Administration In Sheep Research Articles

Фармакокинетика и динамика выведения остаточных количеств амоксициллина при внутримышечном и подкожном введении овцам

Фармакокинетика и динамика выведения остаточных количеств амоксициллина при внутримышечном и подкожном введении овцам

Fosfatriclaben, a prodrug of triclabendazole: Preparation, stability, and fasciolicidal activity of three new intramuscular formulations

In this study, we present the preparation, stability, and in vivo fasciolicidal activity of three new intramuscular formulations in sheep of a prodrug based on triclabendazole, named fosfatriclaben. The new formulations were ready-to-use aqueous solutions with volumes recommended for intramuscular administration in sheep. The use of poloxamers (P-407 and P-188) and polysorbates (PS-20 and PS-80) in the new formulations improved the aqueous solubility of fosfatriclaben by 8-fold at pH 7.4. High-performance liquid chromatography with UV detection was used to evaluate the stability of fosfatriclaben in the three formulations. High recovery (> 90%) of fosfatriclaben was found for all formulations after exposure at 57 ± 2 °C for 50 h. The three intramuscular formulations showed high fasciolicidal activity at a dose of 6 mg/kg, which was equivalent to the triclabendazole content. The fasciolicidal activity of fosfatriclaben was similar to commercial oral (Fasimec®) and intramuscular (Endovet®) triclabendazole formulations at a dose of 12 mg/kg. In the in vivo experiments, all formulations administered intramuscularly reduced egg excretion by 100%, and formulations F1, F2, and F3 presented fasciolicidal activities of 100%, 100%, and 99.6%, respectively.

Expansion of platform physiologically-based pharmacokinetic model for monoclonal antibodies towards different preclinical species: cats, sheep, and dogs.

Monoclonal antibodies (mAbs) are becoming an important therapeutic option in veterinary medicine, and understanding the pharmacokinetic (PK) of mAbs in higher-order animal species is also important for human drug development. To better understand the PK of mAbs in these animals, here we have expanded a platform physiological-based pharmacokinetic (PBPK) model to characterize the disposition of mAbs in three different preclinical species: cats, sheep, and dogs. We obtained PK data for mAbs and physiological parameters for the three different species from the literature. We were able to describe the PK of mAbs following intravenous (IV) or subcutaneous administration in cats, IV administration in sheep, and IV administration dogs reasonably well by fixing the physiological parameters and just estimating the parameters related to the binding of mAbs to the neonatal Fc receptor. The platform PBPK model presented here provides a quantitative tool to predict the plasma PK of mAbs in dogs, cats, and sheep. The model can also predict mAb PK in different tissues where the site of action might be located. As such, the mAb PBPK model presented here can facilitate the discovery, development, and preclinical-to-clinical translation of mAbs for veterinary and human medicine. The model can also be modified in the future to account for more detailed compartments for certain organs, different pathophysiology in the animals, and target-mediated drug disposition.

Breed-related plasma disposition and faecal excretion of eprinomectin after subcutaneous administration in sheep

Eprinomectin is a member of the avermectin family, exhibiting a broad-spectrum activity as well as a minimal elimination by milk in lactating animals. It is known that pharmacokinetic parameters are fundamental to the rational use of a drug and food safety and these parameters are influenced by different factors. The study aimed to evaluate the plasma dispositions faecal excretion profiles of eprinomectin in Awassi and Cukurova Meat Sheep (CMS) following subcutaneous administration at a dose of 0.2 mg/kg body weight. Heparinized blood and faecal samples were collected at various times between 1 h and 21 days. The plasma and faecal concentrations of eprinomectin were analysed by high-performance liquid chromatography using a fluorescence detector following a liquid-liquid phase extraction procedure. It was observed that eprinomectin concentrations in plasma and faeces were significantly affected by breed. The plasma Tlast, Cmax, AUClast, AUC0-∞, AUMClast, and AUMC0-∞ parameters of eprinomectin were significantly higher (P < 0.014) in Awassi sheep (13.88 ± 1.55 d, 29.81 ± 9.03 ng/mL, 108.05 ± 12.36 ng.d/mL, 116.07 ± 9.35 ng.d/mL, 347.77 ± 40.33 ng.d2/mL, and 486.56 ± 166.25 ng.d2/mL, respectively) compared to CMS (10.00 ± 0.00 d, 19.76 ± 4.51 ng/mL, 64.81 ± 10.54 ng.d/mL, 69.41 ± 10.98 ng.d/mL, 192.00 ± 36.12 ng.d2/mL, and 254.19 ± 52.55 ng.d2/mL, respectively). Similarly, the faecal Cmax, AUClast, and AUC0-∞ parameters of eprinomectin were detected significantly greater in Awassi sheep (3373.27 ± 1499.88 ng/g, 12,428.38 ± 2969.69 ng.d/g, and 12,668.39 ± 3047.32 ng.d/g, respectively) than CMS (2192.57 ± 323.99 ng/g, 9622.78 ± 1356.47 ng.d/g, and 9737.12 ± 1390.92 ng.d/g, respectively). The pharmacokinetic differences of eprinomectin observed between sheep breeds could be attributable to physiological characteristics such as the body fat composition of each breed. In addition, the faecal eprinomectin concentrations were about 110 times higher than those in the plasma of both sheep breeds. In line with the data obtained, eprinomectin found in high concentration in faeces may cause ecotoxicological risk for dung fauna and aquatic organisms having high sensitivity to this compound.

Age-related changes in the pharmacokinetics of meloxicam after intravenous administration in sheep.

The pharmacokinetics of meloxicam was studied in 1-, 6-, and 12-month-old sheep following a single intravenous (i.v.) dose of 1 mg/kg. The experiments were carried out when the Romanov sheep were 1 month old (7.93 ± 0.91 kg), 6 months old (27.47 ± 4.91 kg), and 12 months old (37.10 ± 3.64 kg). Meloxicam concentration in plasma was determined by high-performance liquid chromatography and the data collected were evaluated by non-compartmental kinetic analysis. Meloxicam was detected in the plasma up to 72 h following i.v. administration in all age groups. The volume of distribution at steady state (Vdss ) and total body clearance (ClT ) were significantly higher in 1-month-old (304.87 mL/kg and 16.57 mL/h/kg) than in 12-month-old (193.43 mL/kg and 10.50 mL/h/kg) sheep. The area under the concentration-time curve from 0 to 72 h value of meloxicam was lower in 1-month-old (58.51 h*μg/mL) compared to 12-month-old (92.59 h*μg/mL) sheep. There was no difference in t1/2ʎz value in different age groups. The body extraction ratio values for meloxicam ranged from 0.0186 to 0.0719 after i.v. administration in all age groups. Meloxicam showed an increase in plasma concentration and a decrease in Vdss and ClT in 12-month-old compared to 1-month-old sheep. Compared to 1-month-old and 12-month-old sheep, there was no difference in these parameters in 6-month-old sheep. Because the age of sheep has an influence on the pharmacokinetics of meloxicam, dosage apparently may need to be adjusted for age.

Liposomes are Poorly Absorbed via Lung Lymph After Inhaled Administration in Sheep.

Enhancing the delivery of therapeutic agents to the lung lymph, including drugs, transfection agents, vaccine antigens and vectors, has the potential to significantly improve the treatment and prevention of a range of lung-related illnesses. One way in which lymphatic delivery can be optimized is via the use of nanomaterial-based carriers, such as liposomes. After inhaled delivery however, there is conflicting information in the literature regarding whether nanomaterials can sufficiently access the lung lymphatics to have a therapeutic benefit, in large part due to a lack of reliable quantitative pharmacokinetic data. The aim of this work was to quantitatively evaluate the pulmonary lymphatic pharmacokinetics of a model nanomaterial-based drug delivery system (HSPC liposomes) in caudal mediastinal lymph duct cannulated sheep after nebulized administration to the lungs. Liposomes were labelled with 3H-phosphatidylcholine to facilitate evaluation of pharmacokinetics and biodistribution in biological samples. While nanomaterials administered to the lungs may access the lymphatics via direct absorption from the airways or after initial uptake by alveolar macrophages, only 0.3 and 0.001% of the 3H-lipid dose was recovered in lung lymph fluid and lymph cell pellets (containing immune cells) respectively over 5 days. This suggests limited lymphatic access of liposomes, despite apparent pulmonary bioavailability of the 3H-lipid being approximately 17%, likely a result of absorption of liberated 3H-lipid after breakdown of the liposome in the presence of lung surfactant. Similarly, biodistribution of 3H in the mediastinal lymph node was insignificant after 5 days. These data suggest that liposomes, that are normally absorbed via the lymphatics after interstitial administration, do not access the lung lymphatics after inhaled administration. Alternate approaches to maximize the lung lymphatic delivery of drugs and other therapeutics need to be identified.

Improvement of Albendazole Bioavailability with Menbutone Administration in Sheep.

Simple SummaryAnthelmintic drugs are among those most widely used in veterinary practice. The development of resistance to these drugs is a widespread problem, especially in small ruminants, and represents a serious threat to animal production. Thus, new possibilities to use the available pharmacological groups in a more efficient way should be explored. The objective of this study was to assess the pharmacokinetic interaction between a benzimidazole (albendazole, ABZ) and a choleretic drug (menbutone, MEN) in sheep, and it may result in greater effectivity of this drug against nematode parasites. Plasma concentrations of ABZSO (ABZ active metabolite) were higher when ABZ was administered with MEN. The proposed interaction is a simple, safe, and inexpensive way of increasing the effectivity of this anthelmintic widely used in livestock.The pharmacokinetic interaction between a benzimidazole (albendazole, ABZ) and a choleretic drug (menbutone, MEN) was evaluated in sheep. The plasma disposition of albendazole sulfoxide (ABZSO, active metabolite) and albendazole sulfone (ABZSO2, inactive metabolite) was investigated following an oral administration of albendazole (ABZ) (5 mg/kg) alone or with menbutone (MEN) (intramuscular, 10 mg/kg). Blood samples were collected over 3 days post-treatment, and drug plasma concentrations were measured by high performance liquid chromatography (HPLC). ABZSO was measured from 0.5 to 48 h, and ABZSO2 from 2 to 60 h. No parent drug was detected at any sampling time. Mean maximum plasma concentration (Cmax) and the area under the plasma concentration-time curve (AUC) were 12.8% and 21.5% higher for ABZSO when ABZ and MEN were administered together, which indicates a significant increase in the amount absorbed. The rate of absorption was not modified, with similar values for the time to reach Cmax (tmax) (11.5 h with ABZ + MEN and 10.7 h with ABZ treatment), although no significant differences were observed for these latter pharmacokinetic parameters. Regarding ABZSO2, Cmax, AUC and tmax values were similar after both treatments (ABZ or ABZ + MEN). The results obtained indicate that co-administration of ABZ and MEN may be an interesting and practical option to increase the efficacy of this anthelmintic.

Concentrations of vatinoxan and xylazine in plasma, cerebrospinal fluid and brain tissue following intravenous administration in sheep

ObjectivesTo investigate the extent of vatinoxan distribution into sheep brain, and whether vatinoxan influences brain concentrations of xylazine; and to examine the utility of cerebrospinal fluid (CSF) as a surrogate of brain tissue concentrations for vatinoxan and xylazine. Study designRandomised, blinded, experimental study. AnimalsA total of 14 adult female sheep. MethodsSheep were randomly allocated into two equal groups and premedicated with either intravenous (IV) vatinoxan (750 μg kg–1, VX) or saline (SX) administered 10 minutes before IV xylazine (500 μg kg–1). Sedation was subjectively assessed at selected intervals before and after treatments. At 10 minutes after xylazine administration, a venous blood sample was collected and the sheep were immediately euthanised with IV pentobarbital (100 mg kg–1). Plasma, CSF and brain tissues were harvested, and concentrations of vatinoxan and xylazine were quantified using liquid chromatography–tandem mass spectrometry. Drug ratios were then calculated and the data were analysed as appropriate. ResultsThe brain-to-plasma and CSF-to-plasma ratios of vatinoxan were 0.06 ± 0.013 and 0.05 ± 0.01 (mean ± standard deviation), respectively. Xylazine brain concentrations were not significantly different (835 ± 262 versus 1029 ± 297 ng g–1 in groups VX and SX, respectively) and were approximately 15-fold higher than those in plasma. The CSF-to-brain ratio of vatinoxan was 0.8 ± 0.2, whereas xylazine concentrations in the brain were approximately 17-fold greater than those in CSF, with and without vatinoxan. Conclusions and clinical relevanceVatinoxan did not significantly affect sedation with xylazine or the concentrations of xylazine in the brain. CSF is not a good predictor of xylazine concentrations in the brain, whereas vatinoxan concentrations were concordant between the brain and CSF, using the dosages in this study.

Pharmacokinetics and bioavailability of tildipirosin following intravenous and subcutaneous administration in sheep.

Tildipirosin is a semi-synthetic macrolide antibiotic commonly used in cattle and swine to treat bacterial pneumonia. The objective of this study was to investigate the pharmacokinetic profile of tildipirosin after a single intravenous (i.v.) and subcutaneous (s.c.) administration in healthy lambs. Eighteen lambs were randomly divided into three groups (n=6 each). Lambs received a single s.c. dose of tildipirosin at 4 and 6mg/kg b.w. in group 1 and 2, respectively. Lambs in group 3 received a single i.v. dose of tildipirosin at 4mg/kg b.w. Blood samples were collected at 0, 0.5, 0.75, 1.5, 2, 3, 4, 6, 8, 10, 24, 36, 48hr, and every 24hr to day 21, and thereafter at day 28 posttildipirosin administration. The plasma concentrations of tildipirosin were determined using high-performance liquid chromatography with tandem mass spectrometry detection (LC⁄MS⁄MS). All lambs appeared to tolerate both the intravenous and subcutaneous injection of tildipirosin. Following i.v. administration, the elimination half-life (T1/2 ), mean residence time (MRT), volume of distribution (Vd/F), and total body clearance (Cl/F) were 119.6±9.0hr, 281.9±25.7hr, 521.1±107.2 L, and 2.9±0.5L/hr, respectively. No significant differences in Cmax (657.0±142.8 and 754.6±227.1ng/ml), Tmax (1.21±0.38 and 1.35±0.44hr), T1/2 (144±17.5, 156.5±33.4hr), and MRT (262.0±30.2 and 250.6±54.5hr) were found in tildipirosin after s.c. dosing at 4 and 6mg/kg b.w., respectively. The absolute bioavailability (F) of tildipirosin was 71.5% and 75.3% after s.c. administration of 4 and 6mg/kg b.w., respectively. In conclusion, tildipirosin was rapidly absorbed and slowly eliminated after a single s.c. administration in healthy lambs. Tildipirosin could be used for the treatment and prevention of respiratory bacterial infections in sheep. However, further in vitro and in vivo studies to determine the efficacy and safety are warranted. To our knowledge, this is the first study to determine the tildipirosin pharmacokinetic parameters in sheep plasma.

Pharmacokinetics of Tildipirosin in Ewes after Intravenous, Intramuscular and Subcutaneous Administration.

Simple SummaryPneumonia is a significant cause of death in sheep flocks. Thus, antibiotics are essential for the treatment of bacterial pneumonia to reduce morbidity and mortality, but few drugs are specifically labeled for clinical use in sheep. Many of the antimicrobial clinical prescriptions that occur in sheep are classified as extra-label use, with dosage, administration frequency, indications, and drug withdrawal times usually being extrapolated from information reported in other species. Thus, the objective of this study was to determine the disposition kinetics of tildipirosin after intravenous, intramuscular, and subcutaneous administration in sheep. Throughout the experiment, all ewes were healthy and no adverse reactions were recorded. The apparent volume of distribution was high, indicating a wide distribution in the body, which can be attributed to a significant fraction of tildipirosin inside the cells, and its expected activity against intracellular bacteria. Following intramuscular administration, tildipirosin was rapidly absorbed even to a greater extent when compared to subcutaneous administration. Most of the adsorbed tildipirosin after intramuscular and subcutaneous administrations were available in the body (>70%). In brief, the excellent tolerability of this formulation and the suitable disposition of tildipirosin in the body makes it an alternative for sheep use, in conditions where the administration of antibiotics is needed to observe desired effects with the benefits of scant manipulation of animals.A single-dose disposition kinetics for tildipirosin was evaluated in clinically healthy ewes (n = 6) after intravenous (IV), intramuscular (IM), and subcutaneous (SC) administration of a commercial formulation. Tildipirosin concentrations were determined by high-performance liquid chromatography with ultraviolet detection. Plasma concentration-time data was calculated by non-compartmental pharmacokinetic methods. The apparent volume of distribution (Vz) of tildipirosin after IV administration was 5.36 ± 0.57 L/kg suggesting a wide distribution in tissues and inside the cells. The elimination half-life (t½λz) was 17.16 ± 2.25, 23.90 ± 6.99 and 43.19 ± 5.17 h after IV, IM and SC administration, respectively. Following IM administration, tildipirosin was rapidly absorbed (tmax = 0.62 ± 0.10 h) even to a greater extent than after SC administration. Time to reach peak concentration (tmax) and peak plasma concentrations (Cmax) differed significantly, but both parameters showed a more significant variability after SC than after IM administration. Bioavailabilities after extravascular administration were high (>70%). Therefore, given general adverse reactions that were not observed in any ewe and favourable pharmacokinetics, tildipirosin could be effective in treating bacterial infections in sheep.

Influences of tolfenamic acid and flunixin meglumine on the disposition kinetics of levofloxacin in sheep.

The pharmacokinetics of levofloxacin (4 mg/kg), administered both alone and in combination with tolfenamic acid (2 mg/kg) and flunixin meglumine (2.2 mg/kg), was established after intravenous administration in sheep. Plasma levofloxacin concentrations were assayed by high-performance liquid chromatography and analysed according to the two-compartment open model. Following the administration of levofloxacin alone, the mean distribution half-life, elimination half-life, total clearance, volume of distribution at steady state and area under the plasma concentration-time curve were 0.20 h, 1.82 h, 0.39 L/h/kg, 0.96 L/kg and 10.40 h × µg/mL, respectively. Tolfenamic acid and flunixin meglumine caused a slow elimination and increased plasma concentrations of levofloxacin in combination administration. Levofloxacin, with an alteration in the dosage regimen, can be used effectively with tolfenamic acid and flunixin meglumine for the therapy of infections and inflammatory conditions in sheep.

Pharmacokinetics of levosulpiride after single-dose administration by different routes in sheep (Ovis aries Linnaeus)

Levosulpiride (LSP) is the (−)-enantiomer of sulpiride and might represent a valid alternative to the current drugs used for the synchronization in small ruminants. The aim of this study was to provide the pharmacokinetic profile of LSP after intravenous (IV), intramuscular (IM) and oral (PO) administration in sheep. Six healthy female sheep underwent a randomized cross over study design with a wash out period of 1 week. Each animal at the completion of the study received 50 mg of LSP by IV, IM and PO administrations. Plasma samples were collected prior and up to 24 h and, after the extraction procedure, samples were analysed by HPLC with spectrofluorometric detection. LSP concentrations were quantifiable until 10 and 8 h after IV and IM administration, respectively. After PO administration plasma concentrations were low and quantified until 4 h in all the animals. Clearance (121.5 ml/Kg) was fast and volume of distribution (241 ml/Kg h) small; half-life was short and very similar after both IV (1.80 h) and IM (1.66 h) administrations. The bioavailability after IM and PO was high (about 70%) and extremely low (about 6%), respectively. IV and IM groups showed a good correlation between AUC and the LSP dose express in mg/Kg, but very low correlation was found for the PO route. In conclusion, PO administration of LSP is not recommended in sheep while IV and IM administration show comparable PK profiles.

Pharmacokinetics of the Protein Microbicide 5P12-RANTES in Sheep following Single-Dose Vaginal Gel Administration.

5P12-RANTES, a chemokine analogue that potently blocks the HIV CCR5 coreceptor, is being developed as both a vaginal and rectal microbicide for prevention of sexual transmission of HIV. Here, we report the first pharmacokinetic data for 5P12-RANTES following single-dose vaginal gel administration in sheep. Aqueous gel formulations containing low (1.24-mg/ml), intermediate (6.18-mg/ml), and high (32.0-mg/ml; suspension-type gel) concentrations of 5P12-RANTES were assessed via rheology, syringeability, and in vitro release testing. Following vaginal gel administration to sheep, 5P12-RANTES concentrations were measured in vaginal fluid, vaginal tissue, and serum over a 96-h period. All gels showed non-Newtonian pseudoplastic behavior, with the high-concentration gels exhibiting a greater viscosity and cohesive structure than the intermediate- and low-concentration gels. In in vitro release testing, >90% 5P12-RANTES was released from the low- and intermediate-concentration gels after 72 h. For the high-concentration gel, ∼50% 5P12-RANTES was detected, attributed to protein denaturation during lyophilization and/or subsequent solvation of the protein within the gel matrix. In sheep, 5P12-RANTES concentrations in vaginal fluid, vaginal tissue, and serum increased in a dose-dependent manner. The highest concentrations were measured in vaginal fluid (105 to 107 ng/ml), followed by vaginal tissue (104 to 106 ng/ml). Both of these concentration ranges are several orders of magnitude above the reported half-maximal inhibitory concentrations. The lowest concentration was measured in serum (<102 ng/ml). The 5P12-RANTES pharmacokinetic data are similar to those reported previously for other candidate microbicides. These data, coupled with 5P12-RANTES's potency at picomolar concentrations, its strong barrier to resistance, and the full protection that it was observed to provide in a rhesus macaque vaginal challenge model, support the continued development of 5P12-RANTES as a microbicide.

Pharmacokinetics of a new ivermectin/praziquantel suspension after intramuscular administration in sheep

A new oil suspension containing 0.10% ivermectin (IVM) and 15% praziquantel (PZQ) (Tivm+pzq) for intramuscular injection was developed for sheep, and its pharmacokinetics was investigated in sheep. The quality of the new product met the technical standards set by the Ministry of Agriculture of the People’s Republic of China. In pharmacokinetics, the commercially available single-component products approved by the Chinese Ministry of Agriculture and widely used in the livestock industry in China were selected as reference products (Rivm and Rpzq). The results showed that all of the IVM pharmacokinetic parameters of Tivm+pzq were similar to those of the reference. However, after adminstraion of Tivm+pzq, mean residence time (MRT) and plasma elimination half-life (t1/2z) were 20.36h and 11.65h, which were 2.61 and 3.22 times longer than those of Rpzq (7.81h and 3.62h). In summary, the MRT and t1/2z of PZQ in Tivm+pzq were prolonged and IVM pharmacokinetic parameters were similar to commerical product, therefore the new injection may be an alternative choice for sheep to control parasites sensitive to IVM and PZQ.

Comparative pharmacokinetics of enrofloxacin, danofloxacin and marbofloxacin following intramuscular administration in sheep

The aim of this study was to determine and compare the pharmacokinetic profiles of enrofloxacin (ENF), danofloxacin (DNF) and marbofloxacin (MBF) after intramuscular administration in sheep. A total of 18 cross-bred healthy sheep were used in the study. The animals were allocated into three groups of six such that the mean weight of animals in each group was similar. In Group I (ENF) was given intramuscularly at a dose rate of 2.5mg/kg, in Group II (DNF) was given intramuscularly at a dose rate of 1.25mg/kg and in Group III (MBF) was given intramuscularly at a dose rate of 2mg/kg. Heparinized blood samples were collected between 0.5 and 48h after treatment.The results indicated that MBF produced a significantly higher maximum plasma concentration (Cmax:1.43±0.50μg/ml) with quicker absorption (tmax: 1.00±0.00) and larger area under the concentration vs. time curve (AUC: 8.36±2.58μgh/ml) as compared with ENF (Cmax: 0.88±0.13μg/ml, tmax: 1.66±0.47, AUC: 5.64±2.52μgh/ml) and DNF (Cmax: 0.70±0.08μg/ml, tmax: 1.33±0.23, AUC: 3.00±0.65μgh/ml) following intramuscular administration of drugs. Similarly, the mean residence time (MRT: 6.37±0.59) and the half-life (t1/2λz: 9.50±1.86) was significantly longer MBF group than ENF (MRT: 4.54±0.79, t1/2λz: 3.06±0.39) and DNF (MRT: 4.04±0.17, t1/2λz: 3.52±0.22) groups.In this study, regarding ENF, DNF and MBF, three of fluoroquinolones antibacterial agents with common usages in sheep at recommended doses, with intramuscular administration were compared in pharmacokinetic parameters and as a result, marbofloxacin was found significantly the highest in rate to reach the maximum concentration in plasma.

Pharmacokinetics and antinociceptive effects of tramadol and its metabolite O-desmethyltramadol following intravenous administration in sheep

Although sheep are widely used as an experimental model for various surgical procedures there is a paucity of data on the pharmacokinetics and efficacy of analgesic drugs in this species. The aims of this study were to investigate the pharmacokinetics of intravenously (IV) administered tramadol and its active metabolite O-desmethyltramadol (M1) and to assess the mechanical antinociceptive effects in sheep.In a prospective, randomized, blinded study, six healthy adult sheep were given 4 and 6 mg/kg tramadol and saline IV in a cross-over design with a 2-week wash-out period. At predetermined time points blood samples were collected and physiological parameters and mechanical nociceptive threshold (MNT) values were recorded. The analytical determination of tramadol and M1 was performed using high performance liquid chromatography. Pharmacokinetic parameters fitted a two- and a non-compartmental model for tramadol and M1, respectively. Normally distributed data were analysed by a repeated mixed linear model.Plasma concentration vs. time profiles of tramadol and M1 were similar after the two doses. Tramadol and M1 plasma levels decreased rapidly in the systemic circulation, with both undetectable after 6 h following drug administration. Physiological parameters did not differ between groups; MNT values were not statistically significant between groups at any time point. It was concluded that although tramadol and M1 concentrations in plasma were above the human minimum analgesic concentration after both treatments, no mechanical antinociceptive effects of tramadol were reported. Further studies are warranted to assess the analgesic efficacy of tramadol in sheep.

A (14)C-leucine absorption, distribution, metabolism and excretion (ADME) study in adult Sprague-Dawley rat reveals β-hydroxy-β-methylbutyrate as a metabolite.

Leucine is an essential branched-chain amino acid that acts as a substrate for protein synthesis and as a signaling molecule. Leucine not incorporated into muscle protein is ultimately oxidized through intermediates such as β-hydroxy-β-methylbutyrate (HMB) which itself is reported to enhance muscle mass and function in rats and humans. HMB has been reported in the plasma following oral leucine administration in sheep and pigs but not in Sprague–Dawley rats, the standard preclinical model. Therefore, we conducted radiolabeled absorption, distribution, metabolism and excretion (ADME) studies in rats using a low (3 mg/kg) or high dose (1,000 mg/kg) of 14C-leucine. Blood, tissue, and urine samples were analyzed for 14C-leucine and its metabolites by HPLC–MS. Our results show for the first time that 14C-HMB appears in plasma and urine of rats following an oral dose of 14C-leucine. 14C-leucine appears in plasma as 14C-α-ketoisocaproic acid (KIC) with a slower time course than 14C-HMB, a putative product of KIC. Further, two novel metabolites of leucine were detected in urine, N-acetyl leucine and glycyl leucine. Mass balance studies demonstrate that excretory routes accounted for no more than 0.9 % of the radiolabel and approximately 61 % of the dose was recovered in the carcass. Approximately 65 % of the dose was recovered in total, suggesting that approximately one-third of the leucine dose is oxidized to CO2. In conclusion, this study demonstrates endogenous production of HMB from leucine in adult rats, a standard preclinical model used to guide design of clinical trials in nutrition.

Administration of Dalteparin in Sheep for Cardiac Interventions

Background: Ovine models are widely used in cardiovascular research because of their comparability to the human cardiovascular system. Sheep are well available, easy to handle, mostly indulgent and anesthesia is similar in comparison with humans. Nevertheless, differences are known concerning the composition of blood constituents and rheological properties as well as oral administration and resorption of some drugs. Amongst those, platelet inhibitors, vitamin K antagonists and low molecular weight heparin (LMWH) exhibit different pharmacodynamics. During implantation of heart valves it is essential to reduce the coagulation ability with the aim of preventing thromboembolic events. Concurrently, it is essential to avoid any bleeding complications by accumulation of anticoagulants. In most sheep experiments for cardiovascular research the anticoagulant regime follows the guidelines for humans in the lack of knowledge about specific ovine requirements. To date, no standardized anticoagulation strategy for the ovine model using LMWH is established. This study aimed to establish a reliable regime for LMWH administration in sheep at high risk of thromboembolic events. Target was an anti-factor-Xa (AFXa) level of 0.6 to 0.8 units known from human studies to be preventive and therapeutic at moderate to high risk of thromboembolism. The primary aim of the study was to improve the antithrombotic management after pulmonary valve implantation in three sheep. These results were then applied and re-evaluated during minimally-invasive heart valve implantation within four sheep. Materials and Methods: Seven adult grey horned heath ewes (mean body weight 43.4 kg) were included in this study prior to heart valve implantation. The study design regarded interventional heart valve implantation as an intermediaterisk situation for thromboembolic events. During a period of two weeks a weekly incremental dose of dalteparin was administered once a day at 7 AM subcutaneously. Venous blood samples were collected three times per day to monitor the response over 24 hours. The first measurement of anti-factor-Xa was conducted immediately before administration of heparin (baseline). The second measurement was conducted four hours and the last measurement 12 hours after administration. The starting dose in week 1 was 250 IU (international units). The following dose in week 2 comprised 350 IU. The dose with an anti-factor-Xa level closest to 0.6 to 0.8 units was tested in four sheep in which a pulmonary valve was implanted transvenously. Results: Data showed a peak concentration of anti-factor-Xa four hours after administration. 12 hours after injection the level had decreased to 50% of the peak level and 24 hours after administration there was no measurable level of anti-factor-Xa left. Sheep needed 350 units dalteparin once daily to achieve an anti-factor-Xa level of 0.6 to 0.8 units. No thromboembolic event occurred in those four sheep which received the weight- adapted dose of dalteparin (350 IU/ day) according to the results of the dose-finding study after the implantation of a transcatheter pulmonary valve. The macroscopic and histologic results showed no signs of any thrombotic affection of the graft. Conclusions: Sheep require much greater quantities of dalteparin (LMWH) than humans to achieve comparable blood levels of anti-factor-Xa.

Population Pharmacokinetics of Amitriptyline After Intrathecal, Epidural, and Intravenous Administration in Sheep.

Amitriptyline (AMI) is a lipophilic, tricyclic antidepressant with analgesic properties that could potentially be used for epidural (EPI) analgesia. However, no pharmacokinetic data are available for AMI in spinal spaces. The objective of this study was to evaluate the spinal disposition and intrathecal (IT) bioavailability of AMI after IT and EPI administration. Six Lacaune ewes received 3 consecutive administrations of AMI. They initially received 10 mg of AMI administered intravenously, then 5 mg of AMI administered intrathecally, and 50 mg of AMI injected into the EPI space. Consecutive administrations were separated by intervals of 2 hours. A simultaneous microdialysis technique was used to determine the EPI and IT concentrations of AMI. Population analysis with S-ADAPT software was used to evaluate the pharmacokinetic parameters. Following intravenous administration, the clearance and central compartment (Vc) in plasma were 1.32 L/min and 147 L, respectively. Concentration-time profiles for the IT and EPI compartments were highly variable after transmeningeal diffusion. The IT Vc after IT administration and the EPI Vc after EPI administration were 2.4 and 48.9 mL, respectively. Less AMI transferred from the EPI to the IT space than from the IT to the EPI compartment, with bioavailabilities of 1.3% and 55%, respectively. Simultaneous population analysis for AMI demonstrated differences in EPI and IT pharmacokinetics following the EPI and IT administration of this drug. The IT bioavailability of AMI after EPI administration is relatively low.

A highly water soluble benzimidazole derivative useful for the treatment of fasciolosis

This study describes the synthesis of compound (7), a highly hydrosoluble phosphonooxymethyl prodrug of compound alpha (4). Compound (7) improved the aqueous solubility of its precursor compound (4) by 50,000 times and it is stable at neutral pH. The prodrug showed faciolicidal activity when evaluated in vitro against excysted Fasciola hepatica metacercariae. The in vivo evaluation of (7) was carried out via oral, intramuscular and subcutaneous administration in sheep artificially infected with F. hepatica metacercariae. At an intramuscular dose of 4mg/kg, the activity of (7) was similar to that of compound alpha (4) at an oral dose of 15mg/kg.