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Topic:Drug
The topic of drugs and horses encompasses the study of various pharmacological agents used in equine medicine for therapeutic purposes. This includes the administration of medications for pain management, disease treatment, and performance enhancement. The pharmacokinetics and pharmacodynamics of drugs in horses are key areas of research, as they determine the absorption, distribution, metabolism, and excretion of these substances. Additionally, the topic covers the detection and regulation of substances in competitive equestrian sports to ensure fair play and animal welfare. This page compiles peer-reviewed research studies and scholarly articles that explore the effects, safety, and regulatory aspects of drug use in equine health and performance.
Effect of probenecid on disposition kinetics of ampicillin in horses. The effect of an oral dose of probenecid on the disposition kinetics of ampicillin was determined in four horses. An intravenous bolus dose (10 mg/kg) of ampicillin sodium was administered to the horses on two occasions. On the first occasion the antibiotic was administered on its own, and on the second occasion it was administered one hour after an oral dose of 75 mg/kg probenecid. The plasma concentration of probenecid reached a mean (+/- se) maximum concentration (Cmax) of 188-6 +/- 19.3 micrograms/ml after 120.0 +/- 21.2 minutes and concentrations greater than 15 micrograms/ml were present...
Efficacy of buparvaquone as a therapeutic and clearing agent of Babesia equi of European origin in horses. We evaluated the efficacy of buparvaquone in eliminating infection with Babesia equi of European origin in carrier horses and in splenectomized horses with experimentally induced acute infection. When administered at the rate of 5 mg/kg of body weight, IV, 4 times at 48-hour intervals, buparvaquone prompted rapid abatement of parasitemia. However, secondary and tertiary recrudescent parasitemias invariably returned with establishment of the carrier state. Buparvaquone, at the dosage evaluated, had transitory therapeutic efficacy against acute B equi infection in splenectomized horses, but was ...
Treatment of respiratory infections in horses with ceftiofur sodium. Ceftiofur sodium was evaluated as a therapy for respiratory infections in horses. This cephalosporin antimicrobial was administered intramuscularly every 24 h and at a dose of 2.2 mg/kg (1.0 mg/lb) of body weight. The efficacy of ceftiofur sodium was compared with that of a positive control drug, ampicillin sodium (recommended dose of 6.6 mg/kg [3 mg/lb], given every 12 h). Both treatments were continued for 48 h after clinical symptoms were no longer evident (maximum of 10 days). Fifty-five (55) horses with naturally acquired respiratory infections were included in the study; 28 were treated ...
Effects of alternation of drug classes on the development of oxibendazole resistance in a herd of horses. Anthelmintic schedules that alternate between drug classes are widely used in horses. However, the results of investigations in which ovine nematode parasites were used have established that alternation of drug classes does not delay the development of drug resistance. This field study was designed to assess the effect of alternation of drug classes on the development of oxibendazole (OBZ) resistance in benzimidazole (BZD)-resistant equine small strongyles. A privately owned herd of horses was used for this study. These animals grazed the same pasture and had been treated with the same anthelm...
Detection of methandienone (methandrostenolone) and metabolites in horse urine by gas chromatography-mass spectrometry. The metabolic transformation of methandienone (I) in the horse was investigated. After administration of a commercial drug preparation to a female horse (0.5 mg/kg), urine samples were collected up to 96 h and processed without enzymic hydrolysis. Extraction was performed by a series of solid-liquid and liquid-liquid extractions, thus avoiding laborious purification techniques. For analysis by gas chromatography-mass spectrometry, the extracts were trimethylsilylated. Besides the parent compound I and its C-17 epimer II, three monohydroxylated metabolites were identified: 6 beta-hydroxymethand...
Thermospray liquid chromatography-mass spectrometry of corticosteroids. A high-performance liquid chromatographic method was developed for thermospray mass spectrometric analysis of steroidal hormones. Using a Nova-Pak C18 reversed-phase column and isocratic elution with a solvent comprised of 25 mM ammonium formate in 30% acetonitrile, corticosteroids were separated within 10 min. This solvent also permitted ultraviolet absorbance detection down to 220 nm with low-nanogram sensitivity. The use of acetonitrile was favourable for thermospray mass spectrometric analysis because mass spectra were obtained with a pseudomolecular ion as the base peak. A combination of ...
Rifampin disposition in the horse: effects of age and method of oral administration. The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The...
A comparison of the sedative effects of three alpha 2-adrenoceptor agonists (romifidine, detomidine and xylazine) in the horse. The sedative effects of a new alpha 2-adrenoceptor agonist, romifidine, were compared with those of xylazine and detomidine. Five horses were treated with two doses of romifidine (40 micrograms/kg body weight and 80 micrograms/kg body weight), two doses of detomidine (10 micrograms/kg body weight and 20 micrograms/kg body weight) and one dose of xylazine (1 mg/kg body weight) given by intravenous injection using a Latin-square design. The dose of 80 micrograms/kg romifidine appeared equipotent to 1 mg/kg xylazine and 20 micrograms/kg detomidine, although at these doses both xylazine and detomi...
Bioavailability and bioequivalence of veterinary drug dosage forms, with particular reference to horses: an overview. The route of administration and formulation of the dosage form affect the bioavailability (rate and extent of absorption) of a drug and may thereby influence the intensity and duration of the pharmacological effect. Location of injection site may affect the plasma concentration profile of drugs administered as aqueous suspensions or sustained release parenteral preparations (procaine penicillin G). When absorption influences the rate of elimination ('flip-flop' phenomenon), the apparent half-life of the drug will be increased (cefazolin sodium, i.m.; meclofenamic acid, p.o.). Absorption genera...
Effects of xylazine on ventilation in horses. The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P less than 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute a...
Multisystemic eosinophilic epitheliotropic disease in a horse: attempted treatment with hydroxyurea and dexamethasone. Equine multisystemic eosinophilic epitheliotropic disease is rare in horses. The clinical signs vary according to the organs affected, the skin and gastrointestinal tract being most commonly involved. This paper gives the first reported description of a horse with multisystemic eosinophilic epitheliotropic disease in the United Kingdom and the attempts to treat it. The horse showed dermatological, gastrointestinal, hepatic, pulmonary and pancreatic involvement. Some improvement was seen when the horse was treated with corticosteroid and hydroxyurea.
Effect of changes in urine pH on plasma pharmacokinetic variables of ampicillin sodium in horses. The effect of urine pH on plasma disposition of ampicillin sodium was evaluated. A single dose of 10 mg/kg of body weight was administered IV to Thoroughbreds with alkaline (pH greater than 8.0) or acidic (pH less than 4.5) urine. Urine alkalinity was achieved and maintained by oral administration of up to 400 mg of sodium bicarbonate/kg/d, and acidity was achieved and maintained by oral administration of up to 400 mg of ammonium chloride/kg/d. Ampicillin sodium was measured in the plasma of horses by use of an agar diffusion microbiological assay with Bacillus subtilis as the test organism. T...
Relation between pharmacokinetics of amikacin sulfate and sepsis score in clinically normal and hospitalized neonatal foals. Pharmacokinetic values after IV administration of amikacin sulfate were determined for clinically normal and hospitalized foals during the first week of life. The relations between drug disposition and sepsis score and serum creatinine concentration also were studied. In clinically normal foals, differences in sepsis score, serum creatinine concentration, and pharmacokinetic variables of amikacin were not found between foals 1 to 3 and 4 to 7 days old. In hospitalized foals, sepsis score, serum creatinine concentration, area under the curve, area under the moment curve, and mean residence time...
Pharmacokinetics of phenobarbital in horses after single and repeated oral administration of the drug. Six healthy mature horses were orally administered a single dose of phenobarbital (26 mg/kg of body weight), then multiple doses (13 mg/kg) orally for 42 consecutive days. Seventeen venous blood samples were collected from each horse after the single dose study and again after the last dose on day 42. Plasma phenobarbital concentration was determined by use of a fluorescence assay validated for horses. Additional blood samples (n = 11) were collected on days 8 and 25 to determine peak and trough concentrations, as well as total body clearance. Phenobarbital disposition followed a one-compartme...
Entomophthoromycosis due to Conidiobolus. Entomophthoromycosis due to Conidiobolus coronatus is a granulomatous infection characterized by lesions that originate in the inferior turbinate, spread through ostia and foramina to involve the facial and subcutaneous tissues and paranasal sinuses. The majority of the cases have been described from areas of tropical rainforest in West Africa, agricultural and outdoor workers (aged 20-60 years) being the ones most frequently affected. The fungus is common in soil and decaying vegetation. Infection probably occurs by implantation of the spores of the fungus in nasal mucosa. C. incongruus is a ...
Detection of diuretics in horse urine by GC/MS. The use of diuretics in horses subject to doping control is prohibited. Thus, a sensitive screening procedure is required to identify the chemically different diuretics. We communicate here a method to detect three commonly employed acidic diuretics: bumetanide, ethacrynic acid, and furosemide. A liquid-liquid extraction on Extrelut 3 was performed at weak acidic and basic conditions using ethyl acetate as organic solvent. For analysis by GC, the diuretics were methylated on-column in the presence of MSTFA/TMAH, avoiding the commonly employed highly toxic derivatizing agent methyl iodide. For ...
Bioavailability of two ibuprofen oral paste formulations in fed or nonfed ponies. The bioavailability and pharmacokinetics of ibuprofen, a nonsteroidal antiinflammatory drug, was studied in healthy Shetland ponies. Ibuprofen was administered IV, as a suspension, and as a solid solution oral paste to ponies from which food was withheld. The suspension paste was also administered to ponies that received hay and water ad libitum. Both formulations had an absolute bioavailability of about 80%. Bioavailability was not influenced by feeding.
Clinical pharmacokinetics in veterinary medicine. Veterinary and human pharmacology differ principally in the range of species in which drugs are used and studied. In animals, as in humans, an understanding of the dose-effect relationship can be obtained by linking pharmacokinetic behaviour with pharmacodynamic information. Studies of different classes of drugs support the assumption that the range of therapeutic plasma concentrations in animals is generally the same as in humans. The requirement for species differences in dosage or administration rate (dose/dosage interval) may be attributed to variations in pharmacokinetic behaviour or phar...
Effect of probenecid on the pharmacokinetics of flunixin meglumine and phenylbutazone in healthy mares. Pharmacokinetic values for flunixin meglumine (1 mg/kg of body weight) and phenylbutazone (4 mg/kg) dosages were determined after a single IV injection with and without concurrent intragastric administration of probenecid (50 mg/kg) in 6 healthy mares. Significant difference was not apparent in the pharmacokinetic values of flunixin meglumine with and without concurrent probenecid administration. Significant (P less than or equal to 0.05) increase was evident in the 12-hour mean concentration of phenylbutazone (11.45 +/- 1.66 micrograms/ml without probenecid; 14.56 +/- 1.20 micrograms/ml with ...
Aerosol pirbuterol: bronchodilator activity and side effects in ponies with recurrent airway obstruction (heaves). The dose of aerosol pirbuterol that could be administered safely to ponies (weight approximately 200 kg) was determined by observation for sweating, trembling and excitement and measurement of heart and respiratory rates during cumulative administration of the drug. Sweating, trembling and excitement were first observed following a dose of 2,400 micrograms and became more severe at 3,200 micrograms. These effects were accompanied by an increase in heart rate but not a change in respiratory rate. When 3200 micrograms was administered without prior administration of lower doses, side effects wer...
Plasma elimination and urinary excretion of procaine after administration of different products to standardbred mares. Plasma and urinary concentrations of procaine were examined in Standardbred mares after subcutaneous administration of various doses (80 mg to 1600 mg) of procaine hydrochloride. Regardless of dose, peak plasma procaine values occurred within 1 h, but remained detectable in a dose-dependent manner, with procaine present at 1 h with the 80 mg dose and 6 h at the 1600 mg dose. Similarly, peak urinary procaine concentrations were attained within 1.5 to 3 h, irrespective of dose, while detection time was dose-dependent, being 23 h for 80-200 mg doses but as long as 30-54 h with the 1600 mg dose. W...
Disposition of gentamicin administered intravenously to horses with sepsis. Plasma concentration of gentamicin was measured 1, 4, and 6 hours after IV administration in 35 hospitalized adult horses on days 1, 3, 5, and 10 of treatment. The mean apparent elimination rate constant beta was 0.53 +/- 0.10 h-1 on day 1 for horses with normal plasma creatinine concentration and 0.41 +/- 0.13 h-1 for horses with abnormally high plasma creatinine concentration. There was no significant difference between beta of the hospitalized horses and of 6 healthy horses treated with gentamicin, but total clearance for the hospitalized horses with normal plasma creatinine concentration w...
Evaluation of threshold doses of drug action in the horse using hematocrit values as an indicator. This study was designed to explore the use of hematocrit values as possible indicators of the threshold doses of adrenergic drugs in the performance horse. Acepromazine, detomidine, and fluphenazine were tested for their effects on hematocrit values, with the threshold dose for these effects investigated. Hematocrit values were shown to be quite sensitive to the administration of acepromazine with doses as low as 50 micrograms/horse producing detectable depressions in hematocrit values for up to 2 hours. Increasing the dose increased the magnitude of the effect, but did not appear to prolong i...
A comparison of injectable anaesthetic regimens in mules. Three combinations of injectable anaesthetic agents were compared in nine adult mules. The combinations were xylazine/ketamine (X/K), xylazine/butorphanol/ketamine (X/B/K), and xylazine/tiletamine-zolazepam (X/T). Measured variables were heart rate, respiratory rate, systolic blood pressure, arterial blood pH, PCO2 and PO2, recumbency time and number of attempts to stand. Quality of induction and recovery, muscle relaxation and response to stimulus were evaluated subjectively. Recumbency time was significantly (P < 0.05) longer with X/B/K and X/T than with X/K. Mules required significantly mor...
The veterinary importance of the toxic syndrome induced by ionophores. Monensin, lasalocid, salinomycin, narasin and maduramicin are carboxylic ionophores intended for use as anticoccidial drugs for poultry and as growth promotants for ruminants. Generally, ionophores have been found safe and effective in the target animals receiving recommended dosage levels. However, toxic syndromes can result from overdosage and misuse situations. More information and reports of adverse reactions are available for monensin than the other ionophores because of monensin's longstanding and widespread use in the poultry and livestock industries. Care must be exercised in the diagn...
The influence of surgery and anaesthesia on the pharmacokinetics of pethidine in the horse. The plasma concentration of pethidine was measured in 16 horses, after its administration intravenously (i.v.) at a dose rate of 1 mg/kg bodyweight (bwt). In eight animals studied before surgery, the plasma levels of the drug decreased in a bi-exponential manner with a distributive half life of 3 mins and an elimination half life of 57.7 mins. Total body clearance was 17.7 ml/kg bwt/min. The remaining horses were investigated immediately after a period of anaesthesia and surgery and in these animals the drug exhibited smaller volumes of distribution (V1 cand Vdarea) and a significantly lower c...
Pharmacokinetics of tolfenamic acid in the horse. The pharmacokinetics of tolfenamic acid were studied in five ponies after an intravenous (iv) administration (2 mg/kg bodyweight [bwt]) and in four horses after an oral administration (30 mg/kg bwt) of tolfenamic acid. The plasma levels were determined by high pressure liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS). For the iv administration, a three-compartment model was used to represent the plasma concentration-time curve of the drug. The elimination half-life of the compound was 6.1 +/- 1.5 h, the total body clearance was 72.4 +/- 16.7 ml/kg bwt/h and the ste...
