Trembath P W, Boobis S W, Richens A
J Int Med Res. 1979;7 Suppl 1:4-15.
Theophylline and its derivatives, such as aminophylline, have an established role as bronchodilators, although their mode of action in man is not clear. There is circumstantial evidence that therapeutic doses of theophylline may have a phosphodiesterase inhibiting effect, thus potentiating the effects of cyclic AMP. However, it remains to be established whether this is the primary mode of action of theophylline at the biochemical level. The pathways of theophylline metabolism have been clarified, although most of the enzymes involved have not been characterized. Hepatic microsomal enzyme induction by polycyclic hydrocarbons will increase the rate of theophylline elimination. There are a number of factors which influence theophylline clearance in adults, which is known to be highly variable. These factors include obesity, smoking habit, diet and the presence of such diseases as hepatic cirrhosis, acute pulmonary oedema, cor pulmonale and viral respiratory infection. There is a good correlation between plasma theophylline level and bronchodilator effect. This can be demonstrated at plasma levels as low as 5 microgram/ml, although optimal levels are usually greater than 10 microgram/ml. Unacceptable toxicity usually occurs in association with plasma levels greater than 20 microgram/ml. The maintenance of adequate plasma theophylline levels by the use of a sustained-release aminophylline tablet is discussed.
茶碱及其衍生物，如氨茶碱，作为支气管扩张剂已有明确作用，尽管其在人体中的作用方式尚不清楚。有间接证据表明，治疗剂量的茶碱可能具有磷酸二酯酶抑制作用，从而增强环磷酸腺苷（cAMP）的作用。然而，在生化水平上，这是否为茶碱的主要作用方式仍有待确定。茶碱的代谢途径已得到阐明，尽管大多数参与的酶尚未被鉴定。多环烃对肝微粒体酶的诱导会增加茶碱的消除速率。有许多因素会影响成年人的茶碱清除率，已知其变化很大。这些因素包括肥胖、吸烟习惯、饮食以及肝硬化、急性肺水肿、肺心病和病毒性呼吸道感染等疾病的存在。血浆茶碱水平与支气管扩张作用之间存在良好的相关性。这在血浆水平低至5微克/毫升时即可表现出来，尽管最佳水平通常大于10微克/毫升。血浆水平大于20微克/毫升时通常会出现不可接受的毒性。本文讨论了使用缓释氨茶碱片维持足够血浆茶碱水平的问题。
