Table 2.

Guidance times for withholding substances that may interfere with NIS-mediated thyroid radio-pharmaceutical uptake prior to imaging

Interfering substanceRecommended time to withhold prior to imaging
Anti-thyroid drugsPertechnetate imaging Can be continued 123I or 131I 2–4 days
Thyroxine (T4) therapy4–6 weeks
Triiodothyronine (T3) therapy2 weeks
Exogenous iodine (eg water-soluble iodinated contrast)6–8 weeks
AmiodaroneGreater than 6 months
  • Adapted from Balon et al.8