A prospective trial on the effect of body mass index and sex on plasma octreotide levels in patients undergoing long-term octreotide LAR therapy.

OBJECTIVES Octreotide long acting repeatable (LAR) is commonly used to control the symptoms of patients with functional neuroendocrine tumors. Unfortunately, most patients escape control over time and require higher LAR doses or more frequent rescue therapy to remain asymptomatic. Previous work has shown that body weight and monthly LAR dose will significantly affect circulating plasma octreotide levels in patients undergoing therapy. METHODS To determine if other parameters change circulating plasma octreotide levels, we prospectively studied 82 patients undergoing long-term LAR therapy. RESULTS Multivariate analysis demonstrated that the plasma octreotide levels decrease by approximately 3.4% for each unit of body mass index (BMI) increase (P = 0.03), adjusting for sex and monthly LAR dose. Plasma octreotide levels for females were approximately 47.6% higher than those for males (P = 0.045), adjusting for BMI and monthly LAR dose. Initial and subsequent octreotide LAR doses should take into consideration sex and BMI. Males are estimated to require 14.1-mg (SD, 7.25) higher monthly LAR doses than females with the same BMI. CONCLUSIONS We have shown that plasma octreotide levels are affected by not only monthly LAR dose but also BMI and sex. We hope these observations will make choosing initial and subsequent octreotide LAR doses easier for physicians.