Potential cardiovascular consequences of switching from atorvastatin to generic simvastatin in the Netherlands

The statin authorisation form implemented in the Netherlands in January 2009 has led to significant switching of patients from atorvastatin to generic simvastatin, but often to less than equipotent doses. We sought to assess the potential consequences of this.

A modelling analysis was undertaken using data from a pharmacy database covering the majority of drug prescriptions in the Netherlands. Recent meta-analyses provided data on the dose-specific, lipid-modifying potencies of atorvastatin and simvastatin, and the relationship between reduction in low-density lipoprotein cholesterol (LDL-C) achieved by statin therapy and relative reduction in risk of cardiovascular disease (CVD).

In the first quarter of 2009, 33.7%, 47.2% and 19.1% of Dutch patients initially on atorvastatin were switched to less potent, equipotent and more potent doses of simvastatin, respectively. The net effect was estimated to be a 6.8% increase in LDL-C. Assuming a pre-switch LDL-C of 2 mmol/L, the predicted relative increases (95%CI) in the risks of all-cause mortality and major cardiovascular events were 1.7% (0.9%-2.6%) and 2.8% (1.6%-4.1%), respectively.

In the Netherlands, policy-driven switching from atorvastatin to generic simvastatin led overall to less potent doses being used, with possible significant clinical implications.