- Statins are often feared for the myopathy that is encountered as a side effect.
- Muscle injury is uncommon with statin therapy alone, with a frequency of 2 to 11 percent for myalgias, 0.5 percent for myositis, and less than 0.1 percent for rhabdomyolysis.
- Incidence of myopathy increases on concomitant administration of fibrates, niacin, erythromycin or fluconazole.
- Enhanced susceptibility to statin-associated myopathy occurs in patients with acute or chronic renal failure, obstructive liver disease, and hypothyroidism.
- Patients can experience statin-induced myalgias without an elevation in serum creatine kinase (CK or CPK) concentration. In myositis or rhabdomyolysis the CK levels rise above 1000.
- Muscle symptoms usually begin within weeks to months after starting statins. Myalgias, weakness, and serum CK concentrations usually return to normal over days to weeks after drug discontinuation. Acetaminophen can be used for symptomatic treatment.
- Fluvastatin (LESCOL 20, 40 mg; LESCOL XL 80 mg) appears to have less intrinsic muscle toxicity and can be tried if atorvastatin or rosuvastatin are causing myalgia. Drawback is that it is very expensive.
- In the absence of clinical symptoms, a CK level more than 10 times the upper limit of normal is an indication for discontinuing the statin. Patients should drink large quantities of fluids to facilitate renal excretion of myoglobin.
- Hypothyroidism is a potential cause of dyslipidemia and hypothyroidism may predispose patients to statin-induced myopathy. Furthermore, an elevated CK is a common finding in uncontrolled hypothyroidism. One should check a TSH level prior to initiating statin therapy.
- Clinical experience suggests that alternate day dosing may improve the tolerability of statins in patients experiencing myalgias, and this strategy can reasonably be tried in patients unable to tolerate daily statin therapy.
- Routine monitoring of serum creatine kinase (CK) levels is not recommended in patients on statins, but it is useful to obtain a baseline CK level for reference purposes prior to starting statin therapy. Patients treated with statins should be alerted to report the new onset of myalgias and weakness.