Page 532 - Problem-Based Feline Medicine

524 PART 7 SICK CAT WITH SPECIFIC SIGNS

Sulfonamides, metronidazole and possibly fluoro- Presumably quantification of vitamin K dependent fac-
quinolones may exacerbate vitamim K antagonist tor activities could also demonstrate a deficiency.
rodenticide poisoning.
Actinomycin D, an anti-tumor antibiotic, may be a NON-STEROIDAL ANTI-INFLAMMATORY
vitamin K antagonist, but the clinical relevance of this DRUGS
in cats is not known.
Classical signs
● None (with respect to bleeding).
Diagnosis
Abnormal bleeding associated with antibiotic ther-
Clinical signs
apy and improvement upon withdrawing therapy.
Non-steroidal anti-inflammatory drugs (NSAIDs) are
If vitamin K deficiency or antagonism is causing bleed-
being prescribed with increasing frequency for analge-
ing, hemostatic testing reveals prolonged PT ± prolonged
sia in cats.
ACT and aPTT, and improvement in coagulopathy
with vitamin K1 injection (assuming normal liver Similar to aspirin, non-selective NSAIDs impair
function). platelet function by inhibition of cyclooxygenase-1.
● Sub-clinical effect may be documented by PIVKA This may result in prolonged bleeding times and
time and quantification of vitamin K dependent fac- increased surgical hemorrhage in humans and dogs.
tor activities using techniques similar to factor VIII The effect on bleeding time in cats has not been well
quantification in hemophilia A. investigated, but, given that aspirin has minimal effects
on BMBT in the cat, NSAIDs are also likely to have
minimal effects.
ANTI-THYROID DRUGS
Diagnosis
Classical signs
History of drug therapy.
● Epistaxis, oral hemorrhages.
● Prolonged bleeding following procedures. If a cat receiving one of these drugs has abnormal
bleeding, another cause of the bleeding should be ruled
out.
Clinical signs

Spontaneous bleeding (e.g. epistaxis, oral hemor- MISCELLANEOUS DRUGS
rhages, melena) and excessive bleeding (e.g. following
venepuncture or surgery) due to anti-thyroid drugs Classical signs
(propylthiouracil, methimazole, carbimazole) is usually
● None (with respect to bleeding).
due to thrombocytopenia caused by peripheral
destruction or megakaryocytic hypoplasia.

Methimazole and carbimazole may interfere with acti-
Clinical signs
vation of the vitamin K-dependent clotting factors II,
VII, IX and X. This effect in cats is minimal – PIVKA Numerous drugs inhibit platelet aggregation in various
time may be increased, but an increase in PT is unlikely. species in vitro. These include:
● Anesthetic and sedative agents: acepromazine,
diazepam, ketamine, propofol and halothane, but
Diagnosis
not barbiturates or isoflurane. Acepromazine and
Increased PIVKA time compared to baseline in a hyper- propofol do not inhibit platelet function in normal
thyroid cat being treated with an anti-thyroid drug. dogs.