Inotrope

An inotrope is an agent that alters the force of muscular contractions. More specifically, inotropy refers to the contractility of the heart. Inotropes are therefore medications used to alter the strength of heart muscle contraction.

Positive Inotropes: These agents increase the force of myocardial contraction. This leads to increased cardiac output. Positive inotropes achieve this by increasing intracellular calcium concentration, which facilitates interaction between actin and myosin in the muscle fibers. Examples include catecholamines (like dopamine and epinephrine), cardiac glycosides (like digoxin), and phosphodiesterase inhibitors (like milrinone). They are commonly used in the treatment of heart failure, cardiogenic shock, and other conditions characterized by reduced cardiac output.

Negative Inotropes: These agents decrease the force of myocardial contraction. While this might seem counterintuitive, negative inotropes can be beneficial in certain conditions, such as hypertrophic cardiomyopathy, where excessive contractility contributes to symptoms. They also reduce myocardial oxygen demand. Examples include beta-blockers (like metoprolol) and calcium channel blockers (like verapamil).