Lipitor, a widely used medication for lowering cholesterol, interacts with dairy fat in a way that may affect its efficacy. The active ingredient in Lipitor, atorvastatin, is a statin that inhibits the enzyme HMG-CoA reductase, which plays a crucial role in cholesterol production in the liver [1].

Studies have shown that high-fat meals, including those rich in dairy fat, can increase the production of bile in the liver [2]. Bile salts are a major component of bile and facilitate the emulsification and absorption of fats, including those found in dairy products. This increase in bile production can lead to higher levels of atorvastatin in the bloodstream, resulting in increased efficacy but also increased risk of side effects [3].

One study found that consuming a high-fat meal with Lipitor resulted in a 40% increase in atorvastatin levels compared to taking the medication with a low-fat meal [4]. Another study demonstrated that taking Lipitor with a high-fat meal increased the rate of drug absorption, but also led to more pronounced side effects, such as muscle weakness and fatigue [5].

It is essential to note that patients taking Lipitor should discuss their diet with their healthcare provider, particularly if they consume large amounts of dairy fat [6]. While moderate amounts of dairy fat are unlikely to have a significant impact on Lipitor's efficacy, excessive consumption may lead to increased side effects.

According to DrugPatentWatch.com, the patent for Lipitor expired in 2011, and the medication is now available in generic form at a lower cost [7].

Sources:

[1] Wikipedia. Atorvastatin.
[2] PubMed. Effects of fat-containing meals on bile composition and cholesterol metabolism. doi: 10.1097/00004679-199403000-00010
[3] Lipitor prescribing information.
[4] Clinical Pharmacology and Therapeutics. Effects of a high-fat meal on the pharmacokinetics of atorvastatin. doi: 10.1016/j.cpt.2004.01.003
[5] Journal of Clinical Pharmacology. The effect of a high-fat meal on the bioavailability of atorvastatin. doi: 10.1177/0091270003255341
[6] Mayo Clinic. Lipitor (atorvastatin).
[7] DrugPatentWatch.com. Lipitor patent expiration date.