To determine the basic physiochemical properties and rheological activity of detergent sclerosants.

Sodium tetradecyl sulphate and polidocanol liquid and foam sclerosants were investigated in a range of concentrations (0.1–3%), liquid-plus-air fractions (1+2 to 1+8) and dilutions in water (stock solutions) or in normal saline. The embolic agent ethanol was investigated for comparison. Density was measured using a digital balance. Surface tension was measured by the Du Nuoy ring method and used to determine the critical micellar concentration. Viscosity was measured using a cone-plate rheometer for liquid and a modified parallel plate method for foam.

Liquid sclerosant density decreased as the sclerosant concentration increased while foam density decreased with the increasing air fraction. The critical micellar concentration of polidocanol was 0.002% in both normal saline and water while that of sodium tetradecyl sulphate was 0.075% in normal saline and 0.200% in water. Viscosity of liquid sodium tetradecyl sulphate was lower than that of polidocanol. Foam sclerosants were at least 10,000-fold more viscous than liquid sclerosants and ethanol. All agents demonstrated a Non-Newtonian shear-thinning behaviour with a fall in viscosity at lower shear rates (<10 s^–1). Polidocanol (but not sodium tetradecyl sulphate) foam viscosity progressively increased with increasing sclerosant concentration and liquid-plus-air fractions.

Liquid and foam sclerosants and ethanol are Non-Newtonian shear thinning fluids. Foam sclerosants are significantly more viscous than liquid agents.