'New reasons to avoid mixing juice and medicine'

What did the media say?

The media reported new research that some fruit juices might actually reduce the effects of some medicines, preventing patients from benefitting from them.

What did the research show?

Whilst it is already known that grapefruit juice can increase the absorption of certain drugs, this study demonstrates it can also have the opposite effect.

Scientists gave a healthy group of volunteers the antihistamine drug, fexofenadine, and then asked them to drink either a single glass of grapefruit juice, water containing naringin (the active substance in grapefruit juice) or water.

When the drug was taken with grapefruit juice, only half of it was absorbed by the body. This did not happen with those that drank water alone.

Naringin also blocked the effectiveness of the drug. They found that it seemed to block OATP1A2, a medicine uptake transporter that carries drugs from the small intestine to the bloodstream. This would have prevented the drug from being properly absorbed.

As well as grapefruit juice, both orange and apple juices appear to contain naringin like substances that also block OATP1A2. In other experiments, both have been found to lower the absorption of anticancer agents, beta blockers, immuno-suppressants and antiobiotics.

The findings were outlined at the 236th National Meeting of the American Chemical Society in Philadelphia last week.

What did the researchers say?

Study lead Dr David Bailey, a professor of clinical pharmacology at the University of Western Ontario said: ‘This is just the tip of the iceberg. I’m sure we’ll find more and more drugs that are affected this way.’ He recommended patients should take their medicines only with water.

What does this mean for nursing practice?

Colette McCreedy, the National Pharmacy Association’s Director of Pharmacy Practice and Chief Pharmacist said: ‘The effect on grapefruit juice on some medicines is well established and where this applies it is clearly detailed in Patient Information Leaflets.

‘This new research showing that apple and orange juice may enhance or reduce the effects of some medicines is interesting but it is only one study. Usually further research is needed to establish that these interactions are significant.’

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