Stability of thiotepa (lyophilized) in 0.9% sodium chloride injection

The stability of thiotepa in a new formulation of the drug was studied. Vials of Thioplex (Immunex), a relatively new lyophilized formulation of thiotepa, were reconstituted with sterile water and diluted with 0.9% sodium chloride injection in polyvinyl chloride infusion bags to thiotepa concentrations of 0.5, 1, and 3 mg/mL. The solutions were stored at 8 and 25 degrees C in ambient light and analyzed at 0, 8, 24, and in most cases 48 hours for thiotepa concentration and chloro-adduct formation by stability-indicating high-performance liquid chromatography. Thiotepa 1 and 3 mg/mL was stable for 48 hours at 8 degrees C and for 24 hours at 25 degrees C. Thiotepa 0.5 mg/mL was not stable at either temperature. Storage at 8 degrees C slowed but did not prevent chloro-adduct formation and loss of potency. The pH tended to increase with time; turbidity remained low. Thiotepa (lyophilized) 1 and 3 mg/mL in 0.9% sodium chloride injection was stable for 48 hours at 8 degrees C and for 24 hours at 25 degrees C; the drug was unstable when diluted to 0.5 mg/mL and stored under the same conditions.