Furanocoumarins in grapefruit juice blamed for drug interactions
New research suggests that furanocoumarins are the ingredients in grapefruit juice responsible for enhancing systemic exposure — with potentially dangerous consequences — to drugs that are substrates for CYP3A4.
Scientists based at the University of North Carolina, Chapel Hill, selectively
removed furanocoumarins from grapefruit juice and then studied the juice’s
effect on the pharmacokinetics of felodipine (a CYP3A4 substrate).
In a randomised study, 18 volunteers took 10mg felodipine with each of
three juices: orange juice, grapefruit juice and grapefruit juice without
furanocoumarins. Blood samples were collected over 24 hours to measure
felodipine blood levels.
The researchers found that grapefruit juice without furanocoumarins behaved
like
orange juice and did not cause an interaction with felodipine.
“
This is the best evidence to date that furanocoumarins are the active
ingredients in grapefruit juice that cause the interaction with medicines,” said
Paul Watkins, professor of medicine and director of the university’s
clinical research centre.
The researchers suggest that it may be possible to add furanocoumarins
to formulations of certain drugs that tend to be poorly or erratically
absorbed to improve their oral delivery.
The findings are published in The American Journal of Clinical Nutrition (2006;83:1097). |
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