Nisoldipine (ND) has low oral bioavailability (5%) due to first-pass metabolism. Previously, solid lipid nanoparticles (SLNs) of ND were reported. In this study, nanostructured lipid carriers (NLCs) of ND are developed to enhance the oral bioavailability. ND-NLCs were prepared using hot homogenization-ultrasonication method, using oleic acid and trimyristate as liquid lipid and solid lipid, respectively. Prepared NLCs are evaluated for an optimal system using measuring size, zeta potential, entrapment efficiency, in-vitro release and in-situ absorption studies. Further, in vivo pharmacokinetic (PK) studies of NLC were conducted in rats comparison with SLN and suspension as controls. Size, ZP and EE of optimized NLCs were found to be 110.4 ± 2.95 nm, -29.4 ± 2.05 mV and 97.07 ± 2.27%, respectively. Drug loaded into NLCs was converted to amorphous form revealed by differential scanning calorimeter (DSC) and X-ray diffractometry (XRD) technique and nearly spherical in shape by scanning electron microscopy (SEM) studies. Drug release and absorption of ND were prolonged from ND-NLCs and ND-SLNs. From the PK results, NLCs showed 2.46 and 1.09-folds improvement in oral bioavailability of ND compared with suspension and SLNs formulations, respectively. Taken together, the NLCs and SLNs are used as carriers for the enhancement of oral bioavailability of the ND.

Ropinirole (RP), is a selective dopamine agonist that is used alone or with other medications to treat the symptoms of Parkinson’s disease (PD). RP has low bioavailability of only about 50% due to the first-pass metabolism, and it requires frequent dosing during oral administration. The objective of the current research was to develop RP loaded solid lipid nanoparticles (RP-SLNs), nanostructured lipid carriers (RP-NLCs), and their corresponding hydrogels (RP-SLN-C and RP-NLC-C) that might improve efficacy in PD treatment. RP nanoparticles were prepared by homogenization aided probe sonication method and optimized based on particle size, polydispersity index (PDI), zeta potential (ZP), assay, entrapment efficiency, and in vitro release studies. Optimized formulations were converted to hydrogel formulations using Carbopol 934 as a gelling polymer and optimized based on rheological and release characteristics. Optimized formulations were further evaluated using differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM), freeze-drying, and stability study at refrigerated and room temperatures. The optimized RP-SLN formulation showed particle size and entrapment efficiency of 213.5±3.8 nm and 77.9±3.1% compared to 190.6±3.7 nm and 85.7±1.7% for optimized RP-NLC formulation. PXRD supplemented and confirmed DSC results, RP was entrapped in a molecularly dispersed state inside the core of the lipid nanocarrier. Furthermore, RP loaded lipid nanocarriers revealed a spherical shape in SEM images. In vitro release studies demonstrated sustained release profiles for RP from SLNs, NLCs, and their hydrogels over 24 h and were stable over three months at 4ºC and 25ºC storage conditions. Keywords: Parkinson’s disease, Ropinirole, Solid lipid nanoparticles, Nanostructured lipid carriers, Hydrogel.

Oral bioavailability of drugs is mainly limited due to the poor aqueous solubility, enhanced chemical degradation, reduced permeation and/or first pass metabolism. Various novel delivery systems are developed for improved oral bioavailability of these drugs such as modified orals, buccal, transdermal and osmotic delivery systems. Colloidal carrier systems such as nanoparticles, lipid nanoparticles, nanoemulsions, microspheres, liposomes, resealed erythrocytes and transfersomes were also developed to enhance the oral delivery. Among these, solid lipid nanocarriers (SLNs) also gain much attention on the enhancement of oral bioavailability. SLNs are submicron sized nanoparticles and composed of solid lipid, surfactants and cosurfactants. The enhanced oral bioavailability of poorly soluble drugs from SLNs might be due to the reduced particle size, bypassed presystemic metabolism, and enhanced gastric mucosa permeability. Vast literature is available for the advantages, limitations, preparation methods, evaluation parameters and application of SLNs in different routes. This review mainly focused on list of drugs developed as SLNs and considered as an alternative approach to enhance the oral bioavailability based on pharmacokinetic as well as pharmacodyanmic parameters was discussed. Keywords: Oral bioavailability, solubility, first-pass metabolism, solid lipid nanoparticles, pharmacokinetics, pharmacodynamics.