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.
LeBlanc PH, Caron JP.Xylazine was administered into the epidural space of nine horses to facilitate various perineal manipulations (ie rectovaginal laceration repair, replacement of prolapsed rectum and urethral extension). The resulting caudal analgesia was sufficient for all procedures. The duration of analgesia from a single injection of epidural xylazine (0.17 to 0.22 mg/kg bodyweight) was at least 3.5 h. No horses were ataxic during or after the treatment. This trial demonstrates that xylazine given into the epidural space of horses provides prolonged regional analgesia which is sufficient for clinical use.
Puigdemont A, Riu JL, Guitart R, Arboix M.The propafenone kinetics after intravenous (i.v.) administration have been studied in the horse by a comparative analysis of compartmental and noncompartmental models. The pharmacokinetic parameters showed a large distribution (Vdss = 1021 +/- 211 L) and a high clearance (CI = 7019 +/- 1746 mL/min) of the drug. The plasma concentrations were very low, under 1 microgram/mL, in most cases; after 30 min these concentrations can be considered as nonefficient for the treatment of arrhythmia. There were no significant differences between pharmacokinetic parameters found with the use of compartmental...
Stevenson AJ, Weber MP, Todi F, Mendonca M, Fenwick JD, Kwong E, Young L, Leavitt R, Nespolo R, Beaumier P.A study of the effects of intravenous administration of either 150 mg or 250 mg of furosemide to standardbred mares pre-treated with other drugs was undertaken to determine whether a unique pattern of drug elimination into urine and from plasma for each compound occurred. Furosemide significantly reduced the plasma concentrations of codeine compared to control 2-6 h after furosemide administration. In contrast, the plasma concentrations of theophylline, phenylbutazone, pentazocine, guaifenesin and flunixin were not markedly altered by furosemide. In the case of acepromazine, clenbuterol and fe...
Goetz TE, Ogilvie GK, Keegan KG, Johnson PJ.Cimetidine, an H2 histamine antagonist, was used in the clinical management of progressive, multifocal melanomatosis in 3 adult gray horses. Prior to treatment, the tumors had increased rapidly in size and number in 2 horses (duration of 6 and 27 months, respectively) and slowly in the third horse (duration of 48 months). All 3 horses were treated with cimetidine (2.5 mg/kg of body weight, PO, q 8 h) for 2 months to 1 year. During treatment, the number and size of the melanomas decreased substantially (50 to 90%). The progression of the disease was halted in 2 horses and controlled in the thir...
Sutherland IH.Following the development of a unique claim structure encompassing both nematode and arthropod species, ivermectin was first introduced as a veterinary parasiticide in 1981. For cattle(c), sheep(s), horses(h) and pigs(p) injectable(c,s,p), oral(c,s,h) and topical(c) products are available delivering ivermectin at 200 to 500 micrograms/kg. Efficacy extends to nematodes of the gastrointestinal and respiratory tracts, conjunctival sac and soft tissues. Among the arthropod parasites claims have been established for the biting fly Haematobia irritans(c), the screw-worm Chrysomyia bezziana(c), larva...
Kaegi B.25 horses which entered the clinic for minor surgery, received ketamine (2.2 mg/kg i.v.) for induction of anesthesia after previous sedation with xylazine (1.1 mg/kg i.v.). As soon as the horses were in the lateral recumbency, the benzodiazepine derivate climazolam was administered at a dose of 0.1 mg/kg i.v. (10 horses) or 0.2 mg/kg i.v. (15 horses). The anesthesia was maintained with repeated injections of ketamine (1.1 mg/kg i.v. every 9-12 minutes). At the end of the surgery, 20 minutes after the last ketamine injection, Ro 15-3505, a benzodiazepine antagonist, was injected at a dose of 0....
Lindsay WA.Topical medications and bandages play an important role in the management of equine wounds. Certain water-soluble antibacterial ointments (povidone-iodine, polymixin-neosporin-bacitracin) may be appropriate for use on contaminated wounds. A well-designed equine bandage is usually composed of primary, secondary, and tertiary layers. Because so many different products are available, the practitioner is advised to become familiar with the handling characteristics of a few. Because of the irregular contours of the equine limb, only products that stretch and conform should be used. Bandages should ...
McCrindle CM, Ebedes H, Swan GE.Two Arabian horse stallions with behavioural problems were treated with long-acting neuroleptics in order to facilitate corrective training. Perphenazine enanthate, administered intramuscularly at a dose of 0.5 mg kg-1 had an effect for 30 d. Pipothiazine palmitate (1 mg kg-1) induced tranquilization of 30 d duration as well as extra-pyramidal clinical signs, ataxia and aphagia. Neither horse showed prolapse of the penis or haemolysis.
Friedman DS, Schoster JV, Pickett JP, Dubielzig RR, Czuprynski C, Knoll JS, Wolfgram LJ.The fungal organism Pseudallescheria boydii was isolated from the cornea of a Quarter Horse with ulcerative keratitis. Despite aggressive hourly medication through a subpalpebral lavage system, with drugs including miconazole and natamycin, the cornea developed a stromal abscess. Orbital exenteration was performed after 3 weeks. The fungal isolate was later determined to be resistant to all 8 antifungal drugs tested. Microscopic examination of the cornea revealed fungal hyphae throughout the corneal stroma and penetrating the Descemet membrane. Pseudallescheria boydii has not been implicated p...
Rutkowski JA, Ross MW, Cullen K.Effects of xylazine HCl (0.5 mg/kg of body weight, IV) and/or butorphanol tartrate (0.04 mg/kg, IV) or neostigmine methylsulfate (0.022 mg/kg, IV) on myoelectric activity of the cecum and right ventral colon were studied in 4 conscious female ponies. Eight bipolar Ag/AgCl electrodes were sequentially placed on the seromuscular layer of the cecum (6 electrodes) and right ventral colon (2 electrodes). Recordings began 30 minutes before and continued for 90 minutes after drug administration. Each drug or drug combination was studied on 2 occasions in each pony. Two major patterns of coordinated s...
French DD, Klei TR, Taylor HW, Chapman MR.Twenty-one mixed-breed pony foals, reared and maintained under parasite-free conditions, were used to test the efficacy of ivermectin in oral drench and paste formulations (200 micrograms/kg) against 11-day-old migrating larvae of Parascaris equorum. Three replicates of 4 foals and 3 replicates of 3 foals were formed on the basis of age. Foals in replicates of 4 were randomly allocated to be indicators, or to receive vehicle (control) or ivermectin paste or ivermectin liquid. Foals in replicates of 3 were randomly allocated to receive vehicle or ivermectin paste or ivermectin liquid. The recov...
Merritt AM, Campbell-Thompson ML, Lowrey S.Five 5 to 6 month old horses were surgically prepared with silver electrodes sutured to the serosa of gastric antrum, duodenum and proximal portions of the jejunum. Normal migrating motility complex (MMC) periodicity was determined during daytime hours in horses that were fed and horses from which food was withheld for 24 hours. Periodicity was defined as time span from the end of one period of regular spike activity (RSA) to the end of the next RSA in the MMC. The periodicity was 120.5 +/- 9.5 (SEM) minutes in horses from which food was withheld, and was 125.7 +/- 20.3 minutes in horses fed h...
Staudacher G.23 horses and one donkey with congestive heart failure are treated with a standardized methyldigoxin dose (0.0032 mg/kg of body weight). The therapy is controlled by the serum concentration of the cardiac glycoside. 4 horses have a higher and 13 horses a lower serum concentration as necessary for therapeutic approach. The influence of additional diseases and medications is demonstrated. Finally a rule for the evaluation of the individual therapeutic glycoside-dose is given.
Wagner-Mann CC, Hankes G, Purohit RC, Harrison I, Pablo L, Boudreaux MK, Boosinger TR, Conti J.This study evaluated the pony as a potentially suitable model for vascular implant research. Healthy, conditioned ponies were randomly assigned to one of three groups: group I, carotid artery autografts (n = 6); group II, e-PTFE carotid interpositional grafts (n = 5); and group III, e-PTFE carotid interpositional grafts plus aspirin (10 mg/kg) and dipyridamole (3.5 mg/kg) drug administration. It was found that autografts remained patent longest (mean = 396.2 days; grafts were still patent at time of writing) followed by group III grafts (157.5 days), with group II grafts remaining patent for t...
Burrows GE, MacAllister CG, Tripp P, Black J.The potential for interactions between chloramphenicol, phenylbutazone, acepromazine and thiamylal and chloramphenicol, rifampin, and phenylbutazone were evaluated in two groups of experiments. In the first, five horses were given thiamylal intravenously (iv) (6.6 mg/kg) after pretreatment with acepromazine, and the time of recumbency was determined. Administration of chloramphenicol iv (25 mg/kg) 1 h prior to anaesthesia significantly lengthened the recumbency time from 21.8 +/- 4.8 mins to 36.0 +/- 8.3 mins. There was an apparent but not statistically significant decrease in recumbency time ...
Rugh KS, Jiang B, Hatfield DG, Garner HE, Hahn AW.Using a recently developed nonlinear algorithm which identifies reference points on left ventricular pressure waveforms and other waveforms, we analyzed heart rate recovery in ponies after strenuous treadmill exercise. Each pony performed exercise tests with and without premedication with atropine methyl nitrate. Resting and exercise heart rates were 54 +/- 3 and 209 +/- 6 beats/min, respectively, without premedication and 85 +/- 8 and 212 +/- 5 beats/min, respectively, following atropine premedication. Post-exercise heart rate recovery without premedication was best described by a biexponenti...
Clark ES, Becht JL.This article discusses the various drugs that affect the equine gastrointestinal tract. Drugs that alter intestinal motility, that protect the gastrointestinal tract, and that alter secretions, as well as analgesics, appetite stimulants, and orally administered antimicrobial agents are reviewed.
Hagedorn HW, Meiser H, Zankl H, Schulz R.The tricyclic antidepressant doxepin, representing a 5:1 mixture of trans- and cis-isomers, owns tranquilizing properties. This compound has been associated with illicit medication of racing horses, and therefore should be considered in doping control. Because analysis of doxepin in equine body fluids has not been documented in the literature, a highly sensitive analytical method was developed to individually monitor the doxepin isomers in blood and urine of horses by the use of gas chromatography/mass spectrometry. Following a dose of 1 mg doxepin-HCl/kg intravenously (i.v.), both the isomers...
Brown MP, Gronwall RR, Martinez DS, Beal C.Six healthy pony foals, from 2 to 11 days of age, were given a single IM injection of amikacin sulfate (250 mg/ml) at a dosage rate of 7 mg/kg of body weight. Serum amikacin concentrations were measured serially over a 24-hour period. The mean peak serum concentration was 14.7 micrograms/ml at 0.5 hour. The elimination rate constant for amikacin was 0.24/hour, the elimination half-life was 3.0 hours, and the apparent volume of distribution was 0.58 L/kg.
Brown MP, Gronwall RR, Cook LK, Houston AE.Ormetoprim (OMP)/sulphadimethoxine (SDM) combinations
have been used in the treatment of fowl cholera, colibacillosis,
salmonellosis, infectious coryza, and other bacterial infections in
poultry (Mitrovic et al. 1969; Maestrone et al. 1979). The drug
combination has also been used in the treatment of colibacillosis
in neonatal pigs (Brandt and Maestrone 1980) and Pasteurella
pneumonia in cattle (Ames et al. 1987). Serum concentrations and
pharmacokinetics of SDM (Oh-Ishi and Nakajima 1964; Durr et
al. 1980) and OMP/SDM (Brown et al. 1989) after intravenous or
oral administration to ad...
Karawya MS, El-Keiy MA, Wahba SK, Kozman AR.A chromatographic separation of amphetamine, methylamphetamine and ephedrine from horse urine is possible on alkaline Silica Gel G plates developed with acetone-methanol (1:3). After elution, the bases are determined colorimetrically. The intensity of the violet colour resulting from the nitration of amphetamine is measured in a Unicam SP1300 colorimeter using filter No. 1 (sensitivity 50–250 μg). The colour produced by the interaction of methylamphetamine, sodium nitro-prusside, acetaldehyde and triethanolamine is measured at 590 mμ (sensitivity 200–2,000 μg). Ephedrine was determined ...