Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood. According to the sources provided, there is no evidence to suggest that Lipitor can increase antihistamine side effects. However, Lipitor can interact with other medications and supplements, so it is important to discuss all medications and supplements with a healthcare provider before taking Lipitor.

The first source provided, Drug Patent Watch [1], provides information on the patent status of Lipitor and its generic versions. This source does not provide any information on the potential interaction between Lipitor and antihistamines.

The second source, GoodRx [2], lists medications that can cause nightmares and disturbing dreams, including some antihistamines. However, Lipitor is not listed as a medication that can cause these side effects.

The third source, NHS [3], provides information on taking Lipitor with other medications and supplements. According to this source, Lipitor can interact with certain medications, including some antibiotics and antifungal medications. However, there is no mention of antihistamines.

In conclusion, based on the sources provided, there is no evidence to suggest that Lipitor can increase antihistamine side effects. However, Lipitor can interact with other medications and supplements, so it is important to discuss all medications and supplements with a healthcare provider before taking Lipitor.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.goodrx.com/drugs/side-effects/medications-that-cause-nightmares-and-disturbing-dreams
[3] https://www.nhs.uk/medicines/atorvastatin/taking-atorvastatin-with-other-medicines-and-herbal-supplements/