As you have likely noticed in your pharmacology courses, there is a long list of cardiac medications that can be used to treat a wide variety of cardiac conditions. 

If you find yourself working in veterinary cardiology, you will likely become familiar with many of these medications.

If you opt to work in general practice, though, you really only need to be  highly familiar with a handful of cardiac medications. While you may occasionally encounter patients taking other medications, it will likely be rare enough that you can consult a reference as needed.

Learning these three cardiology medications will help you answer most of your client’s cardiology medication questions:

1. Furosemide

Furosemide, or Lasix^®, is commonly used in small animal patients with congestive heart failure (CHF). It is a potent diuretic, acting on the Loop of Henle to remove excess fluid from the body. 

Furosemide can be administered orally or parenterally. It has a wide dosing range; most veterinarians start pets on a relatively low oral dose (except in severe cases of CHF) and titrate the dose up. If a pet presents in acute CHF, high doses of injectable furosemide may be used in the acute stage, with a gradual dose taper and transition to oral medications. Furosemide dosing ranges vary from 1-8 mg/kg in dogs and 0.5-5 mg/kg in cats. 

Side effects of furosemide include nausea, vomiting, and dehydration (with azotemia). Hypochloremia, hypokalemia, and hyperglycemia may also occur. Patients receiving furosemide need frequent blood work monitoring because there is often a balancing act between removing enough fluid to prevent CHF while maintaining adequate hydration to support kidney function.

2. Pimobendan 

Pimobendan, or Vetmedin^®, is a positive inotrope and arteriodilator that is labeled for the treatment of CHF in dogs. It has also been used off-label in cats. 

Pimobendan is administered by mouth twice daily, on an empty stomach. The labeled dose in dogs is 0.5 mg/kg/day divided into two doses. Similar dosing is often recommended for cats. 

Side effects include inappetance, lethargy, and diarrhea. In the case of an accidental overdose, hypotension may also be observed.

3. Enalapril 

Enalapril, or Enacard^®, is an ACE inhibitor that is often used to manage CHF in dogs and cats. This medication reduces circulating levels of angiotensin II (a vasoconstrictor) and aldosterone (which promotes sodium retention). Most veterinarians consider enalapril to be less valuable than furosemide and pimobendan in managing CHF, but it is a helpful adjunct medication that should be used when possible. (If owner finances or side effects require discontinuing one of these three medications, enalapril is often the medication that is discontinued.) 

Enalapril is administered orally and may be given once or twice daily. Dogs and cats typically receive doses of 0.5-1 mg/kg/day. 

Side effects of enalapril include inappetance, vomiting, and diarrhea. Rarely, the combination of enalapril and furosemide can result in acute renal failure; owners should monitor their pets closely when starting treatment with these medications. Patients receiving enalapril need regular blood work monitoring. 

Other Cardiac Medications

While furosemide, pimobendan, and enalapril are the most common cardiac medications in small animal general practice, you may also see patients that are taking other cardiac medications. While you likely do not need a high degree of familiarity with these medications, it may be helpful if you can at least recognize them by drug type. 

Hydrochlorothiazide and spironolactone are diuretics. These medications are often used as adjuncts to furosemide if furosemide alone is not providing effective diuresis. 

Many of the other cardiac medications you will encounter are antiarrhythmics.  Quinidine, procainamide, lidocaine, propranolol, atenolol, carvedilol, sotalol, amiodarone, diltiazem, amlodipine, digoxin, and mexiletine are all used to control cardiac arrhythmias. 

Clopridogel (Plavix^®) may be used as an anticoagulant in cats at risk of saddle thrombus, and sildenafil (Viagra^®) may be used to treat pulmonary hypertension. 

Summary 

While the number of cardiac medications available can seem overwhelming, focusing on the three medications that are commonly used to treat CHF will prepare you to address most cardiology patients that you will encounter in your first job as a general practice vet tech.