The Pediatric Trials Network (PTN) is undertaking a groundbreaking study to assess the safety of commonly used off-patent medications when they are given to breastfeeding mothers. The Pharmacokinetics and Safety of Commonly Used Drugs in Lactating Women and Breastfed Infants (CUDDLE) tracks how different drugs are passed through breastmilk to determine dosing levels that are safe for both mom and baby. It is common for new mothers to have symptoms or medical conditions that must be treated with drugs. These mothers often struggle with their decision to take their medications because of the fear that the drugs will harm their children. With this study, PTN aims to find doses of commonly used drugs that are safe for both mothers and their breastfed infants. The study has enrolled participants since 2018 and continues to enroll approximately 50 lactating women, per drug, along with their breastfed infants, for each drug studied. Initially nine off-patent drugs are studied, including medications used to treat bacterial infections, depression and anxiety, high blood pressure, diabetes, and chronic pain. This study marks the milestone in completing study enrollment for these nine off-patent drugs: Azithromycin, Clindamycin, Labetalol, Metformin, Nifedipine, Ondansetron, Oxycodone, Sertraline, and Tranexamic Acid. This BPCA-PTN Data Coordinating Center supports in part of the CUDDLE study in FY 2024.