Use of atropine-diphenoxylate compared with hyoscyamine to decrease rates of irinotecan-related cholinergic syndrome.

Background: Cholinergic syndrome is a well established acute adverse reaction associated with irinotecan. Cholinergic side effects can be ameliorated or prevented with anticholinergic agents. To date, no formal studies have compared atropine-diphenoxylate and hyoscyamine as premedications for prophylaxis of the cholinergic syndrome with irinotecan infusion. Objectives: To compare the incidence of cholinergic syndrome with irinotecan using atropine-diphenoxylate or hyoscyamine as premedication. Methods: We conducted a retrospective, single-center, nonrandomized, cohort study of adult patients treated with atropine-diphenoxylate or hyoscyamine as premedication before receiving irinotecan. For all irinotecan infusions, intravenous atropine was administered for patients experiencing any cholinergic reaction. Results: A total of 532 irinotecan cycles (354 cycles for atropine-diphenoxylate group; 178 cycles for hyoscyamine group) were analyzed in 80 patients. Overall incidence of cholinergic syndrome did not differ between atropine-diphenoxylate (8.2%) and hyoscyamine (9.0%) groups (P = .76). The incidence of cholinergic syndrome after the first cycle of irinotecan was similar between the 2 arms, atropine-diphenoxylate (14.6%) and hyoscyamine (10.7%), with P = .74. The most common cholinergic symptoms documented were abdominal pain or cramping, and diarrhea. Limitations: This study was subjected to vulnerabilities to bias and random error because of its observational retrospective design and small number of participants. Conclusions: Lack of difference in the incidence of cholinergic syndrome observed in irinotecan-treated patients suggests atropinediphenoxylate and hyoscyamine may both be effective prophylactic options. The findings support the need for a larger, randomized study to assess and compare these agents with other potential premedications such as scopolamine and atropine in prevention of irinotecan-related cholinergic syndrome.