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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.
Endothelin receptor alterations in equine airway hyperreactivity. The purpose of this study was to evaluate the role of endothelin-1 (ET-1) and its receptors in the airway hyperreactivity of horses with obstructive pulmonary disease associated with summer pasture (SPAOPD). The right diaphragmatic lobe of the lung of 8 clinically healthy (unaffected) and 8 SPAOPD-affected horses was collected immediately after euthanasia. Bronchial rings (4 mm wide) were prepared and mounted in organ baths and attached to force transducers interfaced with a polygraph. Four rings were used to study each ET-1 receptor; 1 ring served as the control, and the other 3 were incubate...
Thermographic study of in vivo modulation of vascular responses to phenylephrine and endothelin-1 by dexamethasone in the horse. In vitro, glucocorticoids potentiate vasoconstriction of equine digital vessels to catecholamines and this has been implicated as a mechanism of glucocorticoid-induced laminitis. This observation has never been confirmed in vivo. Objective: To study the effects of glucocorticoid therapy on vasoconstrictor responsiveness in the horse in vivo. Methods: In a blinded, randomised cross-over experiment, 9 horses were treated with either dexamethasone (0.1 mg/kg bwt i.v. q. 24 h) or saline i.v. for 6 days. The changes in local average skin temperature before (baseline) and after intradermal injection...
Antimicrobial regional limb perfusion in horses. Regional limb perfusion involves administration of an antimicrobial solution into the vasculature of a selected portion of the limb that has been isolated from the systemic circulation by controlled application of a tourniquet. The technique provides high antimicrobial concentrations in the region of interest and greatly contributes to the elimination of infection.
Effects of phenylbutazone alone or in combination with flunixin meglumine on blood protein concentrations in horses. To assess effects of treatment with phenylbutazone (PBZ) or a combination of PBZ and flunixin meglumine in horses. Methods: 24 adult horses. Methods: 13 horses received nonsteroidal antiinflammatory drugs (NSAIDs) in a crossover design. Eleven control horses were exposed to similar environmental conditions. Treated horses received PBZ (2.2 mg/kg, PO, q 12 h, for 5 days) and a combination of PBZ and flunixin meglumine (PBZ, 2.2 mg/kg, PO, q 12 h, for 5 days; flunixin meglumine, 1.1 mg/kg, IV, q 12 h, for 5 days). Serum samples were obtained on day 0 (first day of treatment) and day 5, and total...
The use of mitomycin C as an adjunctive treatment for equine ocular squamous cell carcinoma. To assess the effectiveness of topical mitomycin C application as an alternative adjunctive therapy to CO2 laser ablation in the treatment of equine ocular squamous cell carcinoma. Methods: A retrospective clinical study of eight client owned horses in which 10 affected eyes were treated for ocular squamous cell carcinoma over a 17 month period. (March 2003 to August 2004). Methods: Each horse was given a general anaesthetic to allow CO2 laser ablation of the lesion(s). Mitomycin C at a concentration of 0.4 mg/mL was then applied intraoperatively to the affected areas for 1 or 5 minutes. Posto...
Lack of clinical efficacy of a phosphodiesterase-4 inhibitor for treatment of heaves in horses. Phosphodiesterase-4 (PDE 4) enzyme inhibitors have been shown to have anti-inflammatory properties in various animal disease processes and therefore could be effective drugs for the treatment of equine airway diseases. The purpose of this study was to evaluate the efficacy and adverse effects of the PDE 4 inhibitor L-826,141 in horses with heaves. In a blinded parallel design, horses with heaves exposed daily to moldy hay were given a placebo for 14 days and then administered either L-826,141 (n = 6; loading dose of 1 mg/kg IV followed by 0.5 mg/kg IV q48h) or dexamethasone (n = 6; 0.04 mg/kg ...
Acute effects of prostaglandin F(2alpha) on systemic oxytocin and progesterone concentrations during the mid- or late-luteal phase in mares. The acute effects of prostaglandin F(2alpha) (PGF) on circulating oxytocin and progesterone concentrations were characterized in mares during the mid- or late-luteal phase. Pony mares were randomly assigned to the following experimental groups based on treatment with PGF (2.5mg) or saline on Day 8 or Day 13 (Day 0=ovulation): PGF-8, PGF-13, saline-8, or saline-13 (n=7/group). Mares were fitted with indwelling, jugular vein catheters and two blood samples (-5 and 0 min) were collected prior to treatment. Treatments were administered into the jugular vein (0 min) and blood collection continued t...
The influence of butorphanol dose on characteristics of xylazine-butorphanol-propofol anesthesia in horses at altitude. To characterize behavioral and physiological responses to short-term, unsupplemented intravenous (IV) anesthesia in healthy horses at high altitude (2240 m), and to test the hypothesis that the dose of butorphanol modifies the response of the horse to propofol anesthesia following xylazine pre-medication. Methods: Randomized prospective butorphanol dose cross-over experimental design. Animals Eight healthy horses, 13 +/- 6 (mean +/- SD) years of age, and weighing 523 +/- 26 kg. Methods: Each horse was anesthetized three times with at least 3 weeks between each anesthesia. After collecting pre-...
Antibacterial activity of cefquinome against equine bacterial pathogens. Cefquinome is known for its use as an antibacterial drug in cattle and pigs. The objective of this study was to evaluate the antibacterial activity of cefquinome against equine pathogenic bacteria. The minimum inhibitory concentration (MIC) of cefquinome was determined for a total of 205 strains, which had recently been isolated in Europe from diseased horses (respiratory infection, foal septicaemia). The bactericidal activity was tested against 19 strains using the time killing method. The post-antibiotic effect (PAE) and post-antibiotic sub-MIC effect (PA SME) were determined against 12 stra...
Pharmacokinetics and tissue distribution of doxycycline after oral administration of single and multiple doses in horses. To determine pharmacokinetics, safety, and penetration into interstitial fluid (ISF), polymorphonuclear leukocytes (PMNLs), and aqueous humor of doxycycline after oral administration of single and multiple doses in horses. Methods: 6 adult horses. Methods: The effect of feeding on drug absorption was determined. Plasma samples were obtained after administration of single or multiple doses of doxycycline (20 mg/kg) via nasogastric tube. Additionally, ISF, PMNLs, and aqueous humor samples were obtained after the final administration. Horses were monitored for adverse reactions. Results: Feeding ...
Influence of gastrointestinal tract disease on pharmacokinetics of lidocaine after intravenous infusion in anesthetized horses. To determine the disposition of lidocaine after IV infusion in anesthetized horses undergoing exploratory laparotomy because of gastrointestinal tract disease. Methods: 11 horses (mean +/- SD, 10.3 +/- 7.4 years; 526 +/- 40 kg). Methods: Lidocaine hydrochloride (loading infusion, 1.3 mg/kg during a 15-minute period [87.5 microg/kg/min]; maintenance infusion, 50 microg/kg/min for 60 to 90 minutes) was administered IV to dorsally recumbent anesthetized horses. Blood samples were collected before and at fixed time points during and after lidocaine infusion for analysis of serum drug concentration...
Effects of an alveolar recruitment maneuver on cardiovascular and respiratory parameters during total intravenous anesthesia in ponies. To evaluate pulmonary and cardiovascular effects of a recruitment maneuver (RM) combined with positive end-expiratory pressure (PEEP) during total intravenous anesthesia in ponies. Methods: 6 healthy adult Shetland ponies. Methods: After premedication with detomidine (10 microg/kg, IV), anesthesia was induced with climazolam (0.06 mg/kg, IV) and ketamine (2.2 mg/kg, IV) and maintained with a constant rate infusion of detomidine (0.024 mg/kg/h), climazolam (0.036 mg/kg/h), and ketamine (2.4 mg/kg/h). The RM was preceded by an incremental PEEP titration and followed by a decremental PEEP titrati...
Medical treatment of osteoarthritis in the horse – a review. The medical treatment of osteoarthritis (OA) in the horse is one of the most utilized therapeutic regimens in the equine practice. It is important to understand the anatomy of synovial joints and the pathophysiology of the disease process to treat OA adequately. Once a thorough understanding of the disease process is comprehended the proper combination of systemic nonsteroidal anti-inflammatory drugs (NSAIDs), intraarticular steroids, viscosupplementation and chondroprotectants can be used to treat the disease and inhibit further progression of degenerative changes to the cartilage surface. Th...
Analgesic effects of epidural administration of hydromorphone in horses. To evaluate the effects of epidural administration of hydromorphone 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 hydromorphone (0.04 mg/kg) or a control solution (20 mL of sterile water) administered epidurally into in the first intercoccygeal space. Treatments were administered at time intervals of > or = 7 days. Electrical stimulation was applied for 6 hours after epidural injection over the dermatomes of the perineal, sacral, lumbar, and t...
Clinical field efficacy and safety of pyrantel pamoate paste (19.13% w/w pyrantel base) against Anoplocephala spp. in naturally infected horses. Clinical field trials were conducted at five geographical locations in the USA (Oklahoma, Wisconsin, Tennessee, Virginia and Idaho) to evaluate the efficacy and safety of pyrantel pamoate paste (19.13%, w/w, pyrantel base) administered at the recommended dosage of 13.2 mg pyrantel base/kg (6.0 mg pyrantel base/lb) body weight (b.w.) against tapeworm infections of Anoplocephala spp. in naturally infected horses. Horses at each study site were allocated by restricted randomization based on the cestode status (positive or negative) of pre-treatment fecal egg counts to complete sets of four animal...
[Recombinant antibodies: a new application in scorpion envenomation?]. Serotherapy is the only specific treatment for envenomation. The antibodies are obtained after the purification of serum from hyperimmunised horses and are used after fragmentation in the form of polyclonal Fab or F(ab)'2. The anti-venom sera are heterogeneous, and their protective effect is often weak. The administration of these preparations induces risks of immediate or delayed side effects: hypersensitivity reactions, anaphylactic shock and serum sickness. This observation led us to develop new forms of antibodies produced by molecular engineering, capable of specifically neutralizing the ...
Clinical efficacy of local administration of ceftiofur in a Staphylococcus aureus infection in tissue cages in ponies. Ceftiofur concentrations in an infected and uninfected environment were compared and the efficacy of locally administered ceftiofur was evaluated in an experimental infection with Staphylococcus aureus in tissue cages. Eight ponies had tissue cages (TCs) implanted s.c. on each side of the neck. Into one of the cages 150 mg of ceftiofur was administered and fluid samples were taken to determine ceftiofur concentrations. After 1 week the other TC was infected with S. aureus and subsequently treated with 150 mg ceftiofur administered locally into the TC once daily for 21 days. Samples of fluid we...
Pharmacological characterization of alpha1-adrenoceptors in equine digital veins. Alpha-adrenoceptors mediate contractile responses in equine digital veins (EDVs) and arteries. Vascular smooth muscle alpha(1)-adrenoceptor subtypes have been implicated in a number of conditions, such as acute equine laminitis, and are therapeutic targets for the treatment of this condition. Digital veins, rather than arteries, were investigated in the present study because they have been specifically implicated in the pathophysiology of acute laminitis. The order of potency of a series of alpha(1)-adrenoceptor-selective agonists and antagonists was determined in isolated rings of EDVs under ...
Regional differences in the in vitro penetration of hydrocortisone through equine skin. Little is known about the transdermal penetration of hydrocortisone in the horse and, although commercial formulations containing hydrocortisone are registered for topical use in the horse, there have been no studies investigating the movement of this glucocorticoid through different regions of equine skin. Skin was harvested from the thorax, groin and leg (dorsal metacarpal) regions of five Thoroughbred geldings and frozen (-20 degrees C) until required. Defrosted skin was placed in Franz-type diffusion cells and the amount of radiolabelled ((3)H) hydrocortisone, in a saturated solution of un...
A multicenter evaluation of the effectiveness of Quest Gel (2% moxidectin) against parasites infecting equids. Controlled trials with a common protocol were conducted in Idaho, Illinois and Tennessee to evaluate anthelmintic effectiveness of Quest Gel (QG; 2% moxidectin) against lumenal parasites in horses. Candidate horses were required to have naturally acquired nematode infections, as confirmed by presence of strongylid eggs in feces. At each site, 24 equids were blocked on the basis of pretreatment strongyle fecal egg counts (EPG) and randomly assigned to treatments within blocks. Within each block of two animals, one received QG on Day 0 at a dosage of 0.4 mg moxidectin/kg b.w. and one was an untr...
Constant rate infusion for topical ocular delivery in horses: a pilot study. To assess the efficacy and kinetics of a continuous infusion modality for topical ophthalmic drug delivery via subpalpebral lavage in horses. Methods: Five ophthalmically normal horses Methods: A constant-rate continuous delivery pump was used to apply 0.01% fluorescein solution to the eyes of five ophthalmically normal horses via subpalpebral lavage. Fluorescein was applied at a rate of 0.14 mL/h for 72 h. Tear samples were collected from the ventral conjunctival fornix at regular intervals via capillary tube and tear fluorescein concentrations were determined via spectral assay. Laboratory s...
Qualitative and quantitative evaluation of equine respiratory mechanics by impulse oscillometry. The long-established conventional reference technique (CRT) for measuring respiratory mechanics in horses lacks sensitivity and there is a need for further refinement in new technology, such as the impulse oscillometry system (IOS). Objective: To evaluate the potential use of the IOS as a clinical respiratory function test and compare it to the current CRT in horses suffering from common upper and lower airway dysfunctions. Methods: Six healthy horses were tested before and after induction of a unilateral nasal obstruction (UNO) or transient left laryngeal hemiplegia (LLH). Six heaves-affected...
Molecular diagnosis of anthelmintic resistance. Conventional and real time polymerase chain reaction-based tests have been developed for the diagnosis of anthelmintic resistance (AR) in populations of several small and large ruminant as well as horse gastro-intestinal nematode species. To date, molecular markers that correlate well with AR are available only for the detection of benzimidazole resistance. Recently, however, a single nucleotide polymorphism was found in vitro to be of functional relevance for reduced drug efficacy to macrocylic lactones. The focus of the present review, therefore, is the molecular mechanism of action of these...
Intravenous continuous infusion of lidocaine for treatment of equine ileus. To determine if intravenous lidocaine is useful and safe as a treatment for equine ileus. Methods: Prospective double-blinded placebo-controlled trial. Methods: Horses (n = 32) with a diagnosis of postoperative ileus (POI) or enteritis and that had refluxed >20 L or had been refluxing for >24 hours. Methods: Refluxing horses were administered lidocaine (1.3 mg/kg intravenously [IV] as a bolus followed by a 0.05 mg/kg/min infusion) or saline (0.9% NaCl) solution placebo for 24 hours. Variables evaluated included volume and duration of reflux, time to 1st fecal passage, signs of pain, anal...
Effects of topical nitroglycerine patches and ointment on digital venous plasma nitric oxide concentrations and digital blood flow in healthy conscious horses. To measure and compare palmar digital venous plasma nitric oxide (NO) concentrations and digital arterial blood flow after application of topical nitroglycerine (NTG). Methods: Experimental study. Methods: Healthy adult horses (n=8). Methods: Digital blood flow was measured by an ultrasonic Doppler flow probe surgically implanted around the medial palmar digital artery. Blood was collected from a catheter placed in the medial palmar digital vein for quantification of NO. NTG patches, NTG ointment or control patches were placed over the palmar digital vessels at the level of the fetlock. Two ho...
In vitro effects of bethanechol on equine gastrointestinal contractility and functional characterization of involved muscarinic receptor subtypes. The goal of this study was to investigate the effect of bethanechol (BeCh) on contractility patterns of smooth muscle preparations of equine duodenum descendens, jejunum, caecum and pelvic flexure in vitro. Concentration-response relationships were developed for BeCh using in vitro assays with and without preincubation of muscarinic (M) receptor antagonists for M2 and M3 receptors. BeCh induced a significant, concentration-dependent increase in contractile response in equine intestine in specimens with circular orientation. The maximal effect was largest for jejunal specimens with no differenc...
Medullary plasma pharmacokinetics of vancomycin after intravenous and intraosseous perfusion of the proximal phalanx in horses. To study the pharmacokinetics of vancomycin in plasma obtained from the medullary sinusoids of the proximal phalanx (P1) after intravenous (IV) and intraosseous (IO) regional limb perfusion (RLP). Methods: Experimental study. Methods: Twelve horses. Methods: IV and IO RLP were performed in 2 groups (n = 6) of horses. Vancomycin hydrochloride (300 mg in 60 mL 0.9% NaCl) was randomly infused in 1 front limb, with the contralateral limb as control (60 mL 0.9% NaCl). A hole was drilled in the lateral cortex of P1, and blood samples from the medullary sinusoids of P1 were collected before infusion,...
