Hicon

DRUG DESCRIPTION

HICON™ is a kit which provides a solution of Sodium Iodide I-131 with
a radioconcentration of 37 gigabecquerels/mL (1,000 millicuries/mL). Each mL
of the concentrated solution contains 37 GBq of no-carrier-added Sodium Iodide
I-131, < 2 mg of Disodium Edetate Dihydrate USP as a stabilizer, < 4.4
mg of Sodium Thiosulfate Pentahydrate USP as a reducing agent, and < 40 mg
of Dibasic Sodium Phosphate Anhydrous USP. The pH of the solution is between
7.5 and 9.0.

The concentrated solution provided with HICON™ is intended for use in
the preparation of capsules and solution of varying strengths for oral administration
for therapy.

Sodium Iodide I 131 Solution USP is designated chemically as Na 131I (MW 153.99,
CAS 7790-26-3).

Hard gelatin capsules provided for the preparation of the Sodium Iodide I-131
final dosage form contain approximately 300 mg of Dibasic Sodium Phosphate Anhydrous
USP as the absorbing buffer.

Physical Characteristics

Iodine I-131 decays by beta emission and associated gamma emission with a physical
half-life of 8.04 days.¹ Photons that are useful for detection and
imaging are listed in Table 1.

Table 1 : Principal Radiation Emission Data

Radiation	Mean % per Disintegration	Mean Energy (keV)
Beta-4 (average)	89.3	191.6
Gamma-14	81.2	364.5

External Radiation

The specific gamma-ray constant for iodine I-131 is 15.8 μC•kg^-1•MBq^-1•hr^-1
(2.27 R/mCi-hr) at 1 cm. The first half-value thickness of lead (Pb) for iodine
I-131 is 0.24 cm. A range of values for the relative attenuation of the radiation
emitted by this radionuclide that results from interposition of various thicknesses
of Pb is shown in Table 2. For example, the use of 2.55 cm of Pb will decrease
the external radiation exposure by a factor of about 1,000.

Table 2 : Radiation Attenuation by Lead Shielding

Shield Thickness (Pb) cm	Coefficient of Attenuation
0.24	0.5
0.89	10-1
1.6	10-2
2.55	10-3
3.73	10-4

To correct for physical decay of iodine I-131, the fractions that remain at
selected intervals after the time of calibration are shown in Table 3.

Table 3 : Physical Decay Chart: Iodine I-131, Half-Life 8.04
Days

Days	Fraction Remaining	Days	Fraction Remaining	Days	Fraction Remaining
0*	1.000	11	.388	22	.151
1	.918	12	.356	23	.138
2	.842	13	.327	24	.127
3	.773	14	.300	25	.116
4	.709	15	.275	26	.107
5	.651	16	.253	27	.098
6	.597	17	.232	28	.090
7	.548	18	.213	29	.083
8	.503	19	.195	30	.076
9	.461	20	.179
10	.423	21	.164
*Calibration time