Statin-induced myopathy following the use of a calcium channel blocker in a transplant patient

Abstract

Adrian Coleman and Mee Onn Chai discuss the case of a transplant recipient who developed myopathy as a result of a drug interaction between a calcium channel blocker (CCB) and a common cholesterol-lowering medication. They also describe the use of CCBs in the management of hypertension. Case study Mr SL is a 45-year-old Caucasian man with a body mass index of 24 kg/m2. His primary diagnosis for renal failure is hypertension, but he also has familial hypercholesterolaemia. He received a kidney transplant 6 months ago after spending a year on haemodialysis, and his transplanted kidney was considered a good immunological match, with a low risk of rejection. Mr SL's kidney function was stable with an estimated glomerular filtration rate (eGFR) of 45 ml/min/1.73 m2. The aim for his tacrolimus concentrations were between 4–7 mcg/l and his pre-dose level was 6 mcg/l. At his review, it was identified that his average blood pressure (BP) reading was 160/90 mmHg and the transplant consultant added nifedipine modified-release tablets (10 mg, twice-daily) to his BP medications ( Table 1 ). Four weeks later, Mr SL contacted the transplant team when he felt generally unwell with fatigue and muscle pain. Following blood tests, it was identified that his eGFR decreased to 30 ml/min/1.73 m2 and his tacrolimus trough level was 10 mcg/l. His C-reactive protein (CRP) was normal, white blood cell count was not elevated, and viral screen was negative. He did not have a temperature, his BP was 130/85 mmHg, and his creatinine kinase (CK) was elevated at 3000 mmol/l (normal range 40–100 mmol/l). The team's conclusion was that he was suffering with statin-induced myopathy, caused by a combination of interactions between nifedipine, tacrolimus and high-dose simvastatin. Nifedipine and tacrolimus were discontinued and repeat tacrolimus levels were requested for 1 weeks' time along with a review by one of the medical team. At the review, Mr SL claimed the muscle pain was resolving, and following another blood test, his CK reduced to 1300 mmol/l, eGFR returned to his baseline of 45 ml/min/1.73m2 and his tacrolimus level was back to within his normal range. His BP remained high at 155/90 mmHg and so it was decided to start amlodipine 5 mg once-daily. The team agreed to review the need for another cholesterol-lowering agent once the symptoms had completely resolved and his CK was within normal limits.