Determination of serum atorvastatin concentrations in lipid-controlling patients with and without myalgia syndrome

The cholesterol-reducing drug atorvastatin is widely used in hyperlipidemic patients and it is crucial to consider its potential myotoxic effect when adjusting the prescription for patients. The aim of this study was to establish a simple high-performance liquid chromatography method that would be applicable for the quantitative determination of high serum atorvastatin concentrations in patients for the assessment of myalgia. The average recovery of atorvastatin from the extraction using ethyl acetate was 85.1%. The extract was dried, re-dissolved in methanol, and subjected to chromatographic separation using a reverse-phase C18 analytical column and a mobile phase consisting of 61.3% methanol in 0.05 M sodium phosphate buffer at pH 3.5. The concentration of atorvastatin was quantitatively determined by measuring the absorbance at 247 nm and β-naphthoflavone was used as an internal standard. The lower limits of detection and quantification of atorvastatin were 1.2 ng/mL and 3.0 ng/mL, respectively. There was a good linear relationship (r = 0.999) of the peak area and atorvastatin within a concentration range of 3.0–150 ng/mL in human serum. Among 61 lipid-controlling patients with detectable serum atorvastatin concentrations, 7 patients had myalgia and their serum concentrations were not significantly greater than those in patients without myalgia.