Solid Lipid Nanoparticles and Nanostructured Lipid Carriers of Loratadine for Topical Application: Physicochemical Stability and Drug Penetration through Rat Skin

Purpose: To prepare solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) of loratadine (LRT) for the treatment of allergic skin reactions.
Methods: SLN and NLC were prepared by high pressure homogenization method. Their entrapment efficiency (EE) and loading capacity (LC) were determined. The physical stability of nanoparticles was investigated during 6 months of storage at room temperature (RT), 4 and 40^o C. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and laser diffraction (LD) were used for the investigation of drug:excipient compatibility, thermal behaviour and particle size of the nanoparticles. In vitro release and ex vivo skin penetration of LRT were studied. Nanoemulsions (NE) were also prepared and characterized for comparison.
Results: Nanoparticles sizes ranged from 0.222 ± 0.011 μm to 0.252 ± 0.014 μm (D50 as a value based on the volume distribution, the maximum particle diameter below which 50 % of the sample volume exists) They were obtained with high drug payloads (> 90.67 %). LRT was compatible with the other excipients after 6 months. Particle size did not significantly alter particularly at RT. The highest release rate was obtained with NE (1.339 ± 0.026 mcg/ml/h) followed by NLC (1.007 ± 0.011 mcg/ml/h) and SLN (0.821 ± 0.012 mcg/ml/h), indicating anomalous transport (p < 0.05). Penetration profiles of LRT through skin were statistically similar for SLN and NLC (p > 0.05). NE showed the highest penetration rate (0.829 ± 0.06 mcg/cm²/h) (p < 0.05).
Conclusion: SLN and NLC of LRT are alternative formulations for immediate treatment of allergic skin reactions with prolonged drug delivery via reservoir action.

Keywords
Loratadine; Transdermal delivery; Controlled drug delivery; Solid Lipid nanoparticles; Nanostructured lipid carriers; Allergy