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.
Fedde MR, Erickson HH.Blood was taken from 49 Thoroughbred horses before and after racing at the track to determine if frusemide modified the apparent viscosity of the blood and to determine the effects of changes in shear rate and packed cell volume (PCV), associated with strenuous exercise, on apparent and relative viscosities. Small increases in apparent viscosity of the blood (at a specified PCV and shear rate) occurred in horses given frusemide compared to those receiving no frusemide; however, no differences were seen in relative viscosity. Although 2 groups of horses, those receiving frusemide before racing ...
Raisis AL, Hodgson JL, Hodgson DR.Twenty-one compromised neonatal foals hospitalised at the Rural Veterinary Centre (RVC) during 1993 were studied to determine i) serum gentamicin concentrations obtained when gentamicin was administered at 3.3 mg/kg bwt twice daily i.m.; ii) factors which contributed to inter-foal variation in serum gentamicin concentrations achieved and iii) clinical efficacy of gentamicin therapy in foals with confirmed septicaemia. Septicaemia was confirmed in 7 foals with positive blood cultures and suspected in 8 foals with a sepsis score > 11. Peak serum concentrations (Ps) were > 6 microg/ml in al...
Soliman GA.The pharmacokinetic behaviour of gentamicin sulphate (3.4 mg/kg bwt) was studied following its intramuscular injection to a group of horses and to another group of horses premedicated with sodium methyl arsinate (2 mg/kg bwt) or imidocarb dipropionate (4.8 mg/kg bwt). Considerable differences were observed in the pharmacokinetics of gentamicin in pre-medicated horses and in horses which had received the antibiotic alone. Peak serum concentration of gentamicin (9.85 +/- 0.05 and 11.15 +/- 0.15 micrograms/ml) were attained within 1.45 +/- 0.05 and 0.92 +/- 0.04 h in arsinate and imidocarb-medica...
Oukessou M, Alsouss L.The body disposition of sulfadimidine (SDM), sulfadiazine (SDZ), sulfamethoxypyridazine (SMPZ) and a trimethoprim-sulfadimethoxine combination (TMP-SDMX) was investigated in the donkey. The four sulfonamides and TMP were injected intravenously at doses of 20 mg/kg (SDM, SDZ, SMPZ), 12.5 mg/kg (SDMX) and 2.5 mg/kg (TMP). The body clearance (ClB) of SDZ (1.70 +/- 0.14 ml/min/kg) was significantly higher than those of SDM (1.13 +/- 0.18 ml/min/kg), SMPZ (1.10 +/- 0.09 ml/min/kg) and SDMX (0.75 +/- 0.04 ml/min/kg). In contrast, the volume of distribution at steady state (Vss) was similar for the f...
Chua HC, Stewart B, Lim BH, Lee HK.A chromatographic method was developed to detect and confirm the presence of chlorpropamide (I) in horse plasma samples, for antidoping control. The plasma sample (1 ml) was extracted with dichloromethane and screened by high-performance liquid chromatography, and confirmation of the drug's presence was accomplished by using gas chromatography-mass spectrometry (GC-MS). The limit of detection was found to be 3.5 ng/ml at a signal-to-noise ratio of three. Derivatization of I with N,O-bis-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane allowed for highly stable, accurate and sen...
Valk N, Doherty TJ, Blackford JT, Abraha TW, Frazier DL.The effect of phenylbutazone on gastric emptying in horses was determined by measuring serum concentrations of acetaminophen. Gastric emptying was determined in normal fasted horses (n = 6), horses given endotoxin intravenously (n = 6), horses given intravenous phenylbutazone (n = 6), and horses given intravenous phenylbutazone plus endotoxin (n = 6). The mean time to reach maximum serum acetaminophen concentration (Tmax), the maximum serum concentration (Cmax), and the area under the serum acetaminophen concentration versus time curve (AUC) were compared among treatment groups. Phenylbutazone...
Wasfi IA, Zorob OM, Boni NS, Hadi AA, Agha BA, Elghazali M.The activity of hepatic mixed function oxidases was compared in horses and camels (Camelus dromedarius) by studying the pharmacokinetics of antipyrine in seven camels and five horses following intravenous administration of a single dose of antipyrine (25 mg/kg). The data obtained (mean +/- SEM and median in brackets) in camels and horses, respectively, were as follows: the elimination half-lives were 3.25 +/- 0.23 (3.19) and 3.09 +/- 0.25 (2.90) hr; the apparent volumes of distribution (area method) were 0.691 +/- 0.045 (0.648) and 0.642 +/- 0.034 (0.676) l/kg; the volumes of distribution at s...
Gómez de Segura IA, De Rossi R, Santos M, López San-Roman J, Tendillo FJ, San-Roman F.To determine the analgesic, sedative, and cardiopulmonary effects of epidural ketamine in the horse. Methods: Six healthy horses (three males and three females) weighing between 350 and 450 kg. Methods: Three doses of ketamine were selected (0.5, 1, 2 mg/kg). Two months before the beginning of experiments, the carotid artery was exteriorized, and 1 week before experiments began, an epidural catheter was placed percutaneously in all animals with the tip located 12 cm cranially in the midsacrum. One week later, either saline (control) or one of three doses of ketamine was injected epidurally. Ea...
Weiss DJ, Evanson OA, McClenahan D, Fagliari JJ, Dunnwiddie CT, Wells RE.To determining whether inhibition of platelet aggregation prevents development of carbohydrate overload-induced alimentary laminitis. Methods: 22 healthy adult ponies. Methods: Acute laminitis was induced by oral administration of corn starch/wood flour to 16 ponies, 8 of which were treated with a synthetic analogue of the platelet fibrinogen receptor antagonist peptide (RPR) RGDS (arginine-glycine-aspartic acid-serine) 110885; 6 ponies served as negative controls. Blood was collected before and at 4, 8, 12, 24, 28, and 32 hours after administration of carbohydrate overload, and PCV, total pla...
Bennett RC, Taylor PM, Brearley JC, Johnson CB, Luna SP.This prospective clinical study compared the physiological effects of two commonly used anaesthetic induction techniques in horses maintained with halothane. One hundred horses admitted for elective surgery were randomly allocated to receive either guaiphenesin (to effect) and thiopentone (5 mg/kg), or detomidine (20 microg/kg) and ketamine (2 mg/kg) for the induction of anaesthesia after acepromazine premedication. Anaesthesia was maintained with halothane in oxygen. There were no significant differences in breed, age, sex, weight, type of surgery and duration of anaesthesia between the group...
Marr K, Marsh K, Hernandez L, Cunningham FM, Lees P.Leukotrienes, products of the 5-lipoxygenase pathway of arachidonic acid metabolism, possess properties consistent with their involvement in a range of inflammatory diseases. In this study the pharmacokinetics and pharmacodynamics of the selective 5-lipoxygenase inhibitor, fenleuton, have been examined in the horse. Orally administered fenleuton (four 5 mg kg(-1) doses, given once daily) was absorbed from the gastrointestinal tract, and penetrated readily into tissue cage exudate, the ratio of the plasma:exudate AUC0-48h being 0.90+/-0.02 (n=6). Ionophore-stimulated leukotriene (LT) B4 synthes...
Brink P, DeGraves F, Ravis WR, Johansen D, Campbell JD, Duran SH.To determine intravascular and intrasynovial pharmacokinetics of the R and S enantiomers of ketoprofen after i.v. and i.m. administration to horses. Methods: 6 healthy adult mares. Methods: Horses were weighed and ketoprofen (2.2 mg/kg of body weight) was administered i.v. Blood and synovial fluid samples were obtained and analyzed for concentrations of the R and S enantiomers by means of a modified reverse-phase stereospecific high-pressure liquid chromatographic method. Three weeks later, the procedure was repeated, except that ketoprofen was given IM. Protein binding of ketoprofen enantiome...
Manohar M, Goetz TE.The present study was carried out to examine the effects of nitric oxide synthase inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME) on the right atrial as well as on the pulmonary arterial, capillary, and venous blood pressures of horses during rest and exercise performed at maximal heart rate (HRmax). Experiments were carried out on seven healthy, sound, exercise-trained Thoroughbred horses. Using catheter-tip manometers, with signals referenced at the point of the shoulder, we determined phasic and mean right atrial and pulmonary vascular pressures in two sets of experiments [con...
Hinchcliff KW, McKeever KH.The effect of blood volume repletion after frusemide administration on the right atrial and pulmonary artery pressure responses of horses to exercise has not been reported. We examined right atrial and pulmonary artery pressure and plasma atrial natriuretic peptide concentration (ANP) responses to an incremental exercise test in 6 Standardbred mares. Horses were treated, in a 3 way cross over design, with isotonic saline, frusemide (1 mg/kg bwt, i.v.), and frusemide followed 3 h later by lactated Ringer's solution (12 ml/kg bwt, i.v.). Three and a half hours after saline or frusemide administr...
Aboul-Enein HY, Van Overbeke A, Vander Weken G, Baeyens W, Oda H, Deprez P, De Kruif A.Racemic ketoprofen is a non-steroidal anti-inflammatory drug used to treat musculoskeletal and colic conditions in horses. The enantioselective chiral inversion of ketoprofen administered to horses has been studied by use of cellulose tris(4-methylbenzoate), also known as Chiralcel OJ-R, as chiral stationary phase; acetonitrile - 0.02 M perchlorate buffer (pH 2.0)-methanol, 60:15:25 (v/v/v) was used as mobile phase. Before chromatography, to effect adequate chiral interaction with the chiral stationary phase ketoprofen was derivatized with 9-aminophenanthrene, under acid conditions, after soli...
Chou CC, Chen CL, Asbury AC, Webb AI, Vickroy TW.To develop an ELISA that is sensitive and suitable for measurement of immunoreactive acepromazine (ACP) in horse serum and urine and to determine the acute effects of exercise on immunoreactive ACP values in Thoroughbreds. Methods: 12 healthy Thoroughbreds (5 mares, 5 geldings, 2 stallions), aged 2 to 8 years. Methods: A commercially available antibody and a horseradish peroxidase-conjugated oxime derivative of immunoreactive ACP were used to develop a one-step ELISA. Horses were used in a crossover design study to evaluate possible effects of treadmill exercise on serum and urine ACP concentr...
Merritt AM, Burrow JA, Hartless CS.To evaluate the effect on equine duodenal motility of some analgesic agents commonly used to treat colic. Methods: 4 healthy adult healthy horses--2 mares and 2 geldings--which were carrying an indwelling gastric cannula made of silastic rubber. One horse also carried 2 long-term indwelling bipolar electrodes that had been sutured onto the duodenum and jejunum. Methods: To ensure an empty stomach, solid food was withheld from horses for around 20 hours prior to an experiment. Using videoendoscopic guidance, an 8-F catheter with 3 small, discrete pressure sensors was passed through the gastric ...
Guglick MA, MacAllister CG, Clarke CR, Pollet R, Hague C, Clarke JM.To determine pharmacokinetics of i.v., i.m., and oral administration of cefepime in horses and to compare pharmacokinetics of i.m. administration of cefepime with those of ceftiofur sodium. Methods: 6 clinically normal adult horses. Methods: Horses received 3 doses of cefepime (11 mg/kg of body weight, PO; 2.2 mg/kg, i.v.; and 2.2 mg/kg, i.m.) and 1 dose of ceftiofur (2.2 mg/kg, i.m.). Two horses also received L-arginine, p.o. and i.v., at doses identical to those contained in the cefepime dihydrochloride-L-arginine preparations previously administered. Blood samples were collected for 24 hour...
Dyke TM, Sams RA.The objective of this study was to determine the urinary excretion of methylxanthines in horses following ingestion of chocolate over eight days. The study was performed in response to gas chromatography-mass spectrometry (GC-MS) confirmation of the presence of caffeine in a positive urine test in a racehorse. The trainer of the horse alleged that he often administered chocolate-coated peanuts as treats to his horses, and he believed that the ingestion of chocolate was responsible for the positive urine test. The urinary excretion of theobromine and caffeine after the ingestion of chocolate-co...
Ammann VJ, Vrins AA, Lavoie JP.The effects of beclomethasone dipropionate on pulmonary function and arterial blood gas values were investigated in horses with chronic obstructive pulmonary disease (COPD). Six mature mares, diagnosed as having COPD based on clinical signs, cytological examination of bronchoalveolar lavage and pulmonary function testing, were used. Beclomethasone dipropionate (3750 microg) was administered b.i.d. for a 2 week period with a metered dose inhaler using a mask. Pulmonary function tests and arterial blood gas analyses were performed at weekly intervals, starting before beclomethasone administratio...
Manohar M, Goetz TE, Sullivan E, Griffin R.The present study was carried out to examine the effects of phenylbutazone treatment on the pulmonary haemodynamic effects of frusemide in strenuously exercising horses. Using catheter mounted manometers, whose in vivo signals were referenced at the point of the shoulder, heart rate, right atrial, right ventricular and pulmonary vascular pressures were measured in 3 different sets of experiments. Seven Thoroughbreds were subjected to 1) control (no medications), 2) frusemide control and 3) phenylbutazone + frusemide. The experiments were carried out in random order and were separated by 7 days...
Lester GD, Merritt AM, Neuwirth L, Vetro-Widenhouse T, Steible C, Rice B.To determine the effect of erythromycin lactobionate (ERY) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum. Methods: 6 healthy adult ponies. Methods: After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were administered directly into the cecal apex. The following drug concentrations were tested: ERY, 0.01, 0.10, 1.0, and 10.0 mg/kg of body weight; ERY, 0.10 mg/kg bolus; and saline (0.9% NaCl) solution, 10 ml. All treatments, ...
Dyke TM, Sams RA, Hinchcliff KW.To measure renal clearance of antipyrine and urinary excretion of antipyrine (AP) metabolites in horses by use of validated high-performance liquid chromatography (HPLC) methods. Methods: 8 Standardbred mares. Methods: HPLC methods for measurement of AP in equine plasma and AP and its metabolites in equine urine were validated. Antipyrine (20 mg/kg of body weight) was administered i.v., and blood samples and urine specimens were collected over 24 hours. Results: Median plasma clearance of AP in horses was 6.2 ml/min/kg, of which < 2% could be attributed to renal clearance. Urinary excretion...
Wilcke JR, Crisman MV, Scarratt WK, Sams RA.To determine pharmacokinetic variables that describe disposition of ketoprofen after its i.v. administration to foals < 24 hours old. Methods: 6 healthy foals (1 male and 5 females); mean age, 12.5 (range, 8.5 to 17) hours at time of dose administration. Methods: Ketoprofen was administered i.v. to foals at a dosage of 2.2 mg/kg of body weight. Ketoprofen concentration in plasma samples was analyzed, using high-performance liquid chromatography. Concentration versus time profiles were analyzed according to standard pharmacokinetic techniques. Blood samples were obtained from foals by jugula...
Delbeke FT, Baert K, De Backer P.Urinary and plasma concentrations of the nonsteroidal anti-inflammatory drug tiaprofenic acid were determined following oral and intramuscular administration of a dose of 1 g to five fasted horses. Quantitation was performed by high-performance liquid chromatography (HPLC). The limit of quantitation (LOQ) was 0.1 microg/ml and 0.5 microg/ml in 2 ml plasma and 1 ml urine, respectively. Assay precision and extraction recovery were between acceptable values. Tiaprofenic acid pharmacokinetics were described by non-compartment analysis of the data. Absorption was faster after oral administration as...
MacDonald KD, Hart KA, Davis JL, Berghaus LJ, Giguère S.Seizures are a common manifestation of neurological disease in the neonatal foal and are an important cause of morbidity and mortality in this population. Current antiepileptic options are effective, but often have undesirable adverse effects, short duration of action and high cost. Levetiracetam has an ideal safety and pharmacokinetic profile in multiple species, including the adult horse, and may be a safe and cost-effective alternative anticonvulsant in neonatal foals. Due to differences in drug disposition and clearance dosages in neonates, dosing recommendations in other species or adult ...
Gold JR, Grubb T, Court M, Villarino NF.Acetaminophen is a common analgesic and antipyretic drug used in human medicine and might be an alternative to nonsteroidal anti-inflammatory drugs for treating pain and pyrexia in foals. The pharmacokinetics and safety of differing doses of acetaminophen have not been investigated in foals. Objective: To determine the plasma pharmacokinetics and any changes in haematology and biochemistry profiles following oral administration of single doses of acetaminophen at 10, 20, and 40 mg/kg to foals. Methods: Randomised cross-over pharmacokinetic study. Methods: Six Quarter Horse (two colts and fou...
Rees WA, Harkins JD, Woods WE, Blouin RA, Lu M, Fenger C, Holland RE, Chambers TM, Tobin T.Amantadine is an antiviral agent effective against influenza A viruses. We investigated 1) the antiviral efficacy, 2) analytical detection, 3) bioavailability and disposition, 4) pharmacokinetic modelling and 5) adverse reactions of amantadine in the horse. In vitro, amantadine and its derivative rimantadine suppressed the replication of recent isolates of equine-2 influenza virus with effective doses (EDs) of less than 30 ng/ml. Rimantadine was more effective than amantadine against most viral isolates; we suggest a minimum plasma concentration of 300 ng/ml of amantadine for therapeutic effic...
Menendez MI, Phelps MA, Bertone AL.To the date, no reports exist of the pharmacokinetics (PK) of betamethasone (BTM) sodium phosphate and betamethasone acetate administered intra-articular (IA) into multiple joints in exercising horses. The purpose of the study was to determine the PK of BTM and HYD concentrations in plasma and urine after IA administration of a total of 30 mg BTM. Eight 4 years old Thoroughbred mares were exercised on a treadmill and BTM was administered IA. Plasma and urine BTM and HYD were determined via high performance liquid chromatography spectrometry for 6 weeks. Concentration-time profiles of BTM and H...
Soma LR, Gallis DE, Davis WL, Cochran TA, Woodward CB.Phenylbutazone (PBZ) was administered (8.8 mg/kg of body weight) every 24 hours for 5 consecutive days, orally for the first 4 days and IV on day 5. The half-life (t 1/2) after this daily administration was 6.2 hours and the volume of distribution was 0.152 +/- 0.014 L/kg; the bioavailability after oral administration was 91.8 +/- 2.5%. The plasma concentration of PBZ at experimental hour (EH) 24 (24 hours after the 1st oral dose) was 1.7 +/- 0.39 micrograms/ml and increased to 4.2 +/- 0.29 micrograms/ml at EH 48 (24 hours after the 2nd oral dose). Values at EH 72, 96, and 120 (24 hours after ...
Freeman SL, England GC.To compare sedative effects of romifidine following IV, IM, or sublingual (SL) administration in horses. Methods: 30 horses that required sedation for routine tooth rasping. Methods: Horses (n = 10/group) were given romifidine (120 microg/kg) IV, IM, or SL. Heart rate, respiratory rate, head height, distance between the ear tips, thickness of the upper lip, response to auditory stimulation, response to tactile stimulation, and degree of ataxia were recorded every 15 minutes for 180 minutes. Tooth rasping was performed 60 minutes after administration of romifidine, and overall adequacy of sedat...
Crosignani N, Luna SP, Dalla Costa T, Pimenta EL, Detoni CB, Guterres SS, Puoli Filho JN, Pantoja JC, Pigatto MC.We investigated the thermal, electrical and mechanical antinociceptive and physiological effects (heart rate, respiratory rate, arterial blood pressure, head height and abdominal auscultation score), and pharmacokinetics, of 0.5 mg/kg of the injectable formulation (ORAL) or nanoparticulated methadone (NANO) given orally, in six adult mares, using a crossover, blind and prospective design. Repeated-measure models were used to compare parametric data between and within treatments, followed by Tukey's test. Nonparametric data were analysed with Wilcoxon signed-rank, adjusted by Bonferroni tests....
Umar MA, Fukui S, Kawase K, Itami T, Yamashita K.Cardiovascular effects of total intravenous anesthesia using ketamine-medetomidine-propofol drug combination (KMP-TIVA) were determined in 5 Thoroughbred horses undergoing surgery. The horses were anesthetized with intravenous administration (IV) of ketamine (2.5 mg/kg) and midazolam (0.04 mg/kg) following premedication with medetomidne (5 µg/kg, IV) and artificially ventilated. Surgical anesthesia was maintained by controlling propofol infusion rate (initially 0.20 mg/kg/min following an IV loading dose of 0.5 mg/kg) and constant rate infusions of ketamine (1 mg/kg/hr) and medetomidine (1.25...
Zientek KD, Anderson DF, Wegner K, Cole C.A method for the extraction and quantitation of procaine in equine plasma was developed for use with liquid chromatography-mass spectrometry (LC-MS). Procaine was isolated from equine plasma by liquid-liquid extraction at pH 11 with dichloromethane using procaine-d10 as an internal standard. Quantitation was achieved by LC-MS using a 3-microm C-18 column coupled to an electrospray ionization source on a linear ion-trap mass spectrometer. The limit of detection and limit of quantitation was determined to be 50 and 200 pg/mL, respectively. The lowest limit of detection determined by previous met...
Yi R, Sandhu J, Zhao S, Lam G, Loganathan D, Morrissey B.Efaproxiral (RSR 13) is an experimental synthetic allosteric modifier of haemoglobin (Hb) that acts by increasing the release of oxygen from Hb to the surrounding tissues. It has been shown to increase maximum oxygen uptake (VO(2max)) in a canine skeletal muscle model. The ability to increase maximal muscle oxygen uptake makes efaproxiral a potential performance-enhancing agent and is therefore prohibited by the World Anti-Doping Agency. In this study, a method for the detection and elimination of efaproxiral in equine plasma and urine after a 2.5 g intravenous administration of efaproxiral ...
Orsini JA, Moate PJ, Boston RC, Norman T, Engiles J, Benson CE, Poppenga R.In two studies, six healthy adult horses were given imipenem-cilastatin by slow intravenous (i.v.) infusion at an imipenem dosage of 10 mg/kg (study 1) and 20 mg/kg (study 2). The same horses were used in each dosage schedule, with a 2-week washout period between studies. In each dosage group, serial blood and synovial fluid samples were collected for 6 h after completion of the infusion. HPLC was used to determine the imipenem concentration in all samples. Imipenem was well tolerated by all horses at both dosages; no adverse effects were noted during the study period or during the 24-hour pos...
Slocombe JO, Cote JF.Twenty horses were treated with ivermectin either by nasogastric tube with a liquid formulation for sheep or per os with a paste formulation for horses at a dosage of 200 mug/kg of body weight. Fecal samples were collected from these horses and from ten untreated horses at the time of treatment and every 2 wk thereafter for up to 10 wk. The samples were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin Double Centrifugation procedures.There were no signs of toxicosis in horses treated with ivermectin. Strongyle eggs were found in the feces of all horses b...
Kuroda T, Nagata SI, Tamura N, Kinoshita Y, Niwa H, Mita H, Minami T, Fukuda K, Hobo S, Kuwano A.To determine plasma pharmacokinetics of metronidazole and imipenem following administration of a single dose PO (metronidazole, 15 mg/kg) or IV (imipenem, 10 mg/kg) in healthy Thoroughbreds and simulate pleural fluid concentrations following multiple dose administration every 8 hours. Methods: 4 healthy Thoroughbreds. Methods: Metronidazole and imipenem were administered, and samples of plasma and pleural fluid were collected at predetermined time points. Minimum concentrations of metronidazole and imipenem that inhibited growth of 90% of isolates (MIC90), including 22 clinical Bacteroides iso...
Dirikolu L, Karpiesiuk W, Lehner AF, Tobin T.Toltrazuril sulfone (ponazuril) is a triazine-based antiprotozoal agent with clinical application in the treatment of equine protozoal myeloencephalomyelitis (EPM). In this study, we synthesized and determined the bioavailability of a sodium salt formulation of toltrazuril sulfone that can be used for the treatment and prophylaxis of EPM in horses. Toltrazuril sulfone sodium salt was rapidly absorbed, with a mean peak plasma concentration of 2400 ± 169 (SEM) ng/mL occurring at 8 h after oral-mucosal dosing and was about 56% bioavailable compared with the i.v. administration of toltrazuril sul...
Hackett RP, Ducharme NG, Ainsworth DM, Erickson BK, Erb HN, Soderholm LV, Thorson LM.To determine whether dorsal displacement of the soft palate (DDSP) results in pulmonary artery hypertension and leads to increases in transmural pulmonary artery pressure (TPAP); to determine whether pulmonary hypertension can be prevented by prior administration of furosemide; and to determine whether tracheostomy reduces pulmonary hypertension. Methods: 7 healthy horses. Methods: Horses were subjected to 3 conditions (control conditions, conditions after induction of DDSP, and conditions after tracheostomy). Horses were evaluated during exercise after being given saline (0.9% NaCl) solution ...
Ingvast-Larsson C, Paalzow G, Paalzow L, Ottosson T, Lindholm A, Appelgren LE.The pharmacokinetics of theophylline were determined in Standardbred trotters after single intravenous and oral administration. A bi-exponential equation was fitted to the intravenous data and a tri-exponential equation to the oral data. The biological half-life of theophylline was found to be 14.8 h, the volume of distribution 1.02 l/kg and the total plasma clearance 0.86 ml/kg/min. The oral absorption of the drug was complete (bioavailability 108%) and rapid (absorption half-life 0.4 h).
Dyson DH, Pascoe PJ, McDonell WN.The purpose of this study was to determine the heart rate (HR) and blood pressure (BP) effect of glycopyrrolate in anesthetized horses with low HR ( 5 beats/min within 10 min), glycopyrrolate (same dose) was administered. Heart rate increased by > 5 beats/min in 3 out of 9 horses following the initial glycopyrrolate treatment. Overall changes in HR and mean BP were not significantly different, while systolic and diastolic BP increased significantly (P 5 beats/min, which was significant. A significant increase in BP was produced following treatment with 2.5 micrograms/kg BW, but not followi...
Boone LH, DeGraves FJ, Klein CE, Cole RC, Schumacher J.To assess onset of analgesia for 3% chloroprocaine hydrochloride and 2% mepivacaine hydrochloride when used for median and ulnar nerve blocks in lame horses. Methods: 6 naturally lame horses. Methods: A crossover experiment was conducted. Horses were assigned to 1 of 2 treatment groups (3% chloroprocaine or 2% mepivacaine first). Median and ulnar nerve blocks were performed in the lame limb with the assigned treatment. Lameness was objectively evaluated before treatment administration and at various points for 120 minutes after treatment with a wireless inertial sensor-based motion analysis sy...
Bhavnani BR, Woolever CA.[3H]Equilin [3H-labeled 3-hydroxy-1,3,5(10), 7-estratetraen-17-one] was administered iv to a pregnant mare in the 10th month of gestation. Maternal urine was collected for 3 days, and blood samples were taken 35 min and 3, 6, 12, and 24 h after the injection. The half-life of the disappearance of radioactivity from the blood was approximately 2.5 h. Over 90% of the administered dose was excreted in the first 24 h. The urine was extracted, hydrolyzed, and fractionated. The bulk of the radioactive material (75%) was present in the phenolic sulfate fraction from which radiochemically pure equilin...
Boyd EH, Allen WE.Plasma concentrations of neomycin were measured following intrauterine infusion of 3.3 mg/kg bodyweight neomycin sulphate. Mares in oestrus absorbed approximately 6 per cent of neomycin infused whereas mares in a luteal phase absorbed 56 per cent. The volume of infusate also affected absorption as increased volume resulted in decreased absorption. The decreased absorption both during oestrus and when large volumes were used was probably due to reflux of antibiotic through the cervix.
Hilton HG, Magdesian KG, Groth AD, Knych H, Stanley SD, Hollingsworth SR.Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used systemically for the treatment of inflammatory ocular disease in horses. However, little information exists regarding the ocular penetration of this class of drugs in the horse. Objective: To determine the distribution of orally administered flunixin meglumine and firocoxib into the aqueous humor of horses. Methods: Fifteen healthy adult horses with no evidence of ophthalmic disease. Methods: Horses were randomly assigned to a control group and 2 treatment groups of equal sizes (n = 5). Horses assigned to the treatment groups rece...
Berlin S, Wallstabe S, Scheuch E, Oswald S, Hasan M, Wegner D, Grube M, Venner M, Ullrich A, Siegmund W.Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative. Objective: To evaluate the pharmacokinetic ...
Rumpler MJ, Kandala B, Vickroy TW, Hochhaus G, Sams RA.Glycopyrrolate (GLY) is an antimuscarinic agent that is used in humans and domestic animals primarily to reduce respiratory tract secretions during anesthesia and to reverse intra-operative bradycardia. Although GLY is used routinely in veterinary patients, there is limited information regarding its pharmacokinetic (PK) and pharmacodynamic (PD) properties in domestic animals, and an improved understanding of the plasma concentration-effect relationship in racehorses is warranted. To accomplish this, we characterize the pharmacokinetic-pharmacodynamic (PK-PD) actions of GLY during and after a 2...
Willette C, Aarnes TK, Lerche P, Ricco-Pereira C, Ballash GA, Bednarski RM.To assess anesthetic induction, recovery quality and cardiopulmonary variables after intramuscular (IM) injection of three drug combinations for immobilization of horses. Methods: Randomized, blinded, three-way crossover prospective design. Methods: A total of eight healthy adult horses weighing 470-575 kg. Methods: Horses were administered three treatments IM separated by ≥1 week. Combinations were tiletamine-zolazepam (1.2 mg kg), ketamine (1 mg kg) and detomidine (0.04 mg kg) (treatment TKD); ketamine (3 mg kg) and detomidine (0.04 mg kg) (treatment KD); and tiletamine-zolazepam (2.4 mg ...
Bessonnat A, Vanore M.Evaluate the effect of repeated doses of topical 1% cyclopentolate hydrochloride alone and in combination with topical 2.5% phenylephrine on pupil diameter (PD), tear production (STT-1), intraocular pressure (IOP), digestive function (gut motility and feces production), and heart rate (HR). Methods: Six healthy mares. Methods: In a prospective, randomized, controlled, and crossover design study, the left eye of six healthy mares was administered 0.2 mL of cyclopentolate alone and in combination with 0.2 mL of phenylephrine. The drugs were administered 3 times a day for 1 day, twice a day fo...
Koupai-Abyazani MR, Esaw B, Laviolette B.Urine and serum samples collected from four standard-bred mares after and oral regimen administration of methocarbamol were extracted and analyzed. The method consisted of enzyme hydrolysis followed by a one-step liquid-liquid extraction, separation on a reversed-phase (RP-18) column, and detection using an ultraviolet (UV) detector. The confirmation was carried out using a liquid chromatography-atmospheric pressure ionization-mass spectrometry (LC-API-MS) system. Maximum methocarbamol concentrations of 1498, 1734, 1547, 2322 micrograms/mL in urine and 4.9, 1.7, and 3.6 micrograms/mL in serum ...
Duesterdieck-Zellmer KF, Moneta L, Ott JF, Larson MK, Gorman EM, Hunter B, Löhr CV, Payton ME, Morré JT, Maier CS.To determine effects of intraarticularly administered tiludronate on articular cartilage in vivo, eight healthy horses were injected once with tiludronate (low dose tiludronate [LDT] 0.017 mg, n = 4; high dose tiludronate [HDT] 50 mg, n = 4) into one middle carpal joint and with saline into the contralateral joint. Arthrocentesis of both middle carpal joints was performed pre-treatment, and 10 min, 24 h, 48 h, 7 and 14 days after treatment. Synovial nucleated cell counts and total solids, tiludronate, sulfated glycosaminoglycan (sGAG), chondroitin sulfate 846 epitope (CS-846, a measure of aggr...
Roska S, Morello S, Rajamanickam V, Smith LJ.Effects of lactated Ringer's solution (LRS) and hetastarch 130/0.4 (HES) on colloid osmotic pressure (COP), plasma osmolality (OSM) and total protein (TP) were investigated in 18 inhalational-anaesthetised healthy horses. Horses received 4-6 ml/kg LRS (LRS; n=9) or HES (HES; n=9) from anaesthesia induction through 60 min, after which all were administered LRS. COP, TP and OSM were measured before premedication (baseline), postinduction and 30 (n=18), 60 (n=18), 90 (n=18) and 120 (n=12) minutes. Baseline COP, OSM and TP were not different between groups. TP decreased in both groups at all t...
Igwe OJ, Blake JW.The disposition kinetics of pemoline after iv and oral administration of 2.4 mg/kg of the drug were studied. The elimination half-life was 39.4 hr. The mean volume of distribution was 1.5 liters/kg indicating extensive tissue distribution and sequestration for an amphoteric drug. Plasma protein binding determined by in vitro equilibrium dialysis was concentration dependent. The mean binding capacity was found to be 0.80 mu-mol/g, an apparent dissociation constant of 3.73 X 10(-5) molar, and a total plasma protein concentration of 64.7 g/liter. The mean systemic availability by oral administrat...
King JN, Gerring EL.The effect of cisapride was evaluated on the normal fasting bowel motility of four ponies with chronically implanted electromechanical transducers. Cisapride was infused over 60-min periods at 0.05 mg/kg (n = 4), 0.1 mg/kg (n = 5) and 0.25 mg/kg (n = 5). It produced marked and prolonged increases in electrical and mechanical activity at all sites examined. In the stomach there was increased total contraction activity with increased contraction amplitude and a slight reduction in rate. In the small intestine there was an increase in irregular (phase II) activity with an increase in number and a...
