Brooks S M, Sholiton L J, Werk E E, Altenau P
J Clin Pharmacol. 1977 May-Jun;17(5-6):308-18. doi: 10.1002/j.1552-4604.1977.tb04610.x.
The effect of ephedrine (nine patients) and theophylline (seven patients) on dexamethasone metabolism was studied before and after three weeks of drug therapy in 16 asthmatics. Five patients were studied similarily but treated with placebo. After treatment with ephedrine, there was a mean decrease in plasma dexamethasone half-life (t1/2) of 132 minutes, or 36 per cent (P less than 0.025), and mean increase in metabolic clearance rate (MCR) of 148 liters/day, or 42 per cent (P less than 0.001). Increase in the excretion of urinary radioactivity, predominantly in the conjugated fractions, was noted. In contrast, theophylline and placebo therapy resulted in no significant changes in dexamethasone t1/2 or MCR. The rate of urinary excretion of radioactivity was reduced after theophylline treatment. Since ephedrine accelerates labeled dexamethasone clearance while theophylline does not, caution is necessary when prescribing ephedrine for asthmatics requiring long-term therapy with dexamethasone and probably other corticosteroids. It would appear from the present investigation that theophylline is a more appropriate bronchodilator for these patients.
在16名哮喘患者中，研究了麻黄碱（9例）和茶碱（7例）在为期三周的药物治疗前后对地塞米松代谢的影响。另有5名患者接受了类似研究，但使用的是安慰剂。接受麻黄碱治疗后，血浆地塞米松半衰期（t1/2）平均缩短132分钟，即36%（P<0.025），代谢清除率（MCR）平均增加148升/天，即42%（P<0.001）。观察到尿放射性排泄增加，主要是结合部分。相比之下，茶碱和安慰剂治疗对地塞米松t1/2或MCR无显著影响。茶碱治疗后尿放射性排泄率降低。由于麻黄碱可加速标记地塞米松的清除，而茶碱则不能，因此在为需要长期使用地塞米松及可能其他皮质类固醇治疗的哮喘患者开麻黄碱处方时需谨慎。从目前的研究来看，茶碱对这些患者来说是更合适的支气管扩张剂。
