Whitten D L, Myers S P, Hawrelak J A, Wohlmuth H
School of Natural and Complementary Medicine, Southern Cross University, Lismore, NSW, Australia.
Br J Clin Pharmacol. 2006 Nov;62(5):512-26. doi: 10.1111/j.1365-2125.2006.02755.x. Epub 2006 Sep 29.
The aim of this systematic review was to assess the quality and outcomes of clinical trials investigating the effect of St John's wort extracts on the metabolism of drugs by CYP3A.
Prospective clinical trials assessing the effect of St John's wort (SJW) extracts on metabolism by CYP3A were identified through computer-based searches (from their inception to May 2005) of Medline, Cinahl, PsycINFO, AMED, Current Contents and Embase, hand-searches of bibliographies of relevant papers and consultation with manufacturers and researchers in the field. Two reviewers selected trials for inclusion, independently extracted data and recorded details on study design.
Thirty-one studies met the eligibility criteria. More than two-thirds of the studies employed a before-and-after design, less than one-third of the studies used a crossover design, and only three studies were double-blind and placebo controlled. In 12 studies the SJW extract had been assayed, and 14 studies stated the specific SJW extract used. Results from 26 studies, including all of the 19 studies that used high-dose hyperforin extracts (>10 mg day(-1)), had outcomes consistent with CYP3A induction. The three studies using low-dose hyperforin extracts (<4 mg day(-1)) demonstrated no significant effect on CYP3A.
There is reasonable evidence to suggest that high-dose hyperforin SJW extracts induce CYP3A. More studies are required to determine whether decreased CYP3A induction occurs after low-dose hyperforin extracts. Future studies should adopt study designs with a control phase or control group, identify the specific SJW extract employed and provide quantitative analyses of key constituents.
本系统评价旨在评估研究圣约翰草提取物对CYP3A介导的药物代谢影响的临床试验的质量和结果。
通过对Medline、Cinahl、PsycINFO、AMED、《现刊目次》和Embase进行基于计算机的检索（从创刊至2005年5月）、手工检索相关论文的参考文献以及咨询该领域的制造商和研究人员，确定评估圣约翰草提取物对CYP3A介导的代谢影响的前瞻性临床试验。两名评价者选择纳入试验，独立提取数据并记录研究设计的详细信息。
31项研究符合纳入标准。超过三分之二的研究采用前后设计，不到三分之一的研究采用交叉设计，只有3项研究为双盲且安慰剂对照。12项研究对圣约翰草提取物进行了分析，14项研究说明了所使用的具体圣约翰草提取物。26项研究的结果，包括所有19项使用高剂量金丝桃素提取物（>10mg/天）的研究，其结果与CYP3A诱导一致。3项使用低剂量金丝桃素提取物（<4mg/天）的研究对CYP3A无显著影响。
有合理证据表明高剂量金丝桃素圣约翰草提取物可诱导CYP3A。需要更多研究来确定低剂量金丝桃素提取物后是否会出现CYP3A诱导作用降低。未来的研究应采用有对照期或对照组的研究设计，确定所使用的具体圣约翰草提取物，并对关键成分进行定量分析。
