High-performance liquid chromatographic assay for the determination of 2'-deoxy-3'-thiacytidine (lamivudine) in human plasma

Preclinical Pharmacokinetics of Lamivudine and Its Interaction with Schisandra chinensis Extract in Rats

Schisandra chinensis (Turcz.) Baill. (S. chinensis) extract and its active ingredient, schizandrin, have been used as a botanical medicine and dietary supplement for the treatment of hepatitis. Lamivudine is an antiretroviral drug and is used to treat hepatitis B viral infection. The aim of this study was to develop an ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the measurement of lamivudine and to determine the pharmacokinetic behaviors of an aqueous-ethanol extract of S. chinensis in rats. The separation was performed on a phenyl column maintained at 40 °C. The experimental animals were distributed into three groups: (1) lamivudine alone (10 mg/kg, i.v.); (2) lamivudine (10 mg/kg, i.v.) + pretreatment with S. chinensis (3 g/kg, p.o.); and (3) lamivudine (10 mg/kg, i.v.) + pretreatment with S. chinensis (10 g/kg, p.o.). The experimental results indicated that neither treatment with lamivudine alone nor pretreatment with S. chinensis (3 or 10 g/kg) significantly changed the pharmacokinetic parameters. In conclusion, based on the above preclinical experimental model, the combination of lamivudine with the herbal extract of S. chinensis did not exhibit significant pharmacokinetic interactions. These data offer useful information for assessing the preclinical safety of nutritional supplementation with lamivudine.

Hollow mesoporous structured molecularly imprinted polymer as adsorbent in pipette-tip solid-phase extraction for the determination of antiretrovirals from plasma of HIV-infected patients

In this work a hollow mesoporous structured molecularly imprinted polymer was synthetized and used as adsorbent in pipette-tip solid-phase extraction for the determination of lamivudine (3TC), zidovudine (AZT) and efavirenz (EFZ) from plasma of human immunodeficiency virus (HIV) infected patients by high-performance liquid chromatography (HPLC). All parameters that influence the recovery of the pipette tip based on hollow mesoporous molecularly imprinted polymer solid-phase extraction (PT-HM-MIP-SPE) method were systematically studied and discussed in detail. The adsorbent material was prepared using methacrylic acid and 4-vinylpyridine as functional monomers, ethylene glycol dimethacrylate as crosslinker, acetonitrile as solvent, 4,4'-azobis(4-cyanovaleric acid) as radical initiator, benzalkonium chloride as surfactant, 3TC, and AZT as templates. The simultaneous separation of 3TC, AZT and EFZ by HPLC-UV was performed using a Gemini C18 Phenomenex® column (250 mm × 4.6 mm, 5 μm) and mobile phase consisting of acetonitrile: water pH 3.2 (68:32, v/v), flow rate of 1.0 mL/min and λ = 260 nm. The method was linear over the concentration range from 0.25 to 10 μg/mL for 3TC and EFZ, and 0.05 to 2.0 μg mL^-1 for AZT, with correlation coefficients larger than 0.99 for all analytes. Recovery ± relative standard deviations (RSDs %) were 41.99 ± 2.38%, 82.29 ± 1.63%, and 83.72 ± 7.52% for 3TC, AZT, and EFZ, respectively. The RSDs and relative errors (REs) were lower than 15% for intra and interday assays. The method has been successfully applied for monitoring HIV-infected patients outside the therapeutic dosage.

Rapid determination of lamivudine in human plasma by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatographic method with spectrophotometric detection was developed for the determination of lamivudine in human plasma. Sample preparation was accomplished through protein precipitation with acetonitrile followed by aqueous phase separation using dichloromethane. Lamivudine and the internal standard acyclovir were well separated from endogenous plasma peaks on a Chromolith RP-18e column under isocratic elution with 50 mM sodium dihydrogen phosphate-triethylamine (996:4, v/v), pH 3.2 at 20 °C. Total run time at a flow-rate of 1.5 ml/min was less than 5 min. Detection was made at 278 nm. The method was specific and sensitive, with a lower quantification limit of 40 ng/ml and a detection limit of 10 ng/ml. The absolute recovery was 97.7%, while the within- and between-day coefficient of variation and percent error values of the assay method were all less than 7%. The linearity was assessed in the range of 40-2560 in plasma, with a correlation coefficient of greater than 0.999. The method was successfully applied to a bioequivalence study in healthy volunteers.

Extractive Spectrophotometric Method for the Determination of Lamivudine and Zidovudine in Pharmaceutical Preparations Using Bromocresol Purple

A new spectrophotometric method has been established for the quantitation of lamivudine (LVD) and zidovudine (ZVD) in pharmaceutical preparations. The method is based on the reaction between the investigated drug substances and bromocresol purple (BCP) producing ion-pair complexes in acidic buffers which are suitable for chloroform extraction. The maximum absorbance of these complexes was measured at 424 nm in chloroform. All variables were studied to optimize the reaction conditions. Linearity ranges were found to be 25–250 μg mL−1for LVD-BCP and 50–300 μg mL−1for ZVD-BCP. The developed method was successfully applied for the determination of these drugs in pharmaceutical preparations. Excipients in pharmaceutical formulations did not interfere in the analysis. The results were compared statistically with those obtained by the HPLC method reported in the literature. According to the results, the proposed method can be recommended for quality control and routine analysis.

Development and validation of analytical method for the estimation of lamivudine in rabbit plasma

Lamivudine has been widely used in the treatment of HIV disease. A reliable, sensitive reversed phase high performance liquid chromatography (RP-HPLC) method was developed and validated for lamivudine in rabbit plasma. The method was developed on Hypersil BDS C-18 column (250 mm×4.6 mm, 5 μm) using a mobile phase of 0.25% Triethylamine buffer (pH 3.0): acetonitrile (70:30, v/v). The efficient was monitored by UV detector at 256 nm. The total run time was 15 min with a flow rate of 1.0 mL/min. Calibration curve was linear over the concentration range of 25–2000 ng/mL. The retention times of lamivudine and internal standard (Nelfinavir) were 8.78 min and 10.86 min, respectively. The developed RP-HPLC method can be successfully applied for the quantitative pharmacokinetic parameters determination of lamivudine in rabbit model.

Synthesis, analysis, in vitro characterization, and in vivo disposition of a lamivudine-dextran conjugate for selective antiviral delivery to the liver

A liver-selective prodrug (3TCSD) of the antiviral drug lamivudine (3TC) was developed and characterized. 3TC was coupled to dextran ( approximately 25 kDa) using a succinate linker, and the in vitro and in vivo behavior of the conjugate was studied using newly developed size-exclusion and reversed-phase analytical methods. Synthesized 3TCSD had a purity of >99% with a degree of substitution of 6.5 mg of 3TC per 100 mg of the conjugate. Furthermore, the developed assays were precise and accurate in the concentration ranges of 0.125-20, 0.36-18, and 1-50 microg/mL for 3TC, 3TC succinate (3TCS), and 3TCSD, respectively. In vitro, the conjugate slowly released 3TC in the presence of rat liver lysosomes, whereas it was stable in the corresponding buffer. In vivo in rats, conjugation of 3TC to dextran resulted in 40- and 7-fold decreases in the clearance and volume of distribution of the drug, respectively. However, the accumulation of the conjugated 3TC in the liver was 50-fold higher than that of the parent drug. The high accumulation of the conjugate in the liver was associated with a gradual and sustained release of 3TC in the liver. These studies indicate the feasibility of the synthesis of 3TCS-dextran and its potential use for the selective delivery of 3TC to the liver.

The effect of ABCG2 V12M, Q141K and Q126X, known functional variants in vitro, on the disposition of lamivudine

AIMS

To evaluate the effects of three ABCG2 variants (Q141K, V12M and Q126X), which are known to have altered transport properties in vitro, on the disposition of lamivudine in healthy subjects.

METHODS

To evaluate whether lamivudine is a substrate of ABCG2, intracellular accumulation and vectorial transport of 3H-lamivudine were determined in MDCK-ABCG2 cells. The pharmacokinetic parameters of lamivudine were compared among subjects with four different ABCG2 genotypes, including wild type (seven subjects), K141/K141 (six subjects), Q126/Stop126 (four subjects) and M12/M12 (five subjects) after a single oral dose of 100 mg lamivudine.

RESULTS

The intracellular accumulation of lamivudine in MDCK-ABCG2 cells was significantly lower than that in MDCK-mock cells, but fumitremorgin C reversed the intracellular lamivudine concentration to that of MDCK-mock cells. The ABCG2-mediated transport of lamivudine was saturable and the values of Km and Vmax were 216.5 +/- 58 microm and 20.42 +/- 2.9 nmol h(-1) per 10(6) cells, respectively. After lamivudine administration to healthy subjects, the AUC of lamivudine showed no difference among subjects with different ABCG2 genotypes; 2480 +/- 502, 2207 +/- 1019, 2422 +/- 239, 2552 +/- 698 ng h(-1) ml(-1) for wild type, K141/K141, Q126/Stop126 and M12/M12 genotype, respectively (P = 0.85). The estimated 95% confidence intervals for the mean difference between K141/K141, Q126/Stop126, M12/M12 and wild as reference were (-1053, 507), (-555, 439) and (-552, 696), respectively. No other pharmacokinetic parameters were estimated to be significantly different among four different ABCG2 genotypes tested.

CONCLUSIONS

Lamivudine appeared to be a substrate of ABCG2 in vitro, but the disposition of lamivudine was not significantly influenced by known in vitro functional variants of ABCG2, Q141K, V12M and Q126X in healthy subjects.

Simultaneous quantification of stavudine, lamivudine and nevirapine by UV spectroscopy, reverse phase HPLC and HPTLC in tablets

In the present study, simultaneous quantification of stavudine (SV), lamivudine (LV) and nevirapine (NV) in tablets by UV spectroscopy, reverse phase HPLC (RP-HPLC) and HPTLC methods were developed. In the UV multi-component spectral method, SV, LV and NV was quantified at 266, 271 and 315 nm, respectively. In the RP-HPLC method, the drugs were resolved using a mobile phase of 20 mM sodium phosphate buffer (containing 8 mM 1-octanesulphonicacid sodium salt):acetonitrile (4:1, v/v) with pH adjusted to 3.5 using phosphoric acid on a C18-ODS-Hypersil (5 microm, 250 mm x 4.6 mm) column in isocratic mode. The retention time of SV, LV and NV was 2.85, 4.33 and 8.39 min, respectively. In the HPTLC method, the chromatograms were developed using a mobile phase of chloroform:methanol (9:1, v/v) on precoated plate of silica gel 60 F254 and quantified by densitometric absorbance mode at 265 nm. The Rf of SV, LV and NV were 0.21-0.27, 0.62-0.72 and 0.82-0.93, respectively. Recovery values of 99.16-101.89%, percentage relative standard deviation of <0.7 and correlation coefficient (linear dynamic range) of 0.9843-0.9999 shows that the developed methods were accurate and precise. These methods can be employed for the routine analysis of tablets containing SV, LV and NV.

High-performance liquid chromatographic determination of lamivudine in human serum using liquid–liquid extraction; application to pharmacokinetic studies

A simple, fast, and sensitive high performance liquid chromatographic (HPLC) assay was developed for quantitation of lamivudine in human serum. Lamivudine is polar compound and its extraction from the human serum in previously published HPLC methods involved either protein precipitation or solid phase extraction techniques. However, existence of endogenous peaks which interfere with the drug or appeared as late eluting peaks and lead to long run time of analysis has been reported. Application of either an ion pairing agent in the mobile phase or time consuming column purge has been used in the published methods. Present paper describes liquid - liquid extraction of lamivudine and internal standard (famotidine) using dichloromethane-isopropyl alcohol (1:1, v/v) as an extracting solvent and salting out approach. The mobile phase was a mixture of phosphate buffer (0.05 M) containing triethylamine (1 mL/L, v/v; pH 3.5) and methanol (91:9, v/v) at a flow rate of 2.2 mL/min. The analysis was performed on a column (150 mm x 6 mm i.d.) which was packed with 5 microm particles of ODS packing material. Under these conditions no interference in the assay from any endogenous substance was observed. The limit of quantification was evaluated to be 5 ng/mL. Accuracy and precision of the method were also studied and the technique was shown to be selective and linear into the concentration range of 5-2500 ng/mL. This method has been used in two randomized crossover bioequivalence studies of 100 and 150 mg lamivudine preparations in 12 and 24 healthy volunteers, respectively.

Determination of lamivudine in human plasma by HPLC and its use in bioequivalence studies

A simple, accurate, precise and sensitive high-performance liquid chromatographic (HPLC) method with ultraviolet detection was developed to quantificate lamivudine (3-TC) in human plasma samples from bioequivalence studies. 3-TC and stavudine (internal standard, I.S.) were extracted from 0.5 ml of human plasma by acetonitrile protein precipitation. The method was validated over a concentration range of 0.05-3.00 microg/ml and used in a bioequivalence trial between two lamivudine formulations, to assess its usefulness in this kind of study. FURP-lamivudine (Fundação para o Remédio Popular, Brazil, as test formulation) and Epivir (GlaxoSmithKline, Brazil, as reference formulation) were evaluated following a single 150 mg oral dose to 24 healthy volunteers of both genders. The dose was administered after an overnight fast according to a two-way crossover design. Bioequivalence between the products was determined by calculating 90% confidence intervals (90% CI) for the ratio of Cmax, AUC0-t and AUC0-inf values for the test and reference products, using logarithmic transformed data. The 90% confidence intervals for the ratio of Cmax (0.86-1.06), AUC0-t (0.96-1.04) and AUC0-inf (0.97-1.05) values for the test and reference products are within the 0.80-1.25 interval proposed by FDA and EMEA. It was concluded that the two 3-TC formulations are bioequivalent in their rate and extent of absorption, and thus, may be used interchangeably.

Determination of lamivudine in plasma, amniotic fluid, and rat tissues by liquid chromatography

An HPLC method for the quantification of lamivudine (3TC) in rat plasma, amniotic fluid, placental and fetal tissues has been developed, validated and applied to the study of the placental transport of this drug in the pregnant rat. Placental and fetal tissues were processed using liquid-liquid extraction enhanced by salting out the sample using a saturated solution of ammonium sulfate. Plasma and amniotic fluid samples were processed by protein precipitation using 2 M perchloric acid. Reverse phase chromatography was performed using a phenyl column (5 microm, 150 mm x 2 mm i.d.) under a flow rate of 0.2 ml/min. The mobile phase consisted of 5% methanol in 20 mM dibasic phosphate buffer (pH 6). The method was validated over the range from 0.1 to 50 microg/ml for plasma and amniotic fluid and 0.2-50 microg/ml for the placental and fetal tissues.

Concurrent analysis of nucleoside reverse transcriptase inhibitors in a pool of endogenous nucleosides by short-end injection-capillary electrochromatography on a beta-cyclodextrin-bonded stationary phase

As part of our on-going study of the analysis of anti-human immunodeficiency virus (HIV) nucleosides, a capillary electrochromatography (CEC) method has been developed for the concurrent analysis of nucleoside HIV reverse transcriptase inhibitors (NRTIs) in a pool of endogenous nucleosides. Up to now, beta-cyclodextrin-bonded silica stationary phases have mainly been dedicated to the separation of enantiomers; however, these polysaccharides can be also be used in achiral way. This work aims at showing how CEC performed on a beta-cyclodextrin-bonded silica stationary phase can be used to concurrently resolve zidovudine (AZT), lamivudine (3TC), didanosine (ddA) and its administrated form (ddI), stavudine (d4T) and hivid (ddC) in a mixture of adenosine (A), cytidine (C), guanosine (G), thymidine (T) and uridine (U). The influence of several parameters (pH buffer, ionic strength, acetonitrile content, temperature and voltage) on both the retention times and the retention factors has been investigated using the short-end injection technique to achieve baseline separation in a short-time analysis before quantitation. Moreover, the retention factors of the charged solutes in short-end injection-CEC were calculated using theoretically derived equations, allowing for the actual voltage drop in the packed section of the semipacked CEC capillary.