title: Tryptophan-morphine interactions and postoperative pain.
abstract: Patients undergoing abdominal surgery were infused with saline or the 5-hydroxytryptamine (5-HT) precursor tryptophan starting in the operating room and continuing for three hours in the recovery room. There was a nonsignificant trend for patients who received tryptophan to have higher pain scores. In the saline-treated patients, plasma tryptophan was below the range for normal healthy subjects, and there was a strong positive relationship between plasma tryptophan and morphine requirements. These data, taken together with animal data obtained using the formalin pain test, suggest that a 5-HT system in the brain can antagonize the dissociative state produced by morphine, which helps patients to tolerate pain. When plasma tryptophan falls below normal levels, brain 5-HT falls and morphine requirements are reduced. While tryptophan may potentiate spinal 5-HT function to decrease nociceptive afference in some circumstances, there may be clinical conditions in which the use of tryptophan is contraindicated.
authors.affiliation: Department of Psychology, McGill University, Montreal, Quebec, Canada.
authors.forename: K B
authors.initials: KB
authors.lastname: Franklin
authors.forename: F V
authors.initials: FV
authors.lastname: Abbott
authors.forename: M J
authors.initials: MJ
authors.lastname: English
authors.forename: M E
authors.initials: ME
authors.lastname: Jeans
authors.forename: R A
authors.initials: RA
authors.lastname: Tasker
authors.forename: S N
authors.initials: SN
authors.lastname: Young
mesh_terms: D004311:Double-Blind Method; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007430:Intraoperative Care; D009020:Morphine / Q000097:blood / Q000627:therapeutic use*; D010149:Postoperative Pain / Q000188:drug therapy*; D011182:Postoperative Care; D014364:Tryptophan / Q000097:blood / Q000627:therapeutic use*
chemical_list: D009020:Morphine; D014364:Tryptophan