Takiwasi is a therapeutic community for the treatment of Substance Use Disorders (SUDs) that combines traditional Amazonian medicine (TAM) with modern psychotherapy. One of the plant medicines from TAM used in this protocol is purgahuasca. It is a decoction of the vine Banisteriopsis caapi alone, whose use is traditional among the Awajún and other ethnic groups in Peru. The research began with a field trip to Awajún territory to explore the indigenous use of purgahuasca as an initiation rite. Then, analysis of its application was conducted in the clinical context of Takiwasi. Open-ended and semi-structured interviews with Awajún informants and Takiwasi’s therapeutic staff were performed and analyzed following the narrative methodological approach. Further clinical data on the ingestion of purgahuasca by Takiwasi’s SUD patients were obtained from the internal repository. These indicate that 359 (92.1%) patients reported having had the so-called mareación (dizziness), 299 (76.7%) experienced physical sensations, and 208 (53.3%) had visions. These effects can be related to the psychoactivity of β-Carbolines alkaloids from B. caapi, a medicinal plant that seems to have potential benefits also for SUD, especially giving a key contribution to the patients’ therapeutic process of becoming aware of the personal reasons behind addictive behaviors.