Stability of a mixture of technetium Tc 99m sulfur colloid and lidocaine hydrochloride

The stability of a mixture of technetium Tc 99m sulfur colloid and lidocaine hydrochloride for up to eight hours was studied.

Three vials of technetium Tc 99m sulfur colloid were compounded according to the manufacturer's instructions. From each of the three vials, five samples were withdrawn into syringes with needles: 0.4, 0.45, 0.5, 0.63, and 1 mCi for testing after storage for zero, one, two, four, and eight hours, respectively. Each syringe contained the customary patient dose of 0.4 mCi at the time of testing. Fresh 0.9% sodium chloride injection was used to bring the volume of each syringe to 0.2 mL, and 0.2 mL of lidocaine hydrochloride 1% was added to bring the final volume to 0.4 mL. Measurements of pH, radiochemical purity, and particle size were conducted after the indicated storage times for each group of samples.

The pH of samples showed no substantial change over the eight-hour storage period, with individual values in the range of 4.5-5.5. Radiochemical purity did not change substantially, with values ranging from 98.9% to 99.9%. There was no meaningful change in the amount of radioactivity retained by filtration and no increase in particle size.

Adding lidocaine hydrochloride 1% to syringes containing technetium Tc 99m sulfur colloid and storing the syringes for up to eight hours had no effect on the pH or radiochemical purity of the mixture or on the radioactivity retained by a filter.