Objective—To evaluate SC administration of unfractionated
heparin (UFH) in accordance with a dosing
regimen for high-dose treatment in dogs.
Animals—10 healthy adult Beagles.
Procedures—Two groups of dogs (5 dogs/group)
were given 6 injections of heparin (500 units of
UFH/kg of body weight, SC) at intervals of 8 (experiment
1) and 12 (experiment 2) hours. Blood samples
were collected before and 4 hours after heparin injections
to determine amidolytic heparin activity, activated
partial thromboplastin time (APTT), thrombin time,
antithrombin activity, platelet count, and Hct.
Results—For experiments 1 and 2, mean ± SD
heparin activities before (experiment 1, 1.32 ± 0.20
U/ml; experiment 2, 0.69 ± 0.174 U/ml) and 4 hours
after the last heparin injection (experiment 1, 1.71 ±
0.30 U/ml; experiment 2, 1.10 ± 0.30 U/ml) were higher
than values calculated for the regimen used in
experiment 1. Results of the investigated thrombin
time test system with low thrombin activity were frequently
beyond the measurement range, even with
UFH activities ≥ 0.6 U/ml. Moreover, a severe
decrease of antithrombin activity became evident during
both experiments (eg, in experiment 2 from 95.6
± 4.8 to 59.2 ± 6.6%). In each treatment group, 2
dogs developed hematomas.
Conclusions and Clinical Relevance—Calculations
of the course of heparin activity after a single injection
do not result in a reliable dosing regimen for highdose
heparin treatment in dogs. High-dose treatment
must be monitored for each dog. Thrombin time measured
with low thrombin activity is unsuitable for this
purpose. (Am J Vet Res 2001;62:1887–1891)
OBJECTIVE To determine a treatment protocol for SC administration of dalteparin to cats on the basis of currently available detailed pharmacokinetic data and to assess the effect of SC administration of dalteparin to cats on coagulation variables such as activated partial thromboplastin time (aPTT), thrombin time, and results for thromboelastometry, compared with effects on anti–activated coagulation factor X (anti-Xa) activity.
ANIMALS 6 healthy domestic shorthair cats.
PROCEDURES Cats received 14 injections of dalteparin (75 anti-Xa U/kg, SC) at 6-hour intervals. Blood samples were collected before and 2 hours after the first and second injections on days 1, 2, and 4. Anti-Xa activity was measured by use of a chromogenic substrate assay, aPTT and thrombin time were measured by use of an automated coagulometer, and viscoelastic measurements were obtained with thromboelastrometry.
RESULTS 2 hours after the second injection, the target peak anti-Xa activity range of 0.5 to 1.0 U/mL was achieved in all cats, whereas median trough values remained below this range. Peak anti-Xa activity had only minimal effects on coagulation variables; the maximum median ratio for aPTT (in relationship to the value before the first dalteparin injection) was 1.23.
CONCLUSIONS AND CLINICAL RELEVANCE Results of this study indicated that this treatment protocol resulted in reproducible anti-Xa activity in cats that was mostly within the targeted peak range of anti-Xa activity recommended for humans. Treatment in accordance with this protocol may not require routine coagulation monitoring of cats, but this must be confirmed in feline patients.