Grapefruit, orange and apple juices can harm the body's ability to absorb certain medications and make the drugs less effective, said a Canadian study released this week in the United States.

The research showed that these juices can decrease the effectiveness of certain drugs used to treat heart disease, cancer, organ-transplant rejection and infection, "potentially wiping out their beneficial effects," it said.

David Bailey, a professor of clinical pharmacology with the University of Western Ontario and leader of the study, was the first researcher to identify grapefruit juice's potential to increase the absorption of certain drugs two decades ago, possibly turning some doses toxic.

The new findings came as part of his continuing research on the subject, and were presented at the 236th annual meeting of the American Chemical Society on Philadelphia, Pennsylvania.

"Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs undergoing intestinal uptake transport," AFP quoted Bailey as saying.

"The concern is loss of benefit of medications essential for the treatment of serious medical conditions."

Healthy volunteers took fexofenadine, an antihistamine used to fight allergies, along with either a glass of grapefruit juice, a glass of water with naringin (which gives the bitter taste to grapefruit juice), or plain water.

Those who drank the grapefruit juice absorbed only half the amount of fexofenadine, compared to those who drank plain water.

Researchers said the water with naringin served to block "a key drug uptake transporter, called OATP1A2, involved in shuttling drugs from the small intestine to the bloodstream."

Among the drugs affected by consumption of grapefruit, orange and apple juices are: etoposide, an anticancer agent; beta blockers (atenolol, celiprolol, talinolol) used to treat high blood pressure and prevent heart attacks; and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole).

The drug-lowering interaction also affected cyclosporine, a drug taken to prevent rejection of transplanted organs, and more drugs were expected to be added to the list as the research continued.

Bailey said patients should consult with a doctor about taking medications with juice, and stick to plain water when taking most medications

本周在美国发表的一项加拿大研究声称，葡萄柚、桔子和苹果的果汁会对人体吸收某些药物的能力有害，而且会使药物降低疗效。

研究表明这些果汁会降低某些药物对治愈心脏病、癌症以及器官移植排斥和感染的疗效。研究说：“果汁会潜在地抹杀药物的疗效。”

David Bailey 是西安大略大学临床药理学的教授，同时也是此项研究的领导者。二十年前他是第一个确认葡萄柚的果汁有增加吸收某些药物潜在性的研究者，他认为果汁会有可能把一些药剂变得有毒性。

新的发现延续了这个课题的研究，并且发表在第236届宾夕法尼亚州费城的美国医学协会年会上。

宾夕法尼亚州费城的美国医学协会引用Bailey的话说：“最近我们发现葡萄柚和这些其它水果的果汁会在实质上降低某些在肠内吸收流动的口服药物的吸收.”

“让人担心的是那些对治愈严重的医学疾病非常重要的药物失去了药用。”

健康志愿者服用非索非那定— 一种用于抗过敏抗组胺药物，同时喝一杯葡萄柚果汁、一杯柚皮甙水（使葡萄柚果汁带有苦味）或者白水。

和那些喝白水的人比较，那些喝了葡萄柚果汁的人仅吸收了一半量的非索非那定。

研究者称有柚皮甙的水能阻碍一种叫“OATP1A2的重要的药物传送者，它负责把药物从小肠送到在体内循环的血液中。”

这些受饮用葡萄柚汁、桔子汁和苹果汁影响的药物有：抗癌剂；用于治疗高血压和心脏病的阻滞剂（阿替洛尔，塞利洛尔，肽利诺罗）；和一些抗生素（环丙沙星，左氧氟沙星，伊曲康唑）。

降低药物相互作用还会影响到环孢菌素，一种用于防止器官移植排斥的药物，而其更多的药物还会随着研究的进展而添加到这个名单中。

Bailey 说病人应该咨询医生是否能用果汁服药，而且在服用大多数药物时应坚持喝白水。