Inclusion Criteria:  1. Meet the following two conditions:  Planned administration of pyrotinib ≥ 21 days;  Grade 1-3 diarrhea after taking pyrotinib, and it is planned to continue taking pyrotinib;  2. Age ≥ 18 years old;  3. ECOG PS 0-2；  4. Life expectancy ≥ 6 months;  5. Voluntarily join the study, sign informed consent, have good compliance and are willing to cooperate with follow-up  Exclusion Criteria:  Those who may be allergic to pyrotinib or excipients; It has many factors affecting the absorption of oral drugs, such as inability to swallow, nausea and vomiting, etc; Patients with biliary obstruction; Participate in other diarrhea related clinical trials; Female patients during pregnancy and lactation, female patients with fertility and positive baseline pregnancy test, or female patients of childbearing age who are unwilling to take effective contraceptives during the whole test period; according to the researchers' judgment, there are serious diseases that endanger the safety of patients, or affect the patients to complete the study (including, but not limited to, severe hypertension and severe diabetes, which can not be controlled by drugs). Any other circumstances in which the investigator believes that the patient is not suitable to participate in this study.