Examination of the Rate and Extent of Drug Released from Commercial Topical Delivery Systems During Wear: An Example with Lidocaine Topical Systems.

OBJECTIVE: This study aimed to determine the extent and rate of lidocaine released in vivo from two bioequivalent topical delivery systems (TDS) by using complementary assessments: pharmacokinetic analysis in healthy human volunteers, and residual lidocaine in TDS following 12 h of wear. The goal was to explore a potentially more clinically meaningful strength presentation than percent active pharmaceutical ingredient loaded in topical systems. METHODS: A three-arm, open-label, crossover clinical study was conducted in 23 human subjects, with 5% lidocaine topical systems from two manufacturers, and intravenous lidocaine administration. Residual drug and LC-MS/MS analyses were performed on worn TDS and serum samples. The rate and extent of drug released from the TDS during wear were determined through (1) calculations of consumed lidocaine via analysis of residual drug in worn TDS, and (2) a pharmacokinetic approach via derivation of the absolute clearance and serum lidocaine concentration at steady state. RESULTS: Overall the pharmacokinetic approach underestimated the amount transferred to the subject and exhibited greater variability, which may relate to natural inter-subject variability in pharmacokinetic parameters. Further, lidocaine TDS are intended for localized, not systemic, delivery and this may also explain some of the variability seen in the systemic serum concentrations. CONCLUSIONS: The residual drug and pharmacokinetic approaches align well for transdermal formulations, but the differences in administration route (topical versus transdermal) all but eliminates the potential use of the pharmacokinetic approach unless additional compartmental modeling is explored.

Quantitative chromatographic method development for residual lidocaine in topical systems and biological samples.

Background: The aim of this work was to develop and validate sensitive and efficient analytical methods for estimating systemic drug exposure and residual drug following the application of topical delivery systems. Materials & methods: Lidocaine was extracted using a liquid-liquid extraction technique from commercial topical products and analyzed using ultra high-performance liquid chromatography. A separate LC-MS/MS method was developed for analyzing human serum samples. Results & conclusion: The developed methods were successfully applied for estimating lidocaine content in two commercial products demonstrating 97.4-104.0% for product A and 105.0-110.7% for product B. The LC-MS/MS method displayed successful analysis of lidocaine from human serum samples. The developed methods are recommended for quantifying systemic exposure and residual drug analysis of topical systems.

Structure-mechanics and improved tableting performance of the drug-drug cocrystal metformin:salicylic acid.

Drug-drug cocrystals (DDC) represent a unique subset of pharmaceutical materials offering distinct advantages in combination therapies, pharmacokinetics, and patient compliance. However, their structure-function relationships are rarely reported despite its central importance in successful medicine. A material-sparing approach consisting of a molecular and structural perspective is reported to evaluate tabletability of a model DDC, metformin:salicylic acid, relative to its components: metformin HCl (MET) and sodium salicylate (SAL). MET alone displayed a very poor tabletability, which could be attributed to its isotropic and stiff interaction topology. SAL displayed a highly anisotropic interaction topology with layers of strongly hydrogen-bonded salicylate molecules promoting deformation and tabletability. This is also confirmed by its low moduli. DDC yielded intermediate stiffness and elastic anisotropy material with an improved plastic flow and overall better tabletability. Overall, DDC is a promising therapeutic class requiring the physical-mechanical evaluation to assure their processability to enjoy their therapeutic advantages.

Statistical optimization and validation of a novel ultra-performance liquid chromatography method for estimation of nintedanib in rat and human plasma.

Aim: A high throughput ultra-performance liquid chromatography (UPLC)-ultraviolet method for quantification of nintedanib in rat and human plasma was developed and optimized using chemometrical approach. Method: Design of experiment and multivariate statistical approach was used for definition of optimized method. Final separation was performed using protein precipitation method on ACQUITY HSS T3 C18 column in isocratic mode using potassium phosphate buffer (pH 7.5): acetonitrile. Results: Method was validated as per US-FDA guidelines linearly from 15-750 ng/ml. All quality control samples showed <15% relative standard deviation for precision and 85-115% accuracy along with >98% extraction recovery. Conclusion: The developed method is easily applicable in determining pharmacokinetic parameters in preclinical subjects along with successful implementation for quantification in human plasma samples.