Pharmacokinetics in horses involves the study of how drugs are absorbed, distributed, metabolized, and excreted in equine species. This field of study provides insights into the time course of drug concentrations within the horse's body and helps in understanding the effects of various pharmaceuticals. Key parameters in equine pharmacokinetics include absorption rates, bioavailability, half-life, and clearance. These parameters can vary significantly due to factors such as age, breed, and health status of the horse. This page compiles peer-reviewed research studies and scholarly articles that explore the pharmacokinetic profiles of different drugs in horses, aiming to optimize dosing regimens and improve therapeutic outcomes in equine medicine.
Kim JY, Choi MH, Kim SJ, Chung BC.A high-performance liquid chromatographic-tandem mass spectrometric (HPLC/MS/MS) method for the determination of 19-nortestosterone and its esters (cyclopentanepropionate, phenylpropionate, and decanoate) in equine plasma is achieved using an atmospheric pressure chemical ionization (APCI) interface in selected reaction monitoring (SRM) mode. The two internal standards used were 16,16, 17-(2)H(3)-19-nortestosterone for 19-nortestosterone and methenolone acetate for its esters. The steroids studied were extracted from plasma samples with a mixture of diethyl ether/n-hexane (9:1, v/v). The quant...
Mills ML, Rush BR, St Jean G, Gaughan EM, Mosier D, Gibson E, Freeman L.To determine the serum and synovial fluid concentrations of ceftiofur sodium after intraarticular (IA) and intravenous (IV) administration and to evaluate the morphologic changes after intraarticular ceftiofur sodium administration. Methods: Strip plot design for the ceftiofur sodium serum and synovial fluid concentrations and a split plot design for the cytologic and histopathologic evaluation. Methods: Six healthy adult horses without lameness. Methods: Stage 1: Ceftiofur sodium (2.2 mg/kg) was administered IV. Stage 2: 150 mg (3 mL) of ceftiofur sodium (pHavg 6.57) was administered IA into ...
Lakritz J, Wilson WD, Marsh AE, Mihalyi JE.To determine effects of prior feeding on pharmacokinetics and estimated bioavailability of orally administered microencapsulated erythromycin base (MEB) in healthy foals. Methods: 6 healthy foals, 3 to 5 months old. Methods: Foals were given 2 doses of MEB (25 mg/kg of body weight, PO). One dose was administered after food was withheld overnight, and the other was administered after foals had consumed hay. The study used a crossover design with a 2-week period between doses. Blood was collected via a jugular vein prior to and at specific times after drug administration. Concentrations of eryth...
Alberts MK, Clarke CR, MacAllister CG, Homer LM.To determine the pharmacokinetics of acetazolamide administered IV and orally to horses. Methods: 6 clinically normal adult horses. Methods: Horses received 2 doses of acetazolamide (4 mg/kg of body weight, IV; 8 mg/kg, PO), and blood samples were collected at regular intervals before and after administration. Samples were assayed for acetazolamide concentration by high-performance liquid chromatography, and concentration-time data were analyzed. Results: After IV administration of acetazolamide, data analysis revealed a median mean residence time of 1.71 +/- 0.90 hours and median total body c...
Soma LR, Birks EK, Uboh CE, May L, Teleis D, Martini J.Seven hundred and eighty-eight Standardbred pacers competing in 8378 races at one racetrack were analysed to determine the effects of the administration of prerace frusemide on racing times (RT). Frusemide was administered i.v. 4 h before the race to pacers diagnosed with exercise-induced pulmonary haemorrhage (EIPH). Of the pacers, starting in the 1997 racing season, 32.5% received prerace frusemide. This study demonstrated that administration of frusemide prior to racing significantly decreased RT. There was an overall significant decrease (P<0.00001) in RT of 0.67 s. The overall RT for h...
Lakritz J, Wilson WD, Marsh AE, Mihalyi JE.To determine pharmacokinetics and plasma concentrations of erythromycin and related compounds after intragastric administration of erythromycin phosphate and erythromycin estolate to healthy foals. Methods: 11 healthy 2- to 6-month-old foals. Methods: Food was withheld from foals overnight before intragastric administration of erythromycin estolate (25 mg/kg of body weight; n = 8) and erythromycin phosphate (25 mg/kg; 7). Four foals received both drugs with 2 weeks between treatments. Plasma erythromycin concentrations were determined at various times after drug administration by use of high-p...
Ohmura H, Nukada T, Mizuno Y, Yamaya Y, Nakayama T, Amada A.To determine a safe and efficacious dose of flecainide acetate for treating equine atrial fibrillation (Af), the safe dosage level was determined by injecting 1, 2, or 3 mg/kg i.v. of 1% flecainide acetate solution at a rate of 0.2 mg/kg/min to five clinically healthy horses. Clinical signs and the ECG were monitored (HR, PR, QRS, and QT intervals) and blood was taken to measure the plasma flecainide concentration pre- and post-administration. No abnormal signs were observed in the 1- or 2-mg/kg groups, while agitation was observed in three of five horses in the 3-mg/kg group. The QRS, and QT ...
Haines GR, Brown MP, Gronwall RR, Merritt KA.Serum concentrations and pharmacokinetics of enrofloxacin were studied in 6 mares after intravenous (IV) and intragastric (IG) administration at a single dose rate of 7.5 mg/kg body weight. In experiment 1, an injectable formulation of enrofloxacin (100 mg/mL) was given IV. At 5 min after injection, mean serum concentration was 9.04 microg/mL and decreased to 0.09 microg/mL by 24 h. Elimination half-life was 5.33 +/- 1.05 h and the area under the serum concentration vs time curve (AUC) was 21.03 +/- 5.19 mg x h/L. In experiment 2, the same injectable formulation was given IG. The mean peak ser...
Lehner AF, Almeida P, Jacobs J, Harkins JD, Karpiesiuk W, Woods WE, Dirikolu L, Bosken JM, Carter WG, Boyles J, Holtz C, Heller T, Nattrass C....Remifentanil (4-methoxycarbonyl-4-[(1-oxopropyl)phenylamino]-1-piperidinepropionic acid methyl ester) is a mu-opioid receptor agonist with considerable abuse potential in racing horses. The identification of its major equine urinary metabolite, 4-methoxycarbonyl-4-[(1-oxopropyl)phenylamino]-1-piperidinepropionic+ ++ acid, an ester hydrolysis product of remifentanil is reported. Administration of remifentanil HCl (5 mg, intravenous) produced clear-cut locomotor responses, establishing the clinical efficacy of this dose. ELISA analysis of postadministration urine samples readily detected fentany...
Uboh CE, Soma LR, Luo Y, McNamara E, Fennell MA, May L, Teleis DC, Rudy JA, Watson AO.To compare the pharmacokinetics of penicillin G and procaine in racehorses following i.m. administration of penicillin G procaine (PGP) with pharmacokinetics following i.m. administration of penicillin G potassium and procaine hydrochloride (PH). Methods: 6 healthy adult mares. Methods: Horses were treated with PGP (22,000 units of penicillin G/kg of body weight, i.m.) and with penicillin G potassium (22,000 U/kg, i.m.) and PH (1.55 mg/kg, i.m.). A minimum of 3 weeks was allowed to elapse between drug treatments. Plasma and urine penicillin G and procaine concentrations were measured by use of...
Törneke MK, Ingvast-Larsson JC, Johansson JM, Appelgren LE.To determine pharmacokinetics of terbutaline in healthy horses and to relate serum terbutaline concentrations with the drug's pharmacodynamic effects. Methods: 6 healthy horses. Methods: Horses were given terbutaline i.v. (10 microg/kg of body weight) and, 1 week later, p.o. (100 microg/kg). Responses to drug administration (eg, heart rate and serum lactate concentration) were measured. Serum terbutaline concentration was measured by means of gas chromatography with mass spectrometry. Protein binding was determined in vitro. Results: Following i.v. administration, median maximum serum terbutal...
Myshkin AE, Khromova VS.Histidin has been shown to effectively inhibit coagulation of horse oxyhemoglobin (HbO(2)) modified by mercury(II) ion bound to reactive thiol groups of protein. Kinetic parameters were measured and the histidin-to-mercury binding constant was kinetically estimated. Histidin, as other pharmaceutically acceptable compounds with some mercury-binding capacity, has been suggested to alleviate mercury intoxication conditions.
Hill DW, Hyde WG, Kind AJ, Greulich D, Hopkins S.Aramine (metaraminol bitartrate) has been found in the possession of horse trainers and veterinarians who have been investigated for possible inappropriate drug administration to racing horses. Metaraminol (3-hydroxyphenylisopropanolamine) is a sympathomimetic amine that directly and indirectly affects adrenergic receptors, with alpha effects being predominant. Because it has the potential to affect the performance of a racing horse, its use is prohibited. In the present study, methods for the detection of metaraminol were developed. Metaraminol was found to be extracted with poor recovery ( 9...
Bermingham EC, Papich MG, Vivrette SL.To determine the pharmacokinetics of enrofloxacin administered IV and orally to foals. Methods: 5 clinically normal foals. Methods: A 2-dose cross-over trial with IV and oral administration was performed. Enrofloxacin was administered once IV (5 mg/kg of body weight) to 1-week-old foals, followed by 1 oral administration (10 mg/kg) after a 7-day washout period. Blood samples were collected for 48 hours after the single dose IV and oral administrations and analyzed for plasma enrofloxacin and ciprofloxacin concentrations by use of high-performance liquid chromatography. Results: For IV administ...
Marlin DJ, Roberts CA, Schroter RC, Lekeux P.The respiratory stimulant lobeline has been used in equine clinical practice to increase inspiratory and expiratory airflow rates at rest in order to facilitate investigation of both lower and upper airway function. Some of the responses to lobeline in the pony have been reported, but the detailed time course, effect of dose, possible side effects and reproducibility associated with lobeline administration have not been described in the horse. Respiratory airflow rates and oesophageal pressure were measured with a Fleisch No. 5 pneumotachometer and lightweight facemask and a microtip pressure ...
Bryant JE, Brown MP, Gronwall RR, Merritt KA.The objectives of this study were to determine the pharmacokinetics and tissue concentrations of doxycycline after repeated intragastric administration, and to determine the minimum inhibitory concentrations (MIC) for equine pathogenic bacteria. In experiment 1, 2 mares received a single intragastric dose of doxycycline hyclate (3 mg/kg bwt). Mean peak serum concentration was 0.22 microg/ml 1 h postadministration. In experiment 2, 5 doses of doxycycline hyclate (10 mg/kg bwt), dissolved in water, were administered to each of 6 mares via nasogastric tube at 12 h intervals. The mean +/- s.e. pea...
Bosken JM, Lehner AF, Hunsucker A, Harkins JD, Woods WE, Karpiesiuk W, Carter WG, Boyles J, Fisher M, Tobin T.Isoxsuprine is routinely recovered from enzymatically-hydrolyzed, post-administration urine samples as parent isoxsuprine in equine forensic science. However, the specific identity of the material in horse urine from which isoxsuprine is recovered has never been established, although it has long been assumed to be a glucuronide conjugate (or conjugates) of isoxsuprine. Using ESI/MS/MS positive mode as an analytical tool, urine samples collected 4-8 h after isoxsuprine administration yielded a major peak at m/z 554 that was absent from control samples and resisted fragmentation to daughter ions...
Lescun TB, Adams SB, Wu CC, Bill RP.To develop a method for continuous infusion of gentamicin into the tarsocrural joint of horses, to determine pharmacokinetics of gentamicin in synovial fluid of the tarsocrural joint during continuous infusion, and to evaluate effects of continuous infusion of gentamicin on characteristics of the synovial fluid. Methods: 12 healthy adult horses. Methods: An infusion catheter consisting of flow control tubing connected to a balloon infuser was used. Gentamicin solution (100 mg/ml) was infused in the right tarsocrural joint and balanced electrolyte solution was infused in the left tarsocrural jo...
Roussel AJ, Hooper RN, Cohen ND, Bye AD, Hicks RJ, Bohl TW.To evaluate the effect of erythromycin on motility of the ileum, cecum, and pelvic flexure of horses during the postoperative and post-recovery periods. Methods: 8 healthy adult horses. Methods: Horses were anesthetized and bipolar electrodes were implanted in smooth muscle of the ileum, cecum, and pelvic flexure. Approximately 4, 16, and 24 hours (postoperative recording sessions) and at least 8 days (post-recovery recording session) after surgery, myoelectric activity was recorded before and after administration of erythromycin (0.5 mg/kg). Results: Following erythromycin administration, myo...
Stanley SM.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.
Furr M, Kennedy T.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...
Törneke K, Larsson CI, Appelgren LE.Isoxsuprine is used in veterinary medicine as a vasodilating agent. The drug has been detected in the urine of horses up to 6 weeks after the cessation of administration. In the present study, the distribution pattern of 3H-isoxsuprine was investigated using whole body autoradiography in mice to find a possible site of retention. Melanin was the only place of retention identified. Additional in vitro studies showed an affinity of isoxsuprine to both melanin and keratin. The K(d) values were 0.02 mmol/l and 1 mmol/l, and the B(max) values were 0.2 micromol/mg and 2 micromol/mg, respectively. A ...
Baeyens WR, Van der Weken G, Haustraete J, Aboul-Enein HY, Corveleyn S, Remon JP, GarcÃa-Campaña AM, Deprez P.The group of LiChrospher ADS (alkyl-diol silica) sorbents that make part of a unique family of restricted-access materials, have been developed as special packings for precolumns used in the LC-integrated sample processing of biofluids. The advantage of these sorbents lies in the direct injection of untreated biological fluids, that is without sample clean-up, the elimination of the protein matrix with a quantitative recovery together with an on-column enrichment. The present method is based on previous work applying UV detection at 260 nm for ketoprofen determinations. Plasma samples introduc...
Haffner JC, Fecteau KA, Held JP, Eiler H.Under laboratory conditions and in clinical experiments, bacterial collagenase has proven to be effective in hydrolyzing placenta and detaching cotyledon from caruncle in the bovine species. Laboratory studies in which placental samples were incubated with collagenase have also demonstrated that collagenase is 3.7 times more effective in hydrolyzing equine placenta than bovine placenta. This led to the hypothesis that collagenase may be a potential treatment for mares with retained placenta. However, that collagenase may hydrolyze the uterine wall and perforate the uterus was a concern. It was...
Sasaki N, Yoshihara T.Seven Thoroughbred horses were laparotomized and Force Transducers were fixed on the proximal jejunal and cecal serosa. After observation of the digestive tract motility in consciousness, cisapride (0, 0.5, 0.75 or 1 mg/kg) was orally administered. In horses treated with 0.75 mg/kg or 1.0 mg/kg cisapride, the migrating contraction (MC) of the jejunum was significantly increased in frequency.
Wierdl M, Morton CL, Danks MK, Potter PM.Butyrylcholinesterases (BuChEs; acylcholine acylhydrolase; EC 3.1.1.8) have been demonstrated to convert the anticancer agent CPT-11 (irinotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin) into its active metabolite SN-38 (7-ethyl-10-hydroxycamptothecin). In addition, significant differences in the extent of drug metabolism have been observed with BuChEs derived from different species. In an attempt to understand these differences, we have isolated the cDNA encoding a horse BuChE. Based upon the NH2-terminal amino acid sequence of a purified horse BuChE, we designed deg...
Lohmann KL, Roussel AJ, Cohen ND, Boothe DM, Rakestraw PC, Walker MA.To evaluate the correlation between halftime of liquid-phase gastric emptying (T50), determined with nuclear scintigraphy using technetium Tc 99m pentetate, and absorption variables of orally administered acetaminophen. Methods: 6 mature horses. Methods: Technetium Tc 99m pentetate (10 mCi) and acetaminophen (20 mg/kg of body weight) were administered simultaneously in 200 ml of water. Serial left and right lateral images of the stomach region were obtained with a gamma camera, and T50 determined separately for counts obtained from the left side, the right side and the geometric mean. Power ex...
Love CC, Strzemienski PJ, Kenney RM.Serum concentration of ampicillin, a semisynthetic penicillin, was measured in mares at various time intervals up to 24 hours after intrauterine infusion of 3 g of ampicillin. Blood samples were drawn immediately before infusion and at 1-, 4-, 10- and 24-hour intervals after infusion. At postinfusion hour 24, two endometrial biopsy specimens were obtained to measure endometrial concentrations of ampicillin. Blood was drawn twice as part of the 24-hour postinfusion sample collection, once before removal of the biopsy specimens and again 5 minutes after removal of the biopsy specimens. After dru...
Shults T, Kownacki AA, Woods WE, Valentine R, Dougherty J, Tobin T.In horses given (rapid IV) methylphenidate (Ritalin, alpha-phenyl-2-piperidinacetic acid methyl ester; 0.70 mg/kg), plasma concentrations of the drug decreased rapidly at first, with an apparent alpha half-life of about 19 minutes, and then more slowly, with an apparent beta half-life of about 2.4 hours. These data were well fitted by a 2-compartment open model. In blood, about 40% of the methylphenidate present was in the plasma fraction, and of this, about 80% was plasma-protein bound. If given by subcutaneous or IM injection, plasma concentrations of methylphenidate peaked in about 1 hour a...
Stevenson AJ, Weber MP, Todi F, Mendonca M, Fenwick JD, Young L, Kwong E, Chen F, Beaumier P, Timmings S.The variability in plasma and urine equine procaine measurement between three independent laboratories using current methods led to the development of a sensitive, reliable, and reproducible high-performance liquid chromatographic method. Standardbred mares were administered either a penicillin G procaine preparation intramuscularly or procaine hydrochloride subcutaneously, and blood and urine were collected at defined time intervals. By HPLC the detection limits for procaine in plasma and urine were 1 and 10 ng/mL, respectively. In contrast procaine in plasma could not be detected by GC-NPD, ...
Specht TE, Brown MP, Gronwall RR, Rib WJ, Houston AE.Serum concentrations of metronidazole were determined in 6 healthy adult mares after a single IV injection of metronidazole (15 mg/kg of body weight). The mean elimination rate (K) was 0.23 h-1, and the mean elimination half-life (t1/2) was 3.1 hours. The apparent volume of distribution at steady state was 0.69 L/kg, and the clearance was 168 ml/h/kg. Each mare was then given a loading dose (15 mg/kg) of metronidazole at time 0, followed by 4 maintenance doses (7.5 mg/kg, q 6 h) by nasogastric tube. Metronidazole concentrations were measured in serial samples of serum, synovia, peritoneal flui...
Knych HK, Stanley SD, Harrison LM, Mckemie DS.The use of corticosteroids, such as betamethasone, in performance horses is tightly regulated. The objective of the current study was to describe the plasma pharmacokinetics of betamethasone as well as time-related urine and synovial fluid concentrations following intra-articular administration to horses. Twelve racing-fit adult Thoroughbred horses received a single intra-articular administration (9Â mg) of a betamethasone sodium phosphate and betamethasone acetate injectable suspension into the right antebrachiocarpal joint. Blood, urine, and synovial fluid samples were collected prior to and...
Gittel C, Schulz-Kornas E, Sandbaumhüter FA, Theurillat R, Vervuert I, Larenza Menzies MP, Thormann W, Braun C.To evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies. Methods: Prospective single-group interventional study. Methods: A group of six healthy adult research ponies (four mares, two geldings). Methods: Ponies were sedated with intravenous (IV) detomidine (0.02 mg kg) and butorphanol (0.01 mg kg) for an unrelated study. Additional IV detomidine (0.004 mg kg) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg) and keta...
Ellis EJ, Ravis WR, Malloy M, Duran SH, Smyth BG.Six horses were administered either 15 or 20 mg/kg body weight (b.w.) procainamide (PA) as an intravenous (i.v.) dose over 10 min. The plasma concentrations of PA and N-acetylprocainamide (NAPA) as well as the pharmacodynamic effect (prolongation of the QT interval) were monitored. The PA plasma concentrations could be described by a one-compartment model with a t1/2 of 3.49 +/- 0.61 h. The total body clearance of PA was 0.395 +/- 0.090 l/hr/kg and the volume of distribution was 1.93 +/- 0.27 l/kg. As observed after PA administration, NAPA (an active metabolite) had a t1/2 longer than PA of 6....
Stewart HL, Engiles JB, Richardson DW, Levine DG.To describe the bactericidal and fungicidal properties of a 0.0005% chlorhexidine (CHD) solution potentiated with EDTA-Tris buffers (CHD-EDTA-Tris) and evaluate the safety of 0.0005% CHD-EDTA-Tris in the upper respiratory tract (URT) of normal horses. Methods: Clinical, prospective study. Methods: Eight healthy, skeletally mature horses. Methods: In vitro-serial dilutions of CHD-EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal and fungicidal activity against Aspergillus fumigatus, Escherichia coli, Staphylococcus aureus, Streptococcus equi subspecies ssp. equi, Streptococcus equi ...
Sarasola P, McKellar QA.A regime for administration of ampicillin sodium by continuous intravenous infusions to horses was designed. The aim was to achieve plasma ampicillin concentrations between 5 and 10 micrograms/ml over a 4-h period. A 2 mg/kg bodyweight loading dose of ampicillin sodium was administered intravenously at the beginning of the infusion in order to achieve steady-state plasma concentrations rapidly. The infusion system subsequently administered ampicillin at a rate of approximately 19.2 micrograms/min/kg bodyweight. The plasma concentrations obtained over the infusion period correlated very well wi...
Mercer MA, Davis JL, McKenzie HC, Messenger KM, Schaefer E, Council-Troche RM, Werre SR.Acetaminophen has been evaluated in horses for treatment of musculoskeletal pain but not as an antipyretic. Objective: To determine the pharmacokinetics and efficacy of acetaminophen compared to placebo and flunixin meglumine in adult horses with experimentally induced endotoxemia. Methods: Eight university owned research horses with experimentally induced endotoxemia. Methods: Randomized placebo controlled crossover study. Horses were treated with acetaminophen (30 mg/kg PO; APAP), flunixin meglumine (1.1 mg/kg, PO; FLU), and placebo (PO; PLAC) 2 hours after administration of LPS. Plasma ...
MacAllister CG, Lowrey F, Stebbins M, Newman MS, Young B.The ponies were apparently healthy and 6-20 months of age. In Study 1, gastric lesions were created by transendoscopic electrocautery in the non-glandular gastric mucosa, adjacent to the margo plicatus in 9 ponies which were then treated with water, 12 mg cimetidine HCl/kg bwt or 18 mg cimetidine HCl/kg bwt per os every 12 h for 35 days. In Study 2, gastric lesions were similarly induced in 9 ponies in the non-glandular mucosa and also in the glandular mucosa just below the non-glandular lesion on the greater curvature of the stomach. The ponies were treated with water, 8 mg cimetidine/kg bwt ...
Cummings LE, Guthrie AJ, Harkins JD, Short CR.Gentamicin sulfate, equivalent to 4 mg of gentamicin base/kg of body weight, was administered IV to 6 Thoroughbred foals on day 1 (12 to 24 hours of age) and at 5, 10, 15, and 30 days after birth. On day 40 after parturition, gentamicin was given to the mares at a dosage similar to that used in foals. Decay of serum gentamicin concentrations was best described by a 2-compartment model. Among foals, the overall elimination rate constant at 30 days of age was significantly (P less than 0.05) greater than at days 1, 10, and 15. There was, however, no difference in the overall elimination rate con...
Mills PC, Ng JC, Auer DE.The effect of the acute-phase response (APR) on the activity of the hepatic drug-metabolizing system (DMS) and on the binding of phenylbutazone to plasma proteins was investigated in the horse. An APR was induced by intramuscular injections of Freund's complete adjuvant in five horses and, five days later, these horses together with five clinically normal horses were shot and the right ventral lobe of each liver removed. The hepatic microsomal fractions from the liver samples were isolated and significantly lower (p < 0.01) concentrations of cytochromes P450 and b5 and activities of aniline...
Harkins JD, Karpiesiuk W, Woods WE, Lehner A, Mundy GD, Rees WA, Dirikolu L, Bass S, Carter WG, Boyles J, Tobin T.Mepivacaine is a local anaesthetic drug that is widely used in equine medicine and is classified by the Association of Racing Commissioners International (ARCI) as a Class 2 foreign substance that may cause regulators to impose significant penalties if residues are identified in post-race urine samples. Therefore, an analytical/pharmacological database was developed for this agent and its metabolites. Using an abaxial sesamoid local anaesthetic model, it was determined that the highest no-effect dose (HNED) for its local anaesthetic effect was 2 mg. Using enzyme-linked immunosorbent assay (ELI...
Underwood C, Collins SN, van Eps AW, Mills PC, Allavena RE, Bailey SR, Medina Torres CE, Meizler A, Pollitt CC.No validated laminitis drug therapy exists, yet pharmaceutical agents with potential for laminitis prevention have been identified. Many of these are impractical for systemic administration but may be effective if administered locally. This study compared intraosseous infusion of the distal phalanx (IOIDP) with systemic intravenous constant rate infusion (CRI) to determine which was more effective for lamellar marimastat delivery. Ultrafiltration probes were placed in both forefeet of five horses to collect lamellar interstitial fluid as lamellar ultrafiltrate (LUF). Marimastat solution (3.5â€...
Fernández-Varón E, Cárceles CM, MarÃn P, Martos N, Escudero E, Ayala I.To study the pharmacokinetics of difloxacin (5 mg/kg) following IV, IM, and intragastric (IG) administration to healthy horses. Methods: 6 healthy mature horses. Methods: A crossover study design with 3 phases was used (15-day washout periods between treatments). An injectable formulation of difloxacin (5%) was administered IV and IM in single doses (5 mg/kg); for IG administration, an oral solution was prepared and administered via nasogastric tube. Blood samples were collected before and at intervals after each administration. A high-performance liquid chromatography assay with fluorescence ...
Cárceles-RodrÃguez CM, Fernández-Varón E, MartÃn-Gimenez T, Aguirre C, Arion A, RodrÃguez MJ, Ayala I.Insulin dysregulation (ID) is a common metabolic disorder in horses. Recently, incretin hormone release has been suggested to be involved in ID in horses. In human medicine, metformin and sitagliptin are commonly used in combination for metabolic syndrome. This combination could be useful in treating ID in horses. However, no pharmacokinetics data have been reported in this species. The objective of the present study was to establish the plasma concentration-time profile and to derive pharmacokinetics data for a combination of metformin and sitagliptin in horses after enteral administration. S...
Bonilla AG, Causeret L, Torrent-Crosa A.This study investigated the pharmacokinetics of ceftiofur after intravenous regional limb perfusion (IVRLP). Six horses were involved in 3 IVRLP sessions. For each session, operators with varying clinical experience placed the tourniquet. A wide-rubber tourniquet was applied in the antebrachium as 2 g of ceftiofur in a total volume of 100 mL was injected into the cephalic vein. Plasma and metacarpophalangeal synovial fluid samples were obtained to evaluate perfusate leakage and synovial fluid concentrations of ceftiofur over 24 h. Overall, mean plasma concentrations were not significantly diff...
Sams RA, Gerken DF, Detra RL, Stanley SD, Wood WE, Tobin T, Yang JM, Tai HH, Jegananthan A, Watt DS.Two metabolites of the tranquilizer azaperone were extracted from alkalinized horse urine after treatment with beta-glucuronidase/sulfatase from limpets (Patella vulgata). The metabolites were identified by a combination of independent chemical synthesis and GC/MS and 1H NMR analysis. The metabolites were identified as 1-(fluorophenyl)-4-[4-(5-hydroxy-2-pyridinyl)-1-piperazinyl]-1-butanol, designated as 5'-hydroxy-azaperol, and 1-(fluorophenyl)-4-[4-(5-hydroxy-2-pyridinyl)-1-piperazinyl]-1-butanone, designated as 5'-hydroxyazaperone. A TLC screening test was developed for detecting both metabo...
Nouws JF, Vree TB, Baakman M, Driessens F, Smulders A, Holtkamp J.The plasma disposition of sulfadimidine (SDM) and its metabolites N4-acetylsulfadimidine (N4-SDM), 6-hydroxymethyl-4-methyl-pyrimidine (SCH2OH) and 5-hydroxy-4,6-dimethyl-pyrimidine (SOH), was studied in three horses following intravenous administration of SDM at dose levels of 20 and 200 mg/kg in cross-over trials. The percentages of N4-SDM (0.58-0.90%), SOH (0.83-6.75%) and SCH2OH (0.38-0.71%) in plasma, expressed as a percentage of the total sulfonamide concentration, were small and their plasma concentrations were parallel with SDM from 4 h following administration. At high doses (200 mg/k...
Yu J, Han KS, Lee G, Paik MJ, Kim KR.The enantioseparation of pranoprofen after its addition in racemic form into equine plasma and urine was conducted by chiral liquid chromatography-tandem mass spectrometry in selected reaction monitoring mode. The methods for the assay of both enantiomers were linear (r≥0.9943) in the low range from 0.001 to 0.1μg/mL and high range from 0.01 to 1.0μg/mL with good precision (% RSD≤5.6) and accuracy (% RE=-5.3 to 1.9). When racemic pranoprofen was orally administered to four horses at a single dose of 3.1mg/kg, the median plasma concentrations of (R)-pranoprofen were lower than the levels ...
Clode AB, Davis JL, Salmon J, LaFevers H, Gilger BC.To determine the degree of ocular penetration and systemic absorption of commercially available topical ophthalmic solutions of 0.3% ciprofloxacin and 0.5% moxifloxacin following repeated topical ocular administration in ophthalmologically normal horses. Methods: 7 healthy adult horses with clinically normal eyes as evaluated prior to each treatment. Methods: 6 horses were used for assessment of each antimicrobial, and 1 eye of each horse was treated with topically administered 0.3% ciprofloxacin or 0.5% moxifloxacin (n = 6 eyes/drug) every 4 hours for 7 doses. Anterior chamber paracentesis wa...
Matassa LC, Woodard D, Leavitt RK, Firby P, Beaumier P.Glycopyrrolate (Robinul) is a quaternary ammonium salt which serves as a respiratory enhancing drug. It is reportedly used in horse racing to improve breathing. Extraction of glycopyrrolate from equine urine employing unique solid-phase extraction techniques gave a residue suitable for liquid chromatography-tandem mass spectrometry (LC-MS-MS) and gas chromatography-mass spectrometry (GC-MS). LC-MS-MS analysis employed an extract derived from 5 ml of urine subjected to cation-exchange chromatography. The daughter ion of m/z 318 monitored in the positive-ion mode was m/z 116. Recovery of glycopy...
Gómez-DÃez M, Muñoz A, Caballero JM, Riber C, Castejón F, Serrano-RodrÃguez JM.Pharmacokinetic and pharmacodynamic of IV enalapril at 0.50 mg/kg, PO placebo and PO enalapril at three different doses (0.50, 1.00 and 2.00 mg/kg) were analyzed in 7 healthy horses. Serum concentrations of enalapril and enalaprilat were determined for pharmacokinetic analysis. Angiotensin-converting enzyme (ACE) activity, serum ureic nitrogen (SUN), creatinine and electrolytes were measured, and blood pressure was monitored for pharmacodynamic analysis. The elimination half-lives of enalapril and enalaprilat were 0.67 and 2.76 h respectively after IV enalapril. Enalapril concentrations ...
Schmitz A, Portier CJ, Thormann W, Theurillat R, Mevissen M.Stereoselectivity has to be considered for pharmacodynamic and pharmacokinetic features of ketamine. Stereoselective biotransformation of ketamine was investigated in equine microsomes in vitro. Concentration curves were constructed over time, and enzyme activity was determined for different substrate concentrations using equine liver and lung microsomes. The concentrations of R/S-ketamine and R/S-norketamine were determined by enantioselective capillary electrophoresis. A two-phase model based on Hill kinetics was used to analyze the biotransformation of R/S-ketamine into R/S-norketamine and,...
Vatistas NJ, Snyder JR, Nieto J, Thompson D, Pollmeier M, Holste J.Gastric ulceration has been found to occur in 80-90% of Thoroughbreds in active race training. Previously, variable success has been reported using mucosal surface protectants and H2 receptor antagonist. Omeprazole, a substituted benzimidazole, has been shown to inhibit gastric acid secretion in both man and animals. Fourteen horses, in active race training and with endoscopic evidence of moderated to severe gastric ulceration were divided into 2 groups: Group 1 (7 horses) were given placebo paste orally once daily for 28 days; Group 2 (7 horses) received 1.54 g active omeprazole in the placeb...
Garcia AFS, Dória RGS, Arantes JA, Reginato GM, Neubauer FG, Ribeiro G.Although pharmacokinetic studies of drugs administered by intravenous regional limb perfusion (IRLP) to treat equine orthopedic infections suggest efficient drug distribution in the limbs, it remains unclear whether drug perfusion is affected by the position of the horse during the procedure. This study compared the perfusion of a radiopaque contrast into tissues of the extremities of horses maintained in standing and recumbent positions during an IRLP. Radiopaque contrast was administered through IRLP into the cephalic vein of 10 healthy adult horses under general anesthesia and right lateral...
Stieler Stewart AL, Sanchez LC, Mallicote MF, Muniz AL, Westerterp MS, Burrow JA, MacKAY RJ.Erythromycin (ERY) induces anhidrosis in foals. Azithromycin (AZI) and clarithromycin (CLA), often combined with rifampicin (RIF), are commonly used to treat Rhodococcus equi infections, but effects on sweating have not been investigated. Objective: To determine the effects of AZI, CLA and RIF on sweat responses in normal foals. Methods: Each experiment was a blinded, duplicated, six foal × three period counterbalanced within subjects design (12 foals/experiment). Methods: Antimicrobials were given orally for 5 days. In Experiment 1, ERY, AZI and CLA were given. In Experiment 2, ERY, RIF and ...
Barton MH, Darden JE, Clifton S, Vandenplas M.To validate primer sets for use in reverse transcription quantitative PCR assays to measure gene expression of cytosolic phospholipase A2 (cPLA2) and microsomal prostaglandin E2 synthase 1 (mPGES1) in equine mononuclear cells and determine the effects of firocoxib, a selective cyclooxygenase 2 (COX-2) inhibitor, on COX-2, cPLA2, and mPGES1 gene expression following incubation of mononuclear cells with lipopolysaccharide (LPS). Methods: 8 healthy adult horses. Methods: Peripheral blood mononuclear cells were isolated by density gradient centrifugation and incubated at 37°C with medium alone, f...
Storgaard IH, Kristensen J, Larsen C, Mertz N, Østergaard J, Larsen SW.Intra-articular depot injectables based on in situ suspension formation of ester prodrugs of nonsteroidal anti-inflammatory drugs are promising for management of joint pain. As candidates for this delivery approach, 5 diclofenac ester prodrugs comprising different imidazole-containing promoieties were synthesized and their physicochemical properties characterized. In vitro hydrolysis rates were investigated in buffer solutions, in 40% (v/v) human, equine, canine, and rat plasma, and in 80% (v/v) human and equine synovial fluid. Bioconversion of the prodrugs to diclofenac was found to be enzym...
