Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood. According to the sources provided, there are several medications that may interact with Lipitor, and some of these interactions may cause serious side effects.

For example, drugs that inhibit the liver enzyme CYP3A4, such as clarithromycin, erythromycin, and grapefruit juice, can increase the levels of Lipitor in the blood, which may increase the risk of side effects such as muscle pain and liver damage [1][2]. Additionally, some medications, such as niacin and gemfibrozil, may increase the risk of muscle pain or damage when taken with Lipitor [2].

On the other hand, there are some medications that may decrease the effectiveness of Lipitor, such as rifampin, a medication used to treat tuberculosis [2][3].

It is important to note that this is not a complete list of medications that may interact with Lipitor, and patients should always consult with their healthcare provider before taking any new medications, including over-the-counter drugs and supplements. Patients should also inform their healthcare provider of any pre-existing medical conditions or allergies they may have before taking Lipitor [2].

In conclusion, while Lipitor is generally safe and effective when used as directed, there are several medications that may interact with it and cause serious side effects. Patients should always consult with their healthcare provider before taking any new medications, and inform them of any pre-existing medical conditions or allergies they may have [1][2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.goodrx.com/atorvastatin/interactions
[3] https://www.drugs.com/drug-interactions/atorvastatin,lipitor.html