Comparative And Synergistic Effects Of Caffeine And Albuterol On The Severity Of Exercise-induced Bronchoconstriction.

Abstract

PURPOSE: Previous research has demonstrated a beneficial effect of caffeine on preventing exercise-induced bronchoconstriction (EIB). Therefore, the main aim of this study was extend previous published findings that have demonstrated a beneficial effect of caffeine on EIB by evaluating the comparative and synergistic effects of caffeine and albuterol (b2-agonist) on the severity of EIB. METHODS: Ten asthmatic subjects with EIB participated in a randomized, double-blind double-dummy crossover study. One hour before an exercise challenge, each subject was given 0, 3, 6, or 9mg/kg of caffeine or placebo mixed in a flavored sugar drink. Fifteen minutes before the exercise bout, an inhaler containing either albuterol (180μg) or placebo was administered to each subject. Pulmonary function tests were conducted pre- and post-exercise (1, 5, 10, 15 and 30 min). The exercise challenge comprised of each subject running on a motorized treadmill to volitional exhaustion while breathing dry air from a gas tank. RESULTS: Caffeine significantly reduced (P < 0.05) the mean maximum % fall in post-exercise FEV1 at 6 and 9mg/kg (-9.0±9.2% and -6.8±6.5%) as compared to the double-dummy (placebo; -14.3±11.1%) and baseline (-18.4+7.2%). There was no significant difference (P>0.05) in the post-exercise % fall in FEV1 between albuterol (without caffeine) (-4.0±5.2%) and the 9mg/kg dose of caffeine (-6.8±6.5%). Interestingly, there was no significant difference (P>0.05) in the post-exercise % fall in FEV1 between albuterol (without caffeine) (-4.0+5.2%) and albuterol with 3, 6 or 9mg/kg of caffeine (-4.4±3.8, -6.8±5.6, -4.4±6.0% respectively). Similar changes noted for the post-exercise % fall in FEV1 were also observed for FVC, FEF25-75% and PEF. In addition, it was determined that a dose-response relationship existed between the %fall in post-exercise FEV1 and caffeine dose administered (0, 3, 6 and 9 mg/kg) for all dependent variables. DISCUSSION: These data indicate that moderate (6 mg/kg) to high doses (9 mg/kg) of caffeine can reduce the severity of EIB in a dose-response manner. These data also indicate that no significant difference exists between high doses of caffeine and albuterol which suggests that caffeine may represent an alternative to albuterol reducing the severity of EIB.