Drawing on an ethnographic study of Chagas treatment among migrant domestic workers in Catalonia, conducted between January 2014 and May 2016, and utilizing the concepts of "lay care" and "living labyrinths," this paper explores how the efficacy of parasiticide treatments is experienced within relational and contextually situated frameworks. While pharmaceutical efficacy is often characterized by temporary and uncertain outcomes, the results indicate that lived efficacy is shaped by a complex interplay of embodied sociocultural, political, and historical processes, being continually negotiated and redefined within a broader context of global health values, biomedical technologies, migratory experiences and ethnicity, patient-doctor relationships, personal identities, daily demands, and care practices. The findings emphasize the reflexive management of the condition by those affected and highlight the role of pharmaceuticals as active agents that shape social and cultural dynamics, with significant impacts on social life and healthcare. By examining lived efficacy, the study suggests that limited access to healthcare services is not the sole process preventing treatment for Chagas, providing deeper insights into the logics behind actions related to Chagas pharmaceutical treatments. Incorporating "lay care" practices and perspectives into the therapeutic negotiation process not only acknowledges the complex "living labyrinths" navigated by social groups but also offers a foundation for reflecting on and reimagining alternative forms of care, recognizing their role in social and cultural reproduction.