Page 431 - Feline Cardiology

Generic Name Indications/Drug Dosage and Comments Available sizes
(Brand Name) Type Possible Routes
of Admin.

Nitroglycerin Nitrate vaso- Apply Vasodilator (preferentially venodilator in 2% ointment for
dilator 1/8”–1/4” topical ointment formulation) with variable topical use
(2–5 mm) strip (mild if any) effect. Main indication is acute HM
to hairless skin congestive heart failure, where venodilation
q 6–8 h × 24– increases venous “reservoir” capacity,
48 h (pinna or reducing intravascular hydrostatic pressure
medial thigh); and reducing further immediate edema
or 12 h on, formation. Wear gloves when handling/
12 h off applying, to avoid human transdermal
alternating for absorption (vasodilation causes headaches,
3 days hypotension). Nitrate tolerance signifies loss
of efficacy after approximately 48 h of
continuous treatment. Prevent patient from
licking site of application. No studies have
evaluated it in cats; anecdotally appears
unlikely to be harmful. An intravenous
formula used as a CRI is available for
balanced arterial and venous dilation, but has
not been studied in cats, and nitroprusside is
typically chosen for the purpose of potent
balanced vasodilation in the acute setting.
Nitroprusside Nitrate vaso- 0.5–5 mcg/kg/ Acute potent balanced (arterial and venous) 25 mg/ml
(Nitropress [H]) dilator min vasodilation, typically as part of management Inj
IV CRI, of critical congestive heart failure, as an HM
adjusted PRN afterload and preload reducer. In the cat, the
high prevalence of hypertrophic
cardiomyopathy (where any excess vasodilation
is detrimental via eliciting reflex sinus
tachycardia [causing less diastolic filling time,
more myocardial oxygen consumption, etc.])
means this drug is used infrequently. Constant
(q 5–10 minutes) blood pressure monitoring via
Doppler or direct arterial line is necessary for
confirming normotension during treatment.
Loss of efficacy after 48 h (nitrate tolerance), so
used intermittently if at all. Cyanide poisoning
is possible if high doses used over 1–2 days.
Norepinephrine Catecholamine 0.05–2 mcg/kg/ Main indication is critical hypotension 1 mg/ml
(Levophed [H], min IV CRI, (principal drug action is alpha-agonism). Inj
noradrenaline) adjusted Requires constant blood pressure monitoring HM
PRN during infusion, and dose titration to desired
effect.
Norvasc—see
Amlodipine
Drug Formulary

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