Topic:Pharmacology
Pharmacology in horses involves the study and application of drugs and medications to diagnose, treat, and prevent diseases and conditions in equine species. This field encompasses the understanding of pharmacokinetics and pharmacodynamics specific to horses, including how drugs are absorbed, distributed, metabolized, and excreted by the equine body. Commonly studied pharmacological agents in horses include non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, sedatives, and anthelmintics. Research in equine pharmacology focuses on determining appropriate dosages, understanding drug interactions, and minimizing adverse effects. This page compiles peer-reviewed research studies and scholarly articles that investigate the efficacy, safety, and regulatory aspects of pharmacological interventions in equine veterinary practice.
Pressures in the right side of the heart and esophagus (pleura) in ponies during exercise before and after furosemide administration. Pressures in the right side of the heart and esophagus (pleural) have not been determined in the exercising equine subjects. In the present study, 8 healthy ponies were examined to determine the changes in these variables caused by 2 degrees of exercise done on a treadmill (heart rate:183 +/- 5 beats/min [trot] and 220 +/- 6 beats/min [canter]). Measurements were also made during both degrees of exertion 10 minutes and 120 minutes after furosemide (1.0 mg/kg) administration. It was observed that both gaits resulted in significant increases in pulmonary artery, right ventricular, and right atri...
Effects of xylazine on renal function and plasma glucose in ponies. The intravenous administration of xylazine (1.1 mg/kg bodyweight) in six ponies resulted in a significant increase in urine output over two hours, with maximum flow occurring between 30 and 60 minutes after injection. Urine specific gravity, osmolality and glucose concentration decreased. Renal clearance of endogenous creatinine was unchanged. Significant increases in the excretion of potassium and chloride occurred. Plasma glucose concentration was increased 30 minutes after the administration of xylazine by a mean value of 37 per cent. Serum osmolality and sodium, potassium and chloride conc...
[Flunixin and its use in horses]. Flunixin is a non-steroidal anti-inflammatory agent, with a potent analgesic activity and a slight toxicity. It is largely used in horses, in the form of meglumine salt, for the treatment of inflammatory diseases or colics, and often identified in dopage cases. Physical and chemical properties of the drug, its pharmacological and toxicological properties, and its use in equine species are depicted.
Novel environment suppression of stallion sexual behavior and effects of diazepam. Pony stallions were given sexual behavior trials in experimental "home" and "novel" environments, similar in all major features except location. In the novel environment, erection latency was increased and erection time decreased. Treatment with an anxiolytic benzodiazepine derivative (diazepam) appeared to block these effects.
[14C]monensin balance in bile-fistulated ponies. To measure absorption of monensin or its metabolites and its elimination from the body, [14C]monensin sodium was given orally (1 mg/kg body wt) to two bile-fistulated ponies and iv (8.7 mg) to one bile-fistulated pony. For one orally-dosed pony, 4.7% of the 14C was eliminated in bile, 52% in feces, .7% in urine and 33% remained in the gastrointestinal (GI) tract after 3 d. Total 14C recovery was 90%. For the other orally-dosed pony, 18.3% of the 14C was eliminated in bile, 69% in feces, 1.7% in urine and 7% remained in the GI tract after 4 d. Total 14C recovery was 98%. For the iv-dosed pony, ...
Paroxysmal atrial fibrillation in racehorses. The paper describes five cases of atrial fibrillation detected after racing. In four of them, the arrhythmia disappeared spontaneously within 24 h and they were regarded as paroxysmal in type. In the fifth case, which won its race, the arrhythmia persisted for at least 45 h after racing. It was therefore regarded as an example of persistent atrial fibrillation. It was then treated with quinidine sulphate which restored sinus rhythm. It would seem that paroxysmal atrial fibrillation may be a cause of sudden decrease in racing performance.
Renal toxicity of non-steroidal anti-inflammatory drugs. Non-steroidal anti-inflammatory drugs represent the most heavily prescribed and used class of drugs in human medicine. Most are derivatives of either salicylates, propionic acid, indoleacetic acid, anthranilic acid, pyrazolone, or oxicams. They depress the synthesis of prostaglandins from arachidonic acid by reversible inhibition of the enzyme cyclooxygenase. In the kidney, prostaglandins PGE2 and PGI2 modulate the vasoconstrictor effects of angiotensin II, norepinephrine, and vasopressin. In the presence of volume contraction, anesthesia, or disease states associated with high levels of these...
Modulation of arachidonic acid metabolism in endotoxic horses: comparison of flunixin meglumine, phenylbutazone, and a selective thromboxane synthetase inhibitor. Two cyclooxygenase inhibitors (flunixin meglumine and phenylbutazone) and a selective thromboxane synthetase inhibitor were assessed in the management of experimental equine endotoxemia. Drugs or saline solution were administered to 16 horses 15 minutes before administration of a sublethal dose of endotoxin (Escherichia coli 055:B5). Plasma concentrations of thromboxane B2 (TxB2), prostacyclin (6-keto PGF1 alpha), plasma lactate, and hematologic values and clinical appearance were monitored for 3 hours after endotoxin administration. Pretreatment with flunixin meglumine (1 mg/kg of body weight...
The use of atropine to control heart rate responses during detomidine sedation in horses. Detomidine is a sedative-analgesic which has a pharmacological profile similar to xylazine. There is evidence that the sedative effects are mediated through alpha-2 adrenoceptors. Cardiopulmonary responses were determined using detomidine as the principal agent and as a preanesthetic prior to the induction of general anesthesia. Compatibility with guaifenesin, sodium thia-mylal and halothane were determined. As in the case of xylazine, detomidine produces a slowing of heart rates. This was found to be either sinus bradycardia or heart block. There may be a corresponding increase in systolic bl...
Pharmacokinetics of probenecid and the effect of oral probenecid administration on the pharmacokinetics of cefazolin in mares. The pharmacokinetics and bioavailability of probenecid given IV and orally at the dosage level of 10 mg/kg of body weight to mares were investigated. Probenecid given IV was characterized by a rapid disposition phase with a mean half-life of 14.0 minutes and a subsequent slower elimination phase with a mean half-life of 87.8 minutes in 5 of 6 mares. In the remaining mare, a rapid disposition phase was not observed, and the half-life of the elimination phase was slower (172 minutes). The mean residence time of probenecid averaged 116 minutes for all 6 mares and 89.2 minutes for the 5 mares with...
Dose-related effects of ethylketazocine on nociception, behaviour and autonomic responses in the horse. Sensitive methods for measuring the analgesic, physiological and behavioural effects of opioids in the horse have recently been developed. Fentanyl, a prototypic mu-opiate receptor agonist, has been previously shown to produce a syndrome characterized by marked analgesia and locomotor stimulation as well as tachycardia, tachypnoea and behavioural arousal. To determine whether other opiate receptors mediate some of the actions of the narcotic analgesics in the horse, an agent with activity at kappa- and to lesser extent mu-receptors was studied using a vigorous experimental protocol. Like fenta...
Dimethyl sulfoxide (DMSO): a review. Dimethyl sulfoxide (DMSO) is a very simple compound that has stimulated much controversy in the scientific and popular literature. Fig. 1 It is an aprotic solvent. Therapeutic and toxic agents that are not soluble in water are often soluble in DMSO. DMSO has a very strong affinity for water; on exposure to air, pure DMSO is rapidly diluted. DMSO's physiologic and pharmacologic properties and effects are incompletely understood. Properties that are considered to be particularly important to its therapeutic and toxic effects include: its own rapid penetration and enhanced penetration of other su...
Use of dopamine hydrochloride during general anesthesia in the treatment of advanced atrioventricular heart block in four foals. Heart block is a relatively common arrhythmia in the adult horse. It may be a normal physiologic phenomenon or it may have pathologic implication. Four foals in which advanced heart block developed during anesthesia were unresponsive to atropine sulfate and supportive treatment alone. Resolution of the heart blocks was achieved after the addition of dopamine hydrochloride to the therapeutic regimen.
Neostigmine methylsulfate delays gastric emptying of particulate markers in horses. Eight horses were allotted to 2 groups, each of 4 horses. All horses were given 100 plastic markers intragastrically via a nasogastric tube. One group of animals (control group) was not given medication after marker administration. The other group (test group) was given neostigmine methylsulfate (0.022 mg/kg of body weight) in the subcutaneous tissue at the time of marker administration and 30, 60, and 90 minutes later. All horses were killed 135 minutes after marker administration to locate the beads in the gastrointestinal tract. Gastric emptying of the markers was significantly delayed (P l...
Effects of oral cimetidine on plasma concentrations of phenylbutazone in horses. Phenylbutazone was administered to six Thoroughbred horses in a cross-over study in which the horses received cimetidine pretreatment or no cimetidine pretreatment. Blood samples were collected at various times for 48 h after phenylbutazone administration and the plasma was analysed for phenylbutazone. Cimetidine pretreatment elevated phenylbutazone plasma concentrations during the first 8 h after phenylbutazone administration. The absorption rate, maximum phenylbutazone plasma concentrations and AUC were significantly greater with cimetidine pretreatment. The half-life of phenylbutazone did n...
Use of oxibendazole for control of cambendazole-resistant small strongyles in a band of ponies: a six-year study. Oxibendazole (OBZ; 10 mg/kg of body weight) was administered to ponies at 8-week intervals to control strongylosis in a breeding band of Shetland-type ponies (n = 29 to 50) from October 1978 through September 1984. A similar use of cambendazole (CBZ; 20 mg/kg of body weight) in this band of ponies during the preceding 4-year period resulted in the survival of a CBZ-resistant population (S) of small strongyles. Effectiveness of OBZ treatments was monitored by pre- and posttreatment counts of the number of strongyle eggs per gram of feces (epg) and of the number of strongyle larvae per gram of f...