Harrison T W, Oborne J, Wilding P J, Tattersfield A E
Division of Respiratory Medicine, Nottingham City Hospital, UK.
Thorax. 1999 Feb;54(2):98-102. doi: 10.1136/thx.54.2.98.
Many patients continue to take regular beta agonists, often at high doses, contrary to national and international guidelines. Some studies have suggested that this can worsen asthma control, but whether such patients can reduce their dose of beta agonist and whether they would benefit from this has not been determined. Reduction of beta agonist dose was studied in a placebo controlled parallel group study.
Following a run in period, 33 subjects with asthma taking regular beta agonists were converted to an equivalent dose of terbutaline via a Turbohaler. Two weeks later terbutaline was continued at the same dose or changed to placebo in two stages a week apart. The change over period was covered by an increased dose of inhaled steroid to attenuate any immediate effects of the change in dose. Subjects then attended weekly for six weeks for measurement of forced expiratory volume in one second (FEV1) and the dose of methacholine that produced a 20% fall in FEV1 (PD20). Peak expiratory flow (PEF) and symptom scores were recorded twice daily throughout the study. Exacerbations, lung function, bronchial responsiveness, bronchodilator response, beta agonist use, and symptoms were compared before and six weeks after reduction in the dose of beta agonist.
Twenty five of the 33 subjects completed the study; three patients in each group withdrew due to an asthma exacerbation. The median terbutaline dose fell from 2500 to 500 micrograms/day in the beta agonist reduction group and from 3000 to 2250 micrograms/day in the control group. There were small non-significant changes in FEV1, PEF, symptom scores and PD20 methacholine over the course of the study. The FEV1 response to a beta agonist was greater in those who reduced their beta agonist dose than in the control group although the final FEV1 achieved was the same.
Patients with asthma taking high doses of beta agonists can reduce the amount of beta agonist they use without a significant change in their asthma control. There was no evidence of improved asthma control with beta agonist dose reduction.
许多患者继续常规服用β受体激动剂，且剂量常常很高，这与国内和国际指南相悖。一些研究表明，这可能会使哮喘控制恶化，但此类患者能否减少β受体激动剂剂量以及他们是否会从中获益尚未确定。在一项安慰剂对照平行组研究中对减少β受体激动剂剂量进行了研究。
在一段导入期后，33名规律服用β受体激动剂的哮喘患者通过都保装置转换为等量的特布他林。两周后，特布他林以相同剂量继续服用，或分两个阶段改为安慰剂，两个阶段相隔一周。转换期通过增加吸入性类固醇剂量来覆盖，以减轻剂量变化的任何即时影响。然后受试者每周就诊六周，测量一秒用力呼气量（FEV1）以及使FEV1下降20%的乙酰甲胆碱剂量（PD20）。在整个研究过程中，每天记录两次呼气峰值流速（PEF）和症状评分。比较β受体激动剂剂量减少前后六周的病情加重情况、肺功能、支气管反应性、支气管扩张剂反应、β受体激动剂使用情况和症状。
33名受试者中有25名完成了研究；每组有3名患者因哮喘加重而退出。β受体激动剂减量组的特布他林中位剂量从每日2500微克降至500微克，对照组从每日3000微克降至2250微克。在研究过程中，FEV1、PEF、症状评分和PD20乙酰甲胆碱有微小的无显著意义的变化。虽然最终达到的FEV1相同，但减少β受体激动剂剂量的患者对β受体激动剂的FEV1反应大于对照组。
高剂量服用β受体激动剂的哮喘患者可以减少β受体激动剂的用量，而哮喘控制情况无显著变化。没有证据表明减少β受体激动剂剂量能改善哮喘控制。
