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Grape fruit juice is known to change the absorption or metabolism of many

different drugs. Although ingestion of grape fruit juice produces small changes

in the absorption of thyroid hormone, it does not seem likely that regular

ingestion of grapefruit juice will significantly affect the absorption or

metabolism of thyroid hormone in patients taking L-thyroxine Effects of

grapefruit juice on the absorption of levothyroxine. Br J Clin Pharmacol. 2005

Sep;60(3):337-41