Lipitor is a brand name for the drug atorvastatin, which belongs to a class of drugs called statins. Statins are commonly used to lower cholesterol levels in the body. Grapefruit juice can interact with some medications, including statins, and cause potentially harmful side effects. 
Grapefruit juice contains compounds called furanocoumarins, which can interfere with the metabolism of certain drugs in the liver. This interference can cause the drug to build up in the body, increasing the risk of side effects. 
The interaction between grapefruit juice and Lipitor can increase the level of Lipitor in the blood, leading to an increased risk of side effects such as muscle pain, liver damage, and kidney failure.  Therefore, it is recommended that people taking Lipitor avoid grapefruit juice or discuss the risks with their healthcare provider. 
In conclusion, grapefruit juice can interact with Lipitor and increase the risk of side effects. Therefore, it is important to avoid consuming grapefruit juice while taking Lipitor or discuss the risks with a healthcare provider.