Cold kit formulation

aka technetium cold kit, lyophilised radiopharmaceutical kit

Many everyday radioactive scan drugs come as a freeze-dried powder in a sealed vial; the hospital pharmacy just adds the freshly produced radioactive solution and the finished injectable drug forms in minutes, no chemistry lab required.

A 'cold kit' is a sterile, pyrogen-free, freeze-dried (lyophilised) vial containing a non-radioactive ligand together with a reducing agent (commonly stannous/tin(II) chloride for technetium chemistry), buffer to set the correct pH for labelling, and stabilisers or fillers. Reconstituting the kit with freshly eluted radionuclide, most often sodium [99mTc]pertechnetate from a molybdenum-99/technetium-99m generator, or 68Ga chloride from a germanium-68/gallium-68 generator, drives rapid complex formation, sometimes at room temperature, sometimes with brief heating (for example 20 minutes in a boiling water bath for some 99mTc-HYNIC peptide kits), yielding an injectable radiopharmaceutical without dedicated radiochemistry infrastructure. Because the cold components are pre-sterilised and sealed, the entire process is a closed, aseptic operation that can be performed safely within a standard hospital nuclear medicine pharmacy rather than a full synthesis laboratory.

Cold kits typically have long, refrigerated shelf lives (commonly 3-12 months at 2-8°C) prior to radiolabelling, but the reconstituted, radiolabelled product itself is usually stable and usable for only a few hours at room temperature. Established 99mTc cold kits cover bone (MDP/HDP), myocardial perfusion (MIBI, tetrofosmin), renal (DTPA, MAG3-type, DMSA), hepatobiliary (mebrofenin), lung perfusion (MAA), lymphoscintigraphy (tilmanocept, nanocolloid), and neuroendocrine (HYNIC-TOC/TATE) imaging. The same general approach, sometimes called 'cold kit labelling', has since been extended to 68Ga-radiopharmaceuticals (for example the FDA/EMA-approved Illuccix and Locametz PSMA-11 kits), reducing the specialised equipment needed for routine PET tracer production. In the US, compounding radiopharmaceuticals, including kit reconstitution outside licensed manufacturing, is governed by USP General Chapter <825>, which sets minimum standards for preparation, dispensing and repackaging and defines beyond-use dating that accounts for radionuclide half-life and radiolytic decomposition.

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How it works

A vial of freeze-dried, sterile, non-radioactive ligand, reducing agent and buffer is reconstituted at the point of use simply by adding the freshly eluted radionuclide solution; the labelling chemistry then proceeds inside the sealed, closed vial without any dedicated synthesis equipment, yielding an injectable dose within minutes.

Strengths

Limitations

Since

99mTc cold kits in routine use since the 1970s; 68Ga cold kits (Illuccix, Locametz) FDA/EMA approved 2021

Dependencies

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Depends on (2)

Molybdenum-99/technetium-99m generators Germanium-68/gallium-68 generators

Needed by (2)

Germanium-68/gallium-68 generators Radiolabelling quality control

Dependencies are what this technology cannot be delivered without: manufacturing steps, instruments, software, upstream methods. See its full chain on the map.