Development of a dissolution test for lamotrigine in tablet form using an ultraviolet method

The Effect of Humidity on the Dissolution Kinetics and Tablet Properties of Immediate-Release Tablet Formulation Containing Lamotrigine

This study aims to find the effects of high (75%) and low (30%) humidity conditions and its correlation with formulation composition on dissolution kinetics of lamotrigine (LMT) from prepared immediate-release tablets during one- and four-week periods. Two types of fillers microcrystalline cellulose (MCC) or anhydrous lactose (LAC), disintegrant sodium starch glycolate (NaSG, 0.5% or 4%), and lubricant magnesium stearate (MgST, 0.25% or 5%) were used. A three-factor two-stage complete factorial design (2³) was used to assess the influence of the composition of the tested formulations. The tablets were produced by direct compression and characterized using a disintegration test, a resistance to crushing test, and dissolution tests (pH 1.2 and pH 6.8). Using Design Expert software, it was concluded that in addition to the effect of fillers on pH 6.8, NaSG has a significant impact after exposure to high and low humidity, as well as its interaction with LAC and MCC. In the dissolution medium pH 1.2, under conditions of high humidity, the content of MgST and NaSG and their interaction show a significant influence. The release rate of LMT was affected by humidity as well as type of excipients and their interactions.

Dual Functionality of Bile Acid: Physical Stabilization of Drugs in the Amorphous Form and Solubility Enhancement in Solution

Drugs containing an amino aromatic nitrogen moiety were stabilized in the amorphous form by the surfactant cholic acid (CA). Coamorphous systems of lamotrigine (LAM), pyrimethamine (PYR), and trimethoprim (TRI) were each prepared with CA. Drug-CA interactions, investigated by IR and solid-sate NMR spectroscopy, revealed deprotonation of the carboxylic acid group in CA and the protonation of the most basic nitrogen of the drug. The coamorphous systems exhibited exceptional physical stability and resisted crystallization at (i) elevated temperatures (>100 °C) and (ii) accelerated storage conditions, 40 °C/75% relative humidity for 15 months. The dissolution performance of each coamorphous system was compared with the respective crystalline drug based on the area under the curve (AUC) of the concentration-time profiles. A 25-fold increase in AUC was observed in the PYR-CA coamorphous system. The solubility enhancement is attributed not only due to drug amorphization but also due to solubilization by CA. The supramolecular synthon approach, through a drug-CA interaction, yielded physically stable coamorphous systems with enhanced aqueous drug solubility.

Lamotrigine therapy in patients after bariatric surgery: Potentially hampered solubility and dissolution

Bariatric surgery is an effective treatment of obesity and related comorbidities. With surgery, the stomach undergoes major anatomical/physiological changes that may affect the oral exposure of drugs, especially marginally soluble weak bases, such as lamotrigine. The aim of this work was to study the solubility/dissolution of lamotrigine in conditions simulating the stomach before vs. after bariatric surgery. Lamotrigine solubility was studied in-vitro, as well as ex-vivo in gastric content aspirated from patients before vs. after bariatric surgery. We then compared the dissolution kinetics of various marketed lamotrigine products in pre- vs. post-operative stomach conditions, different in volume, pH, agitation strength and speed. Decreased lamotrigine solubility with increasing pH (from 1.37 ± 0.09 (pH = 1) to 0.22 ± 0.03 mg/mL (pH = 7)) was obtained. Twelve-fold higher lamotrigine solubility was revealed in gastric content aspirated before vs. after surgery (8.5 ± 0.7 and 0.7 ± 0.01 mg/mL, respectively). Dissolution studies showed that only the lowest dose (25 mg) fully dissolved in the post-surgery stomach conditions, while at higher doses, lamotrigine tablet dissolution was impaired. Neither fast-dissolving tablet, nor tablet crushing, helped resolving this problem. Based on these results, and given that dissolution of the drug dose governs the subsequent absorption, close monitoring of this essential drug is advised after bariatric surgery.

Lamotrigine Nanoparticle Laden Polymer Composite Oral Dissolving Films for Improving Therapeutic Potential of the Hydrophobic Antiepileptic Molecule

Lamotrigine is used for neurological disorders and antiepileptic therapy at frequent dosing due to its poor solubility. The present work aims to study the influence of combining the Lamotrigine nanoparticles and polymer composite oral dissolving film to improve the solubility and dissolution kinetics of the drug. The Lamotrigine-Eudragit E100 nanoparticles were synthesized through solvent evaporation followed by precipitation process, which were laden in oral dissolving films through solvent casting technique. The optimized nanoparticles were assessed for particle size, colloidal stability, drug entrapment efficiency, in vitro release profile, physicochemical characteristics, and cytotoxicity. The optimized polymeric nanoparticles of Lamotrigine: Eudragit E100 (1:0.5) exhibited monodispersed particles with 103 nm average size, +7.96 mV zeta potential, and 82.96% ± 1.2% entrapment efficiency. The composite oral matrix films blended with polyvinyl alcohol and polyvinyl pyrrolidone (0.5:0.5 ratio) incorporated with the polymeric nanoparticles demonstrated >64% drug release within 2 h. The nanoparticles and its composite films exhibited 9- and 11-fold higher drug release than pure drug, respectively. The analytical characterization studies proved the formation of nanoparticles with mild drug-polymer interactions and optimum stability, which resulted in enhanced solubility and dissolution of drug. The nanoparticles displayed lesser cytotoxicity to the normal (Vero) cells at concentration of 10-50 μg/mL compared to pure drug. The optimized polymeric nanoparticle loaded oral films could be suitable for in vivo administration of Lamotrigine at low doses to improve bioavailability and therapeutic efficiency with reduced side effects.

Validation of Rapid Enzymatic Quantification of Acetic Acid in Vinegar on Automated Spectrophotometric System

Vinegar is produced from the fermentation of agricultural materials and diluted acetic acid (diluted with water to 4–30% by volume) via sequential ethanol and acetic acid fermentation. The concentration of acetic acid must be measured during vinegar production. A Community method for analyzing acetic acid in vinegar is a non-specific method based on the assumption that the total acid concentration of the vinegar is attributable to the acetic acid. It consists of titration with a strong base in the presence of an indicator. This test is laborious and has a time-consuming character. In this work, a highly specific automated enzymatic method was validated, for the first time, to quantify the acetic acid in the wine vinegar, in terms of linearity, precision, repeatability, and uncertainty measurement. The results were compared to the Community method of analysis. Regression coefficient ≅ 1 and the normal distribution of residuals in the ANOVA test confirmed the method’s linearity. LLOD (0.946 ppm) and LLOQ (2.00 ppm) defined the method’s sensitivity. The results of the tested and the Community methods, linearly distributed in the Shapiro–Wilk test, confirmed the method’s repeatability. The few anomalous data in the Huber test were due to random errors. The high selectivity of the enzymatic method, which exclusively measures acetic acid concentration, determined the significant differences between the two tests, examined in the accuracy determination. The enzymatic method can be considered applicable since its precision and uncertainty were lower than the Community method values (relative percentage deviations = 10%). The enzymatic method compared to the Community method reduces the analysis time and the risk of errors due to operators (avoid pipetting errors and wrong calculations), minimizes solvent and the sample consumption and guarantees assay quality through method standardization.