Determination of lafutidine in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry: application to a bioequivalence study

Pharmacokinetic Properties of Oral Lafutidine Tablets and the Effect of Food on its Pharmacokinetics in Healthy Chinese Subjects

INTRODUCTION

The aim of this study was to evaluate the pharmacokinetics (PK) of single and multiple doses of oral lafutidine tablets and the effect of food on the PK properties in healthy Chinese subjects. The tolerability and the effect of gender on the PK properties were also evaluated to acquire more PK information.

METHODS

Three PK studies were conducted in 12 healthy Chinese subjects (6 male, 6 female). Study 1 was a single-dose, three-period, three-dose level (10, 20, and 40 mg), three-sequence cross-over study under fasting conditions. Study 2 was a repeat-dose study (10 mg twice daily over 6 days; all 12 subjects). Study 3 was a two-period, two-sequence cross-over single-dose (10 mg) food interaction study. All randomizations (study 1, study 3) were done to ascertain 1:1 gender ratio per sequence. A validated liquid chromatography tandem mass spectrometry (LC/MS/MS) method was used to determine plasma lafutidine concentrations. PK parameters were calculated by the non-compartmental method.

RESULTS

The area under the time-concentration curve (AUC) and maximum plasma concentration (C _max) of lafutidine tablets were dose-independent in the single-dose study among these healthy volunteers. The PK parameters of the multiple-dose study were inconsistent with the single study. After administration of a single dose of 10 mg under either fed or fasting conditions, we found that food may not affect the degree of absorption of the lafutidine tablets, but it may slow down the absorption rate. This is shown by the fact that the AUC showed no significant difference while the peak time was significantly delayed under fed conditions.

CONCLUSION

The PK of lafutidine showed dose proportionality. There was no significant accumulation of lafutidine tablets with multiple dosing. Food did not affect the degree of lafutidine absorption, but it did reduce the rate of absorption. Further study is needed regarding the effect of gender on lafutidine. Lafutidine was well tolerated within the dose range 10-40 mg, and no serious adverse events were observed.

Development and validation of stability-indicating UPLC method for the determination of lafutidine and its impurities in bulk and pharmaceutical dosage form

Background

A simple and rapid stability-indicating, reversed phase ultra-performance liquid chromatography (UPLC) method was developed for the quantitative determination of lafutidine and its four potential impurities.

Results

Separation was achieved on Acquity BEH-shield RP18 UPLC column (3.0 mm × 100 mm, 1.7 μm) under the gradient mode of elution by using mobile phase A (0.02M diammonium hydrogen phosphate/acetonitrile, 80:20 v/v) and mobile phase B (0.02M diammonium hydrogen phosphate/acetonitrile, 30:70 v/v). The flow rate was maintained at 0.5 mL min−1. UV detection was carried out at 276 nm.

Conclusions

Stability-indicating capability of the developed method is established by analyzing forced degradation samples in which the spectral purity of lafutidine is ascertained along with the separation of degradation products from analyte peak. The developed UPLC method is validated as per International Conference on Harmonization guidelines with respect to system suitability, specificity, precision, sensitivity, accuracy, linearity, and robustness.

Characterization of metabolites of a novel histamine H(2)-receptor antagonist, lafutidine, in human liver microsomes by liquid chromatography coupled with ion trap mass spectrometry

The metabolism of lafutidine in human liver microsomes was studied using liquid chromatography/ion trap mass spectrometry with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. A total of 14 metabolites were identified including hydroxylated lafutidine and sulfonyl lafutidine as the major metabolites. The chemical properties and the MS(n) behaviors of lafutidine and all of its identified metabolites were studied in detail. Lafutidine had a fragmentation pattern as a result of homolytic bond cleavage in the MS/MS spectrum. This cleavage can form an odd-electron ion with the loss of furan-2-ylmethyl radical (-81 Da with a proton shift), which then sequentially loses neutral groups in the MS(3) spectrum. This fragmentation sequence was also observed from the metabolites with the unchanged sulfinyl moiety. When the sulfinyl moiety was oxidized to the sulfonyl moiety, this fragmentation sequence did not exist, which could be used to identify S-oxidation metabolites of lafutidine. In general, N-oxides could produce distinct [M+H-O](+) ions under LC/APCI-MS due to the thermal activation in the desolvation region of the API source, which could be used to identify N-oxidation metabolites of lafutidine. In order to avoid the possibility of false positives, the MS/MS spectrum of the [M+H-O](+) ion was compared with that of the non-N-oxidation metabolites or parent drug in the APCI source. If they were consistent, the structure could be finally confirmed. The exact masses for lafutidine and lafutidine N-oxide fragment ions were determined using an LTQ/Orbitrap mass spectrometer.