The bulletin also includes updated prescribing advice for atorvastatin. Many important interactions for simvastatin and atorvastatin relate to drugs that inhibit or induce metabolism via the cytochrome P450 enzyme.
If co-prescription with a drug that increases systemic exposure to statins is unavoidable, start the statin at the lowest dose. The updated advice for atorvastatin provides recommended maximum doses when using with ciclosporin (10mg), clarithromycin (20mg) and itraconazole (40mg).
Ciclosporin interacts with all statins and is contraindicated with rosuvastatin. Statins may affect coumarin anticoagulation and increase the risk of haemorrhagic events. Therefore, INR should be monitored before starting treatment with statins and throughout treatment. Caution is particularly necessary with fluvastatin.
The use of fibrates with statins increases the risk of myopathy and careful monitoring is needed. The recommended maximum daily dose of simvastatin is 10mg when used with fibrates (except fenofibrate).
For rosuvastatin, start with 5mg and do not exceed 20mg during use with fibrates. Ezetimibe has no pharmacokinetic interaction with statins. However, ezetimibe alone is associated with a risk of myopathy and an additive risk with statins cannot be ruled out
Further information: MHRA