Development and validation of a RP-HPLC method for assay of Atorvastatin and its application in dissolution studies on thermosensitive hydrogel-based nanocrystals

Purpose: To develop and validate a novel reverse phase high performance liquid chromatographic (RP-HPLC) method for the quantification of atorvastatin in thermosensitive hydrogel-based nanocrystal formulation.Method: Chromatographic identification was achieved on C18 (5 μm) column using acetonitrile and 0.025 M potassium dihydrogen ortho-phosphate buffer pH 5 (45:55 v/v) as mobile phase, at a flow rate of 1.5 mL/min and using photo diode array detector (PDA) at 246 nm. The developed HPLC method was validated according to International Conference on Harmonisation (ICH) Q2(R1) guidelines and applied to dissolution studies on atorvastatin thermosensitive hydrogel-based nanocrystal formulation, using Lipitor® as standard.Results: Determination was successfully achieved with good peak resolution from atorvastatin nanocrystals and a commercial formulation brand (Lipitor® tablets) without interference of polymer or excipients. The retention time of atorvastatin was 4.5 min and drug response was linear in the range of 0.1 - 0.5 μg/mL with a correlation coefficient of 0.9995. Precision was determined to be between 0.16 - 0.61 percent relative standard deviation (% RSD) for the analyzed samples. The limit of detection and of quantification was 35.6 and 71.2 ng/mL, respectively, which was 10 times higher than a previously reported method. The assay of atorvastatin nanocrystal and Lipitor® gave 99.37 and 99.12 % recovery, respectively. Dissolution studies showed atorvastatin release of 40 and 65 % at 40 min from thermosensitive hydrogel nanocrystal formulation and Lipitor®, respectively indicating sustained release.Conclusion: The method is successfully validated and is specific, linear, precise, and accurate with good robustness. It is applicable to atorvastatin nanocrystal dissolution studies and is a promising quality control tool for atorvastatin analysis in nanoformulations and pharmaceutical dosage forms.Keywords: Atorvastatin, Anticholestermic, Dissolution studies, Hydrogel, Nanocrystal, Thermosensitiv

Chitosan based atorvastatin nanocrystals: effect of cationic charge on particle size, formulation stability, and in-vivo efficacy

Mallesh Kurakula,1 AM El-Helw,2 Tariq R Sobahi,1 Magdy Y Abdelaal11Polymer Research Lab, Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia; 2Department of Pharmaceutics, Faculty of Pharmacy, King Abdulaziz University, Jeddah, Saudi ArabiaAbstract: Cationic charged chitosan as stabilizer was evaluated in preparation of nanocrystals using probe sonication method. The influence of cationic charge densities of chitosan (low CSL, medium CSM, high CSH molecular weights) and Labrasol® in solubility enhancement and modifying the release was investigated, using atorvastatin (ATR) as poorly soluble model drug. Compared to CSM and CSH; low cationic charge of CSL acted as both electrostatic and steric stabilizer by significant size reduction to 394 nm with charge of 21.5 meV. Solubility of ATR-CSL increased to 60-fold relative to pure ATR and ATR-L. Nanocrystals were characterized for physiochemical properties. Scanning electron microscopy revealed scaffold-like structures with high surface area. X-ray powder diffractometry and differential scanning calorimetry revealed crystalline to slight amorphous state changes after cationic charge size reduction. Fourier transform-infrared spectra indicated no potent drug-excipient interactions. The enhanced dissolution profile of ATR-CSL indicates that sustained release was achieved compared with ATR-L and Lipitor®. Anti-hyperlipidemic performance was pH dependent where ATR-CSL exhibited 2.5-fold higher efficacy at pH 5 compared to pH 6 and Lipitor®. Stability studies indicated marked changes in size and charge for ATR-L compared to ATR-CSL exemplifying importance of the stabilizer. Therefore, nanocrystals developed with CSL as a stabilizer is a promising choice to enhance dissolution, stability, and in-vivo efficacy of major Biopharmaceutical Classification System II/IV drugs.Keywords: atorvastatin, anti-hyperlipidemia, chitosan, cationic charge, stability, nanocrystals, in-vivo efficac