Technetium ⁹⁹ᵐTc pertechnetate Other names: Technetium TC-99M pertechnetate

The pertechnetate ion distributes in the body similarly to the iodide ion, but is not organified. In contrast to the iodide ion, the pertechnetate is released unchanged from the thyroid gland.

Pertechnetate concentrates in the thyroid gland, salivary glands, gastric mucosa and choroid plexus. After intravenous administration, it equilibrates with the extracellular space.

Following the administration of sodium pertechnetate Tc-99m as an eye drop, the drug mixes with tears within the conjunctival space. Within seconds to minutes it leaves the conjunctival space and escapes into the inferior meatus of the nose through the nasolacrimal drainage system. During this process the pertechnetate ions pass through the canaliculi, the lacrimal sac, and the nasolacrimal duct. In the event of any anatomical or functional blockage of the drainage system there will be a backflow resulting in tearing (epiphora). Thus, the pertechnetate escapes the conjunctival space in the tears. The majority of the pertechnetate escapes within a few minutes of normal drainage and tearing.

Times to peak concentrations of pertechnetate following intravenous administration are 3.5 hours for cerebral spinal fluid (CSF) and 0.25 to 2 hours for thyroid (euthyroid patients).

The disappearance of pertechnetate from plasma is biexponential with an initial phase of 10 minutes and a terminal phase of 3 hours. The corresponding phases in CSF are less than 1 hour and 11-12 hours, respectively.

Distribution

Pertechnetate distributes throughout the body concentrating in the gastric mucosa, thyroid gland, salivary glands, and urinary bladder.

Elimination

Excretion

Elimination by urinary route is 27% in 1 day, 31% in 4 days, and 34% in 8 days based on rate of excretion.