Table 3.

Free propofol concentrations in the aqueous phase of lipid emulsion and microemulsion propofol and the effects of agents known to reduce propofol-induced pain on aqueous free propofol concentrations

Agents mixed with 5 ml of propofol formulations (concentration, volume)	Lipid emulsion (µg ml−1)		Microemulsion (µg ml−1)
	Control*	Test†	Control*	Test†
None‡	–	12.4 ± 0.7	–	83.9 ± 0.6
Lidocaine (20 mg ml−1, 0.5 ml)	12.3 ± 0.5	12.3 ± 0.6	84.2 ± 0.6	84.0 ± 0.7
Ketamine (50 mg ml−1, 0.2 ml)	12.4 (12.1, 12.5)	12.3 (11.6, 13.2)	83.9 ± 0.5	83.8 ± 0.7
Metoclopramide (5 mg ml−1, 1.0 ml)	12.2 ± 0.6	11.9 ± 0.6	84.0 ± 0.8	84.1 ± 0.8
Ondansetron (2 mg ml−1, 2.0 ml)	12.4 ± 0.7	12.5 ± 0.7	83.8 ± 0.9	83.9 ± 0.8
Thiopental (25 mg ml−1, 2.0 ml)	12.4 ± 0.7	12.2 ± 0.6	83.8 ± 0.9	83.8 ± 0.7
Ephedrine (5 mg ml−1, 0.4 ml)	12.3 ± 0.6	12.4 ± 0.7	83.9 ± 0.7	83.9 ± 0.8

^*Mixture of each propofol formulation (5 ml) and saline (0.2, 0.4, 0.5, 1.0 and 2.0 ml). For controls, pain-reducing agents were replaced with an equal volume of saline.

^†Control and test samples in each propofol formulation were compared to test the effects of agents known to reduce propofol-induced pain on the free propofol concentrations in the aqueous phase (P > 0.05 for all pairwise comparisons).

^‡The free propofol concentrations in the aqueous phase of lipid emulsion and microemulsion propofol were compared (P < 0.001). n = 10 for all control and test samples. Data are presented as mean ± SD or median (25%, 75%).