FDA will not publish a formal guidance document on SSRI-psychedelic washout protocols before November 2027.

The FDA won't issue official written instructions for doctors on how long patients taking SSRI antidepressants need to wait before using psychedelic medicines. Animal studies hint at an interaction risk, but the FDA needs human trial data to write guidance — and that data doesn't exist. FDA guidance documents take 12–24 months to write and approve internally, plus they need public comment periods. Official guidance won't land before November 2027.

Mouse fluoxetine interaction data is mechanistically suggestive but does not constitute the human trial data FDA requires before issuing binding guidance. Guidance documents require internal review cycles of 12–24 months minimum, public comment periods, and cross-division coordination. The 18-month claim in the original prediction is inconsistent with FDA's institutional process speed. Confidence adjusted downward from the original to reflect this process reality.