葡萄柚可能对化疗病人有害
葡萄柚是高血压病人的“禁果”也可能对化疗病人有害
http://health.zaobao.com/pages3/specialists171103.html
林慧慧 (2003-11-17)
向来被认为有助于降低血压、血脂，甚至减肥的水果葡萄柚（grapefruit），其实应该被列为高血压病人的“禁果”。专家警告，这是因为一些常用的降血压药物已被证实与葡萄柚汁产生相互作用，在病人体内引起不良反应。
不过更值得关注的是，研究人员相信，葡萄柚或者从中榨取的果汁，也可能会抑制一些抗癌药物的分解代谢过程，要是没有及时受到控制，药物会在癌症病患体内积累到接近中毒的浓度，对病患造成性命威胁。
虽然葡萄柚汁和抗癌药物之间的相互作用还没获得临床实验证实，但是由于这些抗癌药物和降血压药物需要人体内同一种蛋白质来分解，所以研究人员有理由相信，葡萄柚对化疗病人有害的推测是有根据的。
被怀疑可能与葡萄柚汁产生相互作用的，是两组普遍用来治疗肺癌和乳癌病患的抗癌药物，分别为taxanes和vinca-alkaloids。
国立健保集团属下癌症科医学院吴文子顾问医生指出，基于道德理由，研究人员不能对癌症病人进行这种高危险性的实验，因为这类研究的有效治疗范围狭隘（narrow therapeutic window），也就是说药物的有效剂量以及用药过度的水平，往往只有一线之差，要在两者之间取得平衡并不容易，只要稍有相互作用，病人都会有性命危险。
尽管如此，吴文子医生说，为了安全起见，他们会特别提醒正在接受化疗的癌症病人，在接受每一轮疗程的前后两三天，避免饮用葡萄柚汁。
他说，至于每天需要服药的高血压病人，则最好完全不要吃葡萄柚或饮用掺杂了葡萄柚的果汁，就连那种和葡萄柚一样含有名为bergamottin成分的格雷伯爵茶（Earl Grey Tea）也最好不要碰，以免它们造成体内降血压药物的浓度超出安全水平，引起副作用。
人体内的免疫系统是一道自然防线，有一部分药物在进入全身血液循环前，会先被肝脏自动产生的酶（enzyme）分解代谢，使药效有显著降低的作用，从而减轻像抗癌药物这种外来物质对人体造成伤害。
问题是，葡萄柚汁所含的一些成分，会对这类特定的酶产生抑制作用，造成药物没有被有效分解，从而造成药物在体内血液的浓度显著增加。
吴文子医生所领导的小组，专门对不同药物之间所可能产生的相互作用进行研究。他目前正在着手研究传统中药如人参，对那些接受化疗的癌症病人可能造成的影响。
不少人相信，中药有助于癌症病人调理身体，尤其认为它有助诱发身体免疫力，在减轻化疗对身体造成的伤害方面有很大作用。
吴文子医生说：“这种说法或许没错，中药也许真有助于降低化疗中强力药物的药性，但问题是，与此同时，整个疗程的疗效也会因此被大大削弱，使得疗程无法达到预期效果。”
他透露，初步研究显示，人参确实含有某种成分，会刺激免疫系统产生更多酶来分解抗癌药物，稀释血液内的毒性。
他和所带领的研究小组，将对本地大约20名癌症病人展开临床实验，测试不同剂量的人参对体内抗癌药物的影响。他预计可在一年内完成这项研究。
《联合早报》
Fruit juice cancer danger
http://www.independent.ie/health/latest-news/fruit-juice-cancer-danger-1459405.htmlBy John von Radowitz
Wednesday August 20 2008
Fruit juices including grapefruit, orange and apple can dramatically reduce the effectiveness of heart and cancer drugs, it was claimed yesterday.
Potentially the medicines could be rendered useless if they are taken at the same time as drinking juice, Canadian researchers said.
The evidence emerged from a study in which grapefruit juice was found to shut certain drugs out of the body.
Other fruit juices, notably orange and apple, are thought to have the same effect.
Patients consuming fruit or juice to be healthy run the risk of wiping out the benefits of their medicines -- among them vital treatments for heart disease, cancer, organ transplant rejection and infection, the scientists warned.
For 20 years it has been known that grapefruit juice can boost the potency of some drugs, increasing the risk of an overdose.
Some prescription drugs now carry labels warning patients not to drink grapefruit juice or eat fresh grapefruit at the same time as taking the medicines.
The new research, presented at the national meeting of the American Chemical Society in Philadelphia in America, shows that taking fruit juices with drugs may negate their effects.
In tests, healthy volunteers took fexofenadine -- an antihistamine used to fight allergies.
They swallowed the drug with either a single glass of grapefruit juice, water containing naringin -- the chemical responsible for the fruit's bitter taste --or plain water.
When the medicine was taken with grapefruit juice, only half as much of the drug was absorbed into the body as it was with water.
Study leader Professor David Bailey, from the University of Western Ontario in London, Ontario, said losing half of a drug dose could be critical.
"The concern is loss of benefit of medications essential for the treatment of serious medical conditions,'' he said.
Grapefruit, orange and apple juices all lowered the absorption of the anti-cancer agent etoposide, Prof Bailey added.
They also reduced the potency of certain beta blockers -- used to treat high blood pressure and prevent heart attacks.
- John von Radowitz
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