Lipitor (atorvastatin) is a medication used to lower cholesterol levels in the blood [1]. According to the provided sources, there is no direct evidence to suggest that Lipitor increases the drowsiness caused by antihistamines. However, it is important to note that Lipitor has been associated with side effects such as fatigue and drowsiness [2, 3].

Antihistamines are a class of drugs commonly used to treat allergies and can cause drowsiness as a side effect. GoodRx [2] suggests that some antihistamines may cause nightmares and disturbing dreams. AARP [3] notes that antihistamines are among the medications that can cause chronic fatigue.

It is always recommended to consult with a healthcare provider before taking any medication, including Lipitor and antihistamines. The healthcare provider can provide guidance on the potential side effects of the medications and any potential interactions between them.

Sources:
[1] DrugPatentWatch. Lipitor. https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] GoodRx. Medications that cause nightmares and disturbing dreams. https://www.goodrx.com/drugs/side-effects/medications-that-cause-nightmares-and-disturbing-dreams
[3] AARP. Medications that cause chronic fatigue. https://www.aarp.org/health/drugs-supplements/info-06-2012/medications-that-cause-chronic-fatigue.html