Dear Dr R.N. Hi & Welcome. This can lead to toxic side effects from Lipitor, such as liver or muscle damage. Grapefruit or grapefruit juice contains certain organic compounds called Furanocoumarins which block the action of enzymes responsible for the clearance of cholesterol lowering medication Lipitor (Atorvastatin) resulting in increased levels of Lipitor which can result in toxic effects such as liver or muscle damage. Just one grapefruit or one glass of grapefruit juice could be enough to cause an interaction with Lipitor. There are several other citrus fruits like lemons, lime, tangerines, mandarins, navels, and blood oranges which do not cause such harmful or toxic effects when taken along with Lipitor. Hope this answers your query.