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Topic:Drug
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.
The effect of the acute-phase response on in vitro drug metabolism and plasma protein binding in the horse. The effect of the acute-phase response (APR) on the activity of the hepatic drug-metabolizing system (DMS) and on the binding of phenylbutazone to plasma proteins was investigated in the horse. An APR was induced by intramuscular injections of Freund's complete adjuvant in five horses and, five days later, these horses together with five clinically normal horses were shot and the right ventral lobe of each liver removed. The hepatic microsomal fractions from the liver samples were isolated and significantly lower (p < 0.01) concentrations of cytochromes P450 and b5 and activities of aniline...
Determination of methocarbamol in equine serum and urine by high-performance liquid chromatography with ultraviolet detection and atmospheric pressure ionization-mass spectrometric confirmation. Urine and serum samples collected from four standard-bred mares after and oral regimen administration of methocarbamol were extracted and analyzed. The method consisted of enzyme hydrolysis followed by a one-step liquid-liquid extraction, separation on a reversed-phase (RP-18) column, and detection using an ultraviolet (UV) detector. The confirmation was carried out using a liquid chromatography-atmospheric pressure ionization-mass spectrometry (LC-API-MS) system. Maximum methocarbamol concentrations of 1498, 1734, 1547, 2322 micrograms/mL in urine and 4.9, 1.7, and 3.6 micrograms/mL in serum ...
Structure of glycan moieties responsible for the extended circulatory life time of fetal bovine serum acetylcholinesterase and equine serum butyrylcholinesterase. Cholinesterases are serine hydrolases that can potentially be used as pretreatment drugs for organophosphate toxicity, as drugs to alleviate succinylcholine-induced apnea, and as detoxification agents for environmental toxins such as heroin and cocaine. The successful application of serum-derived cholinesterases as bioscavengers stems from their relatively long residence time in the circulation. To better understand the relationship between carbohydrate structure and the stability of cholinesterases in circulation, we determined the monosaccharide composition, the distribution of various oligo...
Use of yohimbine to reverse prolonged effects of xylazine hydrochloride in a horse being treated with chloramphenicol. A 1-year-old Standardbred gelding had received xylazine hydrochloride (0.75 to 1.00 mg/kg [0.34 to 0.45 mg/lb] of body weight, IV) during 2 surgeries for debridement of a wound. The horse was given chloramphenicol (55 mg/kg [25 mg/lb], PO, q 6 h) for 5 days, and was anesthetized a third time with xylazine (0.75 mg/kg, IM). Five hours after administration of xylazine, the horse remained markedly sedated and had clinical signs of gaseous distention of the large bowel (bloat) requiring trocharization. Administration of yohimbine (0.03 mg/kg [0.01 mg/lb], i.v.) eliminated signs of sedation within ...
Pharmacokinetic study of dipyrone metabolite 4-MAA in the horse and possible implications for doping control. The pharmacokinetic behaviour of dipyrone metabolite 4-MAA in serum was determined in seven horses of different breeds after a single intravenous dose administration. A biexponential formula was fitted to the serum concentration vs. time data. The median half-life of the elimination phase (t1/2 beta) was 4.85 h (range 5.04 h), the median volume of distribution (Vd(area)) was 1.85 L/kg (range 3.2 L/kg) and median of total clearance was 4.0 mL/min/kg (range 2.3 mL/min/kg).
Microphthalmia, brachygnathia superior, and palatocheiloschisis in a foal associated with griseofulvin administration to the mare during early pregnancy. An 18 year old Friesian mare was treated with griseofulvin for dermatomycosis in the second month of pregnancy. Pregnancy was uneventful and after 331 days a male foal was born. The foal showed bilateral microphthalmia, severe brachygnathia superior, and palatocheiloschisis. The lesions were incompatible with life and the animal was euthanized. As similar lesions have been described in other species associated with griseofulvin administration during pregnancy, and the development of the eyes and facial bones in the horse occurs in the second month of pregnancy, the lesions most likely can be a...
The effect of neomycin on the kidney function of the horse. The toxic effect of neomycin on the horse kidney was studied. Twelve horses were used, and were divided at random into three groups of four. The first group was treated twice a day with 10 mg/kg I.M. for 15 days and then euthanised; kidney and liver samples were studied and no histopathological changes were observed. Group 2 was treated with neomycin sulphate as in group 1, and group 3 was used as control. Blood samples were taken at 8.00 h and 20.00 h daily from both neomycin treated and control horses. Serum creatinine, potassium, sodium and urinary creatinine remained without change. On day...
Intramuscular bioavailability of ketoprofen lysine salt in horses. Lysine salts are often used in human pharmaceuticals to increase the solubility and absorption of acidic drugs when these are administered parenterally. In this study the intramuscular bioavailability of ketoprofen administered as the lysine salt was evaluated in horses (n = 5) treated intravenously and intramuscularly (2.2 mg/kg active substance) in a cross-over study. The absorption rate of ketoprofen administered as the lysine salt was rather low: the mean residence time increased from 31.7 min after IV injection to 128.9 min (after IM injection), and the bioavailability was high (mean 92.4...
Acute colitis in adult horses. A review with emphasis on aetiology and pathogenesis. This review article describes the different aetiological agents known or suspected to cause colitis in the adult horse, namely Salmonella spp., Clostridium spp., Ehrlichia risticii, Cyathostomes, fungi, various antibiotics, drugs, and toxins, with emphasis on their mechanism of action. For each of the infectious agents, diagnostic procedures are indicated. The effects of endotoxin can be important in all forms of equine colitis.
A unique metabolite of nimesulide. Nimesulide is a nonsteroidal anti-inflammatory drug recently detected in equine blood and urine samples taken at the race track. The detection of the drug in a blood sample led to the identification of an unknown thin-layer chromatographic (TLC) spot in track urine samples as a metabolite of nimesulide. Characterization of the unknown TLC spot and comparison with the synthesized compound shows that the unknown TLC spot is a previously unreported equine metabolite of nimesulide. The metabolite was identified as resulting from the reduction of the nitro group on nimesulide to an amino group. Thi...
Plasma pharmacokinetics of ranitidine HCl in adult horses. Plasma pharmacokinetics of ranitidine HCl were investigated after intravenous (i.v.) and oral (p.o.) administration of 2.2 mg/kg drug to six healthy adult horses. Concentrations of ranitidine were determined using normal-phase, high-performance liquid chromatography. Plasma concentrations of ranitidine HCl declined from a mean of 5175 ng/mL at 5 min to 37 ng/mL at 720 min after i.v. administration. A three-exponent equation, Cp = A1 x e-k1t + A2 x e-k2t + A3 x e-k3t, best described data for all horses. Mean values for model-independent values calculated from the last quantifiable time point we...
Adverse reactions to veterinary drugs reported in Sweden during 1991-1995. The present article gives a summary of suspected adverse reactions reported by Swedish veterinarians during the period 1991-1995. The summary shows that severe adverse drug-reactions sometimes occur in Swedish veterinary practice. In horses, several cases of acute reactions in animals treated with procaine benzylpenicillin were reported and seven horses died within a few minutes after intramuscular injections of the drug. In cattle and swine most reports referred to the use of antimicrobial agents. In dogs reactions to vaccines were the most frequently reported adverse effects. The reactions w...
Modification of cardiopulmonary and intestinal motility effects of xylazine with glycopyrrolate in horses. Xylazine (XYL) administration in horses is accompanied by significant cardiovascular depression characterized by a 25-35% decrease in cardiac output (CO) which is likely to compromise tissue oxygen delivery (DO2), and usually vagally mediated bradycardia is an important cause of this reduced cardiovascular performance. To examine the possible benefit of preventing the bradycardiac response, 6 healthy horses were treated with intravenous (IV) saline (SAL) or 2.5 micrograms/kg glycopyrrolate (GLY) in a blinded, randomized, crossover trial. Fifteen minutes later, 1 mg/kg XYL was administered IV a...
Corneal concentrations and preliminary toxicological evaluation of an itraconazole/dimethyl sulphoxide ophthalmic ointment. The objectives of this study were to determine the concentration of itraconazole achieved in corneal tissue and aqueous humour after topical application of a 1% itraconazole ointment: to determine the effect of including dimethyl sulphoxide (DMSO) in the ointment on achievable ocular tissue itraconazole concentrations; and to assess if any gross or histopathologic ocular toxicity results from the topical application of 1% itraconazole with or without the addition of DMSO. The experimental trial consisted of 6 horses considered to have normal eyes. Each horse had one eye treated with 0.3 mL of ...
Determination of an effective dose of eltenac and its comparison with that of flunixin meglumine in horses after experimentally induced carpitis. To titrate a clinically effective eltenac dosage (0.1, 0.5, and 1.0 mg/kg of body weight), compared with vehicle only, and to compare efficacy of the most effective eltenac dosage with that of 1.1 mg of flunixin meglumine/kg. Methods: 40 healthy horses, ranked after model induction on the basis of lameness severity, were randomly assigned to 5 treatment groups, with 4 replicates of 10 horses each. Methods: On day -5, after surgical preparation of the left carpal region, 0.7 ml of Freund's complete adjuvant was injected into the intercarpal space. Horses were observed daily, from the day of car...
The effect of doxapram-induced hyperventilation on respiratory mechanics in horses. To investigate the influence of increased respiratory frequency on respiratory mechanics in the horse, measurements were made in two groups of seven tracheostomized horses before and after the administration of doxapram. The horses in group I had normal base line values for respiratory mechanics, whereas the horses in group II had significantly lower values of dynamic compliance (Cdyn), higher respiratory resistance (R), and a higher total change in pleural pressure (delta P). The administration of 0.3 mg kg-1 doxapram intravenously resulted in a significant increase in respiratory frequency (...
Pharmacokinetics of intravenous and oral prethcamide in horses. The respiratory stimulant prethcamide is a mixture of equal parts of crotethamide and cropropamide. A specific and sensitive gas chromatographic method for the determination of crotethamide and cropropamide in horse plasma and urine is described. Both components of prethcamide were extracted from plasma and urine into dichloromethane. The extracts were analyzed by capillary gas chromatography with thermionic detection in the nitrogen-specific detection mode. The lower limits of quantitation were 4.0 ng ml-1 of plasma and 10.0 ng ml-1 of urine. Calibration curves were linear from 2.0-100 ng ml-...
Comparative pharmacokinetics of phenylbutazone and its metabolite oxyphenbutazone in clinically normal horses and donkeys. To compare plasma disposition of phenylbutazone and its metabolite oxyphenbutazone after i.v. administration of phenylbutazone in horses and donkeys. Methods: 4 clinically normal horses and 6 clinically normal donkeys. Methods: Blood samples were collected from each animal at time 0 (before) and 5, 10, 20, 30, 45, 60, 90, 120, 180, 240, 300, 360, and 480 minutes after i.v. administration of a bolus dose of phenylbutazone. Serum was analyzed in triplicate by use of high-performance liquid chromatography for determination of phenylbutazone and oxyphenbutazone concentrations. The serum concentrat...
Collagenolytic activity and its sensitivity to doxycycline inhibition in tracheal aspirates of horses with chronic obstructive pulmonary disease. The collagenolytic activity and its sensitivity to doxycycline inhibition in tracheal aspirates (TA) of horses with chronic obstructive pulmonary disease (COPD) was analyzed with SDS-PA gel electrophoresis (SDS-PAGE), using Type 1 collagen as the substrate. Both autoactive and total collagenase activities were significantly higher in TAs of horses with symptomatic COPD than in TAs of healthy horses. Doxycycline inhibition studies suggest that most of the TA collagenase is of the neutrophil type (MMP-8), but some is derived from other cells such as fibroblasts and monocyte/macrophages (MMP-1) a...
The effect of inflammation on the disposition of phenylbutazone in thoroughbred horses. The effect of inflammation on the disposition of phenylbutazone (PBZ) was investigated in Thoroughbred horses. An initial study (n = 5) in which PBZ (8.8 mg/kg) was injected intravenously twice, 5 weeks apart, suggested that the administration of PBZ would not affect the plasma kinetics of a subsequent dose. Two other groups of horses were given PBZ at either 8.8 mg/kg (n = 5) or 4.4 mg/kg (n = 4). Soft tissue inflammation was then induced by the injection of Freud's adjuvant and the administration of PBZ was repeated at a dose level equivalent to, but five weeks later than, the initial dose. ...
[Natural and synthetic glucocorticoids in the racing horse: a review of the literature]. This review compromises data about endogenous cortisol and its physiological variations in horses. The influence of synthetic glucocorticoids on the endogenous cortisol concentrations is discussed as well. The second part of the review summarizes detection times of therapeutically used glucocorticoids (dexamethasone, betamethasone, triamcinolone, prednisone, prednisolone, methylprednisolone and hydrocortisone) in the horse and their implication for doping control.
Pharmacokinetics and pharmacodynamics of ketoprofen enantiomers in the horse. Pharmacokinetic and pharmacodynamic parameters were established for enantiomers of the non-steroidal anti-inflammatory drug (NSAID) ketoprofen (KTP), each administered separately at a dose level of 1.1 mg/kg to a group of six New Forest geldings, in a three-period cross-over study using a tissue cage model of inflammation. For both S(+)-and R(-)-KTP, penetration into tissue cage fluid (transudate) and inflamed tissue cage fluid (exudate) was rapid, and clearances from exudate and transudate were much slower than from plasma. AUC values were, therefore, higher for exudate and, to a lesser degre...
Cardiopulmonary and gastrointestinal motility effects of xylazine/ketamine-induced anesthesia in horses previously treated with glycopyrrolate. To assess the usefulness of glycopyrrolate (GLY) in preventing the decrease in cardiac index (CI) usually caused by xylazine (XYL)/ketamine (KET)-induced anesthesia in horses. Methods: 6 healthy horses. Methods: Horses were treated with saline solution or 2.5 micrograms of GLY/kg of body weight, administered i.v. 15 minutes later, XYL (1 mg/kg) was administered i.v., followed 5 minutes later by KET (2 mg/kg) administration. The horses were positioned in left lateral recumbency, insufflated with 15 L of oxygen/min, and maintained for 30 minutes on the infusion of 0.05 mg of XYL and 0.1 mg of KE...
Pharmacokinetics of flunixin meglumine in healthy foals less than twenty-four hours old. To determine pharmacokinetic variables that describe the disposition of flunixin after i.v. administration of flunixin meglumine to foals < 24 hours old. Methods: 6 healthy foals, 2 males and 4 females (mean age, 11.6 hours; range, 6 to 22.5 hours). Methods: Flunixin (as flunixin meglumine) was administered to foals at a dosage of 1.1 mg/kg of body weight. Flunixin concentration in plasma samples was analyzed, using gas chromatography/mass spectroscopy. Concentration versus time profiles were analyzed according to standard pharmacokinetic techniques. Blood samples were obtained from foals b...
Effect of bethanechol or erythromycin on gastric emptying in horses. To investigate the prokinetic effect of bethanechol and erythromycin in the upper gastrointestinal tract of healthy horses by measuring the gastric emptying (GE) rate of a radioactive meal. Methods: 4 healthy adult horses. Methods: After food was withheld for 12 hours, horses were given 370 MBq of 99mTc-labeled sulfur colloid incorporated into egg albumen and 37 MBq of 111In-labeled diethyltriaminepentaacetic acid in 120 ml of water via nasogastric intubation. Intravenously administered treatments were 0.9% NaCl solution, erythromycin (0.1 or 1.0 mg/kg of body weight), or bethanechol (0.25 mg/...
Pharmacokinetic interactions between repeated dose phenylbutazone and gentamicin in the horse. This study examined the pharmacokinetics of steady-state phenylbutazone and single bolus intravenous gentamicin when administered together in the horse. The trial design was completed as a cross-over with seven thoroughbred horses. In the first phase each horse received 2.2 mg/kg gentamicin intravenously. After a 2-week washout, each horse received 4.4 mg/kg phenylbutazone intravenously every 24 h for 5 days. On the fourth day each horse received gentamicin as before. Plasma was harvested for gentamicin concentration determination by fluorescence polarization immunoassay and for phenylbutazone...
Identification and characterization of a pyrantel pamoate resistant cyathostome population. Three fecal egg count reduction assays (FECR) and one critical trial were performed to determine the efficacy of pyrantel pamoate (PP) at 6.6 mg base kg-1 on a well managed stud farm in Louisiana where a loss of efficacy was suspected. Efficacy of PP based on FECR varied from 25% in mares to 83% in yearlings. Second treatments with PP 2 weeks following an initial treatment failed to reduce eggs per gram (EPG). A critical trial was performed to determine the cyathostome species resistant to PP. Three strongyle-naive ponies which acquired infections on the farm were used for this purpose. Follow...
Efficacy of an epidural combination of morphine and detomidine in alleviating experimentally induced hindlimb lameness in horses. Amphotericin B-induced synovitis of the left tarsocrural joint was used to create a grade 3 of 4 lameness in 11 horses. Caudal epidural catheters were placed and advanced to the lumbosacral region. Baseline heart and respiratory rates were recorded and horses were videotaped at a walk and trot. Morphine sulphate (0.2 mg/kg) and detomidine hydrochloride (30 micrograms/kg) were administered to treated horses (n = 8) through the epidural catheter; an equivalent volume of physiologic saline solution was administered to control horses (n = 3) through the catheter. At hourly intervals after epidural...
Pharmacokinetics of ceftriaxone in healthy horses. Five healthy Equidae (4 horses and one pony) were given a single i.v. dose of ceftriaxone (50 mg/kg bwt) to determine the pharmacokinetics and concentration in cerebrospinal fluid (CSF). Blood was drawn from an i.v. jugular catheter and CSF from a pre-placed, intrathecal catheter. Serum and CSF concentrations were determined by high performance liquid chromatography. The mean serum concentration of ceftriaxone was 144.7 micrograms/ml 15 min after injection and declined to 0.3 microgram/ml 10 h after injection. The elimination rate constant (lambda 2) was 0.63 +/- s.e. 0.23/h, the elimination h...
