THE CHEMICAL-STABILITY AND STERILITY OF SODIUM THIOPENTAL AFTER PREPARATION

Manufacturer's instructions recommend discarding unused portions of so dium thiopental 24 h after reconstitution. Heeding this recommendation may result in the disposal of a large proportion of prepared thiopent al. Although thiopental is relatively inexpensive, the volume prepared by many anesthesia departments could make this waste significant. To address this possibility, we investigated the chemical stability and s terility of thiopental in pharmacy-prepared, prefilled syringes. Stock solutions of thiopental were mixed and drawn into syringes under ster ile conditions by pharmacists or pharmacy assistants. Fifty-six sample s were stored under refrigeration (3 degrees C); the remaining 56 samp les were stored at room temperature (22 degrees C). Each day for 7 day s, eight samples from each group were analyzed by using high-performan ce liquid chromatography for chemical stability and cultured for micro biological colonization. Differences in thiopental concentration betwe en the room temperature and the refrigerated samples were measured ove r time by using repeated-measures analysis of variance (P less than or equal to 0.05). Three positive culture samples (S. epidermidis and S. hemolyticus) most likely represent laboratory contamination and not c olonization. At 22 degrees C, thiopental remains stable and sterile fo r 6 days and well beyond 7 days at 3 degrees C. Implications: This stu dy examines the shelf life of the anesthetic drug thiopental in pharma cy-filled syringes stored at either room temperature or under refriger ation. The results justify the use of prepared solutions beyond the pa ckage insert recommendation of 24 h.