Effect of unfractionated and low-molecular-weight heparin on platelet aggregation and in vitro bleeding time in dogs

The aim of the present study was to examine the influence of unfractionated heparin (UFH) and low molecular weight heparin (LMWH) on the function of canine thrombocytes. This was performed by adding different concentrations of UFH or LMWH to platelet rich plasma (PRP) or blood of healthy dogs: 0.2, 0.5, 1, 2, 5, 10, 20, and 50 I.U./ml UFH or Anti-FXaU/ml LMWH, respectively (aggregation induced by thrombin additionally: 0.025, 0.05, and 0.1 I.U./ml UFH or Anti-FXaU/ml LMWH.) Platelet aggregation induced by ADP, collagen or thrombin with the BORN method (n = 11) as well as the in vitro bleeding time using the analyzer PFA-100 (n = 5) were examined. Additionally, a specific test assay for ADP induced platelet aggregation was performed which enabled an individual adjustment of the aggregation maximum at 30-40% in the control measurements (n = 6). The most prominent effect was noted in the platelet aggregation induced by thrombin. The aggregation maximum of the platelet aggregation induced by 1 I.U./ml thrombin (final concentration) was significantly lower in all of the testet UFH concentrations > or = 0.025 I.U./ml UFH in comparison to control measurements. If the aggregation was induced by 10 I.U./ml thrombin a significant reduction of the aggregation maximum was restricted to UFH concentrations > or = 0.5 I.U./ml. The addition of LMWH to canine PRP resulted in a distinct decrease (p < 0.01) of the maximum aggregation induced by 1 I.U./ml thrombin in concentrations > or = 0.2 Anti-FXaU/ml LMWH. A slight decrease of the maximum aggregation induced by collagen was only found for UFH at activities > or = 20 I.U./ml. No significant systematic influence could be demonstrated for LMWH on the aggregation induced by collagen as well as for LMWH and UFH on the platelet aggregation induced by ADP. Capillary in vitro bleeding time (closure time) was prolonged only after adding high concentrations of UFH (> or = 10 I.U./ml) and LMWH (> or = 50 Anti-FXaU/ml) to the sample material. The results document the unimportant influence of therapeutic levels of UFH and LMWH on platelet function in dogs. Therefore, the remarkable inhibition of the aggregation induced by thrombin reflects mainly the antithrombin effect.     

Effect of a high single subcutaneous dose of unfractionated heparin on platelet function in dogs

The influence of heparin on different tests of platelet function was investigated in 5 healthy dogs receiving subcutaneously 1000 I.E./kg BW of a commercial unfractionated Sodium heparin preparation. Blood samples were collected before and 4 hours after heparin injection. Besides plasma activity of heparin platelet count, capillary bleeding time with two different methods, platelet aggregation according to Breddin and to Born with the inductors ADP, collagen, and thrombin as well as in vitro bleeding time were measured. The activity of heparin four hours after the subcutaneous heparin application was 1.20 +/- 0.11 I.E./ml. Compared to the starting values no significant influence of this heparin level could be demonstrated on platelet count, platelet aggregation according to Born with the inductors ADP and collagen, platelet aggregation according to the Breddin method as well as in vitro bleeding time (p > 0.05). Only one of the two methods used for measuring the capillary bleeding time showed a slight prolongation compared to the starting value (mean = 77 sec) to 88 sec (p < 0.05). The most significant influence was seen on the platelet aggregation induced by 1 I.U./ml thrombin, whereby the aggregation maximum decreased from 92.0% (mean) to 12.2% (p < 0.001). Whereas the latter result has to be interpreted primarily as a consequence of the anti-thrombin effect of heparin, the results of the other tests in summary illustrate the clinical unimportant influence of heparin on platelet function in dogs.     

The effect of unfractionated heparin on thrombelastographic analysis in healthy dogs

Objective – To determine the effect of single and multiple doses of SQ heparin (200 U/kg) on the thrombelastogram of healthy dogs. Design – Prospective study. Setting – University research facility. Animals – Six random‐source female dogs. Interventions – Baseline parameters, including a CBC with platelet count, prothrombin time, activated partial thromboplastin time (aPTT), and antithrombin were performed. Thrombelastography (TEG) and aPTT were performed hourly for 12 hours after unfractionated heparin dosing (200 U/kg, SQ). Anti‐Xa activity was assayed at 0, 3, 6, and 8 hours. Heparin was then administered every 8 hours for 3 days. The sampling protocol on Day 4 was identical to Day 1. Measurements and Main Results – On Day 1, percentage change from baseline for TEG parameter R, as well as absolute values of K, angle, and maximum amplitude (MA) were evaluated. Statistically significant (P<0.01) prolongation of the R time and a decrease in angle and MA was seen in all dogs by hour 3. R and MA were unmeasurable for most dogs between 3 and 5 hours. All TEG tracings returned to baseline by 12 hours. Day 4 TEG tracings mimicked those on Day 1. Only 1 dog achieved aPTT values outside the reference interval on both days. Anti‐Xa activity levels increased on Day 4 but not on Day 1. Based on post hoc in vitro analysis, prolongation of R time occurred at plasma heparin levels as low as 0.075 U/mL, well below the lower limit of detection of the anti‐Xa activity level assay. Conclusions – Administration of SQ heparin results in progressive changes in the TEG tracing, with maximal change occurring 3–5 hours after dosing. The extensive prolongation of the R time also indicates that TEG may be too sensitive and limits its utility as a monitoring tool for unfractionated heparin therapy.     

Effect of oral administration of prednisolone on thyroid function in dogs

To determine the effect of oral administration of prednisolone on thyroid function, 12 healthy Beagles were given 1.1 mg of prednisolone/kg of body weight every 12 hours for 22 days after 8 days of diagnostic testing of the dogs before treatment with prednisolone. Thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) response tests were performed before treatment (days 1 and 8 of the study) and during treatment (days 21 and 28 of the study). Blood samples were collected daily at 8 AM and 2 and 8 PM to rule out normal daily hormone fluctuations as the cause of a potential decrease in serum triiodothyronine (T3), thyroxine (T4), and free T4 (fT4) concentrations. Serum T3, T4, and fT4 concentrations before treatment and 1 day and 21 days after the first prednisolone dose were compared by analyses of variance. Post-TSH and -TRH serum T3 and T4 concentrations before and during treatment were compared, using the Student t test for paired data. Oral administration of prednisolone significantly (P less than 0.005) decreased serum T3, T4, and fT4 concentrations in the 8 AM and 2 and 8 PM samples obtained 1 day and 21 days after the first prednisolone dose. Serum T4 and fT4 concentrations in 8 AM and 2 PM samples were significantly (P less than 0.05) lower 21 days after the first prednisolone dose than they were at 1 day after the first dose. Before treatment, serum T4 concentration in the 2 PM samples was significantly (P less than 0.05) higher than serum T4 concentration in 8 AM and 8 PM samples.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of oral administration of carprofen on intraocular pressure in normal dogs

The aim of this study was to determine the effect of oral administration of carprofen on intraocular pressure in normal dogs. Twelve young adult beagle dogs were randomly assigned to treatment (n = 6) or control (n = 6) groups. After an 11‐day acclimation period, the treatment group received approximately 2.2 mg/kg carprofen per os every 12 h for 7 days, and the control group received a placebo gel capsule containing no drug per os every 12 h for 7 days. Intraocular pressure (IOP) was measured by a rebound tonometer at three time points per day (8 am, 2 pm, and 8 pm) during the acclimation (days 1–11) and treatment (days 12–18) phases and for 48 h (days 19–20) after the completion of treatment. There was no statistically significant change in IOP for either eye in the dogs receiving oral carprofen during the treatment phase (days 12–18). After day 4, no significant daily IOP changes were seen in control group dogs. Carprofen administered orally every 12 h for 7 days had no effect on IOP in normal beagle dogs. An acclimation period to frequent IOP measurements of at least 5 days is necessary to establish baseline IOP values and minimize possible anxiety‐related effects on IOP measurements.     

Effect of native Lactobacillus murinus LbP2 administration on total fecal IgA in healthy dogs

The objective of the present work was to determine the effect of Lactobacillus murinus strain LbP2 on canine fecal immunoglobulin A (IgA) levels. Seven dogs were orally treated with a 3-mL suspension of L. murinus LbP2 containing 5 × 10⁹ colony-forming units on alternate days for 2 wk. Six dogs were treated with 3 mL of phosphate-buffered saline as placebo. Fecal samples were taken from the rectal ampulla on days 0 and 16, and the total canine fecal IgA concentration was determined with an immunoperoxidase assay kit. The IgA levels of individual dogs were compared with the nonparametric Wilcoxon test. Differences were considered significant when the P-value was less than 0.05. An increase in the total fecal IgA concentration was observed in the 7 dogs after treatment with L. murinus LbP2 (P = 0.01796). No differences were detected between the initial total fecal IgA values and those obtained at the end of placebo treatment. Thus, after oral administration L. murinus LbP2 showed potential immunomodulatory effects, an important property to assess in a microorganism being considered for use as a probiotic.     

Pharmacokinetics of an unfractionated heparin (Liquemin) in the dog after intravenous and subcutaneous application based on heparin activity

In this study pharmacokinetic data for the unfractionated heparin Liquemin were obtained after intravenous and subcutaneous application. Each dosage was examined in 5 healthy, adult Beagle dogs. After intravenous application of 25, 50 and 100 I.U./kg body weight heparin plasma activity of 0.65 +/- 0.15 I.U./ml (mean +/- s), 0.91 +/- 0.10 I.U./ml and 1.94 +/- 0.22 I.U./ml was measured. Subcutaneous applications of 250, 500 or 750 I.U./kg revealed maximum plasma heparin activities of 0.25 +/- 0.10, 0.60 +/- 0.15 and 1.29 +/- 0.24 I.U./ml. The maximum heparin activity in the plasma was observed after 3.8 +/- 1.1 (250 und 500 I.E./kg) or 4.0 +/- 1.0 hours (750 I.E./kg), respectively. Intravenously applicated heparin has a short terminal half-life time (t50) between 22 and 44 minutes. The t50 after subcutaneous application of heparin was distinctly longer. After 250, 500 or 750 I.U./kg the t50 was 3.7 +/- 2.4, 3.5 +/- 1.2 or 5.3 +/- 2.4 hours. Corresponding to this result a lower total clearance (Cltot) was found with increasing doses. Especially the Cltot after subcutaneous injection decreased from 2.08 +/- 0.73 ml/min/kg (250 I.E./kg) to 0.83 +/- 0.27 ml/min/kg (750 I.E./kg). The volume of distribution of heparin corresponded approximately to the plasma volume. The total bioavailability of subcutaneously administered UFH was 53-100% depending on the dosage.     

Comparative plasma dispositions of ivermectin and doramectin following subcutaneous and oral administration in dogs

This study evaluates the comparative plasma dispositions of ivermectin (IVM) and doramectin (DRM) following oral and subcutaneous administration (200 microg/kg) over a 40-day period in dogs. Twenty bitches were allocated by weight in to four groups (Groups I-IV) of five animals each. Animals in the first two groups (Groups I and II) received orally the injectable solutions of IVM and DRM, respectively, at the dose of 200 microg/kg bodyweight. The other two groups (Groups III and IV) received subcutaneously injectable solutions at the same dose rate. Blood samples were collected between 1h and 40 days after treatment and the plasma samples were analysed by high performance liquid chromatography (HPLC) using fluorescence detection. The results indicated that IVM produced a significantly higher maximum plasma concentration (C(max): 116.80+/-10.79 ng/ml) with slower absorption (t(max): 0.23+/-0.09 day) and larger area under the concentration versus time curve (AUC: 236.79+/-41.45 ng day/ml) as compared with DRM (C(max): 86.47+/-19.80 ng/ml, t(max): 0.12+/-0.05 day, AUC: 183.48+/-13.17 ng day/ml) following oral administration of both drugs; whereas no significant differences were observed on the pharmacokinetic parameters between IVM and DRM after subcutaneous administrations. In addition, subcutaneously given IVM and DRM presented a significantly lower maximum plasma concentration (C(max): 66.80+/-9.67 ng/ml and 54.78+/-11.99 ng/ml, respectively) with slower absorption (t(max): 1.40+/-1.00 day and 1.70+/-0.76 day, respectively) and larger area under the concentration versus time curve (AUC: 349.18+/-47.79 ng day/ml and 292.10+/-78.76 ng day/ml, respectively) as compared with the oral administration of IVM and DRM, respectively. No difference was observed for the terminal half-lives ((t(1/2lambda(z)) and mean residence times (MRT) of both molecules. Considering the pharmacokinetic parameters, IVM and DRM could be used by the oral or subcutaneous route for the control of parasitic infection in dogs.     

Chloramphenicol plasma levels in the dog: multiple oral and intramuscular administration

Plasma chloramphenicol levels were determined in five Greyhounds following twice daily dosing with chloramphenicol orally in capsules (100 mg/kg/day) and intramuscularly in an aqueous suspension (33 mg/kg/day). Oral administration provided an average peak mean plasma level of 20.8 μg/ml, and levels >5 μg/ml were maintained for approximately 9.7 hr after each dose. The intramuscular dose was slowly absorbed, produced low plasma levels (maximum 3.6 μg/ml) and had no repository effect. These results indicate that an oral dose rate of 100 mg/kg/day, in divided doses, may provide reasonable plasma levels in the dog, whereas the aqueous suspension of chloramphenicol, given intramuscularly at the manufacturer's suggested dose rate, may not provide plasma levels satisfactory for therapy. Résumé. On a déterminé Ies niveaux de chloramphénicol dans le plasma de cinq lévriers, à la suite d'une administration orale, deux fois par jour de capsules (100 mg/kg/jour) et d'une injection intramusculaire sous forme d'une suspension aqueuse (33 mg/kg/jour). L'administration orale a permis d'atteindre un niveau maximum moyen de plasma de 20,8 μg/ml et des niveaux >5 μg/ml etaient maintenus pendant 9,7 heures environ après l'administration de chaque dose. La dose intramusculaire était absorbée lentement, a donné lieu à des niveaux faibles de plasma (maximum 3,6 μg/ml) et a pu être éliminée. Ces résultats montrent que la dose orale de 100 mg/kg/jour, en doses divisées, peut donner lieu à des niveaux de plasma raisonnables chez le chien, alors que la suspension aqueuse de chloramphénicol, administrée par voie intramusculaire à la dose prescrite par le fabricant, ne donne pas toujours les niveaux de plasma imposés par la thérapeutique. Zusammenfassung. Die Plasmachloramphenicolkonzentration wurde in fünf Greyhounds nach der zweimal täglichen Verabreichung von Chloramphenicol oral in Kapseln (100 mg/kg/ Tag) und intramuscular in einer wässrigen Suspension (33 mg/kg/Tag) bestimmt. Die orale Verabreichung bewirkte einen höchsten mittleren Durchschnittswert der Plasmakonzentration von 20,8 μg/ml, und Konzentrationen von > 5 μg/ml wurden etwa 9,7 Stunden nach jeder Verabreichung aufrechterhalten. Die intramusculäre Dosis wurde langsam absorbiert, erzeugte niedrige Plasmakonzentrationen (maximal 3,6 μg/ml) und hatte keinen Speichereffekt. Diese Ergebnisse lassen darauf schliessen, dass eine orale Verabreichung von 100 mg/kg/Tag, auf mehrere Einzelgaben verteilt, zufriedenstellende Plasmakonzentrationen im Hund ergeben kann, während die wässrige Suspension von Chloramphenicol, intramusculär in der vom Hersteller empfohlenen Dosierung verabreicht, keine für die Therapie ausreichenden Plasmakonzentrationen ergeben könnte.     

Comparison of plasma histamine levels after intravenous administration of hydromorphone and morphine in dogs

This study compared plasma histamine concentrations, behavioral and cardiovascular parameters following intravenous administration of hydromorphone and morphine in conscious dogs. Five adult female dogs received a 15-sec bolus injection of saline, hydromorphone (0.1 and 0.2 mg/kg) or morphine (0.5 and 1.0 mg/kg) randomly at weekly intervals. Blood samples were collected from the jugular vein before and at 1, 2, 5, 15, 30, 60 and 120 min after drug administration. Plasma histamine concentration, noninvasive oscillometric blood pressure, heart rate and rhythm were evaluated. Data were analyzed with repeated measures anova and Tukey-Kramer post hoc test with a 5% significance level. Median plasma histamine increased significantly only after the higher dose of morphine. Maximum plasma histamine measured was 0.8 ng/mL after saline and, after the lower and higher doses, respectively, 10.2 and 9.7 ng/mL for hydromorphone, and 440 and 589 ng/mL for morphine. One dog became hypotensive immediately after receiving the highest dose of morphine. Occasional ventricular premature contractions occurred in one dog after both opioids and dosages. No dogs vomited or defecated, but all salivated profusely with both opioids. Neuroexcitation occurred in four dogs following each opioid. In conclusion, intravenous hydromorphone induced minimal histamine release and was well tolerated by these conscious healthy dogs.