Veterinary Medicine Commons^™

Long Acting, Reversible Veterinary Sedative And Analgesic And Method Of Use, Thomas Tobin

Veterinary Science Faculty Patents

A veterinary composition comprising a guanidine derivative, e.g., guanabenz or guanabenz acetate is provided which produces a rapid acting and long lasting sedative and analgesic effect in a subject animal that is selectively reversible. The use of guanabenz in the horse provides for a safe, effective, long lasting and rapidly reversible sedative and analgesic which can be used on the standing animal. Methods of use of the compositions of the invention are also provided.

Nucleic Acids Encoding Sarcocystis Neurona Antigen And Uses Thereof, Daniel K. Howe

Veterinary Science Faculty Patents

The present invention provides novel isolated nucleic acids encoding antigenic proteins derived from Sarcocystis neurona, or unique fragments thereof. In particular, the invention provides novel isolated nucleic acids encoding membrane-associated polypeptides SnSAG2, SnSAG3, and SnSAG4. Also provided are purified antigenic polypeptide fragments encoded by the novel nucleic acid sequences set forth herein that encode for SnSAG2, SnSAG3, and SnSAG4. Also provided are isolated nucleic acids capable of selectively hybridizing with the nucleic acid from Sarcocystis neurona. The invention also provides vectors comprising the nucleic acids of the invention encoding an antigenic protein derived from Sarcocystis neurona or …

The Use Of A Whole Genome Scan To Find A Genetic Marker For Degenerative Suspensory Ligament Desmitis In The Peruvian Paso Horse, Diane I. Strong

University of Kentucky Master's Theses

Degenerative suspensory ligament desmitis (DSLD) is a debilitating disease of connective tissues seen in many breeds but has become prevalent in the Peruvian Pasohorse. DSLD is believed to be a genetic disorder caused by one primary founder and most likely has a recessive mode of inheritance although a dominant or co-dominant mode of inheritance has not been ruled out.

A genome scan using 259 microsatellite markers was used to test for linkage disequilibrium between one or more markers and DSLD. Two groups of Peruvian Pasohorses were selected from one population including the US and Canada. The only difference between the …

Detection And Confirmation Of Ractopamine And Its Metabolites In Horse Urine After Paylean® Administration, A. F. Lehner, C. G. Hughes, J Daniel Harkins, C. Nickerson, B. Mollett, L. Dirikolu, Jeffrey M Bosken, Fernanda C. Camargo, J. Boyles, A. Troppmann, W. Karpiesiuk, W. E. Woods, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

We have investigated the detection, confirmation, and metabolism of the beta-adrenergic agonist ractopamine administered as Paylean to the horse. A Testing Components Corporation enzyme-linked imunosorbent assay (ELISA) kit for ractopamine displayed linear response between 1.0 and 100 ng/ml, with an 1-50 of 10 ng/ml, and an effective screening limit of detection of 50 ng/mL. The kit was readily able to detect ractopamine equivalents in unhydrolyzed urine up to 24 h following a 300-mg oral dose. Gas chromatography-mass spectrometry (GC-MS) confirmation comprised glucuronidase treatment, solid-phase extraction, and trimethylsilyl derivatization, with selected-ion monitoring of ractopamine-tris(trimethylsilane) (TMS) m/z 267, 250, 179, and 502 …

Development Of A Method For The Detection And Confirmation Of The Alpha-2 Agonist Amitraz And Its Major Metabolite In Horse Urine, A. F. Lehner, C. G. Hughes, W. Karpiesiuk, J Daniel Harkins, L. Dirikolu, Jeffrey M Bosken, Fernanda Camargo, J. Boyles, A. Troppmann, W. E. Woods, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Amitraz (N′-(2,4-dimethylphenyl)-N-[[(2,4-dimethylphenyl)imino] methyl]-N-methyl-methanimidamide) is an alpha-2 adrenergic agonist used in veterinary medicine primarily as a scabicide- or acaricide-type insecticide. As an alpha-2 adrenergic agonist, it also has sedative/tranquilizing properties and is, therefore, listed as an Association of Racing Commissioners International Class 3 Foreign Substance, indicating its potential to influence the outcome of horse races. We identified the principal equine metabolite of amitraz as N-2,4-dimethylphenyl-N′-methylformamidine by electrospray ionization(+)-mass spectrometry and developed a gas chromatographic-mass spectrometric (GC-MS) method for its detection, quantitation, and confirmation in performance horse regulation. The GC-MS method involves derivatization with t-butyldimethylsilyl groups; selected ion monitoring (SIM) of m/z …

A Gc-Ms Method For The Determination Of Isoxsuprine In Biological Fluids Of The Horse Utilizing Electron Impact Ionization, Jeffrey M Bosken, A. F. Lehner, C. G. Hughes, W. E. Woods, F. C. Camargo, J. D. Harkins, J. Boyles, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Isoxsuprine is used to treat navicular disease and other lower-limb problems in the horse. Isoxsuprine is regulated as a class 4 compound by the Association of Racing Commissioners, International (ARCI) and, thus, requires regulatory monitoring. A gas chromatography-mass spectrometry method utilizing electron impact ionization was developed and validated for the quantitation of isoxsuprine in equine plasma or equine urine. The method utilized robotic solid-phase extraction and tri-methyl silyl ether products of derivatization. Products were bis-trimethylsilyl (TMS) isoxsuprine and tris-TMS ritodrine, which released intense quantifier ions m/z 178 for isoxsuprine and m/z 236 for ritodrine that were products of C-C cleavage. …

The Mare Reproductive Loss Syndrome And The Eastern Tent Caterpillar Ii: A Toxicokinetic/Clinical Evaluation And A Proposed Pathogenesis: Septic Penetrating Setae, Thomas Tobin, J. Daniel Harkins, John Ford Roberts, Patricia W. Vanmeter, Tara A. Fuller

Maxwell H. Gluck Equine Research Center Faculty Publications

Reviewing the mare reproductive loss syndrome (MRLS), it is proposed that the fundamental mechanism of this syndrome, which includes early fetal loss, late fetal loss, uveitis, pericarditis, and encephalitis, is tissue penetration by septic barbed setal fragments (septic penetrating setae) from Eastern tent caterpillars (Malacosoma americanum). Once ingested, these barbed setal fragments migrate through moving tissues, followed by rapid hematogenous spread of bacteria, bacterial emboli, and/or septic fragments of setae (septic penetrating setal emboli), collectively referred to as septic materials. Pathogenic bacteria, therefore, enter the horse as hitchhikers on or in the caterpillar setal fragments, and MRLS is caused by …

Addressing The Decline In Reproductive Performance Of Lactating Dairy Cows: A Researcher’S Perspective, William J. Silvia

Animal and Food Sciences Faculty Publications

No abstract provided.

The Mare Reproductive Loss Syndrome And The Eastern Tent Caterpillar: A Toxicokinetic/Statistical Analysis With Clinical, Epidemiologic, And Mechanistic Implications, Manu Sebastian, Marie G. Gantz, Thomas Tobin, J. Daniel Harkins, Jeffrey M. Bosken, Charlie Hughes, Lenn R. Harrison, William V. Bernard, Dana L. Richter, Terrence D. Fitzgerald

Maxwell H. Gluck Equine Research Center Faculty Publications

During 2001, central Kentucky experienced acute transient epidemics of early and late fetal losses, pericarditis, and unilateral endophthalmitis, collectively referred to as mare reproductive loss syndrome (MRLS). A toxicokinetic/statistical analysis of experimental and field MRLS data was conducted using accelerated failure time (AFT) analysis of abortions following administration of Eastern tent caterpillars (ETCs; 100 or 50 g/day or 100 g of irradiated caterpillars/day) to late-term pregnant mares. In addition, 2001 late-term fetal loss field data were used in the analysis. Experimental data were fitted by AFT analysis at a high (P < .0001) significance. Times to first abortion (“lag time”) and abortion rates were dose dependent. Lag times decreased and abortion rates increased exponentially with dose. Calculated dose × response data curves allow interpretation of abortion data in terms of “intubated ETC equivalents.” Analysis suggested that field exposure to ETCs in 2001 in central Kentucky commenced on approximately April 27, was initially equivalent to approximately 5 g of intubated ETCs/day, and increased to approximately 30 g/day at the outbreak peak. This analysis accounts for many aspects of the epidemiology, clinical presentations, and manifestations of MRLS. It allows quantitative interpretation of experimental and field MRLS data and has implications for the basic mechanisms underlying MRLS. The results support suggestions that MRLS is caused by exposure to or ingestion of ETCs. The results also show that high levels of ETC exposure produce intense, focused outbreaks of MRLS, closely linked in time and place to dispersing ETCs, as occurred in central Kentucky in 2001. With less intense exposure, lag time is longer and abortions tend to spread out over time and may occur out of phase with ETC exposure, obscuring both diagnosis of this syndrome and the role of the caterpillars.

Compounds Encoding The Protective M-Like Protein Of Streptococcus Equi And Assays Therefor, John F. Timoney, Sergey Artiushin

Veterinary Science Faculty Patents

The present invention relates generally to molecular compounds which encode the protective M-like protein of Streptococcus equi (SeM), the amino acid compound which is thereby encoded, and compositions of matter which incorporate either the encoding compounds or the cellular components for which they encode. For instance, vaccines which utilize the amino acid compounds or vectors and cell lines useful to make the amino acid compounds described herein are subjects of the present invention. The present invention provides methods to stimulate S. equi-specific immune response in horses. It also provides diagnostic assays for Streptococcus equi.

Clenbuterol In The Horse: Confirmation And Quantitation Of Serum Clenbuterol By Lc-Ms-Ms After Oral And Intratracheal Administration, A. F. Lehner, J Daniel Harkins, W. Karpiesiuk, W. E. Woods, N. E. Robinson, L. Dirikolu, M. Fisher, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Clenbuterol is a β₂ agonist/antagonist bronchodilator, and its identification in post-race samples may lead to sanctions. The objective of this study was to develop a specific and highly sensitive serum quantitation method for clenbuterol that would allow effective regulatory control of this agent in horses. Therefore, clenbuterol-d₉ was synthesized for use as an internal standard, an automated solid-phase extraction method was developed, and both were used in conjunction with a multiple reaction monitoring liquid chromatography-tandem mass spectrometry (LC-MS-MS) method to allow unequivocal identification and quantitation of clenbuterol in 2 mL of serum at concentrations as low as 10 …

Sarcocystis Neurona Diagnostic Primer And Its Use In Methods Of Equine Protozoal Myeloencephalitis Diagnosis, Clara K. Fenger, David E. Granstrom, Alvin A. Gajadhar, Jitender P. Dubey

Veterinary Science Faculty Patents

An amplification primer and probe which can be used in an in vitro diagnostic test for the presence of S. neurona in equine blood or cerebrospinal fluid. Sarcocystis neurona is responsible for the equine condition of protozoal myelitis. The amplification primer is seventeen nucleotides in length and complementary to a unique section of the small ribosomal subunit of Sarcocystis neurona. The primer encompasses nucleotide positions 1470-1487 of the small ribosomal subunit of S. neurona. The primer has the sequence 5' CCATTCCGGACGCGGGT SEQ ID NO:1.

Remifentanil In The Horse: Identification And Detection Of Its Major Urinary Metabolite, A. F. Lehner, P. Almeida, J. Jacobs, J Daniel Harkins, W. Karpiesiuk, W. E. Woods, L. Dirikolu, Jeffrey M Bosken, W. G. Carter, J. Boyles, C. Holtz, T. Heller, C. Nattrass, M. Fisher, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Remifentanil (4-methoxycarbonyl-4-[(1-oxopropyl)phyenylamino]-1- piperidinepropionic acid methyl ester) is a μ-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 fentanyl equivalents in these samples. Mass spectrometric analysis, using solid-phase extraction and trimethylsilyl (TMS) derivatization, showed the urine samples contained parent remifentanil in low concentrations, peaking at 1 h. More significantly, a major peak was identified as …

Effect Of Amitraz And Xylazine On Some Physiological Variables Of Horses, A. Queiroz-Neto, A. B. Carregaro, G. Zamur, J Daniel Harkins, Thomas Tobin, M. I. Mataqueiro, S. C. Gonçalves

Maxwell H. Gluck Equine Research Center Faculty Publications

The effect of the intravenous injection of amitraz (0.1 mg/kg) to horses on cardiac activity, respiratory rate, intestinal motor activity, rectal temperature, sweating and masticating was evaluated and compared to the effect of intravenous administration of xylazine (1mg/kg, iv) on heart rate, respiratory rate and intestinal activity. Amitraz caused a significant decrease in heart activity, respiratory rate and intestinal movements, but these effects were not as pronounced as those caused by xylazine. Amitraz also caused a significant relaxation of the rectal smooth muscle, and an apparent increase in sweating and in the frequency of horses found masticating hay. Rectal temperature …

Formulations And Methods To Treat And Prevent Equine Protozoal Myeloencephalitis, David E. Granstrom, Thomas Tobin

Veterinary Science Faculty Patents

The present invention provides formulations useful to treat EPM. It also provides methods to treat EPM in a horse in need of such treatment, comprising administering a pharmaceutically effective amount of a triazine-based anti-coccidial. Preferred are methods to treat EPM using clazuril, diclazuril, toltrazuril or letrazuril. The present invention also provides methods to prevent S. neurona infection in horses comprising administering a prophylactic amount of a triazine-based anticoccidial. Preferred is a method to prevent S. neurona infection by using clazuril, diclazuril, toltrazuril or letrazuril, alone or in combination with other known therapeutics.

Absence Of Detectable Pharmacological Effects After Oral Administration Of Isoxsuprine, J. Daniel Harkins, G. D. Mundy, S. Stanley, W. E. Woods, R. A. Sams, D. R. Richardson, S. C. Grambow, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Isoxsuprine is reported to be a peripheral vasodilator used in human and veterinary medicine to treat ischaemic vascular disease. In horses, it is generally administered orally to treat navicular disease and other lower limb problems. To deflne the scope and duration of its pharmacological responses after oral administration, 6 horses were dosed with isoxsuprine HCI (1.2 mg/kg bwt) q. 12 h for 8 days and then tested to assess the duration and extent of pharmacological actions. There was no significant difference between isoxsuprine and control treatment values for heart rate, spontaneous activity, sweat production, anal muscle tone, core and skin …

An Overview Of The Methylxanthines And Their Regulation In The Horse, J Daniel Harkins, W. Allen Rees, G. D. Mundy, Scott D. Stanley, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Caffiene, theophylline and theobromine are naturally occurring members of the methylxanthine family;pentoxfylline, dyphylline and enprofylline are structurally related synthetic pharmaceuticals. Caffiene has predominantly central nervous system effects, theophylline, dyphylline and enprofylline have predominantly bronchodilator effects, while theobromine is associated with diuretic responses. Pentoxfylline is thought to increase red cell deformability and facillitate blood flow through capillary beds. The methylxanthines are not highly potent agents; they are typically administered in gram doses and they tend to have relatively long half-lives. They remain detectable in plasma and urine for relatively long periods. Similarly, traces of the naturally occurring members of this family …

The Pharmacologic Effects Of Isoxsuprine, J. Daniel Harkins, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Isoxsuprine is a therapeutic medication used to treat navicular disease and other lower limb problems in horses and is one of the more frequently detected therapeutic agents in racing horses. In crossover studies, horses were administered intravenous and oral isoxsuprine to determine the character and duration of pharmacological effects. Following intravenous administration, isoxsuprine significantly increased heart rate, spontaneous activity, and sweat production. There was an apparent, although statistically insignificant, increase in cutaneous blood flow. Skin temperature decreased below control values, and there was a significant decrease in core temperature. Isoxsuprine also reduced smooth muscle tone. In contrast, after oral dosing, …

Frequency Distribution Of Post Race Urine Ph From Standardbreds Compared With Thoroughbreds: Research And Regulatory Significance, S. D. Stanley, R. A. Sams, J Daniel Harkins, G. D. Mundy, J. Boyles, W. E. Woods, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

The concentration of drugs and drug metabolites in urine samples of racing horses is strongly influenced by urine pH(Tobin, 1981), depending on whether the drugs are weak acids or weak bases. Drugs that are weak acids tend to concentrate in besic urine. In contrast, drugs that are weak bases tend to concentrate in acidic urine. These relationships have a well-established theoretical basis (the Henderson-Hasselbalch relationship) and have been demonstrated repeatedly in experimental animals and man (Tobin, 1981). More recently, evidence suggests that these relationships also occur with clinically and forensically significant agents in equine urine (Wood, et al. 1990; Gerken …

Hordenine : Pharmacology, Pharmacokinetics And Behavioural Effects In The Horse, M. Frank, T. J. Weckman, T. Wood, W. E. Woods, Chen L. Tai, Shih-Ling Chang, A. Ewing, J. W. Blake, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Hordenine is an alkaloid occurring naturally in grains, sprouting barley, and certain grasses. It is occasionally found in post race urine samples, and therefore we investigated its pharmacological actions in the horse. Hordenine (2.0 mgkg bodyweight [bwt]) was administered by rapid intravenous (iv) injection to 10 horses. Typically, dosed horses showed a tlehmen response and defecated within 60 secs. All horses showed substantial respiratory distress. Respiratory rates increased about 250 per cent and heart rates were approximately double that of resting values. All animals broke out in a sweat shortly after iv injection, but basal body temperature was not affected. …

Qualitative Metabolism Assessment Using High Performance Thin Layer Chromatography, Shih-Ling Chang

Veterinary Science Faculty Patents

A method for the qualitative assessment of oxidative drug metabolism deficiencies, preferably for the qualitative assessment of dextromethorphan metabolism, in a subject comprises analyzing a sample fluid from the subject, for example urine, which contains metabolites of a probe drug using high performance thin layer chromatography.

The Detection, Pharmacokinetics And Behavioral Effects Of Diisopropylamine Dichloroacetate (Dada) In The Horse: A Preliminary Report, J.-M. Yang, W. E. Woods, T. J. Weckman, T. W. Wood, S.-L. Chang, J. W. Blake, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

1. Drug administration studies using diisopropylamine dichloroacetate (DADA) and diisopropylamine (DIPA) were conducted in Thoroughbred and Standardbred horses to assess physiological effects and develop detection methods.

2. Four horses received 0.08 mg DADA/kg body wt and showed no changes in heart and respiratory rates or body temperature as measured over a 1-hr period after administration. A transient diuretic effect was found to occur in 2 mares dosed with 0.80 mg DADA/kg body wt.

3. A qualitative detection method using thin-layer chromatography was developed to detect DIPA, the major metabolite of DADA in equine urine. A quantitative detection method (lower limit …

Composition For Topical And Infusion Treatment Of Wounds And Burns, Thomas W. Swerczek

Veterinary Science Faculty Patents

A composition is provided for the treatment of contagious equine metritis, a contagious venereal disease of horses. The composition appears to function as a biological inhibitor and has antibacterial and antifungal activity when applied to the normal flora and secretions of the epidermis and mucous membranes. Also, the composition has antipruritic and anti-inflammatory activity. The composition is efficacious in the treatment of lesions produced by bacteria, fungi, allergies, viruses, trauma, and burns to the epidermis, dermis, muscles and mucous membranes of the surface or in body cavities of animals and man.

The composition preferably comprises an aqueous solution of dextrose, …

Phenylbutazone In The Horse: A Review, Thomas Tobin, S. Chay, S. Kamerling, W. E. Woods, T. J. Weckman, J. W. Blake, P. Lees

Maxwell H. Gluck Equine Research Center Faculty Publications

Phenylbutazone is an acidic, lipophilic, nonsteroidal anti-inflammatory drug (NSAID). It is extensively metabolized in the horse. The metabolites so far identified, oxyphenbutazone, y-hydroxyphenylbutazone and y-hydroxyoxyphenbutazone. account for some 25-30% of administered dose over 24 h. The plasma half-life of phenylbutazone and termination of its pharmacological action are determined primarily by its rate of hepatic metabolism. Phenylbutazone acts by inhibiting the cyclooxygenase enzyme system, which is responsible for synthesis of prostanoids such as PGE?. It appears to act on prostaglalidin-H synthase and prostacyclin synthase, after conversion by prostaglandin-H synthase to reactive intermediates. It markedly reduces prostanoid-dependent swelling, edema, erythema, and hypersensitivity …

Treatment For Contagious Equine Metritis, Thomas W. Swerczek

Veterinary Science Faculty Patents

A composition is provided for the treatment of contagious equine metritis, a contagious veneral disease of horses, which composition comprises an aqueous solution of dextrose, a buffering mixture to provide a pH of about 3.0 to 4.5, and a carrier, the composition being applied topically to external genitalia of horses.

Detection Of Morphine And Its Analogues Using Enzymatic Hydrolysis, Joan Combie, Jerry W. Blake, Thomas E. Nugent, Thomas Tobin

Veterinary Science Faculty Patents

The invention relates to a method for hydrolyzing drug glucuronic acid conjugates present in mammalian body fluids, the conjugates being derived from a narcotic analgesic, antagonist, or agonist-antagonist whose metabolism includes conjugation with glucuronic acid. The method comprises incubating the body fluid sample at from about 60 to about 70° C., for at least about 1 hour, with 3-glucuronidase derived from Patella vulgata, and substantially increases the sensitivity of chromatographic techniques for the detection of morphine and its analogues.

Pharmacokinetics And Protein Binding Of Morphine In Horses, Joan Combie, Thomas E. Nugent, Thomas Tobin

Maxwell H. Gluck Equine Research Center Faculty Publications

Morphine could be detected in horses dosed with 0.1 mg of drug/kg of body weight for up to 48 hours in blood and 144 hours in urine. This dose of morphine elicited no observ­able effects and is a suggested an­algesic dose. Computer analysis revealed that a 3-compartment open system was the best fitting model with a serum half life of 87.9 minutes and a urine half life of 101.1 minutes. Binding to equine serum proteins was linear over a drug con­centration range of 3.88 x 10-5M to 3.50 x 10-aM and averaged 31.6%. In RBC-partitioning experiments, 78.1 % of the …

Drugs And The Performance Horse, Thomas Tobin

Veterinary Science Books

This book presents an unprecedented account of the actions, effects and consequences of drug use in performance horses. Written for horsemen by a veterinarian and world authority on equine drugs, it deals with all classes, types, and uses of drugs. Professor Tobin describes how the drugs act, how they influence performance, and the problems they may cause. He explains the drug testing process and presents the best information available on the clearance times for drugs in horses. The text is written in plain language and with a touch of humor.

Inactivated Equine Rhinopneumonitis Virus Vaccine And Use Thereof, John T. Bryans

Veterinary Science Faculty Patents

An inactivated viral vaccine for protecting horses against disease caused by equine rhinopneumonitis virus is prepared by propagating an equine rhinopneumonitis virus in a susceptible, cloned, diploid equine cell line, harvesting the resulting virus in a serum-free medium, inactivating the virus and neutralizing the inactivating agent, concentrating the virus, and adding an immunological adjuvant thereto. A vaccination program to protect horses against the equine rhinopneumonitis virus is also disclosed.

A Review Of The Pharmacology, Pharmacokinetics And Behavioral Effects Of Procaine In Thoroughbred Horses, Thomas Tobin, J. W. Blake

Maxwell H. Gluck Equine Research Center Faculty Publications

Since procaine has both local anaesthetic and central stimulant actions its presence in the blood or urine of racing horses is forbidden. After rapid intravenous injection of procaine HC1 (2.5 mg/Kg) in thoroughbred mares plasma levels of this drug fell rapidly (t 1/2 alpha = 5 min) and then more slowly (t 1/2 beta = 50.2 min). These kinetics were well fitted by a two compartment open model (Model I). This model gave an apparent Vdbeta for procaine in the horse of about 3,500 litres. Since procaine was about 45% bound to equine plasma protein this gives a true Vdbeta …