Drug interactions are divided into three categories: pharmacokinetic interactions, pharmacodynamic interactions, and compatibility interactions, with the first category being the most common, accounting for about 55%. The incidence of drug interactions increases significantly with the type of medication taken, and the occurrence of drug reactions is mainly moderate, accounting for 77%. Cancer patients are at high risk of drug interactions. Pharmacokinetic interactions Pharmacokinetic interactions can occur in four stages of drug absorption, distribution, metabolism and excretion. 1) Diet The effects are in the absorption of chemotherapeutic drugs and include delayed or reduced absorption, increased absorption, and no effect (see Table 1). Table 1 Food-drug interactions Antineoplastic drugs Food effects Altered pharmacokinetic parameters Fluorouracil (5-FU), methotrexate (MTX), topotecan Delayed absorption Affects peak blood concentration (Cmax) and time to peak blood concentration (Tmax) Capecitabine (CAPE), simustine, malafarin, gefitinib, hexamethonium, nitrogen mustard phenylbutyrate, thiopurine Decreased absorption Affects Area under the curve (AUC) and Cmax Erlotinib, vincristine Increased absorption Affects AUC and Tmax or Cmax Etoposide, 6-mercaptopurine, temozolomide, imatinib No effect No effect on AUC and Cmax