Small Animal Clinical Pharmacology - CYF MEDICAL DISTRIBUTION

ANTICOAGULANTS
be used to treat bradyarrhythmias. Most of the authors’
experience is with the use of terbutaline in dogs with
vagally mediated sinus bradycardia and sinus arrest. In
these dogs, terbutaline can be effective at increasing the
sinus rate and eradicating the sinus pauses.
Formulations and dose rates
Terbutaline is supplied as tablets. The dose must be titrated, usually
starting with 2.5 mg q.8 h per dog PO and increasing as needed. Side
effects include hyperactivity and gastrointestinal disturbances.
Adverse effects
Terbutaline should be used cautiously, if at all, in dogs
with mitral regurgitation due to myxomatous mitral
valve degeneration. The authors have not noted complications
with this drug in this setting but have noted
acute pulmonary edema, possibly secondary to ruptured
chordae tendineae, in dogs treated with salbutamol (albuterol),
another β 2 -agonist.
ANTICOAGULANTS
EXAMPLES
Unfractionated heparin, low molecular weight heparin,
warfarin
Unfractionated heparin
Unfractionated heparin (heparin), a water-soluble
mucopolysaccharide, was first discovered in 1916. It
was named heparin because of its abundance in liver. It
was initially used to prevent the clotting of shed blood,
which eventually led to its use in vivo to treat venous
thrombosis.
Clinical applications
Heparin is used in the treatment of disseminated intravascular
coagulation (DIC) and thromboembolic disease.
Its prophylactic use has been recommended in severe
immune-mediated hemolytic anemia (IMHA) to decrease
the potentially harmful effects of thromboplastic substances
released from hemolyzed red blood cells and to
minimize the danger of developing pulmonary thromboembolism.
However, controlled studies are lacking
and the prophylactic use of heparin in IMHA is not
universally accepted.
Heparin has been used in the management of cats
with thromboembolic disease secondary to hypertrophic
or restrictive cardiomyopathy. It has been given
with acepromazine as an empirical, unproven treatment
to promote collateral vasodilation and prevent growth
of the thrombus.
In the management of DIC, heparin is used to activate
antithrombin in blood products prior to administration
to the patient. Antithrombin, an α 2 -globulin acute-phase
protein produced in the liver, is the natural inhibitor of
serine proteases in the coagulation pathways (factors II,
IX, X, XI, XII and kallikrein). It has little or no activity
against factor VII. When a patient is in a hypercoagulable
state and prothrombin is being actively converted
to thrombin, the antithrombin concentration will be
low (