Xamoterol is a

cardiac stimulant A cardiac stimulant is a substance which acts as a stimulant of the heart – e.g., via positive chronotropic or inotropic An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the fo ...

. It works by binding to the β₁ adrenergic receptor. It is a 3rd generation adrenergic β receptor

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonistic e ...

. It provides cardiac stimulation at rest but it acts as a blocker during exercise.

References

Beta1-adrenergic agonists Cardiac stimulants Inotropic agents 4-Morpholinyl compunds Phenol ethers Phenols {{cardiovascular-drug-stub