title: Effect of octreotide LAR dose and weight on octreotide blood levels in patients with neuroendocrine tumors.
abstract: OBJECTIVE
  Octreotide long acting repeatable (LAR) is widely used for the control of symptoms of functional neuroendocrine tumors. At doses of 30 mg/mo, up to 40% of patients require subcutaneous octreotide "rescue" and up to 40% of patients are given more than 30 mg of LAR/mo. Octreotide acetate binds to the sst2 receptor with an affinity (Kd) of approximately 1 x 10(-9) mol/L (approximately equal to 1000 pg/mL), but higher (approximately equal to 10,000 pg/mL) concentrations of octreotide are required to completely saturate this receptor. Octreotide blood level measurement may be useful to guide LAR therapy in symptomatic patients or in patients who have tumor growth on traditional LAR doses. We hypothesize that LAR doses of 60 mg/mo will produce blood levels of 10,000 pg/mL or greater. At identical monthly LAR doses, patients with higher weights will require more medication to achieve similar plasma octreotide levels than individuals with lower body weights.
  
  
  METHODS
  Trough plasma, serum, urine, and saliva octreotide levels were obtained from 52 patients with carcinoid syndrome receiving 20 (n = 8), 30 (n = 19), or 60 mg LAR/mo (n = 10). Octreotide levels were determined by radioimmunoassay.
  
  
  RESULTS
  The mean +/- SD plasma octreotide levels for patients receiving 20, 30, or 60 mg LAR/mo were 2518 +/- 1020, 5241 +/- 3004, and 10,925 +/- 5330 pg/mL, respectively. Patient weight (kilograms) was inversely related to plasma octreotide levels. There was a significant correlation between plasma octreotide levels and octreotide levels measured in urine, saliva, and serum.
  
  
  CONCLUSIONS
  Frequent measurement of octreotide levels may be useful to guide octreotide therapy in patients with poorly controlled symptoms or those patients experiencing tumor growth.
authors.affiliation: Department of Surgery, Sections of Surgical Endocrinology and Oncology, Louisiana State University and The Veterans Administration Medical Center, New Orleans, LA 70012, USA. ewolte@lsuhsc.edu
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Woltering
authors.forename: Paris M
authors.initials: PM
authors.lastname: Mamikunian
authors.forename: Stanley
authors.initials: S
authors.lastname: Zietz
authors.forename: Seigfried R
authors.initials: SR
authors.lastname: Krutzik
authors.forename: Vay Liang W
authors.initials: VL
authors.lastname: Go
authors.forename: Aaron I
authors.initials: AI
authors.lastname: Vinik
authors.forename: Etta
authors.initials: E
authors.lastname: Vinik
authors.forename: Thomas M
authors.initials: TM
authors.lastname: O'Dorisio
authors.forename: Gregg
authors.initials: G
authors.lastname: Mamikunian
mesh_terms: D000328:Adult; D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000008:administration & dosage*; D001835:Body Weight; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000188:drug therapy* / Q000378:metabolism; D015282:Octreotide / Q000008:administration & dosage* / Q000097:blood*; D017481:Receptors, Somatostatin / Q000378:metabolism
chemical_list: D018931:Antineoplastic Agents, Hormonal; D017481:Receptors, Somatostatin; C093733:somatostatin receptor 2; D015282:Octreotide