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Objectives@#Bioequivalence studies provide evidence that generic drugs can produce the same blood levels as the innovator, suggesting similar efficacy and safety and indicating interchangeability without the need to titrate dosing. This study aimed to compare the rate and extent of absorption of two simvastatin 20 mg tablets of Pascual Laboratories, Inc. with two Zocor 20 mg tablets of Merck Sharp & Dohme (I.A.) Corp. in healthy Filipinos. The study also monitored the safety and tolerability of the medications, under the same conditions. Proof of bioequivalence is required by FDA Philippines to establish the interchangeability of generic products and their innovators. @*Methods@#Twenty-four healthy participants were administered with a single oral dose of two 20 mg simvastatin tablets under fasting conditions, in a randomized, open-label, blind-endpoint analysis, two-way crossover study, with a washout period of one week. Pharmacokinetic blood sampling was done up to 24 h post-dose. Simvastatin was measured using Liquid Chromatography-Tandem Mass Spectrometry with a validated method. The geometric mean ratios for maximum plasma concentration (Cmax) and area under the plasma-concentration-time curve from time zero to the last observed concentration at time 24 h (AUC0-24) were used for bioequivalence. @*Results@#All 24 participants, 12 males and 12 females, completed the study. Mean age was 24.21 years, mean weight was 58.81 kg, and mean BMI was 23.16 kg/m2. The ratios of Cmax and AUC0-24 were 102.17% (90% CI: 89.19-117.03), and 101.29% (90% CI: 86.87-118.10), respectively, and were both within the bioequivalence limits of 80% to 125%. No adverse event was reported and both formulations were well-tolerated.@*Conclusions@#Simvastatin 20 mg tablet of Pascual Laboratories, Inc. and the innovator Zocor 20 mg tablet are bioequivalent. Single two-tablet doses of both products are safe and well tolerated.
Subject(s)
Simvastatin , Hydroxymethylglutaryl-CoA Reductase InhibitorsABSTRACT
AIM: To investigate the safety of bioequivalence (BE) studies of orally inhaled drug products (OIDPs) conducted by Phase I clinical Research Center of our hospital. METHODS: The safety data were collected from 482 healthy subjects enrolled in 20 OIDPs BE studies in Wuxi People's hospital from 2017 to 2022. The difference of adverse events (AEs) between test preparation and reference preparation were compared, as well as the influence of gender, age, mechanism of drug action and device type on AE were analyzed. RESULTS: A total of 102 cases of AEs were occurred in 77 subjects (16.0%, 77/482), 87 cases of AEs were related to experimental drugs, all AEs were mild or moderate, and no serious adverse events occurred. There was no difference in the incidence of AE between test preparation and reference preparation. In addition, gender, age, mechanism of drug action and device type had no significant effects on AEs. CONCLUSION: In 20 bioequivalence studies of OIDPs, OIDPs were safe and well tolerated in healthy subjects after dosing, and safety features of generic OIDPs and original drug were basically similar.
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@#<p style="text-align: justify;"><strong>Objective.</strong> Proof of bioequivalence is important for the interchangeability of pharmaceutically equivalent drug products. This study aimed to compare the rate and extent of absorption of meloxicam 15 mg tablet of Pascual Laboratories, Inc. (Test) with meloxicam 15 mg tablet (Mobic) of Boehringer Ingelheim (Reference) in healthy Filipino men. In addition, the study also determined the safety and tolerability of single doses of the said medications, under the same conditions.</p><p style="text-align: justify;"><strong>Methods.</strong> This was a randomized, open label, blind-endpoint analysis, truncated, crossover study with single drug doses administered in the fasting condition in each of the two treatment periods, separated by a two-week washout period. Pharmacokinetic blood sampling was performed up to 72 h post-dose. Plasma samples were analyzed using a validated liquid chromatography with tandem mass spectrometry technology. The primary endpoints were: area under plasma-concentration-time curve from time zero to the last observed concentration at time 72 h (AUC0-72) and maximum plasma concentration (Cmax) for meloxicam.</p><p style="text-align: justify;"><strong>Results.</strong> Eighteen men (mean age 21.5 years; mean body mass index 22.9 kg/m2) completed the study. When administered one meloxicam 15 mg tablet, the ratios of the geometric means of the primary endpoints AUC0-72 and Cmax, were within the established bioequivalence limits of 80% to 125% compared with Mobic 15 mg tablet: 104.07% (90% Confidence Interval [CI]: 100.26, 108.03), and 103.34% (90% CI: 96.22, 110.97), respectively. No adverse event was reported.</p><p style="text-align: justify;"><strong>Conclusion.</strong> Meloxicam 15 mg tablet of Pascual Laboratories, Inc. and the innovator Mobic 15 mg tablet are bioequivalent. Single doses of both products were safe and well tolerated.</p>
Subject(s)
MeloxicamABSTRACT
A selective, sensitive and rugged liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay has been developed for the simultaneous determination of doxepin (Dox) and its pharmacologically active metabolite, nordoxepin (NDox) in human plasma. The analytes and their internal standards (IS) were extracted from 500 μL of human plasma by liquid-liquid extraction using methyl tert-butyl ether. Chromatographic separation was achieved on Hypurity C8 column (100 mm × 4.6 mm, 5 μm) using a mixture of acetonitrile-methanol (95:5, v/v) and 2.0 mM ammonium formate in 93:7 (v/v) ratio. Detection was accomplished by tandem mass spectrometry in the positive ionization and multiple reaction monitoring acquisition mode. The protonated precursor to product ion transitions studied for Dox, NDox, and their corresponding ISs, propranolol and desipramine, were m/z 280.1-107.0, 266.0 -107.0, 260.1-116.1 and 267.1-72.1, respectively. A linear dynamic range of 15.0–3900 pg/mL for Dox and 5.00– 1300 pg/mL for NDox was established with mean correlation coefficient (r2) of 0.9991 and 0.9993, respectively. The extraction recovery ranged from 86.6％–90.4％ and 88.0％–99.1％ for Dox and NDox, respectively. The intra-batch and inter-batch precision (％ CV) across quality control levels was ≤ 8.3％ for both the analytes. Stability evaluated under different storage conditions showed no evidence of degradation and the ％ change in stability samples compared to nominal concentration ranged from 4.7％ to 12.3％. The method was successfully applied to a bioequivalence study of 6 mg doxepin hydrochloride orally disintegrating tablet in 41 healthy Indian subjects under fasting and fed conditions.
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A highly selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay has been described for the determination of asenapine (ASE) in presence of its inactive metabolites N-desmethyl asenapine (DMA) and asenapine-N-glucuronide (ASG). ASE, and ASE 13C-d3, used as in-ternal standard (IS), were extracted from 300 μL human plasma by a simple and precise liquid-liquid extraction procedure using methyl tert-butyl ether. Baseline separation of ASE from its inactive meta-bolites was achieved on Chromolith Performance RP8e(100 mm × 4.6 mm) column using acetonitrile-5.0 mM ammonium acetate-10% formic acid (90:10:0.1, v/v/v) within 4.5 min. Quantitation of ASE was done on a triple quadrupole mass spectrometer equipped with electrospray ionization in the positive mode. The protonated precursor to product ion transitions monitored for ASE and ASE 13C-d3 were m/z 286.1 → 166.0 and m/z 290.0 → 166.1, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) of the method were 0.0025 ng/mL and 0.050 ng/mL respectively in a linear con-centration range of 0.050–20.0 ng/mL for ASE. The intra-batch and inter-batch precision (% CV) and mean relative recovery across quality control levels were ≤5.8% and 87.3%, respectively. Matrix effect, eval-uated as IS-normalized matrix factor, ranged from 1.03 to 1.05. The stability of ASE under different storage conditions was ascertained in presence of the metabolites. The developed method is much simpler, matrix free, rapid and economical compared to the existing methods. The method was suc-cessfully used for a bioequivalence study of asenapine in healthy Indian subjects for the first time.
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A highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of tadalafil (TAD) in human plasma. TAD and its deuterated internal standard (IS), tadalafil-d3, were extracted from 200 μL plasma using Phenomenex Strata-X-C 33 μ extraction cartridges.Chromatographic analysis was carried out on Synergi? Hydro-RP C18 (100mm × 4.6 mm, 4 μm) column with a mobile phase consisting of methanol and 10mM ammonium formate, pH 4.0 (90:10, v/v),delivered at a flow rate of 0.9 mL/min. Quantitation of the protonated analyte was done on a triple quadrupole mass spectrometer using multiple reaction monitoring via electrospray ionization. The precursor to product ions transitions monitored for TAD and TAD-d3 were m/z 390.3 → 268.2 and m/z 393.1 → 271.2, respectively. The calibration curve was linear over the concentration range of 0.50-500 ng/mL with correlation coefficient, r2 ≥ 0.9994. Acceptable intra-batch and inter-batch precision (≤3.7％) and accuracy (97.8％ to 104.1％) were obtained at five concentration levels. The recovery of TAD from spiked plasma was highly precise and quantitative (98.95％ to 100.61％). Further, the effect of endogenous matrix components was minimal. TAD was found to be stable under different storage conditions in human plasma and also in whole blood samples. The validated method was successfully used to determine TAD plasma concentration in a bioequivalence study with 20 mg TAD tablets in 24 healthy volunteers. Method performance was evaluated by reanalyzing 115 study samples.
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A highly sensitive, rapid and rugged liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) method was developed for reliable estimation of amantadine (AMD), an antiviral drug in human plasma. The analyte and internal standard (IS), amantadine-d6 (AMD-d6), were extracted from 200 μL plasma by solid phase extraction on Phenomenex Strata-X-C 33 μ cartridges. Chromatography was performed on Synergi? Hydro-RP C18 (150 mm × 4.6 mm, 4 μm) analytical column using a mixture of acetonitrile and 10 mM ammonium formate, pH 3.0 (80:20, v/v) as the mobile phase. Detection and quantitation was done by multiple reaction monitoring in the positive ionization mode for AMD (m/z 152.1 → 135.1) and IS (m/z 158.0 → 141.1) on a triple quadrupole mass spectrometer. The assay was linear in the concentration range of 0.50–500 ng/mL with correlation coefficient (r2) ≥ 0.9969. The limit of detection of the method was 0.18 ng/mL. The intra-batch and inter-batch precisions were ≤ 5.42% and the accuracy varied from 98.47% to 105.72%. The extraction recovery of amantadine was precise and quantitative in the range of 97.89%–100.28%. IS-normalized matrix factors for amantadine varied from 0.981 to 1.012. The stability of AMD in whole blood and plasma was evaluated under different conditions. The developed method was successfully applied for a bioequivalence study with 100 mg of AMD in 32 healthy volunteers. The re-producibility of the assay was determined by reanalysis of 134 subject samples.
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A highly sensitive and selective high performance liquid chromatography–tandem mass spectrometry method was developed and validated for the quantification of alverine (ALV) and its active metabolite, para hydroxy alverine (PHA), in human plasma. For sample preparation, solid phase extraction of analytes was performed on Phenomenex Strata-X cartridges using alverine-d5 as the internal standard. The analytes were separated on Symmetry Shield RP18 (150 mm×3.9 mm, 5 μm) column with a mobile phase consisting of acetonitrile and 10 mM ammonium formate (65:35, v/v). Detection and quantitation was done by electrospray ionization mass spectrometry in the positive mode using multiple reaction monitoring. The assay method was fully validated over the concentration range of 15.0–15,000 pg/mL for ALV and 30.0–15,000 pg/mL for PHA. The intra-day and inter-day accuracy and precision (%CV) ranged from 94.00%to 96.00%and 0.48%to 4.15%for both the analytes. The mean recovery obtained for ALV and PHA was 80.59% and 81.26%, respectively. Matrix effect, expressed as IS-normalized matrix factor ranged from 0.982 to 1.009 for both the analytes. The application of the method was demonstrated for the specific analysis of ALV and PHA for a bioequivalence study in 52 healthy subjects using 120 mg ALV capsules. The assay reproducibility was also verified by reanalysis of 175 incurred subject samples.
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The present study describes a simple, reliable and reproducible liquid chromatography–tandem mass spectro-metry method (LC–MS/MS) for the simultaneous determination of allopurinol and its active metabolite, oxypurinol in human plasma for a pharmacokinetic/bioequivalence study. After protein precipitation (PPT) of 100 μL plasma sample with 1.0%formic acid in acetonitrile, the recovery of the analytes and allopurinol-d2 as an internal standard ranged from 85.36% to 91.20%. The analytes were separated on Hypersil Gold (150 mm×4.6 mm, 5 μm) column using 0.1% formic acid-acetonitrile (98:2, v/v) as the mobile phase. Quantification was done using electrospray ionization in the positive mode. The calibration concentration range was established from 60.0 to 6000 ng/mL for allopurinol and 80.0–8000 ng/mL for oxypurinol. Matrix effect in human plasma, expressed as IS-normalized matrix factors ranged from 1.003 to 1.030 for both the analytes. The developed method was found suitable for a clinical study with 300 mg allopurinol tablet formulation in healthy subjects.
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Two-stage designs for the assessment of bioequivalence have been recently accepted in various regulatory authorities.However controlling type Ⅰ error rates around 5％ at targeted power is still a great challenge for applying two-stage method.This paper reviewed the feature of present designs of the two-stage bioequivalence.The decision tree,nominal significance level,and sample size recalculation in previously published methods were also introduced in detail,which would be referential for domestic sponsors in the study of two-stage design bioequivalence.
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An improved high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method has been developed for sensitive and rapid determination of albendazole (ABZ) and its active metabolite, albendazole sulfoxide (ABZSO), in the positive ionization mode. The method utilized solid phase ex-traction (SPE) for sample preparation of the analytes and their deuterated internal standards (ISs) from 100 mL human plasma. The chromatography was carried out on Hypurity C18 column using acetonitrile-2.0 mM ammonium acetate, pH 5.0 (80:20, v/v) as the mobile phase. The assay exhibited a linear re-sponse over the concentration range of 0.200–50.0 ng/mL for ABZ and 3.00–600 ng/mL for ABZSO. The recoveries of the analytes and ISs ranged from 86.03%–89.66% and 89.85%–98.94%, respectively. Matrix effect, expressed as IS-normalized matrix factors, ranged from 0.985 to 1.042 for the both analytes. The method was successfully applied for two separate studies in healthy subjects using single dose of 400 mg conventional tablets and 400 mg chewable ABZ tablets, respectively.
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A rapid and sensitive ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method is described for determination of letrozole in human plasma. Following solid phase ex-traction (SPE) of letrozole and letrozole-d4 on Orochem DVB-LP cartridges, chromatography was per-formed on Acquity UPLC BEH C18 (50 mm ? 2.1 mm, 1.7 mm) column using methanol-0.1%formic acid in water (85:15, v/v) as the mobile phase. Detection was carried out on a triple quadrupole mass spec-trometer with an electrospray source, operated under positive ionization mode. Quantitation of letrozole and letrozole-d4 was done using multiple reaction monitoring (MRM) following the transitions at m/z 286.2-217.0 and m/z 290.2-221.0, respectively. The calibration plots were linear through the con-centration range of 0.10–100 ng/mL (r2Z0.9990) using 100 mL human plasma. The extraction recovery of letrozole ranged from 94.3% to 96.2% and the intra-batch and inter-batch precision was r 5.2%. The method was successfully applied to a bioequivalence study of letrozole after oral administration of 2.5 mg tablet formulation to 16 healthy postmenopausal Indian women. The assay reproducibility was also established through incurred sample reanalysis (ISR) of 74 subject samples.
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The aim of the present study was to assess the bioequivalence of two cephalexin tablet formulations available in the Brazilian market (product A as reference formulation and product B as test formulation). Dissolution efficiency (DE%) was calculated for both formulations to evaluate their
O objetivo do presente estudo foi avaliar a bioequivalência de duas formulações de cefalexina disponíveis no mercado brasileiro (produto A como formulação referência e produto B como formulação teste). A eficiência de dissolução (DE%) foi calculada para ambas as formulações para avaliar suas características biofarmacêuticas. O estudo de bioequivalência oral foi realizado em vinte e quatro voluntários sadios utilizando um desenho cruzado. Uma dose oral única (comprimido contendo 500 mg de cefalexina) de cada produto foi administrada com um período de
Subject(s)
Humans , Cephalexin/pharmacokinetics , Cephalexin/pharmacology , Chromatography, High Pressure Liquid , Therapeutic Equivalency , Urine/chemistryABSTRACT
A selective and rapid high-performance liquid chromatography–tandem mass spectrometry method was developed and validated for the quantification of raltegravir using raltegravir-d3 as an internal standard (IS). The analyte and IS were extracted with methylene chloride and n-hexane solvent mixture from 100 mL human plasma. The chromatographic separation was achieved on a Chromolith RP-18e endcapped C18 (100 mm ? 4.6 mm) column in a run time of 2.0 min. Quantitation was performed in the negative ionization mode using the transitions of m/z 443.1-316.1 for raltegravir and m/z 446.1-319.0 for IS. The linearity of the method was established in the concentration range of 2.0–6000 ng/mL. The mean extraction recovery for raltegravir and IS was 92.6% and 91.8%, respectively, and the IS-normalized matrix factors for raltegravir ranged from 0.992 to 0.999. The application of this method was demonstrated by a bioequivalence study on 18 healthy subjects.
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A simple, rapid and selective liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is developed and validated for quantification of venlafaxine in human plasma with simple liquid-liquid extraction step consisted of extraction with ether and dichloromethane for 10 min and mixing with 1 M sodium acetate in human plasma using fluoxetine as an internal standard (IS). The analyte are separated using an isocratic mobile phase consisted of acetonitrile and 5 mM ammonium formate (4/3, v/v) on a isocratic YMC hydrosphere C18 (2.0x50.0 mm, 3.0 microm) column and analyzed by MS/MS in the multiple reaction monitoring (MRM) mode using the transitions of respective [M+H](+) ions, m/z 278.2-->260.3 and m/z 310.1-->148.1 for quantification of venlafaxine and IS, respectively. The standard calibration curves showed good linearity within the range of 1.0-200.0 ng/mL (r2=0.9986, 1/chi2 weighting). The lower limit of quantification (LLOQ) was 1.0 ng/mL. The retention times of venlafaxine and IS were 0.6 min and 0.7 min that means the potential for the high-throughput potential of the proposed method. In addition, no significant metabolic compounds were found to interfere with the analysis. Acceptable precision and accuracy were obtained for the concentrations over the standard curve range. The validated method was successfully applied to bioequivalence study after 75-mg of venlafaxine sustained-release (SR) capsule in 24 healthy Korean subjects.
Subject(s)
Humans , Ammonium Compounds , Calibration , Chromatography, Liquid , Ether , Fluoxetine , Ions , Liquid-Liquid Extraction , Methylene Chloride , Pharmacokinetics , Plasma , Sodium Acetate , Tandem Mass Spectrometry , Therapeutic Equivalency , Venlafaxine HydrochlorideABSTRACT
A fast,simple and sensitive high performance liquid chromatographic (HPLC) method has been developed for determination of 10α-methoxy-6-methyl ergoline-8β-methanol (MDL,a main metabolite of nicergoline) in human plasma.One-step liquid-liquid extraction (LLE) with diethyl ether was employed as the sample preparation method.Tizanidine hydrochloride was selected as the internal standard (IS).Analysis was carried out on a Diamonsil ODS column (150 mm × 4.6 mm,5 μm) using acetonitrile-ammonium acetate (0.1 mol/L) (15/85,v/v) as mobile phase at detection wavelength of 224 nm.The calibration curves were linear over the range of 2.288-73.2 ng/mL with a lower limit of quantitation (LLOQ) of 2.288 ng/mL.The intra- and inter-day precision values were below 13％ and the recoveries were from 74.47％ to 83.20％ at three qtality control levels.The method herein described was successfully applied in a randomized crossover bioequivalence study of two different nicergoline preparations after administration of 30 mg in 20 healthy volunteers.
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Os estudos de bioequivalência são realizados em humanos, por meio da administração dos medicamentos em estudo pela mesma via extravascular, sob condições experimentais padronizadas, seguida pela determinação das concentrações plasmáticas do fármaco em função do tempo. Nestes estudos considera-se que curvas estatisticamente semelhantes de decaimento sanguíneo de fármacos produzem o mesmo resultado em termos de eficácia e segurança. A partir das curvas de concentração em função do tempo obtidas, determinam-se os parâmetros farmacocinéticos Cmax, tmax e ASC. A bioequivalência entre dois produtos é estabelecida por meio do IC 90%, que deve estar entre 80 a 125% para os parâmetros farmacocinéticos Cmax e ASC. O cronograma de coleta de amostras biológicas é um dos aspectos mais críticos no planejamento de estudos de bioequivalência, pois este afeta diretamente a determinação dos parâmetros farmacocinéticos utilizados na avaliação da bioequivalência. Outro aspecto importante relacionado a este tipo de estudo é a diferença de teor entre os produtos a serem submetidos ao estudo de bioequivalência, que segundo a legislação brasileira vigente, deve ser menor ou igual a 5%. Neste trabalho foram avaliados diferentes cronogramas de coleta de amostras sangue, avaliando-se o impacto destes no resultado final de um estudo de bioequivalência e, além disso, a influência da diferença de teor de fármaco entre dois produtos que levaria à bioinequivalência também foi investigada. Para tanto simulações matemáticas e um estudo in vivo foram conduzidos. O fármaco modelo escolhido foi a cefadroxila, por apresentar características farmacocinéticas e farmacodinâmicas ideais. O programa Microsoft Office Excel 2003 foi utilizado para simular as concentrações plasmáticas e determinar o IC 90%. As simulações foram feitas por meio de dois modelos: modelo baseado em máximos e mínimos de parâmetros farmacocinéticos, e modelo baseado em coeficientes de variação intra e inter-individuais do fármaco. Dez diferentes doses, entre -10% a 20% da dose referência, e 6 cronogramas de coleta foram avaliados. O estudo in vivo foi realizado com quatro doses diferentes de cefadroxila. A bioequivalência entre as doses e em diferentes cronogramas de coleta foi avaliada em 24 voluntários sadios do sexo masculino. Os voluntários receberam as quatro doses do estudo em desenho cruzado, em quatro períodos e quatro seqüências, com washout de 7 dias entre as doses. As concentrações plasmáticas de cefadroxila, até 8 horas após a administração, foram determinadas por cromatografia líquida de alta eficiência com detecção DAD. Os parâmetros farmacocinéticos tmax, Cmax e AUC0-t foram determinados nas diferentes doses e cronogramas de coleta, sendo que o critério para estabelecer-se a bioequivalência foi baseada nos resultados do IC 90% dos parâmetros farmacocinéticos Cmax e AUC0-t. Os resultados obtidos nas simulações mostraram boa correlação com os dados reais obtidos a partir de estudos in vivo. As simulações baseadas em coeficientes de variação intra e inter-individuais descreveram melhor os resultados observados no estudo in vivo. De acordo com os resultados obtidos no estudo in vivo pode-se concluir que cronogramas de coletas com menos amostras são tão eficientes quanto cronogramas de coletas com mais amostras, desde que o tempo de tmax esteja incluído. Em relação ao teor de fármaco, concluiu-se que dois produtos com diferença de teor menor ou igual a 11% ainda são bioequivalentes e que diferença maior ou igual a 14% resultam em bioinequivalência. Observou-se ainda que o parâmetro farmacocinético ASC0-t é mais sensível que Cmax para detectar diferenças
Bioequivalence studies are designed to compare the in vivo performance of different formulations of the same drug or different drug products by a randomized crossover study. Pharmacokinetic parameters are obtained from the drug concentration-time profile in blood, serum, or plasma. The most frequently used pharmacokinetic parameters are area under the plasma or blood concentration-time curve (AUC), maximum concentration (Cmax) and time to achieve maximum concentration (tmax). Bioequivalence is concluded if the average bioavailability of the test formulation is within (80%, 125%) that of the reference formulation, with a certain assurance, that is, an equivalence criterion of 80% to 125% for assessment of bioequivalence based on the ratio of average bioavailability is employed. The logarithmic transformation is used for AUC and Cmax. Accuracy in measuring pharmacokinetics parameters directly affects accuracy of bioequivalence tests. Since the number of blood samples per patient is limited, sampling points should be chosen such that the time concentration profile is adequately defined so as to allow the calculation of relevant parameters. According to guidelines proposed by the National Agency of Sanitary Vigilance of Brazil (ANVISA), bioequivalence studies can be conducted only if the difference in drug content between the reference and test product is less than or equal to 5%. The goals of this study are to evaluate the influence of differences in amount of active moiety present in the formulation and possibility of reducing the number of sampling points in bioequivalence studies and to discuss the impact of these parameters in bioequivalence conclusions. For these approaches, simulations and an in vivo study were done. The drug selected was cefadroxil. Cefadroxil presents ideal pharmacokinetics and pharmacodynamics characteristics for this kind of study, such as high bioavailability, low intra and intersubject variability, short elimination rate and wide therapeutic range. Microsoft Office Excel 2003 software was used to simulate drug concentration-time profiles for different doses and several sampling schedules, and to determine 90% confidence interval. Simulations were done by two models: a) based on assumed maximum and minimum pharmacokinetic parameters values; b) based on assumed intra and intersubject variability. Ten different doses, ranging from -10% to 20% of the reference dose, and six sampling schedules were evaluated. The in vivo study was performed with four different cefadroxil doses. Their relative bioavailability were evaluated in 24 healthy volunteers who received a single oral dose of each preparation. An open, randomized clinical trial designed as four-periods and four sequences crossover with 7-days washout between doses was employed. Plasma samples for assessments of their cefadroxil concentration by HPLC-DAD were obtained over 8 h after administration. Pharmacokinetics parameters tmax, Cmax and AUC0-t were evaluated using different doses and sampling schedules. For the purpose of bioequivalence analysis Cmax and AUC0-t were considered. For each schedule, to claim bioequivalence in average bioavailability, a 90% confidence interval was constructed for ratio of average between test and reference products and compared with (80%, 125%) limits. If the constructed confidence interval falls within the limits, then the two formulations are considered bioequivalent. The results obtained by simulate time-concentration profiles, showed good correlation with real data. Comparing the results obtained through in vivo study and the two simulations models, the simulations based in intra and intersubject variability was more predictive. In conclusion, no significant differences were found between sampling schedules evaluated, since the sampling time around tmax were maintained in sampling schedules. Bioinequivalence was observed when the difference between cefadroxil doses was higher than 14%. The parameter AUC0-t was more sensitive than Cmax to detect differences