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Pharmacopolitics, statin switching and therapeutic substitution: much ado about something

Should doctors think about the costs of the drugs they choose to prescribe? Should patients be made aware of the costs of their drug treatment? Ten or twenty years ago it would have been considered an affront to the sanctity of the doctor–patient relationship to allow such issues to influence treatment. However, times have changed. Today, in the UK we are guided, advised, audited and incentivised to consider cost as one of the primary issues when selecting drug treatment. Where does the balance lie? As clinicians we are usually responsible for individuals rather than populations and as such are tasked with providing the best standard of care according to the current evidence base. However, whilst we are responsible for individual patients, prescribing decisions for statin therapy cannot be regarded in isolation to population issues as they may affect around 20% of the adult population in the UK. Thus savings that can be accrued from costeffective prescribing in this area can be used to subsidise the costs of other more expensive therapies. A secondary argument is about moderate vs. intensive statin therapy, which can be distilled down within primary prevention to a lack of a clinical evidence base, safety concerns and probably the more important argument – cost. This will cease to be regarded with such contention when more expensive branded drugs, such as atorvastatin, are available as cheap generics. Currently there is consensus that statin switching is acceptable provided that population cholesterol levels remain unchanged. If this can be demonstrated then potentially hundreds of million pounds could be saved by eliminating wasteful prescribing of branded statins, as is already happening (1). The debate around switching statins rests on the proposition that the benefit of statins is mediated through their ability to reduce low-density lipoprotein (LDL) cholesterol. Previous attempts to differentiate between statins on grounds of ‘pleiotropic effects’ have not shown differences in clinical outcomes between statins (2,3) and it is well accepted that the more effectively a statin lowers LDL cholesterol the greater is its ability to reducing cardiovascular events (4,5). The 2-year follow-up study by Usher-Smith et al. (6) strengthens their initial report (7) which showed that switching from atorvastatin to simvastatin does not lead to significant changes in serum cholesterol and is not associated with significant adverse effects. Their study was not randomised but rather a preand post-intervention trial employing historical controls and did not measure clinical outcomes. Therefore, the caveats around such studies apply whether the findings are favourable to a policy of switching or not. There has been much media interest in a recently published case–control study undertaken by the manufacturer of atorvastatin; a statin that will retain its patent until at least 2011. This study is based on the hypothesis that switching might have adverse consequences on clinical outcomes (8). The study concluded that there were a greater number of clinical events in subjects switched from atorvastatin to generic statins. Within their dataset, this conclusion was valid, but because they did not examine statin switching at therapeutically equivalent doses, their conclusions cannot be generalised to modern statin switching between equivalent drug-dose combinations. Herein lies the most important aspect of statin switching, that switching for valid economic reasons must be carried out using therapeutically equivalent doses of statins, e.g. atorvastatin 10 mg ⁄ 20 mg to simvastatin 40 mg. This switching also has the added benefit of equivalent clinical end-point data. Altering lipid-lowering therapy at non-equivalent doses is a different process and is not justified. For example, switching to low-dose simvastatin (unless there are interactions that mean a lower dose is therapeutically more efficacious) or from high-dose atorvastatin (40 or 80 mg) doses should not be considered as statin switching; rather it is a fundamental alteration in therapeutic strategy from intensive statin therapy to standard treatment. This may sometimes be justified, but should not be grouped together with statin switching and not justified on health economic grounds. The study by Usher-Smith et al. (6) contrasts with that by Phillips et al. (8) in highlighting the difference between the consequences we might see if robust evidence were available on equivalent dose switching practices and is therefore pivotal to the current switching debate. Usher-Smith et al. (6) conclude that statin switching can be undertaken safely providing it Linked Comment: Usher-Smith et al. Int J Clin Pract 2008; 62: 480–4. Switching is acceptable provided that population cholesterol levels remain unchanged