What Is a Negative Inotrope?

Inotropes are a broad category of medications that affect the heart's contractions and beat. A drug is a negative inotrope if it slows the heartbeat and makes the contraction force weaker. This action benefits those with conditions such as hypertension or arrhythmia. Three medicinal classes belong to this category — beta-blockers, calcium antagonists, and antiarrhythmics — each with its own treatment pros and cons. Treatment with a negative inotrope depends on the condition and the side effects of the prospective medication.

There is a proportional relationship between heartbeat and contraction force. Fast heartbeats require more force to get the blood circulated through the heart. Negative inotrope medications create the opposite condition, where a slow heartbeat is able to pump the blood with less force.

Hypertension is a common health condition that may be treated with a negative inotrope. Caused by the increased flow of blood in the arteries, hypertension benefits from the weakening contractions. Tachycardia, a type of arrhythmia where the heart beats too quickly, can also become balanced with this medication. Other treatment conditions include chronic heart failure and angina.

Beta blockers are the first type of negative inotrope. They are primarily prescribed for hypertension because they lower blood pressure by reducing adrenaline in the heart, and medications that belong to this class include atenolol, metoprolol and bisoprolol. Common side effects include extremity coldness, dizziness, and blurry vision, and potential serious side effects include swelling, bruising, and ease of bleeding. Contraindications may exist for patients with diabetes, lung disease, or upcoming surgeries.

Calcium antagonists can treat hypertension, angina and arrhythmia, and have a negative inotrope effect when they block calcium that would go into the heart's cells and vessels. This action relaxes the vessels and slows blood flow, requiring fewer beats and contractions. Medications in this class include verapamil, felodipine and amlodipine. Common side effects include dizziness, low blood pressure, and nausea, while a potential serious effect includes liver damage. If these medications are given to a patient with a heart condition that has progressed too far, the negative antagonist can actually cause more damage.

The final negative inotrope class is antiarrhythmics. These medications help treat arrhythmia, or improper beats of the heart, by normalizing the heartbeat and making it less likely to speed up. Flecainide, procainamide and disopyramide are examples of medications. Antiarrhythmics are not advised for patients who have previously suffered heart attacks. Lesser side effects include dizziness, nausea, and shortness of breath, while the strong negative inotrope effect can cause another, potentially fatal, heart attack.