title: Coating solid dispersions on microneedles via a molten dip-coating method: development and in vitro evaluation for transdermal delivery of a water-insoluble drug.
abstract: This study demonstrates for the first time the ability to coat solid dispersions on microneedles as a means to deliver water-insoluble drugs through the skin. Polyethylene glycol (PEG) was selected as the hydrophilic matrix, and lidocaine base was selected as the model hydrophobic drug to create the solid dispersion. First, thermal characterization and viscosity measurements of the PEG-lidocaine mixture at different mass fractions were performed. The results show that lidocaine can remain stable at temperatures up to ∼130°C and that viscosity of the PEG-lidocaine molten solution increases as the mass fraction of lidocaine decreases. Differential scanning calorimetry demonstrated that at lidocaine mass fraction less than or equal to 50%, lidocaine is well dispersed in the PEG-lidocaine mixture. Uniform coatings were obtained on microneedle surfaces. In vitro dissolution studies in porcine skin showed that microneedles coated with PEG-lidocaine dispersions resulted in significantly higher delivery of lidocaine in just 3 min compared with 1 h topical application of 0.15 g EMLA®, a commercial lidocaine-prilocaine cream. In conclusion, the molten coating process we introduce here offers a practical approach to coat water-insoluble drugs on microneedles for transdermal delivery.
authors.affiliation: Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409.
authors.forename: Yunzhe
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Chemical Engineering, Texas Tech University, Lubbock, Texas 79409. Electronic address: harvinder.gill@ttu.edu.
authors.forename: Harvinder S
authors.initials: HS
authors.lastname: Gill
mesh_terms: D000279:Administration, Cutaneous; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002626:Chemistry, Pharmaceutical; D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D004355:Drug Stability; D004867:Equipment Design; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D008012:Lidocaine / Q000008:administration & dosage* / Q000737:chemistry / Q000378:metabolism; D000077442:Lidocaine, Prilocaine Drug Combination; D008904:Miniaturization; D009339:Needles; D011092:Polyethylene Glycols / Q000737:chemistry*; D011318:Prilocaine / Q000008:administration & dosage / Q000378:metabolism; D012867:Skin / Q000378:metabolism; D012869:Skin Absorption; D012995:Solubility; D013552:Swine; D013678:Technology, Pharmaceutical / Q000379:methods*; D013696:Temperature; D013997:Time Factors; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D000779:Anesthetics, Local; D020099:Coated Materials, Biocompatible; D004337:Drug Carriers; D000077442:Lidocaine, Prilocaine Drug Combination; D011318:Prilocaine; D014867:Water; D011092:Polyethylene Glycols; D008012:Lidocaine
keywords: coating; dissolution; solid dispersion; solubility; transdermal drug delivery