title: In reply.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Angst
authors.forename: J David
authors.initials: JD
authors.lastname: Clark
mesh_terms: D015760:Alfentanil / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D012054:Reinforcement, Psychology
chemical_list: D000701:Analgesics, Opioid; D015760:Alfentanil