We present adaptable activities for models of drug movement in the human body -- pharmacokinetics -- that motivate the learning of ordinary differential equations with an interdisciplinary topic. Specifically, we model aspirin, caffeine, and digoxin. We discuss the pedagogy of guiding students to understand, develop, and analyze models, progressing in complexity to a system of differential equations. We investigate the effects of parameter values that distinguish various health levels, and dosing that may have toxic effects. Our assignments include modeling in a student-centered, active, and increasingly inquiry-oriented setting through which the mathematics and biology inform and reinforce each other. We include supplemental information regarding inquiry methods, student learning outcomes, a student's commentary about our activities, and support through mathematical communities such as POGIL and SIMIODE.