Study of factors affecting the in vitro release of dexpanthenol from solutions and topical semi-solid preparations

The aim. To identify the factors influencing the in vitro release of dexpanthenol (DP) from solutions and semi-solid preparations. Materials and methods. Dispersed systems containing 5.0 % DP were studied: solutions that were Newtonian liquids and semi-solid preparations (creams, gels and ointment) with non-Newtonian flow behaviour. Rheological studies were performed by rotational viscometry. In vitro release tests were performed using vertical diffusion cells. The content of DP in the receptor medium was determined by liquid chromatography. Results. It has been shown that the greatest values of release parameters of DP were characteristic of its aqueous solution; they decreased when propylene glycol (PG), macrogol 400 (M400), and poloxamer 338 (P338) were added but remained at a high enough level. The inclusion of cationic surfactant and cetostearyl alcohol (CSA) (0.5 : 4.5 % m/m) into the Newtonian liquid led to the formation of disperse system with a plastic flow behaviour and to significant decrease in the DP release. In the case of a cream containing a non-ionic surfactant and CSA, the release parameters of DP were also at a low level. The release of DP from the w/o emulsion-based ointment was minimal. Compared to DP aqueous solution, the rate of DP release from a carbomer-based gel decreased by 2.8 times; when 20 % of a mixture of PG and M400 (10 : 10 % m/m) was added to such a gel, the rate of drug release decreased by another 1.5 times. The fastest and most complete release of DP was observed in the case of the P338-based disperse system, which transformed from a Newtonian liquid into a gel at 32 °C. Conclusions. In vitro release of DP depended on the type of base; rapid and complete release of DP was characteristic of its aqueous solution, and minimal release was observed in the case of hydrophobic ointment. The use of CSA in combination with a surfactant or carbomer to create bases for semi-solid preparations with plastic flow behaviour was a considerable factor that significantly slowed down the release of DP from them. The greatest values of the release parameters of DP were observed in the case of a gel based on P338