Inotropes are a group of medications used to improve the heart's ability to pump blood throughout the body. The medications cause the heart to squeeze tighter to send more oxygenated blood to the body's organs and tissues. They are often used in hospital settings to support the cardiovascular condition of people who have congestive heart failure, shock, and after surgery.
This article will discuss the different kinds of inotropes and their side effects.
Types of Inotropic Drugs and How They Work
Inotropic drugs are medications used for people whose hearts are not pumping effectively. They can be broken down into two categories: positive inotropes and negative inotropes.
When healthcare providers talk about inotropic agents, they are always referring to positive inotropic agents. Negative inotropic effects are considered side effects of certain drugs. When drugs with negative inotropic effects are used in people whose hearts are not pumping effectively, these effects must be considered.
Positive inotropes are medications that increase the heart's contractility, which is the force of the heart muscle to push blood out of the heart's chambers. These medications allow the heart to squeeze tighter and make each heartbeat more effective at pushing blood through the body, improving cardiac output. Cardiac output is the amount of blood the heart pumps every minute.
People whose hearts are weakened from illness or health conditions may need positive inotropes. These drugs can help in the following circumstances:
Cardiogenic shock (very low blood pressure because the heart is not pumping enough blood to the body)
Congestive heart failure (the heart does not provide enough blood flow to meet the body's needs)
Cardiomyopathy (a condition in which the heart muscle is enlarged, thickened, and stiffened)
Inotropic drugs are medications ordered for people who are in the hospital and are very sick. The medication is typically given through an intravenous (IV) line at a continuous rate.
A patient needing inotropic drugs has a cardiac output that is low, meaning the heart is not pumping enough blood to the body. If this problem is not resolved quickly, it can lead to serious complications or death.
Negative inotropes are medications that slow down a person's heart rate and reduce contractility. They reduce the stress on the heart by allowing it to beat with less force.
Conditions that may require a negative inotrope include:
Hypertension (high blood pressure)
Chest pain (angina)
Irregular heart rhythm
Previous heart attack
Negative inotropes can be given through an IV line or as an oral medication, depending on the severity of the patient's condition.
Which Drugs Are Inotropes?
A healthcare provider can choose between many different inotropic drugs. Their decision on which medication will be based on the health history and current medical needs of the person being treated.
Medications that are classified as positive inotropes include:
Medications that have significant negative inotropic effects include:
Calcium channel blockers: Amlodipine, nicardipine, verapamil
Antiarrhythmics: Amiodarone, procainamide, lidocaine
Beta-blockers are often administered to people with heart failure to reduce cardiac stress and thus improve the efficiency of the heartbeat.
Calcium channel blockers and antiarrhthmics are not given to a person to produce a negative inotropic effect. Instead, their negative inotropy is a side effect that must be considered when treating the person with other therapies.
Uses of Inotropic Drugs
Inotropic drugs can treat people whose heart does not pump effectively. Pumping difficulties can result from an illness, a medical condition, or as a result of surgery.
Positive inotropes are given to a person who is very sick. A healthcare provider will choose a medication that provides the necessary effect.
Another medication class called vasopressors is often used in conjunction with positive inotropes. These medications cause the blood vessels to tighten or constrict (make narrower). This increases blood pressure and the return of blood to the heart.
Inotropes are strong medications that change how the heart pumps. These medications can have side effects depending on how the medication works within the body. Potential side effects include:
Hypertension or hypotension (low blood pressure)
Increased heart rate
Electrolyte changes (higher or lower concentrations of important charged molecules in the blood)
Decreased blood flow to the heart (myocardial ischemia)
What Is Inotropic vs. Chronotropic?
An inotropic effect is when medication changes the contractility of the heart. A positive inotrope increases contractility. A negative inotrope decreases contractility.
A chronotropic effect is when medication changes the heart rate (how fast the heart beats). A positive chronotrope increases heart rate. A negative chronotrope decreases heart rate.
A person's cardiac output depends upon both the heart's contractility and heart rate. To increase cardiac output, which is the amount of blood pumped throughout the body, a healthcare provider may use medications that increase contractility and heart rate.
Inotropes are medications used to change the force with which the heart contracts. Positive inotropes increase the heart's contractility and are used when someone's heart is not pumping enough blood throughout the body.
Negative inotropes decrease the heart's contractility and are used to reduce stress on the heart. Inotropes can produce side effects. A healthcare provider will weigh the benefit vs. the risk for the person being treated.