Propofol emulsion-free drug concentration is similar between batches and stable over time.

Abstract

Several samples of generic 1% propofol emulsion from various batches were compared. Free drug concentration was measured using an equilibrium dialysis method. Emulsion stability was evaluated by visible observation and by measuring droplet size distribution and polydispersity during shelf storage for up to 21 months. Small differences in free drug concentration were observed between samples (10.6-16.7 μg/mL), but these differences were not statistically significant (p > 0.05). Emulsion droplet size (235.4-221.1 nm) and polydispersity (0.115-0.095) did not differ statistically over 21 months of storage. All batches were resistant to creaming and other destabilization mechanisms. Batch-to-batch variability does not significantly alter the free drug concentration or stability of propofol formulations. If pain on injection of propofol is in fact related to the free propofol drug concentration, then it is unlikely that batch-to-batch variability causes any changes in pain on propofol injection.