Neratinib Dosing: 240mg Start, Diarrhea Prophylaxis, Hepatic Adjustment

　　1.What It Is

　　Neratinib is an oral,irreversible tyrosine kinase inhibitor targeting the HER2/EGFR family.Rather than broadly killing fast-dividing cells,it locks the kinase activity driving HER2 signaling and slows tumor growth.

　　It is used in adults with HER2-positive breast cancer in two main settings.

　　2.Early Breast Cancer:Extended Adjuvant

　　After completing trastuzumab-based adjuvant therapy:

　　dose:240mg(six 40mg tablets)once daily with food;

　　continue until recurrence or for up to 1 year;

　　take around the same time each day;

　　goal:eradicate micro-residual disease and reduce late relapse.

　　3.Advanced/Metastatic Disease:With Capecitabine

　　For HER2-positive advanced disease after≥2 prior anti-HER2 regimens,use a 21-day cycle:

　　Days 1-21:neratinib 240mg once daily with food;

　　Days 1-14:capecitabine 750mg/m²twice daily;

　　continue until progression or unacceptable toxicity.

　　4.Diarrhea:The Central Management Issue

　　Diarrhea often starts within the first days.Two approaches:

　　Option A:Loperamide prophylaxis(if not escalating)

　　Days 1-14:loperamide 4mg three times daily;

　　Days 15-56:4mg twice daily;

　　After day 56:as needed,max 16mg/day;

　　target:1-2 bowel movements per day.

　　Option B:Two-week escalation

　　Week 1:120mg/day;

　　Week 2:160mg/day;

　　Week 3 onward:240mg/day.

　　Breakthrough diarrhea:fluids,electrolytes,additional antidiarrheals,and possibly hold/reduce dose.Persistent grade 2 or grade 4 diarrhea may require discontinuation.

　　5.Hepatic Impairment

　　mild/moderate:usually no routine reduction,but monitor LFTs;

　　severe(Child-Pugh C):start at 80mg once daily;

　　check ALT/AST/bilirubin,more frequently in the first 3 months;

　　hold for grade 3 liver abnormalities,permanently stop for grade 4.

　　6.Administration and Interactions

　　swallow whole—do not chew,crush,or split;

　　if a dose is missed,skip it;resume next scheduled dose,no doubling;

　　avoid concurrent PPIs;

　　separate H2 blockers by≥2 hours before or 10 hours after;

　　separate antacids by≥3 hours;

　　avoid strong CYP3A4 inhibitors when possible.

　　7.Other Risks to Monitor

　　Beyond diarrhea and hepatotoxicity:

　　nausea,vomiting,abdominal pain,reduced appetite;

　　fatigue,rash,stomatitis;

　　embryo-fetal toxicity—effective contraception for patients with reproductive potential;

　　dehydration/renal impact if diarrhea is poorly controlled.

　　8.One-Line Read

　　Neratinib adds deeper HER2 coverage,but its success depends heavily on proactive diarrhea management—dosing right is less important than managing it carefully.