<p>May increase the serum levels of CYP3A4, CYP2C8 and P-glycoprotein substrates. Increased exposure with CYP3A4 inhibitors (e.g. ketoconazole, clarithromycin, atazanavir, ritonavir). CYP3A4 inducers (e.g. carbamazepine, rifampicin) may reduce exposure to lapatinib. Increased risk of QT prolongation with drugs known to prolong QT intervals (e.g. antiarrythmic agents, cumulative high-dose anthracycline therapy). May increase serum levels of digoxin.</p>