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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.
Renal medullary crest necrosis associated with phenylbutazone therapy in horses. Thirty-five cases of renal medullary crest necrosis morphologically similar to the renal papillary necrosis of analgesic nephropathy as described in man and rats are reported in horses receiving maintenance dosages of phenylbutazone. The primary lesion is a well-demarcated focal medullary necrosis resulting in sequestration of fragments of the renal crest. Renal cortical lesions are considered secondary to the medullary necrosis and consist of segmental pallor as a result of tubular dilatation, filtrate retention, and interstitial edema. Ischemia in concert with phenylbutazone is suggested as ...
Effects of clenbuterol hydrochloride on certain respiratory and cardiovascular parameters in horses performing treadmill exercise. Five standardbred geldings received intravenous clenbuterol hydrochloride and saline in a crossover experiment to evaluate the effects of clenbuterol on certain cardiorespiratory parameters during and after treadmill exercise. The exercise test consisted of four steps. Step 1 at a speed of 76 m per minute, step 2 at 129 m per minute, step 3 at 190 m per minute and step 4 at 236 m per minute. The duration of each step was two minutes, except step 4 which was four minutes. The treadmill was set at a grade of 19 per cent. Before exercise, 30 minutes after clenbuterol or saline administration, art...
Induction of male sex behavior in pony mares with testosterone propionate. Two pony mares were administered 150 mg of testosterone propionate every other day for 20 days (ten injections) and every ten days there-after. An additional two mares and one stallion were not treated and served as controls. Testosterone propionate was dissolved in absolute ethanol and administered subcutaneously. Sex behavior tests were conducted 26 and 40 days after the first injection. Control mares exhibited very little male sex behavior. Both testosterone propionatetreated mares, however, exhibited mounting, sniffing, flehmen, biting and vocalization behavior in the presence of an estrou...
Modulation of equine platelet function by diethylcarbamazine (DEC). Equine platelets, when treated with the anthelmintic drug diethylcarbamazine (DEC), gave a dose-dependent release of radiolabeled serotonin without concomitant aggregation. At levels of the drug that gave only minimal release of radiolabel, marked dose-dependent inhibition of platelet aggregation to three of four platelet agonists tested--adenosine diphosphate (ADP), collagen, and arachidonic acid--was observed. With ADP, inhibition was observed to be reversed by removal of DEC prior to agonist challenge. However, with collagen, inhibition was only partially reduced by prior removal of DEC; wh...
Phenoxymethyl penicillin in the horse: an alternative to parenteral administration of penicillin. This preliminary study evaluated phenoxymethyl penicillin (Penicillin V) as an alternative to parenteral administration of penicillin in horses. Penicillin V was administered orally to five horses at two different doses and plasma levels of the drug were determined at timed intervals. The results were evaluated by regression analysis. Following the administration of penicillin V at a dose of 66,000 IU/kg or 110,000 IU/kg, the mean peak plasma levels obtained were 1.55 micrograms/mL and 2.34 micrograms/mL respectively. A plasma level two to four times above the minimal inhibitory concentration ...
A new analgesic drug combination in the horse. A xylazine and butorphanol drug combination produced minimal and transient hemodynamic effects and no significant respiratory depression when administered to 6 healthy horses. Combining xylazine and butorphanol produced a synergistic analgesic effect and provided good chemical restraint for a standing surgical procedure.
The spectrum of antiviral activities of acyclovir in vitro and in vivo. In vitro sensitivity data suggest that acyclovir should be effective against clinical manifestations of herpes simplex virus types 1 and 2, varicella-zoster virus and possibly Epstein-Barr virus. The clinical potential against herpes simplex virus types 1 and 2 is further supported by results in animal models. Human cytomegalovirus and the veterinary herpes viruses, with the possible exception of equine herpes virus type 1, may be insufficiently sensitive to be amenable to treatment.
Sodium and potassium ion-dependent change in oligomerization of Na,K-ATPase in C12E8 detected by low-angle laser light scattering technique in combination with high performance porous silica-gel chromatography. Approximate molecular weights and the subunit structures of Na,K-ATPase from horse kidney were estimated by means of the combination of porous silica gel chromatography, laser light scattering (LS) and refractive index (RI) measurements in C12E8. When the enzymes were eluted with NaCl- or KCl-containing solution, 3 or 4 protein peaks, respectively were detected except that of low molecular weight range. These peaks were tentatively named Na-1, Na-2, Na-2', Na-3 (NaCl-containing eluents), K-1, K-2, K-3 (KCl-containing eluents), respectively. Na,K-ATPase and K-p-nitrophenylphosphatase activities...
The in vitro effects of EDTA-tris, EDTA-tris-lysozyme, and antimicrobial agents on equine genital isolants of Pseudomonas aeruginosa. Five isolants of Pseudomonas aeruginosa collected from clinical cases of equine genital infection and one standard strain of P. aeruginosa were exposed to various concentrations of ethylene-diaminetetraacetic acid (EDTA) and tris (hydroxymethyl) aminomethane (tris buffer pH 8) and EDTA-tris lysozyme. Colony forming units of the isolants and minimal inhibitory concentrations for 11 antimicrobial agents were determined with each isolant before and after exposure to the EDTA solutions. Decreased cellular viability was found with all six isolants after exposure to the EDTA-tris solutions. Reversal...
Inhibition of motility of bovine, canine and equine spermatozoa by artificial vagina lubricants. The effects of four vaginal lubricants on progressive spermatozoal motility were evaluated. Neat semen was exposed to 0, 5, or 10% (w/v) of H-R, sterile K-Y, nonsterile K-Y or Maxilube lubricating jellies for 10 min at 37 degrees C and then extended to 10x10(6) spermatozoa/ml. Spermatozoal motility was evaluated after 0, 1, 2, 4 and 6 or 8 h of incubation at 37 degrees C. For bovine spermatozoa, sterile K-Y jelly at 10% suppressed motility (P<0.05), but nonsterile K-Y, H-R and Maxilube jellies had no effect. Maxilube was toxic (P<0.01) to canine spermatozoa and is not recommended for use...
A pharmacokinetic study of digoxin in the horse. Digoxin was administered orally and intravenously to seven healthy adult mares and geldings in two separate trials. At a dose of 44 microgram digoxin/kg body weight, the oral study was characterized by an absorption phase with a mean (+/- 1 standard deviation) peak serum digoxin concentration of 2.21 ng/ml (+/- 0.45) at a mean of 2.29 h (+/- 1.52) after administration. A second rise in serum digoxin concentration started about 6-8 h after administration and extended to about 20 h after administration. The mean bioavailability (F) was 23.38% (+/- 5.96). At a dose of 22 microgram digoxin/kg body...
Ivermectin: a potent new antiparasitic agent. Ivermectin is the 22,23-dihydro derivative of avermectin B1, a macrocyclic lactone produced by an actinomycete, Streptomyces avermitilis. It is active at extremely low dosage against a wide variety of nematode and arthropod parasites, apparently by virtue of its action on the mediation of neurotransmission by gamma-aminobutyric acid. It is now in commercial use in various countries for the treatment and control of parasites in cattle, horses, and sheep, and is expected to become available for use in swine and dogs. Since studies with the drug in man are in a preliminary stage, it is not yet kn...
Concentration of nucleotides and deoxynucleotides in peripheral and phytohemagglutinin-stimulated mammalian lymphocytes. Effects of adenosine and deoxyadenosine. Concentrations of purine and pyrimidine ribonucleotides were measured with HPLC in lymphocytes of man, horse, pig and sheep and in rat thymocytes. The ATP concentration was highest in lymphocytes of all species and about 850 pmol/10(6) cells in human and equine lymphocytes, higher in porcine and lower in ovine lymphocytes and rat thymocytes. The GTP concentration was comparable in human, equine and porcine lymphocytes, but lower in ovine lymphocytes. ATP concentration was also measured in lymphocytes of man, horse and pig with a luciferin-luciferase assay. During culturing with or without phyt...
Effect of isometamidium on infections by Trypanosoma vivax and T. evansi in experimentally-infected animals. Assays dealing with the therapeutic and prophylactic activity of isometamidium on experimental infections by Trypanosoma vivax and T. evansi were carried out. The drug was found to be highly effective against T. vivax infection in sheep and cattle in which periods of protection ranging from 118 to 195 days were achieved. No complete effects against infection by T. evansi were observed. The drug was well tolerated in sheep and cattle while side-effects were noted in treated mares. It was concluded that isometamidium could be used to prevent damage and economical losses caused by T. vivax in Ven...
The effect of altrenogest, an oral progestin, on hematologic and biochemical parameters in mares. Twenty mares were assigned to 1 of 4 groups: no altrenogest; altrenogest at 0.044 mg/kg BW; altrenogest at 0.132 mg/kg BW; or altrenogest at 0.220 mg/kg BW. Treatment was administered daily for 86 days. No signs of illness attributable to feeding altrenogest were observed during the trial. Treatment had no effect (P greater than .05) on the following parameters: WBC, differential WBC, platelet number, creatinine, LDH, CPK, total bilirubin, cholesterol, globulin, BSP, and erythrocyte sedimentation rate. When comparing values over time with pretreatment means or among treatment groups, there wer...
Chemical restraint of wild horses: effects on reproduction and social structure. Twenty-three (9 male, 14 female) wild horses (Equus caballus) in the Great Basin Desert were immobilized by ground techniques with succinylcholine chloride during 1,950 person-hr. Induction (means = 2.09 +/- 0.59 min) and recovery (means = 12.4 +/- 5.0 min) were rapid and most animals were returned in less than 10 min to original bands. Dosages ranged from 0.66-0.77 mg/kg body weight and neither abortions nor band changes in group membership resulted. However, a few concerted efforts up to 24 hr were needed to return some animals to original bands and three non-drug related mortalities occurre...
Warfarin: a review with emphasis on its use in the horse. Warfarin or dicoumarol prevents the production of functional clotting factors II, VII, IX and X. Navicular disease and thrombophlebitis are examples of equine thrombotic diseases in which warfarin has been used therapeutically. The initiation of anticoagulant therapy is relatively simple but attending veterinarians must be aware of the potential risks in order to minimize them. These risks include epistaxis, bleeding into the gastrointestinal tract and at the venipuncture site, and increased susceptibility to hematoma formation following local trauma. Vitamin K, especially vitamin K(1) is a sw...
Native American medicinal plants. Anemonin from the horse stimulant Clematis hirsutissima. Anemonin, the dilactone of cyclobutane-1,2-diol-1,2-diacrylic acid derived from the cyclodimerization of protoanemonin, a known blistering agent, was isolated from Clematis hirsutissima, a plant used by the Nez Perce and Teton Sioux nations as a horse stimulant.
Attempted reconstitution of a foal with primary severe combined immunodeficiency. A foal with primary severe combined immunodeficiency, diagnosed within the first two weeks of life, was maintained with its dam in semi-isolation. The foal received continuous prophylactic antibiotic therapy, plasma from a sibling hyperimmunised with equine adenovirus vaccine, and intensive general nursing care. A full sibling female was selected as a bone marrow donor on the basis of red blood cell cross-matching and mixed lymphocyte reactions. Cyclophosphamide was given before two bone marrow transfusions at 35 and 73 days of age. To prevent graft versus host disease graft versus host diseas...
Characteristics of receptors for prostaglandin F-2 alpha in bovine and equine corpora lutea. Prostaglandin F-2 alpha (PGF-2 alpha) receptors of bovine and equine corpora lutea (C.L.) were studied. From both the equilibrium binding data and the dissociation kinetics behaviour, two affinity classes of receptors are evident in the mare, with apparent dissociation constants (Kd) of 1,5 x 10(-9) M and 3.5 x 10(-8) M. Bovine PGF-2 alpha receptors present a homogeneous population of binding sites with Kd = 1 x 10(-8) M. Both bovine and equine C.L. receptors bind PGF-2 alpha in a specific manner; only 13, 14-dihydro-PGF-2 alpha considerably cross-reacts with these receptors. Since in the mare...
Malignant hyperthermia-like reactions in three anesthetized horses. Problems encountered during halothane anesthesia in 3 horses included increasing rectal temperature, muscle rigidity or movement during anesthesia, irregular breathing patterns, and difficulty in stabilizing blood pressure. One horse had prolonged muscle fasciculations and failure to relax after administration of succinylcholine in addition to halothane. That horse developed severe, bilateral myositis of the triceps, lumbar, and gluteal muscles. Problems encountered were similar to those caused by the disease known as malignant hyperthermia.
Induced abortion with two prostaglandin F2 alpha analogues in mares: plasma progesterone changes. Three experiments were conducted to test the abortifacient effects of PGF2 alpha analogues on mares during midgestation (average gestation length 141.5 days). The progesterone concentration was measured by radioimmunoassay. In experiment 1. five mares received an injection of PGF2 alpha analogue (fluprostenol: 500 micrograms intramuscularly) and a second injection either at 24, 48, of 72 h. Although the progesterone concentration decreased (P less than 0.05) an average of 44 per cent in 24 h, none of the pregnancies were terminated. In experiment 2, beginning at least 10 days after experiment ...
Experimental studies of drug-induced impaction colic in the horse. Colic was induced in horses and ponies following topical or intravenous (iv) administration of amitraz, a formamidine acaricide. The condition was characterised by rapid cessation of intestinal sounds, stasis, extensive impaction and tympany throughout the large colon. Three animals that were necropsied had a faecalith obstructing the proximal small colon aboral to marked colonic impaction. A reproducible and reversible impaction colic syndrome could be induced by an iv injection of 1 mg amitraz/kg body weight in solvent. There were immediate central nervous system and intestinal signs. Large ...
