Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood, while antihistamines are drugs used to treat allergies and other conditions such as insomnia, anxiety, and motion sickness. The interaction between Lipitor and antihistamines may depend on the specific type of antihistamine used.

According to Drugs.com, there are no known interactions between Lipitor and antihistamines such as loratadine, cetirizine, and fexofenadine. However, there is a potential interaction between Lipitor and diphenhydramine, which is a first-generation antihistamine commonly used in over-the-counter allergy medications. This interaction may increase the risk of side effects such as dizziness, drowsiness, and difficulty concentrating. Therefore, caution should be exercised when using these medications together, and patients should consult their healthcare provider before taking them.

Verywell Health also notes that there is a potential interaction between Lipitor and grapefruit juice, which can increase the levels of Lipitor in the blood and increase the risk of side effects. Patients should avoid consuming grapefruit or grapefruit juice while taking Lipitor.

In summary, there is a potential interaction between Lipitor and diphenhydramine, but no known interactions with other antihistamines such as loratadine, cetirizine, and fexofenadine. Patients should also avoid consuming grapefruit or grapefruit juice while taking Lipitor. As with any medication, patients should consult their healthcare provider before taking Lipitor with any other medication or supplement.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.drugs.com/drug-interactions/allergy-relief-tablets-with-atorvastatin-1486-14544-276-0.html
[3] https://www.verywellhealth.com/statin-side-effects-and-drug-interactions-698202