Posology : מינונים

4.2   Posology and method of administration
Posology
The activity administered is a matter for clinical judgement. The therapeutic effect is only achieved after several months.

For the treatment of hyperthyroidism
The activity administered depends on the diagnosis, the size of the gland, thyroid uptake, and io- dine clearance. The following target organ doses may be used:
 unifocal autonomy                                 300 – 400 Gy target organ dose multifocal and disseminated autonomy              150 – 200 Gy target organ dose Graves’ disease                                   200 Gy target organ dose In Graves’ disease, multifocal or disseminated autonomy, the above mentioned target organ doses are related to the overall weight of the thyroid gland, however in the unifocal autonomy, the target organ dose is only related to the weight of the adenoma.

The activity administered is usually in the range of 200-800 MBq but repeated treatment may be necessary.

Patients should be rendered euthyroid medically whenever possible before giving radioiodine treatment for hyperthyroidism.
The activity to be administered may be calculated according to the following equation:  target dose (Gy) × target volume (ml)
A MBq =                                                  ×K max. uptake 131I % × effective T ½ (days)

Legend: target dose = is the target absorbed dose in the whole thyroid gland or in an adenoma  target volume = volume of the whole thyroid gland (Graves’ disease, multifocal or disseminated autonomy)
 max. uptake I-131= max. uptake of I-131 in the thyroid gland or nodules in % of the administered activity as established in a test dose.
 effective T ½ = effective half life of I-131 in the thyroid gland

K = 24,67
Other dosimetric procedures may also be used including sodium pertechnetate (Tc-99m) thyroid uptake tests to determine the appropriate target organ dose (Gy).

Fixed dose protocols may also be used.

For thyroid ablation and treatment of metastases
The administered activities following total or subtotal thyroidectomy to ablate remaining thyroid tissue are in the range of 1850-3700 MBq. It depends on the remnant size and radioiodine uptake.
In subsequent treatment for metastases, administered activity is in the range 3700-11100 MBq.

For measuring remnant tissue, metastases and recurrence
For post thyroid ablation (for thyroid remnant, metastases and recurrence): A maximum activity of 400 MBq.

Paediatric population
The activity to be administered in children and adolescent should be determined after performing an individual dosimetry (see section 4.4).

Method of administration

The capsule should be taken fasting and with plenty of liquid and swallowed whole. Before giving the capsule to children, in particular to younger children, it should be ensured that the capsule can be swallowed whole. Giving it with mashed food is recommended.

Administration protocol
1    The tin must be removed from the package and the leadpot must be taken out       2    The lid must be turned gently clockwise until a slight resistance is met, then the lid must be lifted from the leadpot leaving the inner vial in the base.
3    The vial, containing the capsule, must be placed into a measuring device to determine the ac- tivity.
4    The vial must be replaced in the leadpot and the lid must be mounted on the leadpot without turning.
5    The patient must be asked to unscrew the lid of the leadpot and the vial cap simultaneously by turning it three times counterclockwise.
6    The patient must remove the lid, lift the leadpot, and swallow the capsule.