Impact of Alkanediols on Stratum Corneum Lipids and Triamcinolone Acetonide Skin Penetration.

Alkanediols are widely used as multifunctional ingredients in dermal formulations. In addition to their preservative effect, considering their possible impact on drug penetration is also essential for their use. In the present study, the influence of 2-methyl-2,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol on the skin penetration of triamcinolone acetonide from four different semisolid formulations was investigated. Furthermore, confocal Raman spectroscopy measurements were performed to examine the influence of the alkanediols on stratum corneum lipid content and order. Alkanediols were found to increase the penetration of triamcinolone acetonide. However, the extent depends strongly on the formulation used. In certain formulations, 1,2-pentanediol showed the highest effect, while in others the penetration-enhancing effect increased with the alkyl chain length of the alkanediol used. None of the tested alkanediols extracted lipids from the stratum corneum nor reduced its thickness. Notwithstanding the above, the longer-chained alkanediols cause the lipids to be converted to a more disordered state, which favors drug penetration. This behavior could not be detected for the shorter-chained alkanediols. Therefore, their penetration-enhancing effect is supposed to be related to an interaction with the hydrophilic regions of the stratum corneum.

The effect of alkanediols on the release of triamcinolone acetonide from semisolid dosage forms.

Alkanediols are frequently used as alternative antimicrobial preservatives for dermal formulations. However, these substances can also have an influence on the biopharmaceutical properties of the applied preparations. Therefore, the influence 2-methyl-2,4-pentanediol, 1,2-pentanediol, 1,2-hexanediol and 1,2-octanediol on the release of triamcinolone acetonide (TAA) from four different commonly used semi-solid vehicles was investigated. In addition, the solubility of TAA in aqueous alkanediol solutions was evaluated. It was observed that its solubility increases as a function of chain length of the alkanediol, with exception of 1,2-octanediol. This can be related to the corresponding solubility parameters. Despite alkanediols increase the aqueous solubility of TAA, polarization microscopic images revealed that a significant amount of the drug is present in the suspended state in all formulations. Therefore, TAA release was proportional to the square root of time, indicating Higuchi kinetic. Alkanediols modify the release of TAA depending on the used base. The addition of alkanediols to the hydrogel formulation result in a slightly augmented release rate of the drug with increasing chain length of the added alkanediol. In contrast, alkanediols having longer chain lengths diminish the TAA release rate from all tested creams. Consequently, TAA release revealed to be partially inequivalent upon the addition of alkanediols.

Investigations on Alkanediols as Alternative Preservatives in a Nonionic Hydrophilic Cream.

Alkanediols are often used as alternative antimicrobial preservatives for dermal formulations, e.g., hydrophilic creams. These substances show an antimicrobial effect due to their amphiphilic structure. At the same time, their amphiphilic behavior enables various interactions with the cream base itself. Therefore, the effect of four different alkanediols, namely 1,2-pentanediol, 2-methyl-2,4-pentanediol (hexylene glycol), 1,2-hexanediol, and 1,2-octanediol on the physical stability of a nonionic hydrophilic cream was investigated. Further, the incorporation of the alkanediols into lamellar structures of the cream was evaluated using differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) measurements. The interaction with the mixed crystals of the cream was found to increase with raising alkyl chain length of the added alkanediol. As a result, consistency and stability of the cream are slightly impaired. A test for efficacy of antimicrobial preservation according to the European Pharmacopoeia (Ph.Eur.) revealed that the antimicrobial activity is directly linked to the length of the alkyl chain of the alkanediols. 2-Methyl-2,4-pentanediol differs from both findings. This compound has non-vicinal hydroxy groups which result in a reduced amphiphilicity compared to the others. Consequently, it has a smaller impact on the colloidal structure of the cream and shows a comparatively low antimicrobial activity.