title: The partial 5-hydroxytryptamine1A receptor agonist buspirone does not antagonize morphine-induced respiratory depression in humans.
abstract: Based on experiments in rats, serotonin receptor 5-hydroxytryptamine (5-HT)(1A) agonists have been proposed as a potential therapeutic strategy for the selective treatment of opioid-induced respiratory depression. We investigated the clinical applicability of this principle in healthy volunteers. Twelve subjects received 0.43 mg/kg morphine (30 mg for 70 kg body weight) administered intravenously (i.v.) over approximately 2 h. At the start of the morphine infusion, they received in a randomized, double-blind cross-over design 60 mg p.o. buspirone or placebo. Respiratory depression (hypercapnic challenge) and pain (electrical stimuli: 5 Hz sinus 0-20 mA; chemical stimuli: 200 ms gaseous CO(2) pulses applied to the nasal mucosa) were assessed at baseline, at the end of the morphine infusion, and a third time after antagonizing the opioid effects by i.v. administration of 2 mg naloxone. The linear relationship between the minute ventilation and the CO(2) concentration in the inspired air of 1.07+/-0.27 l/mm Hg CO(2) at baseline conditions became shallower (0.45+/-0.23 l/mm Hg CO(2)) after morphine administration (P<0.001), indicating respiratory depression, which was significantly reversed by naloxone (0.95+/-0.43 l/mm Hg CO(2); P=0.001). Co-administration of buspirone had no effect on morphine-induced respiratory depression (slope 0.45+/-0.23 l/mm Hg CO(2) under morphine plus placebo versus 0.38+/-0.25 l/mm Hg CO(2) under morphine plus buspirone; P=0.7). Significant morphine-induced analgesia was observed in both pain models and was reversed by naloxone but unaffected by buspirone. Buspirone significantly increased the nausea induced by morphine (P=0.011). Oral co-administration of a high dose of the clinically available 5-HT(1A) agonist buspirone cannot be advised as a remedy for opioid-induced respiratory depression. This is indicated by its lack of anti-respiratory depressive effects and by the buspirone-associated increase of morphine-induced nausea.
authors.affiliation: pharmazentrum frankfurt/ZAFES, Institute of Clinical Pharmacology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.
authors.forename: B G
authors.initials: BG
authors.lastname: Oertel
authors.forename: A
authors.initials: A
authors.lastname: Schneider
authors.forename: M
authors.initials: M
authors.lastname: Rohrbacher
authors.forename: H
authors.initials: H
authors.lastname: Schmidt
authors.forename: I
authors.initials: I
authors.lastname: Tegeder
authors.forename: G
authors.initials: G
authors.lastname: Geisslinger
authors.forename: J
authors.initials: J
authors.lastname: Lötsch
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects*; D002065:Buspirone / Q000008:administration & dosage / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D009020:Morphine / Q000009:adverse effects*; D009270:Naloxone / Q000627:therapeutic use; D009292:Narcotic Antagonists / Q000627:therapeutic use; D009325:Nausea / Q000139:chemically induced; D010146:Pain / Q000188:drug therapy; D012131:Respiratory Insufficiency / Q000139:chemically induced* / Q000188:drug therapy*; D058825:Serotonin 5-HT1 Receptor Agonists
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D058825:Serotonin 5-HT1 Receptor Agonists; D009270:Naloxone; D009020:Morphine; D002065:Buspirone