In the thirteen closely-typed pages of the protocol for the Tykerb trial that I had to sign before starting to swallow the five bright orange pills each morning (one hour before breakfast), there is the following sentence - in bold.
You...should not eat grapefruit or drink grapefruit juice for the duration of the study. Grapefruit and grapefruit juice contain a certain chemical that interacts with lapatinib.
Peter Ostler, oncologist, said to me: "you don't look like a grapefruit eater, anyhow". (This is designed to trigger one of Norm's contests about what kind of fruit-eaters people look like.)
What is it with grapefruit, do you suppose?