Estimation of intracellular concentration of stavudine triphosphate in HIV-infected children given a reduced dose of 0.5 milligrams per kilogram twice daily.

The antiviral efficacy of stavudine depends on the trough concentration of its intracellular metabolite, stavudine-triphosphate (d4T-TP), while the degree of stavudine's mitochondrial toxicity depends on its peak concentration. Rates of mitochondrial toxicity are high when stavudine is used at the current standard pediatric dose (1 mg/kg twice daily [BID]). Evidence from adult work suggests that half of the original standard adult dose (i.e., 20 mg BID) may be equally effective, with markedly less mitochondrial toxicity. We present a population pharmacokinetic model to predict intracellular d4T-TP concentrations in pediatric HIV-infected patients administered a dose of 0.5 mg/kg BID. Our model predicted that the reduced pediatric dose would result in a trough intracellular d4T-TP concentration above that of the reduced 20-mg adult dose and a peak concentration below that of the 20-mg adult dose. The simulated pediatric intracellular d4T-TP at 0.5 mg/kg BID resulted in median peak and trough values of approximately 23.9 fmol/10(6) cells (95% prediction interval [PI], 14.2 to 41 fmol/10(6) cells) and 14.8 fmol/10(6) cells (95% PI, 7.2 to 31 fmol/10(6) cells), respectively. The peak and trough concentrations resulting from a 20-mg BID adult dose were 28.4 fmol/10(6) cells (95% PI, 17.3 to 45.5 fmol/10(6) cells) and 13 fmol/10(6) cells (95% PI, 6.8 to 28.6 fmol/10(6) cells), respectively. Halving the current standard pediatric dose should therefore not compromise antiviral efficacy, while markedly reducing mitochondrial toxicity.

Monitoring of HAART regime antiretrovirals in serum of acquired immunodeficiency syndrome patients by micellar liquid chromatography.

A methodology based on micellar liquid chromatography to monitor five antiretroviral drugs (lamivudine, stavudine, tenofovir, zidovudine and efavirenz) was proposed. Antiretrovirals were studied in sets of three, corresponding to each highly active antiretroviral therapy (HAART) regime, prescribed to acquired immunodeficiency syndrome (AIDS)-infected patients. Four aqueous micellar mobile phases buffered at pH 7 were optimized to separate these compounds, using sodium dodecyl sulfate as the tensioactive, and 1-propanol or 1-pentanol as the organic modifier. The composition of each mobile phase was optimized for each antiretroviral. The common separation conditions were: C18 apolar column (125 × 4.6 mm, 5 µm particle size), UV detection set at 214 nm, and mobile phase running at 1 mL min(-1) without controlling the temperature. The finally suggested method was validated for five analysed antiretroviral drugs following the US Food and Drug Administration guidelines in terms of: linearity between 0.5 and 50 ppm (r(2) > 0.9995), sensitivity (LOD lower than 0.25 ppm), intra- and inter-day precision (<7.1 and <5.2%, respectively) and accuracy (recovery 88.5-105.3% and 93.5-101.3%, respectively), as well as robustness (<6.5%). The proposed method was used to monitor the level of antiretrovirals in the serum of AIDS patients. The suggested methodology was found to be useful in the routine analysis of antiretrovirals in serum samples.

Exploring dried blood spot sampling technique for simultaneous quantification of antiretrovirals: lamivudine, stavudine and nevirapine in a rodent pharmacokinetic study.

A high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method for the simultaneous quantification of lamivudine, stavudine and nevirapine was developed and validated in dried blood spot (DBS) cards. The analytes were separated using an isocratic mobile phase on a reverse phase column and analyzed by MS/MS in the MRM mode using the respective [M + H]⁺ ions, m/z 230-112 for lamivudine, m/z 225-127 for stavudine, m/z 267-226 for nevirapine, m/z 383-337 for zidovudine (IS). The lower limit of quantification was 1 ng/mL for both lamivudine and stavudine and 10 ng/mL for nevirapine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The method was successfully applied to quantify them in a rat pharmacokinetic study in whole blood, plasma and DBS cards after a single oral co-administration at the dose of 10, 2 and 13 mg/kg for lamivudine, stavudine and nevirapine, respectively, to male Wistar rats. Following oral administration the pharmacokinetic results in all the matrices are in close agreement. Thus accomplishment of this method would facilitate the ease of collection of clinical samples on DBS cards for lamivudine, stavudine and nevirapine during human clinical trials and therapeutic drug monitoring.

Simultaneous determination of lamivudine, stavudine and nevirapine in human plasma by LC-MS/MS and its application to pharmacokinetic study in clinic.

A new high-throughput LC-MS/MS method for the simultaneous determination of lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma is presented, with zidovudine as an internal standard. The analytes were extracted from plasma by protein precipitation and only 150 microL plasma was needed. Chromatographic separation was achieved on a Shiseido C(8) column (150 x 2.0 mm, 5 microm) with a total run time of 6 min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring under positive ionization mode with an electrospray ionization interface. The method was developed and validated over the concentration range of 25-5000 ng/mL for 3TC and NVP and 20-4000 ng/mL for d4T. The method was validated in terms of intra- and inter-day precision (< or = 8.6%), accuracy (within +/- 8.4%), linearity and specificity. The method has been successfully applied to the pharmacokinetic study of a combination treatment of 300 mg lamivudine, 30 mg stavudine and 200 mg nevirapine in 22 healthy male volunteers under fasting conditions.

Simultaneous determination of stavudine and lamivudine in human plasma by high performance liquid chromatography and its application to a bioavailability study.

A high performance liquid chromatographic method with UV detection was developed and validated for simultaneous determination of stavudine and lamivudine in human plasma using solid-phase extraction for sample clean-up. Zidovudine was used as an internal standard. Separation was performed on a C18 column by gradient elution with a mobile phase of 10 mM acetate buffer pH 6.5 and acetonitrile. The UV detection was set at 265 nm. The method proved to be specific, accurate, precise and linear over the concentration ranges of 50-3000 ng/ml for stavudine and 50-5000 ng/ml for lamivudine with correlation coefficients always > 0.996 for both drugs. The intra-day and inter-day precision and accuracy were less than 9.2% for both analytes. The absolute recoveries of both compounds ranged from 93.3 to 97.5%. The method was successfully applied to a bioavailability study of a combined tablet formulation containing 30 mg of stavudine and 150 mg of lamivudine compared with each reference formulation concurrently administered in 26 healthy Thai male volunteers.

Zidovudine and lamivudine reach higher concentrations in ventricular than in lumbar human cerebrospinal fluid.

OBJECTIVE: For the treatment of HIV-1-related brain disease and for the prevention of the brain becoming a viral reservoir, it is important that antiretroviral agents reach sufficient concentrations in the CNS. To date, human brain pharmacokinetic data are solely derived from lumbar cerebrospinal fluid (CSF) and mostly originate from single samples. DESIGN: We determined concentrations of antiretroviral drugs in serial samples of ventricular CSF and compared these to the concentrations in serum and lumbar CSF of these patients. METHODS: Two treatment-naïve HIV-1-infected patients received external ventricular drainage for obstructive hydrocephalus. Starting with a combination antiretroviral regimen (cART), ventricular CSF, and subsequently lumbar CSF, with parallel serum, was frequently collected. Drug concentrations were determined and CSF-to-serum ratios were calculated. RESULTS: High concentrations, resulting in high CSF-to-serum ratios, were found in the ventricular CSF of the three substances zidovudine, lamivudine and indinavir, whereas this was not observed for stavudine, ritonavir, saquinavir and efavirenz. Concentrations of zidovudine and lamivudine were up to four times greater in CSF from the ventricles than in lumbar CSF of the same patient. The zidovudine concentrations in the ventricular CSF exceeded serum concentrations by a factor of 1.4. CONCLUSION: Unexpectedly high concentrations of some antiretrovirals in the ventricular CSF, the site close to the brain parenchyma where HIV is located, should be considered when the cART regimen is aiming at CNS viral replication.

Pharmacokinetics of lamivudine & stavudine in generic fixed-dose combinations in HIV-1 infected adults in India.

BACKGROUND & OBJECTIVES: Antiretroviral drug concentrations are important determinants of clinical response to a drug accounting for both toxicity and efficacy. Several factors such as age, ethnicity, body weight and patients' immune status may influence antiretroviral drug concentrations. The aim of the study was to determine the influence of immunological status, sex and body mass index on the steady state pharmacokinetics of lamivudine (3TC) and stavudine (d4T) in HIV-infected adults, who were undergoing treatment with generic fixed dose combinations (FDC) of these drugs in India. METHODS: Twenty seven HIV-1 infected patients receiving antiretroviral treatment (ART) for at least two weeks at the Government ART clinic at Tambaram, Chennai, took part in the study. Serial blood samples were collected predosing and at different time points after drug administration. Plasma 3TC and d4T levels were estimated by HPLC. RESULTS: The patients' immune status, sex or body mass index had no impact on the pharmacokinetics of 3TC. In the case of d4T, peak concentration was significantly lower in patients with CD4 cell counts < 200 cells/microl than those with > or = 200 cells/ microl (P < 0.05), but were within the therapeutic range. The mean CD4 cell counts increased from 101 cells/microl at initiation of ART to 366 cells/microl at 12 months of treatment. INTERPRETATION & CONCLUSIONS: Blood levels of 3TC and d4T drugs that are part of generic FDCs commonly used by HIV-infected individuals in India were within the therapeutic range and not influenced by nutritional or immune status. There was a significant improvement in CD4 cell counts over 12 months of treatment. Indian generic FDCs manufactured and used widely in the developing world provide effective concentrations of antiretroviral drugs.

Stavudine plasma concentrations and lipoatrophy.

OBJECTIVES: The objective of this study was to determine the correlation between plasma stavudine concentrations and lipoatrophy (LA), one of the major adverse events in patients on stavudine and one of the major reasons to discontinue stavudine. METHODS: Plasma drug concentrations were retrospectively analysed in patients who were on a stavudine-containing regimen for at least 12 months. We defined two groups of patients: 21 patients with LA and 15 patients without LA or other stavudine-related side effects (i.e. neuropathy). RESULTS: We analysed stavudine concentrations in 212 plasma samples: 87 in the control group and 125 in the LA group, with a mean of four plasma samples per person (at least two a year). Demographics were comparable in LA patients and controls, except the duration of stavudine use, which was longer in the LA group: 55 versus 42 months in the control group. Overall, LA patients had higher drug exposure to stavudine when compared with the controls, and this was seen in the geometric concentration ratios (CRs), which were 0.978 and 0.741, respectively (P = 0.04), and also a higher percentage of CR values >1.0, representing a drug concentration above the normal population curve (46% versus 23%, P = 0.02). In addition, the duration of stavudine therapy was independently associated with LA (P = 0.05). In the multivariate analysis, both duration of stavudine (P = 0.05) and CR > 1.0 (P = 0.02) were independently correlated with LA. CONCLUSIONS: Monitoring of plasma stavudine concentrations can be useful to prevent stavudine-related LA.

Determination of abacavir, amprenavir, didanosine, efavirenz, nevirapine, and stavudine concentration in human plasma by MALDI-TOF/TOF.

The interest in therapeutic drug monitoring (TDM) of antiretroviral drugs has grown significantly since highly active antiretroviral therapy (HAART) became a standard of care in clinical practice. TDM is useful to determine the best dosage regimen adapted to each patient. Here, we apply MALDI-TOF/TOF technology to quantify abacavir, amprenavir, didanosine, efavirenz, nevirapine, and stavudine in the plasma of HIV-infected patients, by standard additions analysis. Regression of standard additions was linear over the whole anti-HIV concentration range explored (1.00 x 10(-2)-1.00 pmol/microL). The absolute recovery ranged between 80% and 110%. Values of the drug concentration determined by MALDI-TOF/TOF were in the range of 1.00 x 10(-2)-1.00 pmol/microL. The limit of quantification value was 1.00 x 10(-2)pmol/microL for abacavir, amprenavir, didanosine, efavirenz, nevirapine, and stavudine.

Long-term safety, effectiveness and quality of a generic fixed-dose combination of nevirapine, stavudine and lamivudine.

We assessed the long-term safety, effectiveness and quality of a fixed-dose combination of nevirapine, stavudine and lamivudine (triomune). HIV-1-infected adults initially enrolled in a one-year, open-label, single-arm, multicentre trial in Cameroon were followed for 2 years. Our results support the safety and effectiveness of the triomune combination for first-line treatment of HIV infection. Virological effectiveness appeared to wane somewhat during the second year of treatment, however, and plasma nevirapine concentrations were relatively high.

HIV drug resistance after the use of generic fixed-dose combination stavudine/lamivudine/nevirapine as standard first-line regimen.

Early failures to stavudine/lamivudine/nevirapine used as a generic fixed-dose combination in Mali showed resistance mutations in 50% of cases (mostly M184V and Y181C). No thymidine analogue mutations were seen, suggesting that most nucleoside reverse transcriptase inhibitors could be used in a second-line regimen. This highlights the importance of the accessibility of HIV-RNA assays for monitoring treated patients in resource-poor countries to detect early virological failure in order to preserve future therapeutic options.

Intracellular nucleoside triphosphate concentrations in HIV-infected patients on dual nucleoside reverse transcriptase inhibitor therapy.

BACKGROUND: Intracellular nucleoside reverse transcriptase inhibitor triphosphate (NRTI-TP) concentrations are crucial in suppressing HIV replication. Little is known about how commonly used dual-NRTI regimens affect the intracellular levels of NRTI-TPs, the active form of these drugs. This study investigates the effect of dual-NRTI therapy in intracellular NRTI-TP levels. METHODS: NRTI and NRTI-TP concentrations were evaluated in HIV-infected patients receiving either lamivudine (3TC) and stavudine (d4T) or lamivudine with zidovudine (ZDV); NRTI and NRTI-TP concentrations were determined using a validated HPLC/MS/MS method. Plasma HIV-1 RNA levels were determined at baseline and monthly to examine the relationship between NRTI-TP concentrations and plasma HIV-1 RNA. RESULTS: Forty-one subjects completed the study. 3TC-TP significantly increased between day 1 and week 28 from 1.48 to 5.00 pmol/10(6) peripheral blood mononuclear cells (PBMC; P < 0.0001). NRTI-TP concentrations for d4T and ZDV did not significantly increase, with values at week 28 of 0.011 and 0.02 pmol/10(6) PBMC, respectively. Mean NRTI-TP/plasma ratios were 3%, 0.007% and 0.05% for 3TC, d4T and ZDV, respectively. Linear relationships were observed between ZDV- and 3TC-TP and changes in plasma HIV-1 RNA. CONCLUSION: Of the three drugs studied, only 3TC-TP levels increased significantly between day 1 and week 28. ZDV-TP and 3TC-TP levels were unaffected by dual-NRTI therapy relative to monotherapy, regardless of the combination (3TC-ZDV or 3TC-d4T). Intracellular levels of d4T-TP were similar to previous reports for dual-NRTI therapy; however, in the case of d4T, these values appear lower than those achieved with d4T monotherapy.

Pharmacokinetic evaluation of emtricitabine in combination with other nucleoside antivirals in healthy volunteers.

Emtricitabine is a potent nucleoside reverse transcriptase inhibitor approved as a once-daily drug in combination with other antiretroviral agents for the treatment of HIV infection. Several phase I studies were conducted in healthy volunteers over the course of clinical development to evaluate whether pharmacokinetic drug-drug interactions exist between emtricitabine and other nucleoside antivirals that are extensively eliminated by renal excretion. Potential interactions with stavudine and famciclovir were evaluated in single-dose studies, whereas interactions with zidovudine and its major metabolite, zidovudine glucuronide, were evaluated in a multiple-dose study. Plasma pharmacokinetic profiles and, in some studies, urinary excretion data were evaluated when each drug was administered alone and in combination with emtricitabine. Safety and plasma pharmacokinetic profiles of each drug administered alone or with emtricitabine were consistent with historical data. Statistical analyses indicated that there were no significant interactions between emtricitabine and these 3 nucleoside antivirals.

A single-dose, randomized, open-label, two-period crossover bioequivalence study of a fixed-dose pediatric combination of lamivudine 40-mg, nevirapine 70-mg, and stavudine 10-mg tablet for oral suspension with individual liquid formulations in healthy adult male volunteers.

BACKGROUND: Because of the lack of suitable pediatric antiretroviral (ARV) agents, adult fixed-dose ARVs are commonly used in children. This practice poses concerns about dose inaccuracy, which may lead to resistance or toxicity. OBJECTIVE: The objective of the present study was to evaluate the bioequivalence of a new pediatric fixed-dose combination (FDC) ARV tablet for oral suspension as compared with individual liquid formulations. METHODS: The FDC ARV tablet for oral suspension contained lamivudine 40 mg, nevirapine 70 mg, and stavudine 10 mg. This formulation was compared with 4 mL of lamivudine 10 mg/mL, 7 mL of nevirapine 50 mg/5 mL, and 10 mL of stavudine 1 mg/mL. This was an open-label, balanced, randomized, 2-treatment, 2-period, 2-sequence, single-dose crossover study in 36 Indian male volunteers under fasting conditions. Blood samples were collected before dosing and at 0.167, 0.25, 0.333, 0.5, 0.667, 0.833, 1, 1.25, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 12, 16, 24, 36, 48, 72, 96, 120, 144, 168, and 192 hours after dosing in each period. RESULTS: The mean (SD) age, weight, and height of the Indian volunteers were 24.78 (5.31) years (range, 18-38 years), 57.06 (8.59) kg (range, 45-77 kg), and 165.14 (5.34) cm (range, 156-176 cm), respectively. The mean (SD) values for T(max), C(max), and AUC(0-t) for the FDC and the individual liquid formulations, respectively, were as follows: lamivudine, 0.71 (0.22) and 0.89 (0.50) hour, 594 (167) and 514 (139) ng/mL, 2382 (617) and 2227 (666) ng /mL per hour; nevirapine, 1.7 (1.1) and 2.5 (1.2) hours, 1248 (275) and 1185 (238) ng/mL, 70,372 (14,869) and 71,278 (17,435) ng/ mL per hour; and stavudine, 0.44 (0.11) and 0.43 (0.11) hour, 348 (82) and 395 (107) ng/mL, and 576 (113) and 631 (142) ng/mL per hour. The ratios and 90% CIs for the least-squares mean Cmax and AUC values were found to be within the prespecified range of 80% to 125% for each component. CONCLUSION: The FDC pediatric formulation of lamivudine, nevirapine, and stavudine was bioequivalent to the individual liquid formulations in these fasting, healthy Indian men.

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.

Plasma nevirapine levels and 24-week efficacy of a fixed-dose combination of stavudine, lamivudine and nevirapine (GPO-VIR) among Thai HIV-infected patients.

BACKGROUND: A fixed-dose combination of stavudine, lamivudine, and nevirapine (GPO-VIR) is the most affordable antiretroviral therapy (ART) regimen in Thailand. The data of nevirapine (NVP) level and efficacy of this fixed-dose combination is limited. MATERIAL AND METHOD: Patients who were initiated GPO-VIR in 2004 were enrolled NVP levels at 12 weeks were determined. Patients were followed for 24 weeks. RESULTS: Fifty-nine patients with a mean age of 36.4 years and 54% male were enrolled. Mean body weight was 54.7 kgs. Median baseline CD4 and HIV-RNA were 29 cells/mm3 and 270,000 (5.4 log10) copies/mL, respectively. Mean plasma NVP levels at 12 weeks was 6.4 mg/L. By linear regression, female gender (p = 0.042), and higher weight (p = 0.020) were associated with lower NVP levels. At 24 weeks, 78% achieved undetectable HIV-RNA and median CD4 was 156 cells/mm3. CONCLUSION: NVP levels and 24-week efficacy of GPO-VIR are favorable. According to the affordable cost, GPO-VIR should be an appropriate initial regimen for naïve HIV-infected patients in resource-limited settings.

Validation of high-performance liquid chromatography methods for determination of zidovudine, stavudine, lamivudine and indinavir in human plasma.

OBJECTIVE: Simple methods for the determination of zidovudine (AZT), stavudine (d4T), lamivudine (3TC) and indinavir (INV) in human plasma by reversed-phase liquid chromatography (HPLC) with UV detection were described and validated. METHOD: Solid-liquid extraction procedures were applied to the samples prior to analysis. Chromatography was performed on a C-18 analytical columns and the retention time ranged from 6.8 to 8.0 min for stavudine, 7.5 to 9.0 min for lamivudine, 11.2 to 11.9 min for zidovudine and indinavir. Four methods were validated for specificity, inter-and intra-assay precision and accuracy, absolute recovery and stability. RESULTS: Analytical curve ranged from 10-1600 ng/ml for stavudine, 50-3200 ng/ml for lamivudine, 0.05-5.0 microg/ml for zidovudine and 0.1-10.0 microg/ml for indinavir. Analytes stability during sampling processing and storage were established. Extraction recoveries are higher than 89% for all formulations. CONCLUSIONS: These methods proved to be simple, accurate and precise, and are currently in use in our laboratory for the quantitative analysis of antiretrovirals products in plasma, and for further pharmacokinetics and bioequivalence studies.

Pharmacokinetic parameters of nevirapine and efavirenz in relation to antiretroviral efficacy.

Optimal adherence is essential for successful antiretroviral therapy. We analyzed the relation between minimum plasma drug concentration (Cmin) and total drug exposure over 24 hr (AUC24) with virologic failure for therapy-adherent patients in the nevirapine (NVP) and efavirenz (EFV) groups of the double nonnucleoside study (2NN), which compared the efficacy of NVP and/or EFV together with stavudine and lamivudine. The objective was to find cutoff values of the Cmin and AUC24 below which the risk of virologic failure increased. The relation between Cmin and AUC24 with virologic failure (never a plasma viral load [pVL] < 50 copies/ml or a rebound to two consecutive pVL > 50 copies/ml) was analyzed with proportional hazard analyses. Data were censored at end of study or change of allocated treatment. The risk of virologic failure with NVP (n = 511) started to increase at a Cmin < 3.1 mg/L (hazard ratio [HR], 1.33; 95% confidence interval [CI], 0.89-1.97), but there was no cutoff value below which a statistically significant increased risk occurred. Neither was such a cutoff point identified for the AUC24. The risk of virologic failure with EFV (n = 312) was significantly increased at a Cmin < 1.1 mg/L (HR, 1.95; 95% CI, 1.08-3.54) and an AUC24 < 40 mg x hr x L1 (HR, 1.95; 95% CI, 1.07-3.54). Both cutoff values represent the median values for adherent patients. These associations were driven by patients from Thailand. Adjusting for geographical region made the association between Cmin and AUC24 with virologic failure statistically nonsignificant. The sensitivity of the Cmin values was too low (29% for NVP, 64% for EFV) to be an adequate predictor for virologic failure. We conclude that identifying the Cmin value for the sole purpose of predicting virologic failure in patients who report to be adherent to NVP or EFV is questionable because of the absence of a concentration-response relation (NVP) or the low sensitivity for such a cutoff value (NVP and EFV).

Nevirapine/lamivudine/stavudine as a combined-formulation tablet: bioequivalence study compared with each component administered concurrently under fasting condition.

OBJECTIVE: The objective of the study was to compare the bioequivalence of a fixed-dose combination of a nevirapine 200 mg, lamivudine 150 mg and stavudine 30 mg combination tablet with application of the 3 medications, at the same dosage, concurrently as separate formulations, in healthy, adult subjects under fasting conditions. MATERIAL AND METHODS: An open-label, balanced, randomized, 2-treatment, 2-period, 2-sequence, single-dose, crossover bioavailability study was conducted in 40 subjects with 21-day washout period between each treatment. Blood samples were collected for 168 hours. Plasma concentrations of nevirapine, lamivudine and stavudine were determined using a validated LC-MS-MS method. Noncompartmental pharmacokinetics and statistical analyses were performed using SAS (SAS Institute Inc., Cary, NC, USA) software (SAS System under Windows, Version 8.02). RESULTS: The ratios of least-square means and the 90% confidence intervals of the log-transformed data were calculated for AUC(0-t), AUC(0-inf), and Cmax. The 90% confidence interval for least-square mean ratio between test and reference formulation for log-transformed parameters Cmax, AUC(0-t) and AUC(0-inf) were within the requirements of the 80-125% range. CONCLUSION: The test formulation (Ranbaxy Laboratories Ltd., Gurgaon, India) is bioequivalent to the reference formulations both in terms of rate and extent of absorption after single-dose administration under fasting condition.

A combined-formulation tablet of lamivudine/nevirapine/stavudine: bioequivalence compared with concurrent administration of lamivudine, nevirapine, and stavudine in healthy Indian subjects.

Generic fixed-dose combinations of antiretrovirals are frequently prescribed for the treatment of human immunodeficiency virus infection. A randomized, 2-way study was conducted in 24 fasting, healthy, Indian male subjects to assess bioequivalence between a single combination tablet containing lamivudine, stavudine, and nevirapine (treatment A) with respect to separate marketed tablets administered simultaneously (treatment B). Each subject received treatments A and B separated by 19 days of a drug-free washout period. Plasma concentrations of antiretrovirals, determined by a validated liquid chromatography/tandem mass spectrometry assay, were used to assess pharmacokinetic parameters such as maximum observed plasma concentration and area under the plasma concentration curve. Pharmacokinetic parameters were comparable for either treatment. As geometric mean ratios (% treatment A/treatment B) of log-transformed parameters of area under the plasma concentration curve and plasma concentration, as well as their resultant 90% confidence intervals, were within 80% to 125% and 75% to 133%, respectively, 2 treatments were considered bioequivalent in the extent and rate of absorption. Both treatments exhibited similar tolerability under fasting conditions.