According to ConsumerReports: "A few years back, doctors discovered the "grapefruit effect"—the fact that drinking grapefruit juice affects the way certain blood pressure medications work. More than 40 different meds can have their effects magnified by grapefruit juice. "However, orange juice and apple juice could also interfere with some medications. The medication effect could be either increased or decreased.
In a study, healthy volunteers who took fexofenadine and drank grapefruit, apple or orange juice had decreased absorption of fexofenadine. Grapefruit decreased absorption the most.
This means that fexofenadine (Allegra) may not have the same effect if a patient takes it with grapefruit, apple or orange juice.
References:
Fruit juice and medications don't mix. ConsumerReports.
Image source: Wikipedia, public domain.