Indication: Tucaxen (Tucatinib INN) 150 mg is prescribed for HER2-positive metastatic breast cancer in adults who previously underwent anti-HER2-based treatment in the metastatic setting.

Pharmacology: Tucatinib, a small molecule tyrosine kinase inhibitor (TKI), selectively blocks the HER2 receptor, disrupting its signaling pathways and impeding the growth of HER2-positive cancer cells.

Dosage and Administration: The typical dosage of Tucaxen is 300 mg orally twice daily (totaling 600 mg daily). It’s recommended for continuous administration alongside trastuzumab and capecitabine until disease progression or intolerable adverse effects occur.

Interactions: Tucatinib might interact with drugs affecting cytochrome P450 (CYP) enzymes or those influencing the QT interval. Patients should inform healthcare providers about all medications to prevent potential interactions.

Side Effects: Common side effects of tucatinib include diarrhea, nausea, vomiting, fatigue, reduced appetite, abdominal pain, and elevated liver enzymes. Serious adverse effects may encompass hepatotoxicity, diarrhea-associated dehydration, and interstitial lung disease/pneumonitis.

Precautions and Warnings: Patients on Tucaxen should be monitored for signs of hepatotoxicity, diarrhea-associated dehydration, and interstitial lung disease/pneumonitis. Regular liver function tests are advised, and any symptoms suggestive of liver or lung issues should be promptly reported.

Overdose Effects: In instances of overdose, supportive measures should be implemented. The specifics of tucatinib overdose effects are limited, hence management should focus on addressing symptoms and offering support.