title: Neuroendocrine response to intravenous citalopram in healthy control subjects: pharmacokinetic influences.
abstract: BACKGROUND
  The neuroendocrine response to intravenous citalopram may provide an acute, functional, in vivo measure of the neural serotonin (5-HT) system.
  
  
  OBJECTIVE
  To refine the quantification of acute neuroendocrine responses following intravenous citalopram in studies of 5-HT function.
  
  
  METHODS
  In 75 adult healthy subjects taking part in four similar protocols, we measured plasma prolactin and cortisol, as well as serial citalopram concentrations following intravenous citalopram (10 mg, 20 mg, 40 mg, 0.33 mg/kg) and placebo. The relationship between the AUC for intravenous citalopram during the first 150 min (AUC(150)) and the magnitude of the neuroendocrine response was determined. The role of pharmacokinetic (PK) parameters, as well as sensitivity to placebo injections, in influencing the neuroendocrine response to citalopram was then evaluated.
  
  
  RESULTS
  Citalopram produced a dose-dependent increase in cortisol and prolactin. The maximal increase from baseline correlated significantly but modestly with citalopram's AUC(150) (prolactin r(2)=0.23, P<0.0001; cortisol r(2)=0.3, P<0.0001). Additionally, citalopram's AUC(150) was affected by between-subject differences in both the peripheral and central volume of distribution. However, the neuroendocrine responses to citalopram did not correlate with the responses to placebo.
  
  
  CONCLUSIONS
  The parenteral citalopram challenge test is characterized by a modest concentration-response relationship, with concentration influenced by variable PK factors. Accounting for individual differences in drug distribution may improve the power of the citalopram challenge test, when used as an in vivo measure of central 5-HT function.
authors.affiliation: Department of Psychiatry, Western Psychiatric Institute and Clinic, Pittsburgh, PA, USA. lotrichfe@msx.upmc.edu
authors.forename: Francis E
authors.initials: FE
authors.lastname: Lotrich
authors.forename: Robert
authors.initials: R
authors.lastname: Bies
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Muldoon
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Manuck
authors.forename: Gwenn S
authors.initials: GS
authors.lastname: Smith
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Pollock
mesh_terms: D000328:Adult; D000368:Aged; D000928:Antidepressive Agents / Q000494:pharmacology*; D019540:Area Under Curve; D015283:Citalopram / Q000493:pharmacokinetics* / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007262:Infusions, Intravenous; D008297:Male; D008875:Middle Aged; D011388:Prolactin / Q000097:blood*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology*
chemical_list: D000928:Antidepressive Agents; D015283:Citalopram; D006854:Hydrocortisone; D011388:Prolactin; D017367:Selective Serotonin Reuptake Inhibitors