Different bronchodilating effect of salmeterol and formoterol in an adult asthmatic.

New long-acting beta 2-adrenoceptor agonists, salmeterol and formoterol, have recently been marketed for treatment of asthma, but studies comparing the clinical efficacy of the two drugs have not been published. We report on an asthmatic patient who had a striking difference in bronchodilating effect of the two drugs, formoterol being more effective than salmeterol both in immediate response and during long-term treatment. Although, both formoterol and salmeterol are highly selective for the beta 2-adrenoceptors (comparable to salbutamol and terbutaline), differences in their chemical structure suggest differences in their mechanisms of action or receptor specificity. The clinical implication of our observation appears to be that a less favourable response in an individual patient to one of the long-acting beta 2-agonists should not preclude a trial with another. Future studies comparing the clinical efficacy of formoterol and salmeterol should probably also address the question of responders and nonresponders to these drugs; and furthermore, seek to explore a possible relationship to inherited variance in beta 2-receptors.