title: Clearance of the high intestinal (18)F-FDG uptake associated with metformin after stopping the drug.
abstract: OBJECTIVE
  This study was done to determine whether interruption of metformin before (18)F-FDG PET/CT imaging could prevent the increased (18)F-FDG uptake in the intestine caused by this drug.
  
  
  METHODS
  Included in the study were 41 patients with known type 2 diabetes mellitus who were referred to our department for evaluation of various neoplastic diseases. Patients underwent two (18)F-FDG PET/CT scans, the first while they were on metformin and the second after they had stopped metformin. They stopped metformin and did not take any other oral antidiabetic medication starting 3 days before the second study and their blood glucose level was regulated with insulin when necessary to keep it within the range 5.55-8.33 mmol/l. FDG uptake was graded visually according to a four-point scale and semiquantitatively by recording the maximum standardized uptake value (SUVmax) in different bowel segments. A paired-samples t-test method was used to determine whether there was a significant difference between SUVmax measurements and visual analysis scores of the metabolic activity of the bowel in the PET/CT scans before and after stopping metformin.
  
  
  RESULTS
  Diffuse and intense (18)F-FDG uptake was observed in bowel segments of patients, and the activity in the colon was significantly decreased both visually and semiquantitatively in PET/CT scans performed after patients stopped metformin (p<0.05). There was a statistically significant decrease in activity in the small intestine on visual analysis (p<0.05), but semiquantitative measurements did not show a significant decrease in the SUVmax values in the duodenum or jejunum (p>0.05).
  
  
  CONCLUSIONS
  Metformin causes an increase in (18)F-FDG uptake in the bowel and stopping metformin before PET/CT study significantly decreased this unwanted uptake, especially in the colon, facilitating the interpretation of images obtained from the abdomen and preventing the obliteration of lesions.
authors.affiliation: Department of Nuclear Medicine, Okmeydani Training and Research Hospital, Istanbul, Turkey. tozulker@ttmail.com
authors.forename: Tamer
authors.initials: T
authors.lastname: Ozülker
authors.forename: Filiz
authors.initials: F
authors.lastname: Ozülker
authors.forename: Meral
authors.initials: M
authors.lastname: Mert
authors.forename: Tevfik
authors.initials: T
authors.lastname: Ozpaçaci
mesh_terms: D000368:Aged; D016477:Artifacts; D001692:Biological Transport / Q000187:drug effects; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000000981:diagnostic imaging / Q000187:drug effects*; D008297:Male; D008687:Metformin / Q000008:administration & dosage* / Q000494:pharmacology*; D008875:Middle Aged; D049268:Positron-Emission Tomography; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18; D008687:Metformin