Determination of loratadine and its active metabolite in human plasma by high-performance liquid chromatography with mass spectrometry detection

A non-extraction sequential injection method for determination of loratadine using formation of its ion-association complex with bromocresol purple in acetonitrile

The formation of an ion-association complex (IA) between sulfonephthalein dye and basic nitrogen-containing compound in an organic solvent medium has been for the first time used to develop an automated SIA method. In highly polar aprotic solvents, the tautomeric equilibrium for such dyes is strongly shifted towards the colorless lactonic form. The addition of a basic nitrogen-containing substance leads to the formation of IA with a highly colored quinonoid form, which is accompanied by an increase in the absorbance of the dye band at approximately 400 nm. Protonation of pyridine nitrogen in loratadine, structure and binding places of IA were shown using quantum-chemical calculations. The very simple, direct and non-extraction spectrophotometric SIA method with high throughput of 43 h-1 was developed based on the formation of IA between loratadine and bromocresol purple in the medium of acetonitrile used both as solvent and carrier. The calibration graph was linear in the concentration range from 1.0 to 20 mg L-1 with correlation coefficient of 0.9992. The developed method was successfully applied to the analysis of pharmaceutical formulations.

A novel method to estimate the absorption rate constant for two-compartment model fitted drugs without intravenous pharmacokinetic data

The in vivo performances of most drugs after extravascular administration are fitted well with the two-compartment pharmacokinetic (PK) model, but the estimation of absorption rate constant (k_a) for these drugs becomes difficult during unavailability of intravenous PK data. Herein, we developed a novel method, called the direct method, for estimating the k_a values of drugs without using intravenous PK data, by proposing a new PK parameter, namely, maximum apparent rate constant of disposition (k_max). The accuracy of the direct method in k_a estimation was determined using the setting parameters (k₁₂, k₂₁, and k₁₀ values at high, medium, and low levels, respectively) and clinical data. The results showed that the absolute relative error of k_a estimated using the direct method was significantly lower than that obtained using both the Loo-Riegelman method and the statistical moment method for the setting parameters. Human PK studies of telmisartan, candesartan cilexetil, and tenofovir disoproxil fumarate indicated that the k_a values of these drugs were accurately estimated using the direct method based on good correlations between the k_a values and other PK parameters that reflected the absorption properties of drugs in vivo (T_max, C_max, and C_max/AUC_0-t). This novel method can be applied in situations where intravenous PK data cannot be obtained and is expected to provide valuable support for PK evaluation and in vitro-in vivo correlation establishment.

Developmental Pharmacogenetics of CYP2D6 in Chinese Children: Loratadine as a Substrate Drug

Objective: The elucidation of CYP2D6 developmental pharmacogenetics in children has improved, however, these findings have been largely limited to studies of Caucasian children. Given the clear differences in CYP2D6 pharmacogenetic profiles in people of different ancestries, there remains an unmet need to better understand the developmental pharmacogenetics in populations of different ancestries. We sought to use loratadine as a substrate drug to evaluate the effects of ontogeny and pharmacogenetics on the developmental pattern of CYP2D6 in Chinese pediatric patients.

Methods: Chinese children receiving loratadine treatment were enrolled in the present study. The metabolite-to-parent ratio (M/P ratio), defined as the molar ratio of desloratadine to loratadine of trough concentrations samples at steady-state condition, was used as a surrogate of CYP2D6 activity. Loratadine and desloratadine were determined by LC/MS/MS method. Variants of CYP2D6 were genotyped by polymerase chain reaction for CYP2D6 *4, *10, *41 and long polymerase chain reaction for CYP2D6 *5.

Results: A total of 40 patients were available for final analysis. The mean age was 4.50 (range 0.50–9.00) years and the mean weight was 19.64 (range 7.00–42.00) kg. The M/P ratio was significantly lower in intermediate metabolizers (IMs) compared to normal metabolizers (NMs) (10.18 ± 7.97 vs. 18.80 ± 15.83, p = 0.03). Weight was also found to be significantly associated with M/P ratio (p = 0.03).

Conclusion: The developmental pharmacogenetics of CYP2D6 in Chinese children was evaluated using loratadine as a substrate drug. This study emphasizes the importance of evaluating the developmental pharmacogenetics in populations of different ancestries.

Pharmacokinetics and Tissue Distribution of Loratadine, Desloratadine and Their Active Metabolites in Rat based on a Newly Developed LC-MS/MS Analytical Method

Loratadine (LOR) and its major metabolite, desloratadine (DL) are new-generation antihistamines. The hydroxylated metabolites of them, 6-OH-DL, 5-OH-DL and 3-OH-DL are also active because of their ability to inhibit binding of pyrilamine to brain H₁ receptors and a tendency for distributing to specific immune-regulatory tissues. In this study, a new validated LC-MS/MS method to simultaneously quantify LOR, DL, 6-OH-DL, 5-OH-DL and 3-OH-DL in plasma and tissues was established and applied to an investigation of their pharmacokinetics and target-tissue distribution tendency for the first time. Pharmacokinetics parameters in rat were measured and the results suggest that the body's exposure to active metabolites were much higher than to the prodrug with LOR, but much lower with DL. The tissue distribution study shows that LOR, DL and their active metabolites were widely distributed in the liver, spleen, thymus, heart, adrenal glands and pituitary gland. For immune-regulatory tissues, the concentrations of LOR, DL and their active metabolites in the spleen were much higher than in the thymus, which is related to the spleen, one of the sites where immune responses occur. LOR and its metabolites might inhibit immune-mediated allergic inflammation through the hypothalamic-pituitary-adrenal (HPA) axis. It was also found that the concentration of LOR in the heart was highest after liver and adrenal glands while those of DL, 6-OH-DL and 5-OH-DL in the liver, adrenal glands and spleen were all higher than those in the heart, which suggests that LOR may have a greater tendency to distribute in the heart than its metabolites.

Determination of Loratadine and Its Active Metabolite in Plasma by LC/MS/MS: An Adapted Method for Children

Introduction:

Loratadine (LOR) (Fig. 1), an active H1 receptor antagonist, is often used in the treatment of allergic disorders such as seasonal allergies and skin rash [1]. LOR was clinically approved for symptomatic relief of nasal and non-nasal symptoms of allergic rhinitis in children ≥2years.

Materials and Methods:

An adapted method of liquid chromatography-mass spectrometry (LC/MS/MS) was developed and validated to measure the concentrations of loratadine (LOR) and its active metabolite descarboethoxyloratadine (DCL) from pediatric plasma. After being mixed with the internal standard (IS, propranolol) and precipitated with methanol, samples were centrifuged and 20 μL of the supernatants were injected into the HPLC system. Separation was carried out on a reversed-phase C18 gradient column using a mobile phase consisting of water (containing 0.1 % formic acid) and acetonitrile. The flow rate was 0.5 mL/min and the running time was 5.0 min for each sample.

Results and Conclusion:

Quantitation of LOR, DCL and IS was performed using MRM mode and the transitions were: 383.1 → 337.1 for LOR, 311.1 → 259.0 for DCL and 260.2 → 116.0 for propranolol, respectively. The method was validated according to FDA guidelines, precisions and accuracies met the requirements in all cases. Calibration curves were 0.2–50.0 ng/mL for both LOR and DCL. This method was then applied for a pilot study examining the pharmacokinetics and therapeutic drug monitoring of LOR in children.

Application of the Gastrointestinal Simulator (GIS) Coupled with In Silico Modeling to Measure the Impact of Coca-Cola® on the Luminal and Systemic Behavior of Loratadine (BCS Class 2b)

In the present work, we explored if Coca-Cola^® had a beneficial impact on the systemic outcome of the weakly basic drug loratadine (Wal-itin^®, immediate-release formulation, 10 mg, generic drug product). To map the contribution of underlying physiological variables that may positively impact the intestinal absorption of loratadine, a multi-compartmental and dynamic dissolution device was built, namely the Gastrointestinal Simulator (GIS). The luminal behavior of one immediate-release (IR) tablet of 10 mg of loratadine was tested under four different fasted state test conditions in the GIS: (i) with 250 mL of water and applying a predetermined gastric half-life (t_1/2,G) of 15 min; (ii) with 250 mL of water and applying a t_1/2,G of 30 min; (iii) with 250 mL of Coca-Cola^® and a t_1/2,G of 15 min; (iv) with 250 mL of Coca-Cola^® and a t_1/2,G of 30 min. After initiating the experiments, solution concentrations and solubility were measured in the withdrawn samples, and pH was monitored. To address the impact of the present CO₂ in Coca-Cola^® on the disintegration time of the tablet, additional disintegration experiments were performed in a single-vessel applying tap water and sparkling water as dissolution media. These experiments demonstrated the faster disintegration of the tablet in the presence of sparkling water, as the present CO₂ facilitates the release of the drug. The buffer capacity of Coca-Cola^® in the presence of FaSSGF was 4-fold higher than the buffer capacity of tap water in the presence of FaSSGF. After performing the in vitro experiments, the obtained results were used as input for a two-compartmental pharmacokinetic (PK) modeling approach to predict the systemic concentrations. These simulations pointed out that (i) the present CO₂ in Coca-Cola^® is responsible for the enhancement in drug release and dissolution and that (ii) a delay in gastric emptying rate will sustain the supersaturated concentrations of loratadine in the intestinal regions of the GI tract, resulting in an enhanced driving force for intestinal absorption. Therefore, co-administration of loratadine with Coca-Cola^® will highly likely result in an increased systemic exposure compared to co-administration of loratadine with tap water. The mechanistic insights that were obtained from this work will serve as a scientific basis to evaluate the impact of Coca-Cola^® on the systemic exposure of weakly basic drugs for patients on acid-reducing agents in future work.

Developing a High-performance Liquid Chromatography Method for Simultaneous Determination of Loratadine and its Metabolite Desloratadine in Human Plasma

BACKGROUND

Allergic diseases are considered as the major burden on public health with increased prevalence globally. Histamine H1-receptor antagonists are the foremost commonly used drugs in the treatment of allergic disorders. The target drug in this study, loratadine, belongs to this class of drugs and its biometabolite desloratadine which is also a non-sedating H1 receptor antagonist with anti-histaminic activity being 2.5 to 4 times greater than loratadine. This study aimed to develop and validate a novel isocratic Reversed-phase High-Performance Liquid Chromatography (RP-HPLC) method for rapid and simultaneous separation and determination of loratadine and its metabolite, desloratadine in human plasma.

METHODS

The drug extraction method from plasma was based on protein precipitation technique. The separation was carried out on a Thermo Scientific BDS Hypersil C18 column (5μm, 250 x 4.60 mm) in a mobile phase of MeOH: 0.025M KH2PO4 adjusted to pH 3.50 using orthophosphoric acid (85: 15, v/v) at an ambient temperature. The flow rate was maintained at 1 mL/min and maximum absorption was measured using the PDA detector at 248 nm.

RESULTS

The retention times of loratadine and desloratadine in plasma samples were recorded to be 4.10 and 5.08 minutes, respectively, indicating a short analysis time. Limits of detection were found to be 1.80 and 1.97 ng/mL for loratadine and desloratadine, respectively, showing a high degree of sensitivity of the method. The method was then validated according to FDA guidelines for the determination of the two analytes in human plasma.

CONCLUSION

The results obtained indicate that the proposed method is rapid, sensitive in the nanogram range, accurate, selective, robust and reproducible compared to other reported methods.

Rapid micellar HPLC analysis of loratadine and its major metabolite desloratadine in nano-concentration range using monolithic column and fluorometric detection: application to pharmaceuticals and biological fluids

Background

Loratadine is a commonly used selective non-sedating antihistaminic drug. Desloratadine is the active metabolite of loratadine and, in addition, a potential impurity in loratadine bulk powder stated by the United States Pharmacopeia as a related substance of loratadine. Published methods for the determination of both analytes suffer from limited throughput due to the time-consuming steps and tedious extraction procedures needed for the analysis of biological samples. Therefore, there is a strong demand to develop a simple rapid and sensitive analytical method that can detect and quantitate both analytes in pharmaceutical preparations and biological fluids without prior sample extraction steps.

Results

A highly-sensitive and time-saving micellar liquid chromatographic method is developed for the simultaneous determination of loratadine and desloratadine. The proposed method is the first analytical method for the determination of this mixture using a monolithic column with a mobile phase composed of 0.15 M sodium dodecyl sulfate, 10% n-Butanol and 0.3% triethylamine in 0.02 M phosphoric acid, adjusted to pH 3.5 and pumped at a flow rate of 1.2 mL/min. The eluted analytes are monitored with fluorescence detection at 440 nm after excitation at 280 nm. The developed method is linear over the concentration range of 20.0–200.0 ng/mL for both analytes. The method detection limits are 15.0 and 13.0 ng/mL and the limits of quantification are 20.0 and 18.0 ng/mL for loratadine and desloratadine, respectively. Validation of the developed method reveals an accuracy of higher than 97% and intra- and inter-day precisions with relative standard deviations not exceeding 2%.

Conclusions

The method can be successfully applied to the determination of both analytes in various matrices including pharmaceutical preparations, human urine, plasma and breast milk samples with a run-time of less than 5 min and without prior extraction procedures. The method is ideally suited for use in quality control laboratories. Moreover, it could be a simple time-saving alternative to the official pharmacopeial method for testing desloratadine as a potential impurity in loratadine bulk powder.Graphical abstract

Simultaneous determination of loratadine, desloratadine and cetirizine by capillary zone electrophoresis

PURPOSE

The aim of the study was the development of a simple and rapid analytical procedure for the determination of the most frequently used antihistamine derivatives.

METHODS

A capillary zone electrophoretic method was developed for the simultaneous separation of loratadine, desloratadine and cetirizine. Efforts were focused primarly on the optimisation of the experimental parameters: buffer composition and concentration, buffer pH, applied voltage, temperature, injection pressure and time.

RESULTS

The optimised parameters for the separation were: 25 mM buffer electrolyte, buffer pH 2.5, voltage + 25 kV, temperature 25 °C, injection pressure 50 mbar, injection time 3 seconds, capillary 48 cm (effective length 40 cm) x 50 μm, detection at 240 nm. Under these conditions, the analysis time was below 5 minutes, the order of migration being: desloratadine, cetirizine and loratadine. The developed method was validated in terms of linearity, limits of detection and quantification, intra- and inter-day precision, selectivity and robustness.

CONCLUSION

Capillary zone electrophoresis proved to be a suitable method for the simulatneous determination of the three studied antihistamine derivatives.

Pharmacologically active metabolites of currently marketed drugs: potential resources for new drug discovery and development

Biotransformation is the major clearance mechanism of therapeutic agents from the body. Biotransformation is known not only to facilitate the elimination of drugs by changing the molecular structure to more hydrophilic, but also lead to pharmacological inactivation of therapeutic compounds. However, in some cases, the biotransformation of drugs can lead to the generation of pharmacologically active metabolites, responsible for the pharmacological actions. This review provides an update of the kinds of pharmacologically active metabolites and some of their individual pharmacological and pharmacokinetic aspects, and describes their importance as resources for drug discovery and development.