We did not have information about the use of over-the-counter or
unsubsidised drugs. However, the drugs which are known or suspected
to increase the risk of rhabdomyolysis are prescription-only and
subsidised in NewZealand; hence their dispensing by community pharmacies
would have been identified. Any inpatient use of such drugs
would not have been detected, although just one patient with rhabdomyolysis
and eight matched controls were admitted to hospital in the
30 days before the index date. Finally, we did not have information
about some lifestyle factorswhich have been associatedwithmuscle injury
in statin users (consumption of grapefruit or cranberry juice, low
body mass index) [23], but any uncontrolled confounding by these factors
would be insufficient in magnitude to explain the observed excess
risk in users of 40 mg simvastatin.