Pounsford J C, Saunders K B
Thorax. 1985 Sep;40(9):657-61. doi: 10.1136/thx.40.9.657.
The lowest concentrations of citric acid were measured that caused coughing in 10 normal subjects who inhaled successively higher concentrations. Two subjects did not cough at any concentration. In the remaining eight the threshold concentration was significantly higher when measured in the afternoon than it was in the morning (p less than 0.05). The expected diurnal variation in peak expiratory flow rate (PEFR) was found (significant in the whole group--p less than 0.05); but PEFR did not change significantly when measured before and immediately after coughing caused by citric acid inhalations. In a second group of 10 normal subjects two series of citric acid inhalations were given, separated by one hour. The total number of coughs was significantly lower on the second run (p less than 0.05). Thus diurnal variation and adaptation of the cough response must be taken into account when antitussive drugs are tested.
对10名正常受试者连续吸入浓度递增的柠檬酸，测量引起咳嗽的最低浓度。两名受试者在任何浓度下均未咳嗽。在其余8名受试者中，下午测量的阈值浓度显著高于上午（p<0.05）。发现了呼气峰值流速（PEFR）预期的昼夜变化（在整个组中显著——p<0.05）；但在吸入柠檬酸引起咳嗽之前和之后立即测量时，PEFR没有显著变化。在另一组10名正常受试者中，进行了两组柠檬酸吸入，间隔1小时。第二次试验时咳嗽的总数显著降低（p<0.05）。因此，在测试镇咳药物时，必须考虑咳嗽反应的昼夜变化和适应性。
