Coadministration with quetiapine does not preclude the use of glecaprevir/pibrentasvir. Quetiapine is metabolised by CYP3A4. Concentrations of quetiapine may increase as glecaprevir/pibrentasvir is a weak inhibitor of CYP3A4. Increased concentrations of other CYP3A4 substrates have been observed with glecaprevir/pibrentasvir (27% increase in AUC with midazolam; 45% increase in AUC of tacrolimus) therefore a similar magnitude of increase may be anticipated with quetiapine. Whilst unlikely to be clinically significant in most patients (glecaprevir/pibrentasvir was well tolerated in a recent study in patients with chronic HCV and psychiatric disorders), caution is advised when using higher doses of quetiapine (e.g. over 400mg/day), or with liver impairment, the elderly, patients with cardiac conduction abnormalities or other drugs known to prolong QT interval. Concomitant administration of cytochrome P450 3A4 inhibitors, such as HIV-protease inhibitors, azole-antifungal agents, erythromycin, clarithromycin and nefazodone, is contraindicated in the European label for quetiapine.