Rees P J, Clark T J
Br J Dis Chest. 1983 Jan;77(1):94-7.
The cough threshold to citric acid inhalation was measured in eight subjects by single inhalations of increasing concentrations of citric acid until a cough was consistently produced. The cough threshold was measured before and after 60 mg glaucine, 60 mg codeine and matched placebo on three separate days a week apart. Base-line cough threshold in each subject was consistent from week to week. Codeine increased the threshold by more than one citric acid concentration in three subjects. Placebo and glaucine did not produce a threshold change of more than one citric acid concentration. We conclude that the citric acid threshold is a simple measure of antitussive activity. No such activity was found with glaucine.
通过单次吸入浓度递增的柠檬酸直至持续引发咳嗽，对8名受试者测量吸入柠檬酸的咳嗽阈值。在每周相隔一天的三个不同日子里，分别在服用60毫克海罂粟碱、60毫克可待因及匹配的安慰剂之前和之后测量咳嗽阈值。每个受试者的基线咳嗽阈值每周保持一致。三名受试者服用可待因后咳嗽阈值提高超过一个柠檬酸浓度。安慰剂和海罂粟碱未使咳嗽阈值变化超过一个柠檬酸浓度。我们得出结论，柠檬酸阈值是镇咳活性的一种简单测量指标。未发现海罂粟碱有此类活性。
