Automated high-performance liquid chromatographic analysis of (-)-2'-deoxy-3'-thiacytidine in biological fluids using the automated sequential trace enrichment of dialysate systems

Pharmacokinetics of lamivudine in subjects receiving peritoneal dialysis in end-stage renal failure

AIMS

To establish whether peritoneal dialysis (PD) requires dosing modification from the CL(CR)-corrected lamivudine dose in end-stage renal failure subjects.

METHODS

This was an open-label cohort study. A total of 12 subjects undergoing PD, six continuous ambulatory peritoneal dialysis (CAPD) and six automated peritoneal dialysis (APD), for at least 3 months received lamivudine 10 mg (5 mg ml (-1) x 2 ml) daily for 8 consecutive days, followed by an intensive pharmacokinetic assessment. Urine and dialysate were collected from 0 to 24 h postdose on day 8 where possible. Pharmacokinetic parameters were calculated using noncompartmental techniques.

RESULTS

The plasma pharmacokinetic results demonstrated that peritoneal dialysis clearance (CL(D)) of lamivudine was similar between APD and CAPD patients with median (range) of 0.19 l h(-1) (0.14-0.25) and 0.1 l h(-1) (0.09-0.25), respectively. CL(D) was approximately 1/15th to 1/30th of plasma clearance, demonstrating that peritoneal dialysis does not contribute significantly to overall lamivudine clearance in this patient population. The AUC(0,24 h) of lamivudine given 10 mg daily to APD and CAPD patients was 3430 ng ml(-1) h and 3469 ng ml(-1) h, respectively, similar to historical data obtained in patients with normal renal function administered at the normal dose of 100 mg daily (3781 ng ml(-1) h). There were no clinically significant changes in any safety assessments that were attributable to lamivudine.

CONCLUSIONS

ESRD patients who receive CAPD or APD require no supplemental dosing. These patients should follow the standard dosing reduction for patients infected with HIV or HBV with renal dysfunction.

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 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.

Simultaneous determination of six HIV nucleoside analogue reverse transcriptase inhibitors and nevirapine by liquid chromatography with ultraviolet absorbance detection

An accurate, sensitive and specific reversed-phase high-performance liquid chromatography assay for the simultaneous quantitative determination of the nucleoside reverse transcriptase inhibitors zalcitabine, lamivudine, didanosine, stavudine, zidovudine, and abacavir with the non-nucleoside reverse transcriptase inhibitor nevirapine in human blood plasma is described. The new Polarity dC C(18) silica column used in this method provides better resolution and peak shape than all other columns tested. Also, four different ultraviolet wavelengths were used for accurate and specific quantitation of the analytes. The method was validated over the range of 10-10000 ng/ml for all analytes except zalcitabine (10-5000 ng/ml). This method is accurate (average accuracies of three different concentrations ranged from 97.2 to 105%), and precise (within- and between-day precision measures ranged from 0.5 to 5.1% and 0.5 to 5.6%, respectively), and is currently being used for determination of plasma drug concentrations in our laboratory.

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

A method for the quantification of 2'-deoxy-3'-thiacytidine (lamivudine, 3-TC), which incorporated the use of 3-isobutyl-methylxanthine as internal standard (I.S.) was developed and validated in human plasma, using HPLC with UV absorbance detection. Using solid-phase extraction, 3-TC and I.S. were selectively extracted from human plasma. Subsequently, chromatographic separation was performed using a YMC phenyl column with ion-pair chromatography and detection at 270 nm. The method was validated over a concentration range of 10 to 5,000 ng/ml using 0.5 ml of human plasma. The extraction recovery for both 3-TC and I.S. was greater than 95%. The determination of inter- and intra-day precision (RSD) was less than 10% at all concentration levels, while the inter- and intra-day accuracy (% difference) was less than 6%.

Determination of twelve antiretroviral agents in human plasma sample using reversed-phase high-performance liquid chromatography

A new high-performance liquid chromatography (HPLC) with UV detection assay was developed for the simultaneous determination of protease inhibitors (PIs), nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs, NNRTIs) using a single 1-ml plasma samples. A solid-liquid extraction procedure without internal standard was coupled with two separate reversed-phase HPLC systems; one for the determination of amprenavir, efavirenz, indinavir, nelfinavir, ritonavir, saquinavir (run time=32 min) and one for the determination of abacavir, didanosine, lamivudine, stavudine, nevirapine, zidovudine (run time=40 min). The first requires a mobile phase containing sodium phosphate buffer+ion pair-acetonitrile (50:50, v/v) through a C18 Symmetry column (250x4.6 mm I.D., 5 microm particle size), using variable wavelengths (241, 254 and 261 nm). The second system requires three mobile phases (potassium phosphate buffer+ion pair-acetonitrile) for different elution through a C18 Symmetry Shield column (250x4.6 mm I.D., 5 microm), using a single wavelength (260 nm). Peak-areas are linear; correlation coefficients are better than 0.998 for all compounds, with both inter- and intra-day relative standard deviations lower than 12%. Extraction recoveries are higher than 93% for PIs and NNRTIs and higher than 70% for NRTIs. The method is specific and sensitive and was used to determine trough and peak levels of antiretroviral drugs in HIV infected patients under various combinations of RTIs and PIs.

Membrane-based sample preparation coupled on-line to chromatography or electrophoresis

A review on the use of membranes for on-line sample preparation prior to chromatographic and electrophoretic analysis is provided. The current state-of-the-art of four membrane-based techniques (dialysis, electrodialysis, filtration and membrane extraction) is described by reviewing their principles and applications. Possible future developments are discussed.

Quantitative determination of (-)-2'-deoxy-3'-thiacytidine (lamivudine) in human plasma, saliva and cerebrospinal fluid by high-performance liquid chromatography with ultraviolet detection

A high-performance liquid chromatographic method for the quantitative determination of the HIV reverse transcriptase inhibitor lamivudine ((-)-2'-deoxy-3'-thiacytidine, 3TC, Epivir) in human plasma, saliva and cerebrospinal fluid is described. Lamivudine was extracted from samples using silica extraction columns prior to reversed-phase high-performance liquid chromatography with ultraviolet detection at 270 nm. The method has been validated over the range of 10 (lower limit of quantitation) to 5000 ng/ml using a 0.5-ml sample volume. Between-day and within-day precisions ranged from 3.5 to 9.0%. The assay has been used for the quantitative analysis of lamivudine in plasma and cerebrospinal fluid of HIV-1 infected patients.

Rapid quantitation of (-)-2'-deoxy-3'-thiacytidine in human serum by high-performance liquid chromatography with ultraviolet detection

A rapid, sensitive and specific high-performance liquid chromatographic (HPLC) assay was developed and validated for the measurement of (-)-2'-deoxy-3'-thiacytidine (3TC) in human serum. The method included precipitation of serum proteins by trichloroacetic acid (20%, w/v) treatment followed by centrifugation. The resulting supernatant was directly injected and 3TC was isocratically chromatographed on a reversed-phase C18 column using a mixture of phosphate buffer and methanol (88.3:11.7. v/v) and monitored at 280 nm. The limit of quantitation was 20 ng/ml using 100 microl of serum. The standard curve was linear within the range of 20-10,000 ng/ml. Replicate analysis of three quality control samples (40-1500 ng/ml) led to satisfactory intra- and inter-assay precision (coefficient of variation from 3.0 to 12.9%) and accuracy (deviation from 6.3 to 9.7%). Moreover, sample treatment processes including human immunodeficiency virus (HIV) heat-inactivation, exposure at room temperature and freezing-thawing cycles did not influence the stability of the analyte. This assay was successfully applied to the determination of 3TC serum levels in HIV-infected patients. In addition, preliminary results indicated that this procedure may also be extended to the measurement of 3TC in human plasma and urine.

High-performance liquid chromatographic determination of cytosine-containing compounds by precolumn fluorescence derivatization with phenacyl bromide: application to antiviral nucleosides and nucleotides

A novel precolumn derivatization method for the HPLC determination of cytosine-containing compounds by HPLC is described. Highly fluorescent 2-phenyl-3,N4-ethenocytosine derivatives are produced by a reaction of non-fluorescent cytosine-containing compounds with phenacyl bromide in weakly acidic acetonitrile solution at elevated temperature. The applicability of the method to various biogenic and antiviral compounds is demonstrated. Quantitative determination of cidofovir, a potent antiviral drug currently undergoing evaluation in the clinic for treatment of cytomegalovirus retinitis is also reported. The limit of detection for cidofovir in cynomolgus monkey plasma was 5 ng/ml (ca. 100 fmol on column) with the between-day precision of 16.6, 6.4 and 2.4% for five replicate samples at 20, 160 and 320 ng/ml, respectively. The within-day precision was 15.9, 5.9 and 2.1%, respectively. The method described has broad applicability and may offer significant advantages over existing HPLC methods in antiviral drug development as well as in nucleic acid research.

Renal disposition and drug interaction screening of (-)-2'-deoxy-3'-thiacytidine (3TC) in the isolated perfused rat kidney

PURPOSE

Dideoxynucleoside bases are used for the treatment of acquired immune deficiency syndrome (AIDS), acting by inhibiting reverse transcriptase and preventing human immunodeficiency virus (HIV) replication. Currently, AZT (zidovudine), ddC (zalcitibine), and ddI (didanosine) are available to the medical community to prevent the onset of AIDS in HIV-infected individuals. 3TC (-)-2'-deoxy-3'-thiacytidine, lamivudine), a new dideoxynucleoside base, is currently undergoing Phase II/III trials, and has exhibited anti-HIV replication activity, a favorable adverse event safety profile, and is eliminated via renal mechanisms. Concomitantly administered drugs could potentiate the effects of 3TC due to interaction in the kidney.

METHODS

An isolated perfused rat kidney (IPK) technique was used to screen several clinically relevant drugs for potential interaction with 3TC. The following perfusions were performed: baseline 3TC; and 500 ng/mL 3TC with clinically relevant concentrations of AZT, ddC, ddI, probenecid, trimethoprim, sulfamethoxazole, ranitidine, and cimetidine.

RESULTS

Renal clearance of 3TC was nonlinear between 500 and 5000 ng/mL, decreasing from 3.06 to 1.74 mL/min. Excretion ratio also decreased, from 3.67 (500 ng/mL) to 2.49 (5000 ng/mL), consistent with a decrease in 3TC secretion. AZT, ddI, and ddC elicited no or minimal effects on 3TC elimination at the concentrations studied. However, trimethoprim caused significant reductions in 3TC elimination parameters: clearance and excretion ratio decreased to 1.25 mL/min and 1.43, respectively.

CONCLUSIONS

These results indicate that caution should be exercised when the combination of 3TC and trimethoprim are administered to AIDS patients.