Background The solute carrier organic anion transporter family member 1B1 (SLCO1B1) protein facilitates the hepatic uptake of simvastatin. The SLCO1B1 c.521T>C genetic polymorphism (rs4149056) decreases the function of SLCO1B1 and is a strong predictor of simvastatin-induced myopathy. SLCO1B1 genotyping and pharmacist interpretation of the results are a step forward in personalising statin therapy. Hospital pharmacists have an innovative role in the clinical implementation of SLCO1B1 pharmacogenetic testing for statin therapy in the interests of patient safety.
Purpose To identify the presence of the SLCO1B1 c.521T>C genetic polymorphism in a cohort of cardiac patients on simvastatin to correlate genotype results with myopathy risk.
Material and methods Patients (n=110) on simvastatin were recruited by convenience sampling from the cardiac catheterisation laboratory of an acute general hospital. An EDTA-blood sample was collected from each patient after informed written consent. Genomic DNA was extracted and real-time polymerase chain reaction genotyping to identify the SLCO1B1 c.521T>C (rs4149056) single nucleotide polymorphism was performed using the Sacace biotechnology kits and Rotor-Gene 6000/Q for fluorescence detection. The patient cohort was classified into three genotypes: TT (homozygous wild-type – normal SLCO1B1 function); TC (heterozygous – intermediate SLCO1B1 function); and CC (homozygous variant – low SLCO1B1 function). The 2014 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline, which suggests prescribing a lower simvastatin dose (20 mg/day) or consideration of rosuvastatin instead of simvastatin in patients genotyped as TC or CC, was used for genotype-based therapy recommendations.
Results The 110 patients (all caucasian, 90 males, mean age 65+1.02 years) were genotyped as TT (78.2%, n=86), TC (20.0%, n=22) and CC (1.8%, n=2). Fifteen patients genotyped as TC or CC were on a higher simvastatin dose (40 mg/day) than suggested by the CPIC guideline for SLCO1B1 and simvastatin-induced myopathy.
Conclusion Patients genotyped as TC have mild risk of myopathy and patients genotyped as CC have a higher risk of myopathy compared to patients genotyped as TT or TC. Pharmacists should recommend SLCO1B1 genotyping in patients on statin therapy, interpret test results and suggest therapy recommendations according to genotype to improve patient safety with respect to myopathy.
References and/or acknowledgements Funding: University of Malta Research Grant (PHRRP12–17).
No conflict of interest.
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