Radioiodine therapy using oral administration of Iodine-131 (I) is a widespread employed strategy for the treatment of hyperthyroidism and thyroid cancer. Such a therapy requires well-trained staff, equipment and procedures regarding radiation safety. The aims of this work are to report an incidental experience of radioprotection with a 370 MBq sodium [I] iodide capsule, which arose following vomiting one minute after the oral administration in a nuclear medicine department and assessment of capsule leakage in a stomach like environment by in vitro experiment. Measurements of the radiation dose rate at the different steps of the decontamination procedure were performed and management of the situation described. Dose rate in vomit was 113 µSv/h [directional dose equivalent H'(0.07)] after capsule withdrawal and was decreased by 10 times after the first decontamination attempt. To evaluate the I release following administration to the patient, an in vitro experiment was designed to recap capsules degradation in a stomach like environment including acidic solution (pH 1) and temperature at 35-37°c. A significant release of I (<6%) was observed in the first 2 min of the in vitro experiment. Sodium [I] iodide capsules disruption occurred at 150 s for capsule 1 and 133 s for capsule 2. Incidental contamination with I in the clinics is of important concern in nuclear medicine and precautions that allow optimization and pertinent management of the situation should be known by the nuclear medicine and radioprotection community.