Differential Effects of Acute and Chronic Fluoxetine on Psychedelic-Induced Behavior in Mice: Implications for Clinical Trials.
ACS pharmacology & translational science March 13, 2026 Bo Jarrett Wood, M Frances Vest, Catharine Carfagno et al.
In male mice, chronic treatment with the SSRI fluoxetine (Prozac) reduced the head-twitch response—a behavioral sign of 5-HT2A receptor activation—caused by the psychedelic DOI, while acute fluoxetine had no effect on DOI. The reduced response reversed after a 14-day discontinuation of fluoxetine. Acute fluoxetine also weakened the efficacy (but not potency) of psilocybin, indicating that SSRI-psychedelic interactions may differ depending on the specific psychedelic compound. These results suggest that a history of SSRI use can alter sensitivity to psychedelics in a compound-specific manner, with implications for psychedelic-assisted therapy in people taking SSRIs.