The physical compatibility of thiopentone and propofol mixtures was in
vestigated. The investigations used were macroscopic and microscopic o
bservations, zeta potential and oil droplet size measurements. There w
as no evidence of instability in the mixtures. The thiopentone-propofo
l mixture has the potential advantage of reducing the pain on injectio
n, provides synergistic interaction, does not prolong recovery when us
ed for induction of anaesthesia, may reduce the incidence of convulsio
ns and is cost-effective.