Over 95% of patients in the pivotal study reported diarrhoea on neratinib, most commonly during the first month. The median cumulative duration was 59 days. More than 39% reported diarrhoea of ≥grade 3 severity. More than 16% discontinued neratinib due to diarrhoea. In most cases, diarrhoea was manageable using anti-diarrheal medication, dose hold, dose reduction or discontinuation. It is uncertain at this time whether the diarrhoea can be adequately managed by anti-diarrhoeal prophylaxis.