Rash & Diarrhea Prophylaxis With Capivasertib

Capivasertib is an important treatment option for patients with metastatic hormone receptor-positive breast cancer. Understanding how to decrease the incidence of adverse events will allow patients to stay on the medication longer, potentially deriving greater benefit, and may ultimately result in improved time to next treatment. The investigators hypothesize that cutaneous and diarrheal prophylaxis with antihistamine and loperamide for patients initiating capivasertib will reduce the incidence of grade 2 or greater rash and/or diarrhea at eight weeks.