an insect repellant and/or attractant and is structurally related to aminorex. The synthesis, purification...
Bertone AL, Jones RL, McIlwraith CW.The tarsocrural joints of 11 horses were inoculated with 1.2 to 2.16 x 10(6) viable Staphylococcus aureus organisms susceptible to a trimethoprim-sulfadiazine (TMP-SDZ) combination with minimal inhibitory concentration (MIC) of 0.25 micrograms of TMP/ml and 4.75 micrograms of SDZ/ml. Antimicrobial treatment consisted of oral administration of a TMP-SDZ combination--30 mg/kg of body weight given once daily (group-1 horses) or 60 mg/kg given as 30 mg/kg every 12 hours (group-2 horses). Paired serum and synovial fluid samples were obtained before intra-articular inoculation with the S aureus, aft...
Eales FA.Saffan was injected intravenously on 41 occasions in 11 horses and ponies to investigate its possible use in clinical equine anaesthesia. The optimum dose for induction was 1-90 mg per kg. This dose was divided into two halves, the first half given in five seconds and the second half, containing suxamethonium chloride 0.1 mg per kg, in the next 10 seconds. Induction was associated with excitement for up to 30 secs after the assumption of recumbency. At this dose rate anaesthesia lasted five to eight minutes. Muscle relaxation was poor. Recovery was associated with marked tactile and audible hy...
Emmerich IU.In 2019, one novel pharmaceutical agent for horses or food-producing animals was released on the German market: An injection suspension for horses containing chondrogenic-induced equine allogeneic peripheral blood-derived mesenchymal stem cells as the active ingredient (ArtiCell Forte) is now available. Two established veterinary active pharmaceutical ingredients became accessible for additional species: a salicylanilide anthelmintic oxyclozanide (Distocur) for the treatment and control of fascioliasis in sheep as well as a type-I synthetic pyrethroid permethrin (Z-Itch), which now has additio...
