EFFECT OF PH ON ABSORPTION OF SUFENTANIL CITRATE IN A PORTABLE PUMP RESERVOIR DURING STORAGE AND ADMINISTRATION UNDER SIMULATED EPIDURAL CONDITIONS

Sufentanil (5 mug/ml as citrate) was investigated for its stability wh en diluted with sodium chloride 0.9%, in 100 ml polyvinyl chloride por table pump reservoirs during administration under simulated epidural c onditions at 32-degrees-C for 48 h. Sufentanil was absorbed into the p olyvinyl chloride, resulting in a reduction of 10.9% of the concentrat ion after 48 h. The absorption of sufentanil (5 mug/ml as citrate), al one and in combination with bupivacaine hydrochloride (2 mg/ml), was i nvestigated when diluted with sodium chloride 0.9% in combination with a citrate buffer (pH 4.6), in the same reservoirs under similar condi tions. There was no loss of sufentanil after 48 h in both experiments. The effect of the pH on the absorption of sufentanil in polyvinyl chl oride was investigated at different pH values. After storage for 21 da ys at 32-degrees-C there was 5.1% loss of sufentanil at pH 4 and 80.6% loss at pH 6. The citrate buffer at the optimum pH (4.6) has a low, a cceptable buffer capacity for epidural administration.