Background: Because the valproic derivates are frequently used in the treatment of epilepsy, bipolar disorders, major depression cases, migraines and other neurological disorders at children, the rectal administration is a real advantage.
Aim: In this study we aimed to assess the influence of the formulation on the rheological characteristics of lipophilic suppository bases Suppocire NAI, Witepsol W35, Massa Estarinum299, Lipex403, containing Cetyl alcohol and Solutol HS15, respectively.
Methods: Spreadability was determined by the Pozo Ojeda-Sune Arbussa method. Half a gram suppository was placed on the bottom plaque of the extensiometer, and the upper plaque was added over it. After equal intervals of time (1 minute) different weights (2, 5, 10, 20, 30, 40, 50, 100, 150, 200, 250, 300, 350, 400, 500 g) were placed. Following each weight addition, the diameters of the obtained circles were measured, and the corresponding area was calculated. The viscosity was determined using the Brookfield (DV-II +Pro) rotational viscosimeter. The measurements were performed at 37±0.5°C and 5, 10, 20, 50, 100, 50, 20, 10, 5 rpm.
Results: The experimental results demonstrated that sodium valproate as active substance induces an increase in viscosity and consequently a decrease in the spreading capacity of the lipophilic suppository bases used. Lipex403 (a base consisting in fatty acids) manifests the lowest viscosity compared to the bases consisting in mixtures of glycerides (Suppocire NAI, Witepsol W35, Massa Estarinum 299). Solutol HS15 as emulsifier determines a higher decrease in viscosities and a better spreading capacity than Cetyl alcohol. Sodium valproate suppositories obtained with Lipex403 as excipient base show plastic flow characteristics without thixotropy.
Conclusions: The experimental results demonstrated that sodium valproate as active substance induces an increase in viscosity and consequently a decrease in the spreading capacity of the lipophilic suppository bases used. Solutol HS15 determines a higher decrease in viscosities and a better spreading capacity than Cetyl alcohol.