Patients Switched Away From Established Statin Therapy Experienced A Significant Increase In Relative Risk Of Cardiovascular Events, UK

Main Category: Cardiovascular / Cardiology
Also Included In: Stroke;  Statins;  Cholesterol
Article Date: 06 Sep 2007 - 2:00 PDT

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An large observational study of a United Kingdom primary care database showed that switching patients from Lipitor (atorvastatin calcium) to another statin, simvastatin, was associated with a statistically significant 30 percent increase in the relative risk of a composite endpoint made up of major cardiovascular events, including heart attacks, strokes and certain types of heart surgeries, or death, compared to patients who remained on atorvastatin therapy.

This analysis was presented today at the European Society of Cardiology (ESC) Congress 2007 and is also in press at The British Journal of Cardiology.

The data, which included records from October 1997 to June 2005, were retrospectively analysed from a medical research database of anonymous patient records entered by General Practitioners known as The Health Improvement Network (THIN). The analysis included 9,009 patients who were taking atorvastatin for at least six months and remained on atorvastatin therapy and 2,511 patients who had taken atorvastatin for at least six months and then were switched to simvastatin. Reasons for switching were not available from the database. Since patients were not randomly assigned to each group, the two treatment groups were matched based on certain risk factors and statistical adjustments were made to address any residual imbalances. As with all observational studies, the findings should be regarded as hypothesis generating.

A secondary analysis of the same data showed that patients who were switched from atorvastatin to simvastatin were more than twice as likely to discontinue their treatment compared to those who remained on atorvastatin therapy (adjusted hazard ratio (HR) = 2.15 (95% CI: 1.96, 2.36) p<0.001). The reasons for discontinuation were not available from the database. Disruption in treatment has been associated with poor adherence in previous studies of statins and other medications.

Dr Berkeley Phillips, Cardiovascular Medical Manager at Pfizer, UK and lead author of the study commented; "Whilst recognising the observational nature of database research, this study has highlighted the potential for poorer cardiovascular outcomes in patients switching statin therapy, compared with patients maintained on their current treatment. This raises concerns for policies that encourage widespread statin switching without careful clinical assessment of individual patients. The additional finding of poorer adherence to therapy after changing treatment highlights the importance of close monitoring of patients and auditing of switch programmes to check for compliance, cholesterol control and most importantly cardiovascular outcomes".

Additional Study Information

-- The primary endpoint was time to a first major cardiovascular event, defined as heart attack, stroke, or coronary revascularization (a type of heart surgery), or all-cause death.

-- The individual components making up the primary endpoint were analyzed as secondary endpoints. Compared with patients who did not switch therapy, switching was associated with the following:

- Significant 43 percent increase in the relative risk of major cardiovascular events (p=0.008)
- No difference in all-cause death (p=0.369)

-- The two treatment groups were matched based on risk factors including gender, history of heart attack, diabetes, time since last statin exposure and also by location of general practitioner.

-- The following statistical adjustments were made to address any residual imbalances: age, gender, prior statin exposure, time since last statin exposure, diabetes, history of heart attack, and baseline cholesterol levels.

-- Relative risk is the ratio of the risk of major cardiovascular events or death occurring in the group who switched from atorvastatin to simvastatin versus the risk in the group who remained on atorvastatin.

-- As with all observational studies, the findings should be regarded as hypothesis generating.

About Lipitor ® (Atorvastatin)

Atorvastatin is a prescription only medicine used to lower cholesterol and reduce the risk of cardiovascular disease and has a well-established safety profile.

About Pfizer

Pfizer Inc, the world's largest research-based pharmaceutical company, discovers, develops, manufactures and markets prescription medicines in 9 therapeutic areas. Pfizer is also the world's largest animal health company.

Pfizer Inc employs approximately 105,000 colleagues worldwide, all of whom are devoted to working for a healthier world. Pfizer conducts more biomedical research than any other corporation, and has 14,000 professionals working in R&D sites worldwide, including Sandwich in Kent. Pfizer's research investment in 2005 was more than $7.4 billion.

In the UK, Pfizer Ltd has its UK business headquarters in Surrey and is the major supplier of medicines to the NHS.

http://www.pfizer.com