1) Heart rate reducer 
a drug that induces adrenergic blockade at either ß1- or ß2-adrenergic receptors or at both.
Betablockers are drugs that slow the heartbeat, and are used to: relieve angina, reduce high blood pressure, reduce the risk of a further heart attack, and/or regulate the heart rhythm. Some betablockers also relax the blood vessels. For further information see the HRI document on Drugs.