Introduction Statins have similar side effects that do not always occur at the same rate among the various statins. We present a case of simvastatin-induced muscle toxicity that disappeared when pravastatin
was substituted for the original drug.
Case Outline A 74-year-old male, a nonsmoker, complained of severe nocturnal leg cramps. The patient
also complained that similar painful cramping occurred when he walked rapidly or jogged. Because
some components of his lipid panel exceeded the ‘desirable’ range, and as he had a history of myocardial
infarction, his family physician prescribed simvastatin (40 mg/day). The patient had taken this medication for the past eight years. The painful nocturnal episodes started two years ago and affected either
one or the other leg. Four months ago we discontinued his simvastatin and prescribed pravastatin (80
mg/day). At a follow-up visit six weeks later, the patient reported that his leg pains at night and the pain
experienced after brisk walking had disappeared. Four months after the substitution of pravastatin for
simvastatin, the patient reported that his complete lack of symptoms had continued.
Conclusion These painful muscle cramps were probably caused by an inadequate vascular supply to
the calf and foot muscles. Perhaps a combination of advanced age and atherosclerotic changes created
a predisposition for the simvastatin-induced leg cramps. Pravastatin differs from simvastatin in several
ways. It is not metabolized by cytochrome P450 (CYP) 3A4 oxidases, and thus is not influenced by CYP 3A4
inhibitors like simvastatin. Also, simvastatin is associated with single-nucleotide polymorphisms located
within the SLCO1B1 gene on the chromosome 12 and established myopathy, while pravastatin lacks this
association. These differences may contribute to increased tolerance to pravastatin in this particular case.
