It is well known that statins cause myopathy as a side effect.
A detailed article on this
topic was recently published in the US
, a brief summary of which is presented below:
Statins are drugs like
simvastatin, lovastatin, pravastatin and atorvastatin that are used to reduce
bad or LDL-cholesterol levels.
Statins cause myopathy or a disease of the muscles as a side effect in
up to 10% patients receiving the drugs. Myopathy is seen more commonly with higher doses
of statins. People at an increased risk
for myopathy include those with prior history of muscle pain with
cholesterol-lowering drugs, unexplained cramps or an increase in creatine
kinase levels (creatine kinase is an enzyme released in the blood when a
muscle is damaged). Drugs like simvastatin and atorvastatin are more likely to
cause myopathy. These drugs when combined with other cholesterol-lowering drugs
like gemfibrosil may result in an earlier onset of the side effect.
Other risk factors for
developing myopathy with statins include female sex, older age group, low body
mass index, other health issues like diabetes, hypertension, untreated
hypothyroidism, kidney and liver disease. In addition, alcohol, cocaine use,
increased exercise, and a diet rich in grapefruit juice are also associated
with myopathy. Other drugs like cyclosporine and fluconazole that could
interfere with the metabolism or breakdown of statins in the blood could also
increase the chances of myopathy with statins.
The exact reason why
myopathy occurs with statins is not known, though some theories have been
proposed. Symptoms of statin-induced
myopathy include fatigue, flulike symptoms, muscle cramps at night, weight
loss, an increase in heart rate, nausea, and brown urine.
How does one identify who is
at likely risk for developing myopathy with statins? One way is to measure a
baseline creatine kinase level in all patients before starting treatment with
statins. Some recommend that this test should be done only in people at high
risk for myopathy. Once treatment is started, routine testing for myopathy is
not recommended. Tests for creatine kinase are advised only if the patient
develops muscle symptoms. Treatment should be discontinued in instances where
creatine kinase levels rise to more than 10 times the upper limit of normal, or
those who develop intolerable muscle symptoms.
Patients should be made aware of this complication before treatment
with statins is started and should be asked to report in case of any symptoms.
Most patients recover after
the drug is stopped. Some cases with severe muscle damage may land up with
kidney failure and may require hospitalization and IV fluids.
Once the patient has
recovered from the myopathy, how should the high cholesterol levels be
controlled? Some of the options suggested are, use a lower dose of the same
statin with another drug if necessary; use another statin; or use a drug
belonging to an altogether different class.
1. Statin-Associated Myopathy; Jennifer Shannon et al; US Pharmacist 2012.