<p>Diuretics increase risks of dehydration secondary to vomiting/diarrhoea; prophylactic dexamethasone as an antiemetic may enhance lymphocytopenia; prochlorperazine may increase incidence of akathisia; antineoplastic agents (myelosuppression and diarrhoea). St John&#39;s wort, ketoconazole may reduce irinotecan exposure.</p>