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Topic:Pharmaceuticals
Pharmaceuticals in equine medicine encompass a wide range of drugs and therapeutic agents used to treat various conditions in horses. These substances include analgesics, anti-inflammatories, antibiotics, sedatives, and anthelmintics, among others. Each class of pharmaceuticals is designed to address specific health issues, such as pain management, infection control, or parasitic infestations. The pharmacokinetics and pharmacodynamics of these drugs can vary significantly between horses and other species, necessitating careful consideration of dosage and administration methods. This page compiles peer-reviewed research studies and scholarly articles that explore the development, efficacy, safety, and regulatory aspects of pharmaceuticals used in equine healthcare.
Equine metabolism of buspirone studied by high-performance liquid chromatography/mass spectrometry. The metabolism and urinary excretion of a 100 mg dose of the non-sedating anxiolytic drug buspirone was examined using high-performance liquid chromatography/electrospray ionization mass spectrometry in the positive ion mode. In addition to a significant proportion of unchanged buspirone we were able to detect three major metabolite classes. These were identified as monohydroxy, dihydroxy and dihydroxymethoxy products. Detection of the metabolites and the parent drug was possible in all the urine samples collected (1-12 h) post-administration.
Cerebrospinal fluid and blood concentrations of toltrazuril 5% suspension in the horse after oral dosing. Toltrazuril 5% suspension (Baycox, Bayer Canada, Ontario, Canada) was administered to six adult horses followed by blood collection and assay to determine the concentration of toltrazuril and its principal metabolites, toltrazuril sulfone and toltrazuril sulfoxide. From this data, the maximum concentration (C(max)), elimination half-life (T 1/2), and mean residence times of the plasma were determined from standard pharmacokinetic formulas. After a single oral dose of 10 mg/kg body weight a rapid absorption was found, with a mean peak serum concentration of 11.17 mg/L at 18 hours. Elimination w...
Use of 99mTc-mercaptoacetyltriglycine to evaluate renal function in horses. Ten healthy horses were injected intravenously with 99mTc-MAG3 and the disappearance of radioactivity from the blood was measured. The total body clearance (Cl(B)) and elimination half-life (t1/2(beta)) were 7.9 +/- 1.5 ml/kg/minute and 32.8 +/- 4.1 minutes, respectively. The disappearance of 99mTc-MAG3 from the blood of 2 horses with compromised renal function was also measured. The data suggest that 99mTc-MAG3 is a useful and clinically applicable radiopharmaceutical for measurement of effective renal blood flow in the horse.
Diclazuril in the horse: its identification and detection and preliminary pharmacokinetics. Diclazuril (4-chlorophenyl [2,6-dichloro-4-(4,5-dihydro-3H-3,5-dioxo-1,2,4-triazin-2-yl)pheny l] acetonitrile), is a benzeneacetonitrile antiprotozoal agent (Janssen Research Compound R 64433) marketed as Clinacox . Diclazuril may have clinical application in the treatment of Equine Protozoal Myeloencephalitis (EPM). To evaluate its bioavailability and preliminary pharmacokinetics in the horse we developed a sensitive quantitative high-pressure liquid chromatography (HPLC) method for diclazuril in equine biological fluids. MS/MS analysis of diclazuril in our HPLC solvent yielded mass spectral ...
Equine reproductive pharmacology. This article reviews therapies and strategies commonly used to treat diseases of the mare's genital tract and modulate the reproductive cycle of the mare. Many reproductive treatments are based on historical use and empirical evidence rather than well controlled clinical studies. This article attempts to present practical information in a summary form while highlighting the need for continued research documenting the efficacy and safety of reproductive therapies.
Formulary of common equine drugs. This article presents in easily accessible form a collection of drug names and dose rates for the drugs recommended or referred to by the authors of the individual articles in this issue. Although the formulary provides recommendations for drug use, the reader is cautioned that the responsibility for the choice of agent, formulation, dose, and dose interval lies with the clinician. The author also addresses regulations that govern the use of drugs in competition horses.
Therapeutics of musculoskeletal disease in the horse. Therapeutic medications play a crucial role in the successful therapy of many musculoskeletal diseases that occur in horses. For example, appropriate antibiotic therapy is extremely important in the treatment of diseases caused by infections with microorganisms such as botulism, tetanus, osteomyelitis, and muscle abscesses. In addition, numerous prescription medications and nutritional supplements are available for the treatment of osteoarthritis in horses. Many of these agents currently on the market fall into a new class of drugs called SADMO agents. Unfortunately, the efficacy and mechanism...
Pharmacokinetic interactions between flunixin and sulphadimidine in horses. The pharmacokinetic aspects of sulphadimidine were studied in clinically healthy (control) and Flunixin-medicated horses after a single intravenous and oral administration of 100 mg/kg body weight. Plasma sulphadimidine concentration were determined by high-performance liquid chromatography (HPLC). Following the intravenous injection, all plasma sulphadimidine data were best approximated by a two-compartment open model using sequential, weight non-linear regression. Flunixin induced a 67% increase in the rate of sulphadimidine return to the central compartment from peripheral tissues (K21) and...
Pharmacokinetics and bioequivalence of two suxibuzone oral dosage forms in horses. A disposition and bioequivalence study with a suxibuzone granulated and a suxibuzone paste oral formulation was performed in horses. Suxibuzone (SBZ) is a nonsteroidal anti-inflammatory drug, which was administered to horses (n = 6) at a dosage of 19 mg/kg bwt by the oral route (p.o.) in a two period cross-over design. Suxibuzone is very rapidly transformed into its main active metabolites, phenylbutazone (PBZ) and oxyphenbutazone (OPBZ). Therefore plasma and synovial fluid concentrations of SBZ, PBZ and OPBZ were simultaneously measured by a sensitive and specific high-performance liquid chro...
Pharmacology of anthelmintic resistance in cyathostomes: will it occur with the avermectin/milbemycins? Anthelmintic-resistance has emerged as a problem in several animal industries. In the horse, cyathostome resistance to all available treatments except for the avermectin/milbemycins means that these drugs provide the cornerstone of control. Ivermectin has been available for several years; the related compound moxidectin is more recent. Although we do not know for sure, aspects of moxidectin such as its persistent action and its efficacy against mucosal stages of cyathostomes, may enhance the rate of development of resistance. On the other hand, selection pressure would be reduced if the persis...
Prevention of crib-biting: a review. Crib-biting is a common oral stereotype. Because of perceived deleterious effects on the health and appearance of subjects the prevention of crib-biting is regularly attempted. The resourcefulness of horses in satisfying their motivation to perform this behaviour often frustrates owners' efforts at prevention. This paper reviews the efficacy and observable consequences of attempting to prevent crib-biting by a variety of methods. These include attempts to prevent the grasping of objects, to interfere with air-engulfing and to introduce punishment for grasping and neck-flexion. Other approaches...
Frontiers in anthelmintic pharmacology. Research in anthelmintic pharmacology faces a grim future. The parent field of veterinary parasitology has seemingly been devalued by governments, universities and the animal industry in general. Primarily due to the success of the macrocyclic lactone anthelmintics in cattle, problems caused by helminth infections are widely perceived to be unimportant. The market for anthelmintics in other host species that are plagued by resistance, such as sheep and horses, is thought to be too small to sustain a discovery program in the animal health pharmaceutical industry. These attitudes are both alarmi...
Bupivacaine in the horse: relationship of local anaesthetic responses and urinary concentrations of 3-hydroxybupivacaine. Bupivacaine is a potent local anaesthetic used in equine medicine. It is also classified as a Class 2 foreign substance by the Association of Racing Commissioners International (ARCI). The identification of residues in postrace urine samples may cause regulators to impose significant penalties. Therefore, an analytical/pharmacological database was developed for this medication. The highest no-effect dose (HNED) for the local anaesthetic effect of bupivacaine was determined to be 0.25 mg by using an abaxial sesamoid local anaesthetic model. Administration of the HNED of bupivacaine to eight hor...
Testing for therapeutic medications: analytical/pharmacological relationships and limitations’ on the sensitivity of testing for certain agents. Proper veterinary care of horses requires that horses in training have access to modern therapeutic medication. However, the sensitivity of equine drug testing now allows for detection of pharmacologically insignificant concentrations of many therapeutic medications. In 1995, the Association of Racing Commissioners International (ARCI) resolved that members 'address trace level detection so as not to lead to disciplinary action based on pharmacologically insignificant traces of these substances'. The rationale behind this approach is to prevent overly-sensitive testing from inhibiting the prop...
The elimination profiles of tenoxicam and hydroxytenoxicam in equine urine and serum after a 200-mg oral dose. Tenoxicam (Mobiflex) was administered orally to four standardbred mares at a dose of 200 mg. Elimination profiles of tenoxicam and hydroxytenoxicam were generated based on quantitation of these analytes in urine and serum by liquid chromatography (LC) with ultraviolet detection. Tenoxicam was confirmed by LC-tandem mass spectrometry daughter ion mass spectra in the last postadministration sample in which tenoxicam was detected. The tenoxicam and hydroxytenoxicam urinary elimination profiles had the same shape for the same horse; however, each horse was significantly different from the others. ...
Etodolac in equine urine and serum: determination by high-performance liquid chromatography with ultraviolet detection, confirmation, and metabolite identification by atmospheric pressure ionization mass spectrometry. A high-performance liquid chromatographic method was used for the detection of etodolac in equine serum and urine. The method consisted of a one-step liquid-liquid extraction, separation on a reversed-phase (RP-18) column and detection using an ultraviolet detector. Additional confirmation methods included a HPLC coupled with an atmospheric pressure chemical ionization mass spectrometer (APCI-MS). Free (unbound) etodolac and its conjugates were present in the samples. Concentrations of the drug in the serum and urine samples collected from four standardbred mares after a single oral administra...
Determination of the activity of pyrimethamine, trimethoprim, sulfonamides, and combinations of pyrimethamine and sulfonamides against Sarcocystis neurona in cell cultures. Equine protozoal myeloencephalitis (EPM) is a neurologic syndrome in horses from the Americas and is usually caused by infection with the apicomplexan parasite, Sarcocystis neurona. The activities of pyrimethamine, trimethoprim, sulfachloropyridazine, sulfadiazine, sulfadimethoxine, sulfamethoxazole, sulfamethazine, and sulfathiazole were examined against developing S. neurona merozoites in bovine turbinate cell cultures. A microtiter plate host cell lesion based assay was used to determine the effects of agents on developing merozoites. A cell culture flask assay was used to determine if sele...
Strategic control of gastrointestinal nematode and lungworm infections with eprinomectin at turnout and eight weeks later. Two groups of 10 first-year grazing cattle were either left untreated as controls (group 1) or treated with eprinomectin as a pour-on application at turnout and eight weeks later (group 2). The control group developed a mild infection with gastrointestinal nematodes and lungworms during the season, whereas the treated animals remained healthy. The interval between the treatments allowed the establishment of adult worms, but the egg counts remained negligible. The total number of eggs shed by the treated cattle during the grazing season was significantly smaller than by the controls.
Use of phenytoin to treat digitalis-induced cardiac arrhythmias in a miniature Shetland pony. Two miniature Shetland ponies showing clinical signs of Digitalis purpurea (foxglove) poisoning were examined. One animal died shortly afterwards, but the second was treated successfully with the anti-arrhythmic agent, phenytoin, and was discharged after 16 days.
Arterially perfused eye model of uveitis. To develop an in vitro model of uveitis based on an ex situ perfused eye to evaluate the anti-inflammatory activity of new pharmacological products. Methods: Eyes were removed from more than 60 dogs and 9 horses immediately after euthanasia and perfused with nutrient medium through the lateral long ciliary artery. Perfused eyes produced aqueous humour, and perfusion pressure was adjusted to obtain an intraocular pressure in the physiological range. When the eyes were treated with histamine, a complement C5a analogue peptide and hydrogen peroxide, typical signs of uveitis were produced. These i...
The urinary elimination profiles of diazepam and its metabolites, nordiazepam, temazepam, and oxazepam, in the equine after a 10-mg intramuscular dose. A method for the extraction of diazepam and its metabolites (nordiazepam, temazepam, and oxazepam) from equine urine and serum and their quantitation and confirmation by liquid chromatography-tandem mass spectrometry is presented. Valium, a formulation of diazepam, was administered at a dose of 10 mg intramuscularly to four standard-bred mares. Diazepam is extensively metabolized in the horse to nordiazepam, temazepam, and oxazepam. Diazepam urinary concentrations were found to be less than 6 ng/mL. Nordiazepam was found to be mainly in its glucuronide-conjugated form and was measured out to a...
Pharmacokinetics of cisapride in the horse. The purpose of this study was to determine the pharmacokinetics and absolute bioavailability of cisapride after intravenous (i.v.) and intragastric (i.g.) administration in healthy, adult horses. Five animals received single doses of 0.1 mg/kg, 0.2 mg/kg and 0.4 mg/kg cisapride by the i.g. route in an open, randomized fashion on different occasions separated by a washout period of at least 48 h. Four of these horses were also given a single i.v. dose of 0.1 mg/kg cisapride. Jugular venous blood was collected periodically up to 24 h after dosing. Plasma cisapride concentrations were measured by...
