Page 1354 - Problem-Based Feline Medicine

1346 PART 16 DRUGS

with doses used in dogs (2.2 mg/kg and 1.1 mg/kg on Dermal atrophy has also been reported in a cat treated
alternate days). with phenytoin.
In addition to dose-related marrow toxicity, idiosyn-
cratic severe, irreversible, fatal leukopenia and throm-
PROPYLTHIOURACIL
bocytopenia has also been reported in cats.
They may lack thiopurine methyl transferase (TPMT), Clinical action
the enzyme necessary to degrade the 6-mercaptopurine Anti-thyroid.
active metabolite of azathioprine although this is not
proven.
Why shouldn’t it be used in cats?
The recommended dose in cats (0.3 mg/kg) and the sin- Adverse effects from PTU include lethargy, weakness,
gle size tablet of 25 mg means that reformulation is anorexia and bleeding diathesis due to induction of
necessary as clients must not split the coating of cyto- immune-mediated disease.
toxic drugs.
Nine of 105 cats developed serious side effects in a
Chlorambucil is a better alternative in cats. study of cats with hyperthyroidism.
Methimazole or carbimazole are the preferred drugs of
BENZOCAINE choice for treating feline hyperthyroidism.

Clinical action
Topical local anesthetic.
SCOPOLAMINE

Why shouldn’t it be used in cats? Clinical action
Topical application can cause methemoglobinemia, Anti-emetic.
laryngeal application can cause laryngeal edema.
Why shouldn’t it be used in cats?
CISPLATIN Short half life.

Clinical action Tendency to cause behavioral changes.
Cytotoxic.

SODIUM PHOSPHATE
Why shouldn’t it be used in cats?
Cisplatin causes fatal, acute pulmonary edema in cats
Clinical action
and should not be used in this species.
Retention enemas.
PHENYTOIN Why shouldn’t it be used in cats?
Active ingredients can be rapidly absorbed through the
Clinical action rectal mucosa resulting in potentially fatal hyperphos-
Anti-convulsant. phatemia, hypocalcemia, hypernatremia, hyperosmo-
lality and metabolic acidosis.
Why shouldn’t it be used in cats? Clinical signs observed include depression, ataxia,
vomiting and bloody diarrhea.
Prolonged half life (>40 hours) compared to dogs
resulting in rapid accumulation and development of Dehydrated or debilitated cats are particularly sus-
adverse signs such as sedation, ataxia and anorexia. ceptible.