The efficacy and the incidence of drowsiness with different modified administrations of olanzapine in preventing chemotherapy induced nausea and vomiting

121 Background: Olanzapine is now widely used for preventing chemotherapy-induced nausea and vomiting (CINV). The recommended oral administration is 10 mg at bedtime. However, drowsiness is one of common side effects of olanzapine. Several modified administrations of olanzapine, such as dose reduction and early taken are being tried in clinical practice to avoid drowsiness. Methods: We retrospectively reviewed 500 patients who used olanzapine for CINV from January 2018 to January 2019 in our department. Eligible criteria include patients who used the constant administration of olanzapine for at least four days to prevent acute and delayed CINV. Patients were grouped into three groups according to three different administrations of olanzapine as full dose (10mg), half dose (5 mg), and early taken (10 mg, six hours before bedtime). Eligible patients were randomly selected in each group as a ratio of 1:1:1. The frequency of CINV, the incidence of drowsiness and the duration of olanzapine administration were collected and compared. Results: There are 267 patients met the criteria and 48 patients in each group. The median frequency of CINV per day in all 144 patients was 3, 1, 1 on day 1 to 3 after chemotherapy respectively. The frequency of CINV was not different among three groups. The incidence of drowsiness was 38%, 20%, and 23% in full dose, half dose and early taken groups (P < 0.05). The median days of administration were 5, 10 and 6 days in full dose, half dose and early taken group, respectively. Conclusions: Modified administration of olanzapine, both by dose reduction and early taken, could have similar effect in preventing CINV but reduced the incidence of the side effect as drowsiness. Further study should be done to explore the proper administration of olanzapine in preventing CINV.