[The inhibitory effect of long-acting beta-adrenergic agonists, mabuterol, clenbuterol and fenoterol on "morning dipping" in patients with asthma].

We examined the inhibitory effect of the long-acting beta-adrenergic agonists, mabuterol, clenbuterol and fenoterol on "morning dipping" in ten patients with nocturnal asthma. On the first night, as a control experiment, the subjects received no beta-adrenergic agonist. On the succeeding three nights at 8:00 PM, each subject was orally administered 50 micrograms of mabuterol, 40 micrograms of clenbuterol and 5 mg of fenoterol in a randomized, crossover fashion. Pulmonary function tests (FVC, FEV1.0, PEFR, V50 and V25) were performed at 8:00 PM (just before administration of beta-adrenergic agonist), 9:00 PM, 10:00 PM, 6:00 AM and 8:00 AM. On the night when clenbuterol was administered, there was a significant inhibition of morning dipping at 6:00 AM in FVC (p less than 0.01), FEV1.0 (p less than 0.01), PEFR (p less than 0.01), V50 (p less than 0.01) and V25 (p less than 0.05) compared with the control night. On the nights when mabuterol and fenoterol were administered, there was a significant inhibition of morning dipping at 6:00 AM in FVC (p less than 0.01) and FEV1.0 (p less than 0.01) compared with the control night. Palpitations associated with clenbuterol administration were seen in two subjects. The effect of each beta-adrenergic agonist varied inconsistently among the subjects. These results indicate that clenbuterol is the most effective in inhibiting morning dipping among the long-acting beta-adrenergic agonists examined, but individualization in the choice of beta-adrenergic agonist is mandatory in order to achieve the maximum effect.