Digoxin for the Reinduction of Radioiodine Uptake in Metastatic or Locally Advanced Non-medullary Thyroid Carcinoma

"Participants will be treated with digoxin tablets for 3 weeks. On the first they, participants will start with a starting dosage of 3x0.25mg with 6 hours between each administration. Thereafter they will continue with a dosage of 1x0.25mg. Participants aged \>70 years or with body weight \<55kg will initiate a starting dosage of 3x0.125mg with 6 hours between each administration. Thereafter they will continue with a dosage of 1x0.125mg.~After one week the blood concentration of digoxin will be measured. According to this blood concentration, the dose of digoxin will be adjusted."