Enhanced long-acting simvastatin delivery via effervescent powder-carrying hollow microneedles and nanocrystal-loaded microneedles

Hyperlipidemia and its associated cardiovascular complications are the major causes of mortality and disability worldwide. Simvastatin (SIM) is one of the most commonly prescribed lipid-lowering drugs for the treatment of hyperlipidemia by competitive inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. However, the extensive first-pass metabolism leading to low oral bioavailability and frequent daily doses may lead to poor patient compliance and adverse effects caused by plasma fluctuations. To overcome these challenges, this work purposed two microneedle (MN) delivery strategies for the potential enhancement of SIM delivery. Firstly, nanocrystal (NC) formulations of SIM were investigated, followed by incorporation into a trilayer dissolving microneedle (DMN) design. Furthermore, a novel effervescent powder-carrying MN (EMN) design was developed to enhance intradermal delivery by incorporating the effervescent agents into the drug powder. Both MN approaches exhibited significantly improved permeation and in-skin deposition ability in the Franz cell study, with the ex vivo delivery efficiency of 64.33 ± 6.17 % and 40.11 ± 4.53 % for EMNs and DMNs, respectively. Most importantly, in vivo studies using a female Sprague-Dawley rat model confirmed the successful delivery of SIM from NCs-loaded DMNs (C_max = 287.39 ± 106.82 ng/mL) and EMNs (C_max = 203.05 ± 17.07 ng/mL) and maintain therapeutically relevant plasma concentrations for 15 days following a single application. The enhanced bioavailabilities of DMNs and EMNs were 24.28 % and 103.82 %, respectively, which were both significantly higher than that of conventional oral administration.