Study medication
OSF
The study medication was the tetracycline antibiotic doxycycline, brand name Vibramycin (Pfizer). Study dose (200 mg) was based on a previous study using delay fear conditioning (According to the manufacturer’s information, the drug’s half-life is ∼16 h. Hence, the drug was cleared >99.9% before the recall session 7 d after ingestion. The drug was manufactured, blinded, and randomized separately for males and females, by a GMP-licensed pharmacy (Kantonsapotheke Zurich). Mannitol was used as placebo. Randomization was broken after the last participant completed the study, data were checked for consistency, and the study analysis plan was preregistered on OSF.