According to the sources provided, drowsiness is not listed as a common side effect of Lipitor. However, Lipitor may cause some other side effects such as muscle pain, weakness, and headache [1].

On the other hand, antihistamines are known to cause drowsiness as a common side effect. Some antihistamines may also cause nightmares and disturbing dreams, especially in elderly patients [2]. Additionally, some antihistamines may cause chronic fatigue, which is a feeling of tiredness that persists over a long period [3].

In summary, while drowsiness is not a common side effect of Lipitor, it is a common side effect of antihistamines. Patients taking antihistamines should be aware of the potential for drowsiness, nightmares, and chronic fatigue. As with any medication, patients should consult with their healthcare provider if they experience any side effects or have concerns about their medication regimen.

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.aarp.org/health/drugs-supplements/info-06-2012/medications-that-cause-chronic-fatigue.html