Data were retrieved from the Norwegian Prescription Database covering the total population of 4.6 million in Norway. Outcome measures were the proportion of atorvastatin users switching to simvastatin and changes in the proportion of new statin users receiving simvastatin. Data were based on retail costs for all statin prescriptions dispensed in Norway, and expenditure was measured in Norwegian currency.

They found that the new reimbursement policy for statins has had a great impact on physicians' prescribing of statins in Norway. Among atorvastatin users, 39% switched to simvastatin during the 13 months after implementation of the new regulations. In June 2006, 92% of new statin users received simvastatin.

Even though the one-year prevalence of statin use increased from 6.3% to 6.8% in women and 7.5% to 8.1% in men, the expenditure on statins was reduced by nearly 200 million NOK (Euros 25 million) from the year before implementation of the new regulations compared with the year after implementation. The estimated reduced costs are attributed both to price reductions and an increased proportion of simvastatin users.

Many European countries discuss how switching to the cheaper generics of simvastatin could save money for the public budgets, but very few have yet implemented a switching policy as part of their national regulations or recommendations. Already in December 2004, the Norwegian health authorities distributed the drafted new regulations to interested parties. The increased proportion of simvastatin prescribed to new users observed in the period January to May 2005 reflects that physicians adjusted their prescribing before the new regulations were implemented.

Some patients with established coronary heart disease (CHD) or at high risk of developing CHD may benefit from initiating statin therapy with a high dose of atorvastatin. While the overall number of new atorvastatin users gradually decreased after the new regulations, the proportion of the new atorvastatin users receiving 80 mg increased. This trend may reflect a tendency towards reserving atorvastatin for new patients considered to need aggressive treatment.

Switching to simvastatin was studied only in the population of previous users of atorvastatin. However, the number of other statin users has also decreased after the new regulations, indicating that switching to simvastatin has also occurred among these users. Individuals using 20 mg atorvastatin should be switched to 40 mg simvastatin according to recommendations given by the Norwegian Medicines Agency. Their study has shown that switching decreases with increasing doses of atorvastatin used, reflecting that physicians consider switching to be less appropriate in the higher-dose range. The maximum approved recommended dose for simvastatin is 80 mg, and it is therefore not possible to double the simvastatin dose when switching from a dose of 80 mg atorvastatin. Nevertheless, 17% of patients using 80 mg atorvastatin were switched to simvastatin. Clinical considerations related to achievement of lipid treatment goals or tolerance issues could be reasons for switching from 80 mg atorvastatin to simvastatin, rather than the new reimbursement regulations.

A slightly lower proportion received other cardiovascular drugs in the group of atorvastatin users who switched to simvastatin, compared with those who continued on atorvastatin. However, it is difficult to judge whether these differences reflect a true difference in overall cardiovascular risk in these two groups.

Study strength and limitations
According to the authors, the strength of this study is that it provides detailed information about all dispensed prescriptions of statins to individuals in the total population in Norway. The NorPD contains information that makes it possible to follow each individual over time in order to study changes in pharmacological treatment. This approach eliminates the possibility of selection and recall bias. Several other countries have healthcare databases containing information on drug prescriptions. However, many of these are based on insurance plans that cover only parts of the population, which may introduce selection bias.

The lack of information about baseline clinical characteristics, such as lipid levels and patient cardiovascular risk, as well as clinical outcome measures in the population of statin users, is a limitation of the study. The follow-up period after the new statin regulations was too short to assess changes in treatment outcomes. However, it would be important to follow the population of statin users in the future to ensure that the new statin regulations have no negative impact on cardiovascular morbidity or mortality. Compliance with and persistence of statin treatment related to switching of statins have not been studied.

They concluded that the success of a new reimbursement policy depends on collaboration with the physicians. Their study indicates that physicians acknowledge their responsibility to contribute to cost containment in Norway.

References:
Sakshaug S, Furu K, Karlstad Ø, et al. Switching statins in Norway after new reimbursement policy: a nationwide prescription study. Br J Clin Pharmacol. 2007;64(4):476-81.