| Completed | 4 | 33 | US | Isotretinoin, accutane, dextromethorphan, robitussin pediatric | University of Washington, National Institute of General Medical Sciences (NIGMS) | CYP2D6 Polymorphism | 11/23 | 11/23 | | |
| Recruiting | 4 | 50 | US | Cimetidine 200 MG, Tagamet | University of Washington, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) | Postpartum, Lactation, Drugs in Breast Milk, Mammary Drug Transporters, BCRP, OCT1 | 09/28 | 09/28 | | |