Statin switch debate reopened after new study data
Changing patients from atorvastatin to simvastatin raises the risk of death or major cardiovascular event by a third according to a Pfizer study presented at the European
Society of Cardiology conference in Vienna last week.
The study — which has been reported widely in the national media — has
reopened the row over statin switching.
Researchers examined data from a primary care database of 4.77 million
patients, including 2,511 patients who had been switched, and compared
the switch patients with 9,009 unswitched controls who continued to receive
atorvastatin.
Compared with controls, switched patients had a 43 per cent increased
risk of major cardiovascular events (P=0.008) and a 114 per cent increased
risk of stroke (P=0.009). A 30 per cent greater risk of the combined
end point of all-cause death or major cardiovascular event was observed
for switched patients compared with controls (P=0.03).
Berkeley Phillips, cardiovascular category medical manager at Pfizer
UK and one of the researchers, said: “This study provides further
evidence that patients should be switched only on a case-by-case basis,
and raises questions against switching as a matter of policy.”
But Magnus Hird, pharmacist practitioner at the Bloomfield Medical Centre
in Blackpool, said: “It’s important to point out that this
was an observational study and only suitable for generating a hypothesis.
There is no information on why the switches were carried out, what doses
patients were switched from and to, and all the data were from before
June 2005 when patients would be far less likely to have been switched
to equivalent simvastatin doses.”
He added that 28.2 per cent of the switched cohort had diabetes compared
with 26.3 per cent of those who stayed on atorvastatin and an additional
0.5 per cent in the switched cohort had angina and previous stroke or
myocardial infarction. “These differences might be small on their
own but they could add up to affect the outcome,” said Mr Hird.
Encouraging GPs to switch hyperlipidaemic patients from relatively expensive
statins, such as atorvastatin and rosuvastatin, to simvastatin has been
a major plank of primary care trusts’ prescribing policy.
Cardiovascular lead for Medway PCT and member of the National Institute
for Health and Clinical Excellence lipid modification guideline group
Rubin Minhas said: “This is a poor quality study susceptible to
confounding and bias selection. Switching between equivalent doses of
statins is safe, effective and an efficient use of scarce resources.”
A UK hospital audit published in April compared periods before and after
switching and found mortality was 5 per cent in patients on atorvastatin
but 14 per cent with simvastatin — but its methodology was similarly
criticised.
Chairman of the Primary Care Cardiovascular Society Terry McCormack criticised
newspaper reports of the new study, which failed to report its funding
source or its limitations, saying: “This will have caused false
and unnecessary anxiety among thousands of patients who have quite safely
switched their statins.”
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