The bronchodilatory effects of inhaled beta2 agonists and anti-muscarinic drugs are the mainstay of symptomatic treatment of asthma and Chronic Obstructive Pulmonary Disease (COPD). A new approach is to combine both pharmacological approaches in a single molecule - ie a dual pharmacophore. It will be necessary to explore the relative contribution of the beta2 agonist versus anti-muscarinic bronchodilator properties of such a molecule. One way to do that is to block one of the components. Inhibition of beta2 agonist-mediated bronchodilatation by the non-selective beta-blocker propranolol is an established experimental method. Therefore this method may be useful in exploring the pharmacology of a dual pharmacophore.