The present study was conducted to establish pharmaceutical intervention guidelines to enable hospital pharmacists to provide optimal pharmacotherapy to cancer patients. Many patients who use oral anticancer agents showed favorable drug compliance but insu‹cient drug adherence. It was demonstrated that in order to improve drug adherence, it is important to conduct interventions tailored to the patients' conditions so as to encourage interest in their medications, as well as to gain their understanding on the necessity and the side eŠects of their medications. In adjuvant chemotherapy with tegafur/gimeracil/oteracil potassium (S-1) following surgery for stomach cancer, a serum albumin value <3.5 g/ dL and a creatinine clearance value <80 mL/min were found to signiˆcantly aŠect S-1 dose reduction or termination of the S-1 intake due to side eŠects. Furthermore, patients for whom treatment was discontinued or dosage was reduced demonstrated a large reduction in body mass index. When adding insulin to an at-home high-calorie infusion, the insulin retention rate decreased when the number of grams of sugar level per 1 g of sodium bisulˆte in the infusion (G/g) was 364.6, whereas the insulin retention rate did not decrease when G/g was 466.0. Ourˆndings in the present study can serve as highly useful guidelines when pharmacists working in clinical settings conduct pharmaceutical interventions in pharmacotherapy for cancer.