According to the sources provided, there is no evidence to suggest that Lipitor (atorvastatin) reduces the effectiveness of blood pressure medications. In fact, a study conducted by Pfizer found that adding Lipitor to effective blood pressure treatment provided a significant reduction in heart attacks or deaths from heart attacks over five years [2]. Additionally, a study published in the American Journal of Cardiology found that Lipitor did not significantly affect blood pressure in patients with hypertension [3]. However, it is important to note that every patient is different and may respond differently to medications. It is recommended that patients consult with their healthcare provider before starting any new medications or changing their current medication regimen.

Sources:
[2] https://www.pfizer.com/news/press-release/press-release-detail/adding_lipitor_early_to_effective_blood_pressure_treatment_provided_a_significant_reduction_in_heart_attacks_or_deaths_from_heart_attacks_over_five_years
[3] https://pubmed.ncbi.nlm.nih.gov/21881597/