Lactose intolerance or gastrointestinal adverse drug effect? guidance for oncology pharmacists.

This article examines the impact of lactose excipients in oral oncology medications on patients with lactose intolerance (LI), a condition characterized by gastrointestinal symptoms following lactose ingestion due to lactase enzyme deficiency. A literature review and measurement of lactose content in common oncology tablets and capsules found that the amount of lactose excipient is substantially lower than the typical dietary lactose doses tolerated by most LI patients. Case reports of LI symptoms triggered by excipient lactose are rare and often involve very small patient numbers, with alternative causes such as adverse drug reactions or medical conditions more likely explanations for gastrointestinal symptoms. The article recommends that pharmacists reassure patients about the low lactose content in medications, consider other causes for symptoms, and use a provided flow chart to guide management, while also addressing potential nocebo effects related to lactose concerns.