Effects of Vitamin D Supplementation in Atorvastatin‐Treated Patients: A New Drug Interaction With an Unexpected Consequence

The objective of this study was to determine vitamin D supplementation effects on concentrations of atorvastatin and cholesterol in patients. Sixteen patients (8 men, 8 women; 10 Caucasians, 4 African Americans, 1 Hispanic, 1 Asian), aged 63 ± 11 years (mean ± SD, weight 92 ± 31 kg) on atorvastatin (45 ± 33 mg/day) were studied with and without supplemental vitamin D (800 IU/day for 6 weeks). Levels of vitamin D (1,25‐dihydroxy(OH) and 25 OH‐metabolites), atorvastatin (parent, OH‐acid metabolites, lactone, and lactone metabolites), and cholesterol (total, low‐density lipoprotein (LDL) cholesterol, and high‐density lipoprotein (HDL) cholesterol) were determined at 0.5, 3, and 10 h after dosing. Vitamin D supplementation increased vitamin D‐25‐OH metabolites ( P < 0.0001) without increased 1,25‐dihydroxy vitamin D. Atorvastatin and active metabolite concentrations ( P < 0.001) as well as LDL‐cholesterol and total‐cholesterol levels (97 ± 28 mg/dl vs. 83 ± 30 and 169 ± 35 mg/dl vs. 157 ± 37, P < 0.005) were lower during vitamin D supplementation. The conclusion of the study is that vitamin D supplementation lowers atorvastatin and active metabolite concentrations yet has synergistic effects on cholesterol concentrations. Clinical Pharmacology & Therapeutics (2009); 85 , 2, 198–203 doi: 10.1038/clpt.2008.165