The stability of a sulphite-free epidural analgesic solution containing fentanyl, bupivacaine, and adrenaline.

BACKGROUND

Thoracic epidural infusion analgesia is optimised by using a triple component infusion containing a local anaesthetic, an opioid, and adrenaline. Adrenaline in solution is prone to oxidation, and stabilisers, such as antioxidants (e.g. sulphites) or chelators (edetates), are therefore commonly added. Sulphites may, however, have unwanted effects, especially allergic reactions. The aim of this study was to evaluate the stability of an analgesic infusion solution for epidural administration free of sulphites, containing adrenaline, fentanyl, bupivacaine, and disodium edetate.

METHODS

An epidural infusion solution containing adrenaline 2 μg/ml, fentanyl 2 μg/ml, bupivacaine 1 mg/ml, and disodium edetate 0.18 μg/ml was stored at 2-8°C for 4.5 months. A concentrate 11 times more potent, used for the production of the ready-to-use solution, was stored at 2-8°C for 9 months. Concentrations of the active ingredients were determined, pH was measured throughout the period, the clarity of the solutions was investigated, and the weight of the infusion bags recorded.

RESULTS

After 4.5 months at 2-8°C, the infusion solution contained adrenaline 97.5%, bupivacaine 100.9%, and fentanyl 102.6%. The pH stayed between 4.76 and 4.79, the solutions remained clear, and the weight was 99.9% of that found initially. The solution was also stable for 7 days at room temperature. The concentrate was stable (> 90%) for 9 months at 2-8°C.

CONCLUSION

The solution containing adrenaline, fentanyl, and bupivacaine, stabilised with disodium edetate, is stable for several months at 2-8°C, and at least for 7 days at room temperature without the addition of sulphites.