Enhancing Efavirenz Bioavailability Via Polymer-Based Buccal Administration: Optimization and Characterization of Nanocrystal-Loaded Dissolving Microneedle Delivery Systems.

Efavirenz (EFV) is a widely utilized antiretroviral agent in HIV/AIDS therapy that is known for its efficacy but is also associated with various side effects. For improved drug delivery, buccal administration offers a promising alternative by allowing the drug to enter the systemic circulation directly through the oral mucosa, bypassing the gastrointestinal tract and first-pass metabolism. This study explored the interaction between EFV and different polymers through molecular docking, revealing a strong binding affinity to Pluronic®F-127 (-2.1 kcal/mol). EFV was formulated into nanocrystals (EFV-NC) using Pluronic®F-127 as the stabilizer, characterized by an average particle size of 174.83 ± 15.21 nm, a narrow size distribution (PDI of 0.15 ± 0.013), and good stability (zeta potential of -22.27 ± 1.12 mV). FTIR and XRD analyses revealed polymer-induced alterations in the crystalline structure of the EFV. The EFV-NC formulation enhanced the solubility (up to 400 µg/mL) and achieved 89.58 ± 4.01% drug release within 24 h, following the Higuchi model kinetics for controlled release. EFV-NC-loaded dissolving microneedles (EFV-NC-DMN) demonstrated robust mechanical properties, efficient tissue penetration, and minimal moisture absorption. Ex vivo and in vivo studies revealed that compared with oral EFV, EFV-NC-DMN provided a relative bioavailability of 137.40%, with higher plasma concentrations and prolonged release, highlighting its potential for superior HIV/AIDS management via buccal administration and improved therapeutic outcomes.