Drug formulary

Here are some of the drugs we use in cardiology, along with our preferred doses. For more detailed information regarding uses, contra-indications and side-effects the reader should consult appropriate texts or product data sheets.

Many of these drugs or doses are off-licence but are supported by published research and/or clinical experience. In all cases owners should be informed that the drug is used off license and the relative benefits and possible side effects should be discussed. However, to offer the animal the best care we feel that off license drug use is essential in selected cases.

These recommendations and dose rates are are just guidelines. Appropriate use of all medications is the responsibility of the attending veterinary surgeon.

Abbreviations
VT	Ventricular tachycardia
PO	Per os (by mouth)
IV	Intravenous
SC	Sub-cutaneous
K+	Potassium
AF	Atrial fibrillation
SVT	Supraventricular tachycardia
DCM	Dilated cardiomyopathy
DMVD	Degenerative mitral valve disease
CHF	Congestive heart failure
q8, q12 etc.	Every 8 hours, 12 hours etc.
CRI	Constant rate infusion
BP	Blood pressure
CNS	Central nervous system

Vasodilators

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Benazepril	ACE Inhibitor	D&C	Dogs & Cats: 0.25–0.5 mg/kg PO q24	Treatment of CHF secondary to DMVD/DCM	Prerenal azotaemia (particularly in animals with hypotension or existing azotaemia), hypotension (rare). Use cautiously in animals with existing hypotension.
Enalapril	ACE Inhibitor	D&C	Dogs & Cats: 0.5 mg/kg PO q24	Treatment of CHF secondary to DMVD/DCM	As for benazepril.
Hydralazine	Arteriolar Vasodilator	D&C	Dogs: 0.5–3 mg/kg PO q8-12. Start at low dose. Monitor response.	Severe mitral regurgitation to unload the left ventricle	Monitor BP; may cause weakness, vomiting.
Amlodipine	Calcium Channel Blocker	D&C	Dogs: 0.05–0.1 mg/kg PO q12–24. Cats: 0.625–1.25 mg/cat PO q12-24.	Care in severe left-sided CHF. Possible systemic hypotension, vomiting, dizziness, raised intraocular pressure. Limited experience in cats.	Hypertension; acute mitral regurgitation to unload the left ventricle
Sildenafil	Pulmonary Vasodilator	D&C	Dogs: 0.5–3 mg/kg PO q8-24. Cats: 6.25mg/cat PO q12-24	Pulmonary hypertension (confirmed by echo)	Care in severe left-sided CHF. Possible systemic hypotension, vomiting, dizziness, raised intraocular pressure. Limited experience in cats.

Positive inotropes

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Pimobendan	Inodilator	D (& C)	Dogs: 0.25–0.3 mg/kg PO q12 (1hr before food). Cats: ~0.3 mg/kg PO q12-24.	CHF (DMVD/DCM), preclinical Stage B2 in dogs, preclinical DCM in Doberman pinschers (and likely other breeds), pulmonary hypertension (second-line). Off-label use in cats.	Well tolerated in cats and dogs; avoid in HCM/obstructions; occasional GI upset. Very little evidence base for use in cats.
Dobutamine	Positive inotrope	D&C	Dogs: 2.5-5mcg/kg/min CRI. Cats: 1-5mcg/kg/min CRI	Short term inotropic support for patients with heart failure due to systolic dysfunction.	ICU monitoring; arrhythmia risk.

Diuretics

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Furosemide	Loop Diuretic	D&C	Dogs: (acute) 2–4 mg/kg IV/IM q1–2; (chronic) 1–4 mg/kg PO q8-12. Cats: (acute) 1-2mg/kg IV/IM q2-4; (chronic) 1-3mg/kg PO q8-12.	CHF	Prerenal azotaemia, hypokalemia, dehydration
Torasemide	Loop Diuretic	D&C	Dogs: 0.1–0.6 mg/kg PO q 24hrs. Usually given divided q12. Most dogs stabilise at 0.3mg/kg/day. To transition dogs we typically start at 13th to 15th of the current daily frusemide dose. Cats: 0.75-1.5mg/cat PO q24. To transition in cats dose at 1/20th current daily frusemide dose.	CHF	Potent diuretic; careful monitoring of potassium levels and renal parameters advised
Amiloride + Hydrochlorothiazide	Thiazide diuretic + K-sparing diuretic	D&C	Dogs: 0.5–4 mg/kg PO q 12-24. Start low end of dose range. Cats: 1-2mg/kg PO q24-48	CHF (refractory)	Azotaemia risk. Close monitoring of renal parameters advised. Hyperglycaemia, hypokalaemia, hyponatraemia and hypochloraemia.

Anti-arrhythmics

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Digoxin	Anti-arrhythmic, negative chronotrope	D	Dogs: 3-5mcg/kg PO q12 based on lean bodyweight. Start lower end of dose range particularly larger dogs.	SVT rate control, primarily used to control AF rate in dogs in combination with diltiazem.	Can be proarrhythmic; anorexia, vomiting, diarrhoea, depression.
Atropine	Positive chronotrope	D&C	0.04 mg/kg IM (or IV)	Bradyarrhythmia (vagal)	Tachycardia, dry mouth, constipation. IV administration can precipitate further bradycardia so we generally only use IM.
Theophylline	Positive chronotrope	D	Dogs: 10mg/kg PO q12	Bradyarrhythmias, sinus arrest	CNS stimulation, GI upset.
Terbutaline	Positive chronotrope	D&C	Dogs: 0.2mg/kg PO q 8-12. Cats: 0.625mg/cat PO q 8-12.	Chronotrope + bronchodilation	Excitement, tremors, drug interactions
Cilostazol	Positive chronotrope (PDEIII inhibitor)	D	Dogs: 5-10mg/kg PO q12.	Management of sick sinus syndrome and heart block.	Limited experience.
Lidocaine	Antiarrhythmics (Class I)	D&C	Dogs: 2 mg/kg IV bolus followed by 0.025-0.1mg/kg/min. Cats: 0.25-2.0mg/kg IV followed by CRI 0.01-0.04mg/kg/min.	Ventricular arrhythmias (VT); vagally-mediated AF.	Seizures, CNS signs, caution in cats.
Mexiletine	Antiarrhythmics (Class I)	D	Dogs: 5–8 mg/kg PO q8-12	Ventricular arrhythmias.	Nausea, anorexia, vomiting, depression.
Atenolol	Beta-blocker (antiarrhythmic class II)	D&C	Dogs: 0.2–2.0 mg/kg PO q12. Cats: 6.25-12.5 mg/cat PO q12-24.	Tachycardia, obstructive lesions	Start low; can worsen CHF so typically withdrawn in advanced B2 disease in cats. No evidence in cats that improves outcome in HCM cases.
Sotalol	Beta-blocker + K-channel blocker (Class II & III)	D&C	Dogs: 0.5–3 mg/kg PO q12. Cats:10-20 mg/cat PO q12	Ventricular and supraventricular arrhythmias.	Can decrease heart rate, stroke volume and cardiac output worsening CHF, potentially proarrhythmic
Amiodarone	K+ channel blocker (Class III)	D	Dogs: 10 mg/kg PO q12 for 7d, then 5–7.5 mg/kg q12 for 14 days then 7.5mg/kg PO q24 ongoing.	Refractory VT/SVT	Anorexia, hepatotoxicity, iatrogenic hypothyroidism, pulmonary fibrosis, ocular and dermal lesions.
Diltiazem	Calcium channel blocker (Class IV)	D&C	Dogs: 0.5-3mg/kg PO q12 modified release. Cats: 10 mg/cat PO q8-12.	AF, SVT rate control	Bradycardia.
Ivabradine	If channel blocker	D	Dogs: 0.4-0.6mg/kg PO q12.	Focal junctional tachycardia with isorhythmic AV dissociation.	Limited experience.

Anti-thrombotics

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Clopidogrel	Adenosine phosphate receptor antagonist (anti-platelet-aggregator)	D&C	Dogs: 1.1–3 mg/kg PO q24. Cats 18.75mg/cat PO q24.	Thrombosis prevention	Occasional bleeding (epistaxis, GI). Use recompounded preparations as very bitter taste (do not split tablets in cats).
Aspirin	Thromboxane-A2 inhibition (anti-platelet activation/aggregation)	C	Cats 75mg PO q72.	Thrombosis prevention	Don’t give with other NSAIDs or steroids. Caution in patients with hypotension or renal dysfunction.
Rivaroxaban	Factor Xa inhibitor	D&C	Dogs: 1–2 mg/kg PO q24. Cats: 0.5–1.0 mg/kg PO q24	Thrombosis prevention	Potential for bleeding disorders. Limited experience.

Anti-tussives

Drug name	Drug class	Species (Dog, Cat)	Dose and route of administration	Indications	Precautions / side effects
Diphenoxylate & atropine	Opioid	D	Dogs: 0.2-0.5mg/kg PO q12	Effective cough suppression	Very difficult to source in UK currently (July 2025).
Codeine	Opioid	D	Dogs: 0.5-2mg/kg PO q12	Modest cough suppression	Becoming difficult to source in UK (July 2025).