Grapefruit Effect
Definition
The interaction between grapefruit (juice or fruit) and certain medications, caused by furanocoumarins in grapefruit that irreversibly inhibit CYP3A4 enzymes in the intestinal wall. This can dramatically increase oral drug absorption and blood levels, lasting up to 72 hours after grapefruit consumption.
Example
Drinking grapefruit juice with simvastatin can increase statin blood levels by up to 16-fold, greatly increasing the risk of rhabdomyolysis.