Anesthesia & Analgesia, Vol 86, 208-213, Copyright © 1998 by International Anesthesia Research Society
The chemical stability and sterility of sodium thiopental after preparation
JL Haws, N Herman, Y Clark, R Bjoraker and D Jones
Department of Anesthesiology, Witford Hall Medical Center Lackland Air Force Base, Texas, USA.
Manufacturer's instructions recommend discarding unused portions of sodium
thiopental 24 h after reconstitution. Heeding this recommendation may
result in the disposal of a large proportion of prepared thiopental.
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 sterility of
thiopental in pharmacy-prepared, prefilled syringes. Stock solutions of
thiopental were mixed and drawn into syringes under sterile conditions by
pharmacists or pharmacy assistants. Fifty-six samples were stored under
refrigeration (3 degrees C); the remaining 56 samples were stored at room
temperature (22 degrees C). Each day for 7 days, eight samples from each
group were analyzed by using high-performance liquid chromatography for
chemical stability and cultured for microbiological colonization.
Differences in thiopental concentration between the room temperature and
the refrigerated samples were measured over time by using repeated-measures
analysis of variance (P < or = 0.05). Three positive culture samples (S.
epidermidis and S. hemolyticus) most likely represent laboratory
contamination and not colonization. At 22 degrees C, thiopental remains
stable and sterile for 6 days and well beyond 7 days at 3 degrees C.
Implications: This study examines the shelf life of the anesthetic drug
thiopental in pharmacy-filled syringes stored at either room temperature or
under refrigeration. The results justify the use of prepared solutions
beyond the package insert recommendation of 24 h.
