(681d) Development of a Coating Process to Apply Water-Insoluble Drugs On Microneedles Using Molten Coating Solutions

Microneedles is a promising approach to deliver potent drugs via the skin and other easily accessible parts of the human body. The coated microneedle approach for drug delivery utilizes the microneedle as a carrier of the drug in the form of a thin film coated on the microneedle surface. Insertion of this drug-coated microneedle in the tissue enables drug delivery via dissolution of the water soluble film in to the interstitial fluid. This approach relies on the use of aqueous solutions with water-soluble drugs and coating excipients. To expand the coated microneedle approach to include delivery of lipophilic drugs, we present for the first time the process of coating water-insoluble drugs using molten coating solutions. Polyethylene glycol (PEG) was chosen as a drug solubilizer and emulsifier to form a matrix system, which allows the water-insoluble drug to be dispersed in the molten PEG phase through solubilization or emulsification. Lidocaine, a commonly used local anesthetic was chosen as a model drug to test the feasibility and consistency of the molten coating process. A custom designed microprecision automated coating system was used to fully control the temperature of the molten coating solution, microneedle dipping depth, and coating speed. The results of our study show that the coating films on microneedles are uniform and could provide substantial amount of drug on microneedles. In addition, the PEG matrix could significantly enhance dissolution of the water-insoluble lidocaine in to the tissue. In conclusion, the molten coating process we introduce here offers a practical approach to coat water-insoluble drugs on microneedles.