Medications Commonly Used for Heart Failure

This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian.

Enalapril (Enacard, Vasotec), Benazepril (Lotensin), Lisinopril (Prinivil, Zestril).

These drugs are angiotensin converting enzyme (ACE) inhibitors. ACE inhibitors dilate blood vessels and moderate excess hormone activity that occurs with heart failure, resulting in less resistance in the blood vessels against which the heart must pump. These drugs have improved clinical signs of heart failure and prolonged survival in several studies. An ACE inhibitor may be the only drug needed early in the disease process.

The specific drug used and the individual pet’s disease influence the dose and frequency of administration recommended. Enalapril, Benazepril, and Lisinopril can be given either on an empty stomach or with food.

Adverse effects of ACE inhibitors could include vomiting or diarrhea, deterioration of kidney function, elevation of blood potassium levels, or low blood pressure (hypotension). Other adverse effects that have been reported in people taking the drug include skin rash or itchiness, taste impairment, and certain abnormalities in blood and urine tests.

Furosemide (Lasix, Disal, others)

Furosemide is the diuretic ("water pill") most often used to promote the loss of excess fluid in patients with congestive heart failure. The dosage varies depending on the clinical situation and the patient’s response, but generally the lowest dose that controls signs of congestion is used for chronic therapy. Signs of heart failure decompensation and congestion such as a persistent increase in resting respiratory rate or recurrence of cough may respond to an (often temporary) increase in furosemide dose. In most cases (check with your veterinarian first), if your pet has been doing well on heart failure medication but subsequently develops signs of congestion again, you can increase the dose or add an extra dose of furosemide for a day or so. If this becomes necessary, be sure to discuss each event with your veterinarian – reevaluation additional tests, and/or other therapy adjustments may be necessary.

Adverse effects of furosemide are usually related to excessive fluid and/or electrolyte losses (especially potassium) resulting in dehydration and weakness.

Digoxin (Lanoxin, Cardoxin, Cardoxin LS)

Digoxin is a positive inotropic (refers to the ability to contract) agent that mildly strengthens heart muscle contraction. It also moderates the excess neurohormonal activity that occurs with heart failure and helps control certain heart rhythm abnormalities. Digoxin is not necessarily indicated in every case of heart failure.

Digoxin is best given on an empty stomach since food as well as antacids and kaolin-pectin compounds decrease drug absorption.

The toxic effects of digoxin can be serious and even life threatening so the drug must be carefully dosed. Monitoring of the drug concentration in the blood is recommended. This is often done 7 to 10 days after starting the drug or after making a dosage change. The blood sample is taken 8 to 10 hours after a dose of the drug has been given. Reduced kidney function, dehydration, loss of lean muscle mass, low blood potassium levels, and certain drugs increase the potential for digoxin toxicity.

Adverse/toxic effects can include heart rhythm disturbances, loss of appetite, vomiting, diarrhea, and depression. If you suspect digoxin toxicity, stop giving the digoxin and contact your veterinarian immediately.

Diltiazem (Cardizem, Cardizem CD, Dilacor XR)

Diltiazem is a calcium channel blocker that is used to help control certain heart rhythm disturbances and to promote heart muscle relaxation in hypertrophic cardiomyopathy (especially in cats). In dogs with atrial fibrillation (a rapid, irregular, abnormal heart rhythm) it may be used with digoxin to slow the rate of the heartbeat.

Adverse effects are uncommon at standard doses but can include decreased appetite, slow heart rate, and rarely, other stomach/intestinal or heart effects.

Atenolol (Tenormin) and Propranolol (Inderal)

These drugs, among others, are called beta-blockers. They antagonize the effects of the sympathetic nervous system, and thereby slow the heart rate, reduce the heart’s oxygen demand, and help control certain heart rhythm disturbances. A beta-blocker may be used with digoxin to slow the heartbeat in dogs with atrial fibrillation. A beta-blocker may be useful in cats with hypertrophic cardiomyopathy as well as animals with certain congenital heart malformations.

Adverse effects are usually related to excessive beta blockade and individual animals vary considerably in their response; thus, low doses are used initially and slowly increased to effect. Dosage and frequency of administration also depends on the drug used. Adverse effects can include excessively slow heart rate, worsening of heart failure, low blood pressure, bronchospasm (more likely with Propranolol), depressed attitude, and possibly masking early signs of low blood sugar (especially in diabetics).

Nitroglycerin (NitroBid, Nitrol) and Isosorbide dinitrate (Isordil, Sorbitrate)

These drugs are prescribed sometimes to dilate veins and help reduce congestion. Nitroglycerin ointment is applied to the animal’s skin, often in the groin or armpit area or inside the earflap.

Gloves or an application paper should be used to apply this medicine to your pet. Do not get this medicine on your skin because you will absorb it also.

Isosorbide comes in pill form.

Spironolactone (Aldactone)

Spironolactone is another diuretic that works by a different mechanism from furosemide. It is sometimes used in addition to furosemide in the treatment of chronic, refractory congestive heart failure. Adverse effects relate to excess potassium retention and stomach/intestinal upset. If used with an ACE inhibitor or oral potassium supplement, blood potassium must be monitored closely.

Chlorthiazide (Diuril) or Hydrochlorothiazide (Hydrodiuril)

These drugs are diuretics that are sometimes used with furosemide for refractory heart failure. Adverse effects are usually related to excessive fluid and/or electrolyte losses.

This Pet Health Topic was written by O. L. Nelson, DVM, MS, Diplomate ACVIM (Cardiology & Internal Medicine) Washington State University.

Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.

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