Inhibition of Exercise-Induced Bronchoconstriction by MK-571, a Potent Leukotriene D4–Receptor Antagonist

To the Editor: Manning et al. (Dec. 20 issue)¹ elegantly demonstrated that pretreatment with MK-571, a selective leukotriene D₄—receptor antagonist, markedly attenuated exercise-induced bronchoconstriction in patients with asthma. However, we have some reservations about their methods. The authors claim that treatment with MK-571 afforded almost complete protection in 5 of the 12 subjects (Subjects 2, 3, 4, 6, and 8) studied. However, except for Subject 3, the importance of the protection in these subjects may be questioned. The degree of exercise-induced bronchoconstriction in these four subjects during both the placebo and active-drug phases was less than 15.