Pharmacokinetics of Lidocaine and Its Metabolites Following Vaginal Administration of Lidocaine Gel to Healthy Female Subjects

Development and verification of mechanistic vaginal absorption and metabolism model to predict systemic exposure after vaginal ring and gel application

AIMS

The current work describes the development of mechanistic vaginal absorption and metabolism model within Simcyp Simulator to predict systemic concentrations following vaginal application of ring and gel formulations.

METHODS

Vaginal and cervix physiology parameters were incorporated in the model development. The study highlights the model assumptions including simulation results comparing systemic concentrations of 5 different compounds, namely, dapivirine, tenofovir, lidocaine, ethinylestradiol and etonogestrel, administered as vaginal ring or gel. Due to lack of data, the vaginal absorption parameters were calculated based on assumptions or optimized. The model uses release rate/in vitro release profiles with formulation characteristics to predict drug mass transfer across vaginal tissue into the systemic circulation.

RESULTS

For lidocaine and tenofovir vaginal gel, the predicted to observed AUC0-t and Cmax ratios were well within 2-fold error limits. The average fold error (AFE) and absolute AFE indicating bias and precision of predictions range from 0.62 to 1.61. For dapivirine, the pharmacokinetic parameters are under and overpredicted in some studies due to lack of formulation composition details and relevance of release rate used in ring model. The predicted to observed AUC0-t and Cmax ratios were well within 2-fold error limits for etonogestrel and ethinylestradiol vaginal ring (AFEs and absolute AFEs from 0.84 to 1.83).

CONCLUSION

The current study provides first of its kind physiologically based pharmacokinetic framework integrating physiology, population and formulation data to carry out in silico mechanistic vaginal absorption studies, with the potential for virtual bioequivalence assessment in the future.

Transdermal drug delivery system of lidocaine hydrochloride based on dissolving gelatin/sodium carboxymethylcellulose microneedles

In this study, it was aimed to introduce a transdermal drug delivery system with dissolving microneedles (DMNs) based on gelatin (GEL) and sodium carboxymethyl cellulose (NaCMC) for lidocaine hydrochloride (LidoHCl) delivery. Different ratios of GEL and NaCMC were mixed, loaded with an active agent of LidoHCl, and treated with glutaraldehyde (GTA) as a crosslinker agent. Prepared hydrogels were cast into a silicon mold. Hereby, microneedles (MNs) with 500 µm height, 35° needle angle, 40-µm tip radius, and 960-µm tip-to-tip distance were fabricated. Samples containing LidoHCl 40%, GEL/NaCMC 5:1 (wt/wt), and polymer/GTA ratio 3.1 (wt/wt) showed the highest drug release ability (t < 10 min) with proper mechanical properties in comparison with other samples. Due to the drug release in a short time (fewer than 10 min), this drug delivery system can be used for rapid local anesthesia for pain relief as well as before minor skin surgeries.

Graphical Abstract

Simultaneous determination of lidocaine and its active metabolites in plasma by UPLC-MS/MS and application to a clinical pharmacokinetic study in liver cancer patients with laparoscopic hepatectomy

Lidocaine, widely used as a local anesthetic, has anti-inflammatory and inhibitory effects on tumor recurrence and metastasis. To investigate the pharmacokinetics of lidocaine in liver cancer patients undergoing laparoscopic hepatectomy, a fast and sensitive analytical technique was developed. The method was adequately validated with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to simultaneously determine the concentration of lidocaine and its metabolites in plasma. The chromatographic separation was achieved on an Acquity UPLC BEH C₁₈ column (2.1 × 50 mm, 1.7 µm) by gradient elution with a mobile phase of A (formic acid-water (1:1000, v/v)) and B (formic acid-acetonitrile (1:1000, v/v)). The accuracy and precision were verified within the concentration ranges of 10-5000 ng/mL for lidocaine, 2-1000 ng/mL for monoethylglycinexylidide (MEGX) and 2-500 ng/mL for glycinexylidide (GX). The selectivity, carry-over effect, interference between the analytes and internal standard (IS), precision and accuracy, matrix effect extraction recovery, dilution integrity and stability were satisfactory for the relevant guideline standards. The method was successfully applied to the pharmacokinetic study of lidocaine in liver cancer patients undergoing laparoscopic hepatectomy. After receiving a bolus and continuous infusion, the mean peak concentration of lidocaine was 2097 ng/mL for lidocaine, 336.6 ng/mL for MEGX and 72.66 ng/mL for GX, respectively. The mean peak time was 2.89 h for lidocaine, 5.14 h for MEGX and 9.88 h for GX, respectively. In addition, the mean half-life was 4.19 h for lidocaine and 6.92 h for MEGX. In this study, we found that the metabolism of lidocaine and MEGX might be affected by the hepatic blood flow occlusion or liver injury.

A vaginal nanoformulation of a SphK inhibitor attenuates lipopolysaccharide-induced preterm birth in mice

Aim: Previously, we have shown that inhibition of SphK by the SphK inhibitor-II (SKI II) prevents lipopolysaccharide-induced preterm birth in mice. The aim of this study was to develop a vaginal self-nanoemulsifying drug-delivery system (SNEDDS) for SKI II. Materials & methods: A SKI II-loaded SNEDDS was characterized and tested in a murine preterm birth model. Results: The SNEDDS immediately formed a gel and then slowly emulsified to nanoglobules with over 500-fold enhancement of SKI II solubility at vaginal pH. Intravaginal administration of the SKI II SNEDDS significantly decreased lipopolysaccharide-induced preterm birth in mice. Conclusion: A vaginal nanoformulation of SKI II represents a novel, noninvasive approach to prevent preterm birth.