There is currently no definitive scientific evidence to suggest that taking multivitamins affects the efficacy of Lipitor (atorvastatin), a medication used to treat high cholesterol levels. According to the information provided, Lipitor's mechanism of action involves inhibiting HMG-CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body [1]. This process is unrelated to the functions of multivitamins, which typically include providing essential vitamins and minerals for various bodily functions [2].

However, it is essential to note that certain supplements and medications can interact with each other, potentially affecting their efficacy or increasing the risk of side effects. Therefore, it is always recommended to consult a healthcare professional or pharmacist before combining any medications, including Lipitor, with dietary supplements such as multivitamins [3].

In summary, based on the available information, there is no evidence to suggest that Lipitor's efficacy is directly affected by using multivitamins. Nonetheless, it is always advisable to consult a healthcare professional before combining medications and supplements to ensure safety and effectiveness.

Sources:
[1] "Atorvastatin (Lipitor)". Mayo Clinic. <https://www.mayoclinic.org/drugs-supplements/atorvastatin-oral-route/description/drg-20063002>.
[2] "Multivitamin/multimineral supplements". Harvard Health Publishing. <https://www.health.harvard.edu/staying-healthy/multivitamin-multimineral-supplements>.
[3] "Drug Interactions: What to Know". Cleveland Clinic. <https://my.clevelandclinic.org/health/articles/11885-drug-interactions-what-to-know>.
[4] "Lipitor (Atorvastatin)". Drugs.com. <https://www.drugs.com/lipitor.html>.
[5] "Atorvastatin (Lipitor)". DrugPatentWatch.com. <https://www.drugpatentwatch.com/drugs/atorvastatin>.