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

Lactose intolerance is quite common among people world-wide. Despite this, lactose is often used as a pharmaceutical excipient due to its pharmacologically inactive nature. We reviewed the literature to determine how much lactose can typically be tolerated by patients reporting a history of lactose intolerance and measured the amount of excipient in commonly used solid oral oncology dosage forms. We determined that most patients should be able to tolerate a significantly higher amount of lactose than that found in maximum daily doses of oncology tablets and capsules, based on our literature review and the measured amount of excipient in commonly used solid oral oncology dosage forms. If patients report gastrointestinal symptoms, adverse drug reactions and medical conditions should be considered as more likely causes than lactose intolerance. We created a flow chart for pharmacists to follow when dispensing oral medications to lactose intolerant patients. This chart may assist in patient management if the lactose content of a medication is questioned or if a patient reports gastrointestinal symptoms.