Development and optimisation of biopharmaceutical properties of a new microemulgel of cannabidiol for locally-acting dermatological delivery

Cannabidiol (CBD) is a pleiotropic phytocannabinoid, recently investigated to treat many skin diseases. This study aimed to develop a CBD-loaded O/A microemulsion (CBD-ME) formulated as microemulgel (CBD-MEgel), suitable for local administration. The developed CBD-ME consisted of Solutol HS 15 (20%, surfactant), Transcutol P (9%, cosolvent), isopropyl myristate (5%, oil phase), water (66%) and 1% w/w CBD. Globules had polydispersity index less than 0.23 +/- 0.02 and size of 35 +/- 2 nm; these values did not change after loading CBD and gelling the formulation with Sepigel 305 obtaining a clear and homogeneous formulation with a pH of 6.56 +/- 0.20, suitable for cutaneous application. Viscosity properties were investigated by the rotational digital viscometer, at both 21 +/- 2 degrees C and 35 +/- 2 degrees C. Viscosities of CBD-MEgel were 439,000 +/- 4,243 mPa.s and 391,000 +/- 1,414 mPa.s respectively. The release studies displayed that 90 +/- 24 mu g/cm(2) of CBD were released in 24 h. The CBD permeability, evaluated using Franz diffusion cells and rabbit ear skin, was 3 +/- 1 mu g/cm(2). Skin-PAMPA (TM) gave a CBD effective permeability of (1.67 +/- 0.16) .10(-7) cm/s and an absorbed dose of 115.30 +/- 16.99 mu g/cm(2) after 24 h. Lastly, physical and chemical stability of both CBD-ME and CBD-MEgel were evaluated over a period of 3 months, showing optimal shelf-life at the storage conditions.

Automated summary

The study successfully developed a CBD-loaded microemulsion formulated as a microemulgel, which exhibited optimal physical and chemical stability and was suitable for cutaneous application.