Grapefruit contains organic compounds called furanocoumarins that block an enzyme called CYP3A4 that normally breaks down Latuda and certain other medications. When this enzyme is blocked, levels of Latuda in the blood will be higher than expected, and the intended effect or side effects of the drug will be stronger, even dangerous. People taking Latuda should avoid grapefruit, grapefruit juice, and products containing grapefruit (such as marmalade) because taking them together may increase the risk of side effects such as Parkinson-like symptoms, diabetes, headache, drowsiness, dizziness, or other effects.
Other citrus fruits such as pomelos, limes, and Seville oranges also contain furanocoumarins, and they may also interact with Latuda, but they haven't been studied as closely.