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Topic:Atropine
Atropine is a medication used in equine medicine primarily for its anticholinergic properties, which help to relax smooth muscles and dilate pupils. It is commonly administered in situations requiring the treatment of colic or the dilation of the pupils for ophthalmic examinations. Atropine works by inhibiting the action of the neurotransmitter acetylcholine, leading to decreased gastrointestinal motility and increased heart rate. In horses, its use must be carefully monitored due to potential side effects, such as decreased gut motility and risk of colic. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetics, therapeutic applications, and safety considerations of atropine in equine veterinary practice.
Confirmed Datura poisoning in a horse most probably due to D. ferox in contaminated tef hay. Two out of a group of 23 mares exposed to tef hay contaminated with Datura ferox (and possibly D. stramonium) developed colic. The 1st animal was unresponsive to conservative treatment, underwent surgery for severe intestinal atony and had to be euthanased. The 2nd was less seriously affected, responded well to analgesics and made an uneventful recovery. This horse exhibited marked mydriasis on the first 2 days of being poisoned and showed protracted, milder mydriasis for a further 7 days. Scopolamine was chemically confirmed in urine from this horse for 3 days following the colic attack, whil...
[Pulmonary artery wedge pressure and heart rate measurement during pharmacological stress induction for left cardial function diagnosis in horses with and without heart disease]. In 18 horses, the pulmonary artery wedge pressure and the heart rate were measured during pharmacological stress load. 12 horses were healthy (4 trained, 8 untrained) and 6 horses had a heart disease (3 trained, 3 untrained). Pharmacological stress induction was carried out with the sympathomimetic drug dobutamine at a dosage rate of 7.5 microg/kg/min over 10 minutes of infusion. At the fourth minute, the parasympatholytic drug atropine was administered (5 microg/kg bw), and the heart rate and the pulmonary artery wedge pressure were continuously measured over 26 minutes. During sole dobutamin...
Effect of atropine-dobutamine stress test on left ventricular echocardiographic parameters in untrained warmblood horses. The aim of this study was to investigate the effect of combined atropine low-dose dobutamine stress test on left ventricular parameters in adult warmblood horses, to establish a potential protocol for pharmacological stress echocardiography. Seven healthy untrained warmblood horses aged 9 to 22 years were used. Heart rate (HR) and left ventricular B- and M-mode dimensions were recorded at baseline and during stress testing with 35 microg/kg atropine IV followed by incremental dobutamine infusion of 2 to 6 microg/kg/min. HR increased significantly (P < .05) during the pharmacological challen...
Stress echocardiography in warmblood horses: comparison of dobutamine/atropine with treadmill exercise as cardiac stressors. The purpose of this study was to determine whether the combination of dobutamine and atropine causes cardiac stress equivalent to treadmill exercise. Therefore, electrocardiography and echocardiography were performed on 10 warmblood horses before, during, and after different cardiac stress tests. Stressors consisted of a standardized treadmill exercise and combined administration of dobutamine (7.5 microg/kg/min) and atropine (5 microg/kg). Maxima heart rates were achieved during the treadmill exercise (175 +/- 10 bpm). After exercise, a rapid decrease in heart rate was observed. Subsequently,...
Total intravenous anaesthesia in horses using medetomidine and propofol. To examine the clinical suitability of medetomidine-propofol infusions for total intravenous anaesthesia in horses. Methods: Fifty client-owned horses of mixed breed, age [mean +/- SD (range)] 6.6 +/- 4.4 (0.04-18) years, mass 478 +/- 168.3 (80-700) kg presented for a range of operations requiring general anaesthesia. Methods: Pre-anaesthetic medication was intravenous (IV) medetomidine 7 mug kg(-1). Anaesthesia was induced with IV ketamine (2 mg kg(-1)) and diazepam (0.02 mg kg(-1)). After endotracheal intubation, O2 was delivered (FiO2 > 0.85). Positive pressure ventilation was initiated if ...
Contractile effects of 5-hydroxytryptamine and 5-carboxamidotryptamine in the equine jejunum. The use of human prokinetic drugs in colic horses leads to inconsistent results. This might be related to differences in gastrointestinal receptor populations. The motor effects of 5-hydroxytryptamine (5-HT; serotonin) on the equine mid-jejunum were therefore studied. Longitudinal muscle preparations were set up for isotonic measurement. 5-HT induced tonic contractions with superimposed phasic activity; these responses were not influenced by tetrodotoxin and atropine, suggesting a non-neurogenic, non-cholinergic pathway. The 5-HT receptor antagonists GR 127935 (5-HT(1B,D)), ketanserin (5-HT(2A...
Application of the 51Cr-EDTA urinary recovery test for assessment of intestinal permeability in the horse. Altered intestinal permeability is implicated in the pathogenesis of diverse equine medical conditions including alimentary laminitis and protein-losing enteropathies associated with parasitic infection. The aims of this study were to assess the feasibility of applying the 51Cr-EDTA absorption test for the assessment of intestinal permeability in the horse, and to apply this test in horses with experimentally induced alterations in gastrointestinal function. Four healthy ponies were administered 36 MBq of 51Cr-EDTA via naso-gastric tube, and urine samples were collected into polythene bags str...
Atropine reduces dobutamine-induced side effects in ponies undergoing a pharmacological stress protocol. High-dose dobutamine stress echocardiography has been shown to be cardiotoxic and arrhythmogenic in horses. However, the test may have benefit in practice as a pharmacological challenge of exercise without the treadmill being required. Objective: To investigate the effect of low-dose dobutamine on cardiac performance in ponies previously treated with atropine, in order to develop a pharmacological protocol that allows examination of the equine heart under stimulation. Methods: In 13 healthy Shetland ponies, heart rate (HR), stroke index (SI) and cardiac index (CI) were calculated from pulsed-w...
Use of free conjunctival grafts in horses: ten cases. To assess the effectiveness of free conjunctival grafts in the treatment of horses with a range of keratopathies. Methods: A retrospective clinical study of ten client-owned horses treated at Murdoch University Veterinary Hospital from May 1996 to September 2001. Methods: The suitability of patients for the surgical procedure was assessed using a slit lamp biomicroscope and by direct and indirect ophthalmoscopy. Surgery was performed with the aid of an operating microscope, under general anaesthesia. A subpalpebral ocular lavage catheter was used for administration of topical atropine and anti...
Treatment for a severe reaction to intravenous administration of diatrizoate in an anesthetized horse. A mature horse developed acute signs of bronchoconstriction causing hypoxemia and hypercapnia during anesthesia for computerized tomography of the maxillary sinus after i.v. administration of diatrizoate contrast medium. The horse was treated with aerosolized albuterol, atropine, and oxygen insufflation and recovered uneventfully despite severe hypoxemia and low hemoglobin saturation. The horse's condition continued to improve after treatment, and the horse was discharged with no further complications. Caution is advised with the use of contrast media in anesthetized horses.
The effect of topical administration of atropine sulfate on the normal equine pupil: influence of age, breed and gender. The purpose of this study was to determine the influence of age, breed and gender on vertical pupil diameter (VPD) following a single dose of 1% atropine sulfate ophthalmic solution in the normal equine eye. Methods: Thirty-two horses of various ages, breeds and genders were included. The horses had no history or clinical signs of ophthalmic disease. All horses studied had darkly pigmented irides. Methods: Two milligrams of 1% atropine sulfate ophthalmic solution was topically administered as a single dose in the right eye of each horse on Day 0. The VPD (mm) was measured in both eyes using di...
Muscarinic receptor subtypes mediate vasorelaxation in isolated horse deep dorsal penile vein. To investigate the effect of acetylcholine (ACh) on horse deep dorsal penile vein and to characterize the muscarinic receptor subtypes involved in this response. Methods: Vein rings were mounted in an organ bath chamber, and the isometric tension was recorded. Results: In phenylephrine-contracted veins, ACh (1 nM to 1 microM) induced endothelium-dependent relaxation. The muscarinic receptor antagonist, atropine, produced parallel rightward shifts of the ACh response curves (pA2 = 10.04; pK(B) = 9.98). Carbachol (10 nM to 100 microM) also evoked relaxation in the vein segments, but showed a low...
Quantitative detection of atropine-delayed gastric emptying in the horse by the 13C-octanoic acid breath test. The 13C-octanoic acid breath test has been correlated significantly to radioscintigraphy for measurement of gastric emptying indices in healthy horses. The objective of this study was to investigate the validity of the test for measurement of equine delayed gastric emptying, prior to its potential clinical application for this purpose. A model of atropine-induced gastroparesis was used. Gastric emptying rate was measured twice in 8 horses using concurrent radioscintigraphy and/or breath test after treatment i.v. with either atropine (0.035 mg/kg bwt) or saline in randomised order. Analysis of ...
Effects of pentoxifylline on pulmonary function and results of cytologic examination of bronchoalveolar lavage fluid in horses with recurrent airway obstruction. To determine the effects of pentoxifylline (PTX) administration on lung function and results of cytologic examination of bronchoalveolar lavage fluid in horses affected by recurrent airway obstruction (RAO). Methods: 10 RAO-affected horses. Methods: 6 horses were orally administered PTX (16 g) mixed with corn syrup, and 4 horses were administered corn syrup alone, twice daily for 14 days. Pulmonary function was evaluated before administration (day 0) and on days 8 and 15. Bronchoalveolar lavage (BAL) was performed on days 0 and 15. Reversibility of airway obstruction was assessed by measuring ...
Evaluation of acetaminophen absorption in horses with experimentally induced delayed gastric emptying. To evaluate the correlation between the half-time of liquid-phase gastric emptying (T50) determined by use of nuclear scintigraphy, using technetiumTc 99m pentetate, and absorption variables of orally administered acetaminophen in horses with experimentally delayed gastric emptying. Methods: 6 mature horses. Methods: Delayed gastric emptying was induced by IV injection of atropine sulfate. Twenty minutes later, acetaminophen and technetium Tc 99m pentetate were administered simultaneously via nasogastric tube. Serial lateral images of the stomach region were obtained, using a gamma camera. Pow...
Effects of repeated atropine injection on heart rate variability in Thoroughbred horses. To investigate the effects of repeated atropine injection on heart rate (HR) variability in resting Thoroughbred horses, two microg/ kg of atropine as parasympathetic nervous blockade was injected intravenously every 6 min to a total of 8 microg/kg after intravenous administration of 0.2 mg/kg of propranolol as sympathetic nervous blockade. We recorded electrocardiograms and obtained the HR, then evaluated variation in HR from the power spectrum in terms of low frequency (LF, 0.01-0.07 Hz) power and high frequency (HF, 0.07-0.6 Hz) power. Administration of atropine decreased parasympathetic ne...
Effect of topical 1% atropine sulfate on intraocular pressure in normal horses. OBJECTIVE: To determine the effect of topical 1% ophthalmic atropine sulfate on intraocular pressure (IOP) in ocular normotensive horses. Animals Studied Eleven clinically healthy horses. Procedures IOP was measured bilaterally twice daily, at 8 AM and 4 PM, for 5 days. No medication was applied for the first 2 days of the study. Thereafter, one eye of each horse was treated with 0.1 mL of topical 1% atropine sulfate ointment twice daily (7 AM and 7 PM) for 3 days. The contralateral eye served as a control. In eight of the horses, an additional IOP reading was taken 3 days following cessation ...
Effect of topical atropine on intraocular pressure and pupil diameter in the normal horse eye. The objective was to determine whether topically administered 1% atropine would alter intraocular pressure. The animals studied were four healthy adult horses. Intraocular pressure and pupil diameter were measured prior to and during a 2-day period of treatment with 1% atropine sulfate. No significant changes in intraocular pressure occurred as a result of the treatment with atropine. Pupil diameter increased significantly after atropine was applied. Available information on the outflow of aqueous humor from the horse eye suggests that atropine might reduce intraocular pressure in the horse by...
Systemic effects of topical and subconjunctival ophthalmic atropine in the horse. OBJECTIVE: To identify any systemic effects of topical and subconjunctival administration of atropine sulfate in the horse. Animals studied Six mature grade horses were treated hourly in one eye with topical ophthalmic atropine drops for 24 h. Five horses were treated subconjunctivally in one eye with 3 mg of atropine sulfate. Procedures Pupillary light reflexes, pupil size, electrocardiographic parameters, girth measurements, intestinal motility, and clinical signs of abdominal pain were monitored. RESULTS: Alteration in auscultated gut motility and clinical signs of abdominal pain were the m...
In vitro effects of 5-hydroxytryptamine and cisapride on the circular smooth muscle of the jejunum of horses. To determine effects of cisapride and 5-hydroxytryptamine (5-HT) on the jejunum of horses. Methods: Jejunal muscle strips from 8 horses. Methods: Muscle strips were suspended in isolated muscle baths. Isometric stress responses to 5-HT and cisapride, with and without specific antagonists, were determined. Results: Muscle strips incubated with atropine and tetrodotoxin responded to 5-HT and cisapride with an increase in contractile force. The 5-HT caused a concentration-dependent increase in contractile amplitude, with a maximum response (Emax) of 1,151+/-214 g/cm2 and a molar concentration tha...
Intracellular microelectrode recording to characterize inhibitory neuromuscular transmission in jejunum of horses. To evaluate electrical activity of jejunal circular muscle in horses and characterize electrical responses to stimulation by intrinsic inhibitory neurons. Methods: Portions of jejunum obtained from horses euthanatized for reasons other than gastrointestinal tract disease. Methods: Isolated circular muscle preparations were perfused with oxygenated modified Krebs solution. Glass microelectrodes were used for intracellular recording of membrane potentials from single smooth muscle cells. Electrical activity and responses to electrical field stimulation (EFS) of intrinsic neurons in the presence ...
Effect of nervous excitation on acid secretion in horses. Nervous excitation was induced by various means in horses provided with a gastric cannula. Insulin hypoglycaemia profoundly inhibited the basal acid output and volume secreted from the stomach. No clear effect on acid secretion was noted after administration of bethanechol, as the acid output was covered by the copious secretion of saliva. Atropine almost abolished the basal acid output. Sensoric stimulation by teasing caused a slight but not significant increase in the total acid output. These data suggest that cholinergic excitation might play a role in the stimulation of both volume and aci...
Monthly, daily, and circadian variations of measurements of pulmonary mechanics in horses with chronic obstructive pulmonary disease. To determine temporal variations of pulmonary function in horses without respiratory tract disease (controls) and horses with chronic obstructive pulmonary disease (COPD) and determine whether reversibility of airway obstruction after environmental control can be predicted by response to atropine administration. Methods: 7 COPD-affected and 5 control horses. Methods: Pulmonary function testing was performed monthly during 3 consecutive months, daily for 5 consecutive days, and at 6-hour intervals for 24 hours before and after administration of atropine (0.02 mg/kg of body weight, i.v.) and aft...
Subconjunctivally implanted micro-osmotic pumps for continuous ocular treatment in horses. To evaluate the feasibility of using a subconjunctivally implanted micro-osmotic pump for continuous delivery of medication to the eyes of horses- during a 7-day period. Methods: 4 healthy adult horses. Methods: With horses restrained in a standing position, micro-osmotic pumps were implanted subconjunctivally in each eye for 7 days. The treatment eye received an atropine-loaded micro-osmotic pump (100 microl of 1.5% atropine), and the contralateral eye received a sterile saline-loaded pump (100 microl of 0.9% NaCl) as a control treatment. Pupil size was measured at 12-hour intervals until val...
Adrenergic, cholinergic, and nonadrenergic-noncholinergic intrinsic innervation of the jejunum in horses. To determine the major neurotransmitters that regulate contractile activity in the jejunum of horses. Methods: Jejunal specimens from 65 horses without gastrointestinal tract lesions. Methods: Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscular layer, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 30 and 70 V intensities and at various frequencies on muscle strips maintained at low or high muscle tone. To detect residual nonadrenergic-noncholinergic neurotransmission,...
Modulation of ACh release from airway cholinergic nerves in horses with recurrent airway obstruction. To evaluate the functional status of neuronal alpha2-adrenoceptors (ARs) and beta2-ARs on ACh release in horses with recurrent airway obstruction (RAO), we examined the effects of the physiological agonists epinephrine (Epi) and norepinephrine (NE) and the beta2-agonists RR- and RR/SS-formoterol on ACh release from airway cholinergic nerves of horses with RAO. Because SS-formoterol, a distomer of the beta2-agonist, increases ACh release from airways of control horses only after the autoinhibitory muscarinic receptors are blocked by atropine, we also tested the hypothesis that if there is an M2...
Mediators of anaphylaxis but not activated neutrophils augment cholinergic responses of equine small airways. Neutrophilic inflammation in small airways (SA) and bronchospasm mediated via muscarinic receptors are features of chronic obstructive pulmonary disease in horses (COPD). Histamine, serotonin, and leukotrienes (LTs) are reported to be involved in the exacerbation of COPD, and currently, histamine has been shown to increase tension response to electrical field simulation (EFS) in equine SA. We tested the effects of these mediators and the effects of activated neutrophils on the cholinergic responses in SA. Histamine, serotonin, and LTD4 had a synergistic effect on EFS responses and only an addi...
Post traumatic keratouveitis in horses. Traumatic keratouveitis in horses is characterised by a unilateral, aseptic, vascularising keratitis accompanied by moderate to severe anterior uveitis. In a series of 9 cases of post traumatic keratouveitis, topical and systemic nonsteroidal drugs and atropine were used to control the anterior uveitis while allowing spontaneous corneal healing. Among the 9 cases reported, 6 affected eyes previously treated with local corticosteroids took significantly longer to resolve when compared to 3 eyes in which corticosteroids had not been administered. It was concluded that, in cases of equine post tr...
Acetaminophen as a marker of gastric emptying in ponies. Gastric emptying was evaluated in ponies using the acetaminophen (AP) method. Fifteen minutes after i.v. administration of metoclopramide, erythromycin, yohimbine, atropine or saline, the ponies were given AP by stomach tube. Blood samples for AP analysis were collected at baseline and 15, 30, 45, 60, 75, 90, 105 and 120 min after AP administration. Time to reach peak serum concentration (Tmax), maximum serum concentration (Cmax) and area under the AP serum concentration vs. time curve (AUC) were determined for each treatment group. In the control group, Tmax was 31 min and this decreased sign...
