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

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.

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.

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Study of forced decomposition behavior of lamivudine using LC, LC-MS/TOF and MS(n)

Lamivudine was subjected to forced decomposition conditions of hydrolysis (neutral, acidic and alkaline), oxidation, photolysis and thermal stress, as suggested in the ICH guideline Q1A(R2). The drug showed instability in acid and alkali, while it remained stable in neutral conditions. It also degraded extensively under oxidative environment. It remained stable to light and thermal stress. In total, five degradation products were formed, which could be separated by LC on a C18 column using a gradient method. To characterize the products, first a complete fragmentation pathway of the drug was established by carrying out multi-stage (MS(n)) and MS/TOF accurate mass studies. The same was compared to fragment pattern of the degradation products resulting from LC-MS/TOF studies. The accurate mass values obtained from LC-MS/TOF were used to obtain elemental compositions, and the total information helped in identification of the degradation products. Subsequently, degradation pathway of the drug was laid down, along with mechanisms of formation of the degradation products. There is no previous information on these aspects on the drug in the literature.

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.

High throughput LC-MS/MS method for simultaneous quantification of lamivudine, stavudine and nevirapine in human plasma

A selective and high throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and validated to separate, detect and simultaneously quantify lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma using metaxalone as internal standard (IS). After solid phase extraction (SPE), the analytes and the IS were chromatographed on a Symmetry C18 (150 mmx3.9 mm i.d., 5 microm particle size) column using 5 microL injection volume with a run time of 4.5 min. An isocratic mobile phase consisting of 0.5% glacial acetic acid in water:acetonitrile (20:80, v/v) was used to separate all these drugs. The precursor and product ions of these drugs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring mode (MRM) without polarity switch. The method was validated over the range of 25-3000 ng/mL for 3TC, 20-2000 ng/mL for d4T and 50-5000 ng/mL for NVP. The absolute recoveries for analytes (>or=86%) and IS (98.12%) achieved from spiked plasma samples were consistent and reproducible. Inter-batch and intra-batch precision (%CV) across four validation runs (LLOQ, LQC, MQC and HQC) was less than 10. The accuracy determined at these levels was within +/-8% in terms of relative error. The method was successfully applied to a pivotal bioequivalence study of [60 (3TC)+12 (d4T)+100 (NVP)] mg dispersible tablets in 60 healthy human subjects under fasting condition.

Simultaneous determination of abacavir and zidovudine from rat tissues using HPLC with ultraviolet detection

A simple high-performance liquid chromatography (HPLC) method has been developed and validated for the simultaneous determination of abacavir and zidovudine (AZT) in rat plasma, amniotic fluid, fetal, and placental tissues. Extraction of abacavir, AZT, and the internal standard, azidouridine (AZDU) in amniotic fluid was carried out by protein precipitation. Extraction from plasma, fetal and placental homogenates was achieved by using a salting out technique. Chromatographic separation was performed using a C8 column (150 mm x 4.6 mm, 5 microm). The mobile phase consisted of 12% acetonitrile in 25 mM sodium phosphate buffer (adjusted to pH 7 with sodium hydroxide) for the fetus, placenta, plasma and amniotic fluid samples at a flow rate of 0.8 mL/min. The method was validated over the range from 0.05 to 50 microg/mL for both abacavir and AZT in the four biological matrices. The absolute recovery of abacavir ranged from 79 to 94%, while AZT recoveries ranged from 79 to 90% in the different biological matrices. The internal standard recovery ranged from 90 to 92%. Acceptable intra- and inter-day assay precision (<10% R.S.D.) and accuracy (<10% error) were observed over 0.05-50 microg/mL for all four matrices.

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.