Lipitor is a brand name for atorvastatin, a medication used to lower cholesterol levels in the blood. According to Drug Patent Watch [1], Lipitor is a competitive inhibitor of HMG-CoA reductase, an enzyme that is involved in the production of cholesterol in the liver. This inhibition results in a decrease in the production of cholesterol in the liver, which ultimately lowers the levels of cholesterol in the blood.

Vitamin D is an essential vitamin that is necessary for the body to absorb calcium and maintain healthy bones. According to the Mayo Clinic [3], vitamin D is obtained through exposure to sunlight, diet, and supplements.

There is limited research on the effects of Lipitor on vitamin D absorption. However, a study published in the Journal of Clinical Endocrinology and Metabolism [2] found that atorvastatin use was associated with a lower level of vitamin D in the blood. The study suggests that this may be due to the fact that both atorvastatin and vitamin D are metabolized by the same liver enzyme, cytochrome P450 3A4. This suggests that atorvastatin may interfere with the metabolism of vitamin D, leading to lower levels in the blood.

In conclusion, while there is limited research on the effects of Lipitor on vitamin D absorption, a study suggests that atorvastatin use may be associated with lower levels of vitamin D in the blood due to the medication's interference with the metabolism of vitamin D. It is important for individuals taking Lipitor to discuss their vitamin D levels with their healthcare provider and consider supplementation if necessary.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://pubmed.ncbi.nlm.nih.gov/18754003/
[3] https://www.mayoclinic.org/drugs-supplements-vitamin-d/art-20363792