Tackling statin intolerance with n-of-1 trials (TaSINI) in primary care: protocol for a feasibility randomised trial...

Statins reduce the incidence of cardiovascular disease (CVD) and cause few adverse effects. Half of patients prescribed statins discontinue treatment due to perceived intolerance. Placebo-controlled (blinded) n-of-1 trials have shown people with perceived intolerance that the statin does not cause adverse events and most resume treatment. However, blinded n-of-1 trials are impractical to deliver in routine practice. Tackling Statin Intolerance using n-of-1 trials (TaSINI) will test the feasibility of a general practitioner (GP)-delivered behavioural intervention endorsing an unblinded n-of-1 trial to increase adherence to statins relative to usual care.

TaSINI is a feasibility randomised controlled trial with a nested qualitative substudy. Ninety primary care patients who have discontinued statins due to intolerance or refused treatment will be randomised to an unblinded n-of-1 trial, a blinded n-of-1 trial (positive control) or usual care (negative control). Participants randomised to usual care will be advised to take statin therapy to prevent CVD. In both n-of-1 trial arms, GPs will deliver a behaviourally informed intervention that accessibly explains the benefits of statins, the prevalence of adverse effects and endorse the benefit of experimenting with medication. Participants will alternate between 4 weeks of medication and no medication (unblinded arm) or randomly sorted active and placebo (blinded arm) and will record adherence, symptoms and symptom attributions throughout. After 6 months, GPs will feedback symptom data during active/inactive treatment periods. All participants will be asked if they would like to initiate statin treatment. Measures of feasibility will be met if 4% of invited patients enrol, 50% of participants randomised to n-of-1 trials engage with the experiment and 25% more participants initiate statin in the unblinded n-of-1 arm than in usual care.

This study has been granted ethical approval by North of Scotland Research Ethics Service. The results will be written up for publication and show whether to progress to an effectiveness trial where the primary outcome would be differences in low-density lipoprotein concentration.