Coadministration of atorvastatin (40 mg, single dose) and sofosbuvir/velpatasvir (400/100 mg, once daily) increased atorvastatin Cmax and AUC by 68% and 54%, respectively. This is likely due to inhibition of P-gp and/or BCRP by velpatasvir. The European SmPC for sofosbuvir/velpatasvir advises that no adjustment of sofosbuvir/velpatasvir or atorvastatin is required, but the US Prescribing Information warns for an increased risk of myopathy, including rhabdomyolysis. The amber call reflects the more cautious option. Consider asking patients to self report potential side effects of increased concentrations such as muscle pain. Based on the study data, dose reductions could be discussed for patients prescribed more than 40 mg as this has not been studied.