Bioavailability investigation of two different oral formulations of Tetrazepam

Two different oral tetrazepam (CAS 10379-14-3) formulations (Tetrazepam-ratiopharm film-coated tablets as test preparation and tablets of a reference preparation marketed in France) were investigated in 20 healthy volunteers in order to prove bioequivalence between these preparations. A single 50 mg oral dose was given according to a randomised two-way crossover design in the fasted state. Blood samples for determination of tetrazepam plasma concentrations were collected at pre-defined time points up to 96 h following drug administration. A washout period of 14 days separated both treatment periods. Tetrazepam plasma concentrations were determined by means of a validated LC-MS/MS method. Values of 3873.08 ngh/ml (test preparation) and 3930.69 ngh/ml (reference preparation) for the parameter AUC0-infinity demonstrate an nearly identical extent of drug absorption. Maximum concentrations (Cmax) of 482.08 ng/ml and 465.14 ng/ml were achieved for test and reference preparation. Time to reach maximum plasma concentration (tmax) was 1.39 hours for both preparations. Cmax and AUC0-infinity-values were tested parametrically by an analysis of variance (ANOVA). Bioequivalence was concluded if the 90% confidence intervals of the T/R-ratios were in the range of 80%-125% for AUC0-infinity and 70%-143% for Cmax. Based on the results obtained in this study, bioequivalence between the test and the reference preparation was demonstrated.     

Bioavailability investigation of two different oral formulations of doxepin

Two different oral doxepin (CAS 1668-195) formulations (Doxepin-ratiopharm 25 mg film-coated tablets as test preparation and 25 mg dragées of the reference preparation) were investigated in 30 healthy male and female volunteers in order to prove bioequivalence between these preparations. A single 75 mg oral dose (3 units of test or reference preparation) was given according to a randomised two-way cross-over design in the fasted state. Blood samples for determination of plasma concentration of doxepin and its metabolite N-desmethyldoxepin were collected at pre-defined time points up to 168 h following drug administration. A wash-out period of three weeks separated both treatment periods. Doxepin and N-desmethyldoxepin plasma concentrations were determined by means of a validated LC-MS/MS method. Values of 193,463 pgh/ml (test preparation) and 197,988 pg h/ml (reference preparation) for doxepin as well as values of 313,298 pg h/ml (test preparation) and 306,663 pgh/ml (reference preparation) for N-desmethyldoxepin for the parameter AUC0-infinity demonstrate a nearly identical extent of drug absorption. Maximum concentrations (Cmax) for doxepin/N-desmethyldoxepin of 15,960.06/6,883.69 pg/ml and 18,614.73/6,846.62 pg/ml were achieved for test and reference preparation. Time to reach doxepin maximum plasma concentration (tmax) was 1.98 h for both preparations and for N-desmethyldoxepin tmax was 4.52 h (test preparation) and 4.15 h (reference preparation). Cmax and AUC0-infinity values were tested for statistically significant differences by means of the Two One-Sided T-Tests procedure following ln-transformation of data. Bioequivalence was assumed if the 90% confidence intervals of the T/R-ratios were in the range of 80%-125% for ln-transformed AUC0-infinity and 70%-143% for ln-transformed Cmax. Based on the results obtained in this study, bioequivalence between the test and the reference preparation was demonstrated.     

Pharmacokinetics and bioequivalence study of a generic amlodipine tablet formulation in healthy male volunteers

Two different tablets containing amlodipine besylate (CAS 111470-99-6) (Vazkor 10 mg tablet as test preparation and 10 mg tablet of the originator product as reference preparation) were investigated in 18 healthy male volunteers in order to compare the bioavailability and prove the bioequivalence between both treatments after oral single dose administration. The study was performed according to an open-label, randomized, two-period cross-over design with a wash-out phase of 21 days. Blood samples for pharmacokinetic profiling were taken up to 144 h post-dose, and amlodipine plasma concentrations were determined with a validated LC-MS/MS method. Maximum plasma concentrations (Cmax) of 6,183.7 pg/ml (test) and 5,366.7 pg/ml (reference) were achieved. Areas under the plasma concentration-time curve (AUC(0-infinity)) of 267,231.0 pg x h/ml (test) and 266,061.7 ng x h/ml (reference) were calculated. The median tmax was 5.6 h (test) and 6.1 h (reference). Plasma elimination half-lives (t 1/2) were 46.46 h (test) and 45.34 h (reference). Both primary target parameters AUC(0-infinity) and Cmax were tested parametrically by analysis of variance (ANOVA); 90% confidence intervals were between 93.20%-107.16% (AUC(0-infinity) and 103.36%-123.13% (Cmax). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and Cmax the 90% confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80%-125%.     

Bioequivalence study of two losartan formulations administered orally in healthy male volunteers

The bioavailability of a new losartan preparation (2-butyl-4-chloro-1-[p-(o-1H-tetrazol-5-ylphenyl)benzyl]imidazole-5-methanol monopotassium salt, CAS 114798-26-4) was compared with the reference preparation of the drug in 24 healthy male volunteers, aged between 19 and 32. The open, randomized, single-blind two-sequence, two-period crossover study design was performed. Under fasting conditions, each subject received a single oral dose of 100 mg losartan as a test or reference formulation. The plasma concentrations of losartan and its active metabolite were analyzed by a rapid and sensitive HPLC method with UV detection. The pharmacokinetic parameters included AUC0-36h, AUC0-infinity, Cmax, t1/2, and Ke. Values of AUC0-infinity demonstrate nearly identical bioavailability of losartan from the examined formulations. The AUC0-infinity of losartan was 2019.92+/-1002.90 and 2028.58+/-837.45 ng x h/ml for the test and reference formulation, respectively. The AUC0-infinity of the metabolite was 10851.52+/-4438.66 and 11041.18 +/-5015.81 ng x h/ml for test and reference formulation, respectively. The maximum plasma concentration (Cmax) of losartan was 745.94+/-419.75 ng/ml for the test and 745.74+/-329.99 ng/ml for the reference product and the Cmax of the metabolite was 1805.77+/-765.39 and 1606.22 +/-977.22 ng/ml for the test and reference product, respectively. No statistical differences were observed for Cmax and the area under the plasma concentration-time curve for both losartan and its active metabolite. 90 % confidence limits calculated for Cmax and AUC from zero to infinity (AUC0-infinity) of losartan and its metabolite were included in the bioequivalence range (0.8-1.25 for AUC). This study shows that the test formulation is bioequivalent to the reference formulation for losartan and its main active metabolite.     

Bioavailability investigation of two different oral formulations of citalopram, a so-called 'second generation' antidepressant drug

Citalopram (CAS 59729-33-8) belongs to the so-called 'second generation' antidepressant drugs and is used for the treatment of patients with major depression or other depressive disorders. In the present study, two different oral citalopram formulations (Citalopram-ratiopharm film-coated tablets as test preparation and tablets of a reference preparation distributed in Germany) were investigated in 20 healthy volunteers in order to prove bioequivalence between both preparations. A single 40 mg oral dose was administered according to an open, randomised, two-period cross-over design in the fasted state. Blood samples for determination of citalopram plasma concentrations were collected at pre-defined time points up to 168 h following drug administration. A wash-out period of 21 days separated both treatment periods. Citalopram plasma concentrations were determined by means of a validated HPLC method with fluorescence detection. Maximum plasma concentrations (Cmax), of 34.77 ng/ml (test) and 34.42 ng/ml (reference) were achieved. Areas under the plasma concentration-time curve (AUC0-infinity) of 1,719.69 ng*h/ml (test) and 1,725.71 ng*h/ml (reference) were determined. The results showed nearly identical rate and extent of drug absorption. Also further pharmacokinetic parameters were well comparable with each other. Thus, tmax showed values of 3.29 h (test) and 3.77 h (reference). The plasma elimination half-life (t1/2) was 42.50 h (test) und 44.46 h (reference). Both primary target parameters Cmax and AUC0-infinity were tested parametrically by analysis of variance (ANOVA). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and Cmax the 90 % confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80 %-125 %.     

Pharmacokinetics and bioequivalence study of ranitidine film tablets in healthy male subjects

The aim of the present study was to compare the bioavailability of ranitidine (CAS 66357-35-5) from two different ranitidine hydrochloride (CAS 66357-59-3) film tablets (Ranitab 150 mg film tablets as test preparation and 150 mg film tablets of the originator product as reference preparation). The study was conducted according to an open-label, randomised two-period cross-over design with a wash-out phase of 9 days. Blood samples for pharmacokinetic profiling were taken up to 24 h post-dose, and ranitidine plasma concentrations were determined with a validated HPLC method with UV-detection. Maximum plasma concentrations (Cmax) of 461.8 ng/ml (test) and 450.6 ng/ ml (reference) were achieved. Areas under the plasma concentration-time curve (AUC (0-infinity) of 2,488.6 ng . h/ml (test) and 2,528.8 ng . h/ml (reference) were calculated. The median tmax was 2.83 h (test) and 3.04 h (reference). Plasma elimination half-lives (t1/2) of 2.78 h (test) and 2.89 h (reference) were determined. Both primary target parameters AUC(0-infinity) and Cmax were tested parametrically by analysis of variance (ANOVA) and the 90% confidence intervals were between 91.93 %-106.98 % (AUC (0-infinity) and 92.34%-118.85% (Cmax). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and Cmax the 90 % confidence intervals of the T/R ratios of logarithmically transformed data were in the generally accepted range of 80 %-125 %.     

Comparative bioavailability study of two cefixime formulations administered orally in healthy male volunteers

The bioavailability of a new cefixime ((6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2-(carboxymethoxyimino) acetamido]-8-oxo-3-vinyl-5-thia-1-azabicyclo-[4,2,0]-oct-2-ene-2-carboxylic acid, CAS 79350-37-1) tablet preparation (Loprax) was compared with that of a reference preparation of the drug in 24 healthy male volunteers. The trial was designed as an open, randomized, single-blind, two-sequence, two-period crossover study. Under fasting conditions, each subject received a single oral dose of 400 mg cefixime tablet as a test or reference formulation on 2 treatment days. The treatment periods were separated by a one-week washout period. The plasma concentrations of the drug were analyzed by a rapid and sensitive HPLC method with UV detection. The pharmacokinetic parameters included AUC0-24h, AUC0-infinity, Cmax, t1/2, and Ke. The mean AUC0-infinity of cefixime was 45008.7 +/- 10989.9 and 45221.3 +/- 2155.7 n x h/ml for the test and reference formulation, respectively. The maximum plasma concentration (Cmax) of cefixime was on average 4746.9 +/- 1284 ng/ml for the test and 4726.3 +/- 1206.9 ng/ml for the reference product. No statistical differences were observed for Cmax and the area under the plasma concentration-time curve for test and reference tablets. The calculated 90% confidence intervals based on the ANOVA analysis for the mean test/reference ratios of Cmax, AUC0-infinity and AUC0-24h of cefixime were in the bioequivalence range (94%-112%). Therefore, the two formulations were considered to be bioequivalent.     

Pharmacokinetics and bioequivalence study of doxycycline capsules in healthy male subjects

The aim of the present study was to compare the bioavailability of doxycycline (CAS 564-25-0) from two different doxycycline hyclate (CAS 24390-14-5) capsules (Monodoks 100 mg capsule as test preparation and 100 mg capsule of the originator product as reference preparation) in 24 healthy male subjects. The study was conducted according to an open-label, randomised two-period cross-over design with a wash-out phase of 16 days. Blood samples for pharmacokinetic profiling were taken up to 72 h post-dose, and doxycycline plasma concentrations were determined with a validated HPLC method with UV-detection. Maximum plasma concentrations (Cmax) of 1,715.1 ng/ml (test) and 1,613.3 ng/ml (reference) were achieved. Areas under the plasma concentration-time curve (AUC(0-infinity)) of 28,586.5 ng x h/ml (test) and 29,047.5 ng x h/ml (reference) were calculated. The median tmax was 1.88 h (test) and 2.00 h (reference). Plasma elimination half-lives (t1/2) of 16.49 h (test) and 16.75 h (reference) were determined. Both primary target parameters AUC(0-infinity) and Cmax were tested parametrically by analysis of variance (ANOVA) and the 92.39 %-103.53% (AUC(0-infinity)) and 98.45%-111.74% (Cmax). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and Cmax the 90% confidence intervals of the T/R ratios of logarithmically transformed data were in the generally accepted range of 80 0%-125%.     

Technological evaluation and equivalence assessment of lorazepam tablets in rabbits

Four different oral lorazepam tablets (Tavor tablets as reference preparation and three generic tablet formulations, A, B and C) were investigated after administration to 12 rabbits to evaluate their bioequivalence. A single 2 mg/kg dose was administered orally as powder and lorazepam plasma concentrations were determined by a validated HPLC method. Maximum plasma concentrations (Cmax), of 207 ng/ml (reference), 198 ng/ml (A), 166 ng/ml (B) and 169 ng/ml (C) were achieved. Lorazepam appeared in the plasma at 0.66 h (Tmax) for all formulations, probably because the disintegration step was bypassed due to the pulverization of the administered doses. Areas under the plasma concentration-time curves (AUC(0-t) and AUC(0-infinity)) were determined. The obtained AUC(0-t) values were 556.57 ng h/ml (reference), 554.70 ng h/ml (A), 493.08 ng h/ml (B), and 487.88 ng h/ml (C). ANOVA results (P > or = 0.05) and 90% confidence intervals for the mean ratio (T/R) of AUC(0-t), AUC(0-infinity), and Cmax were within the EMEA acceptance range. Pharmacokinetic and statistical results of this study show that the four tested drug products (Tavor, A, B, C) are to be considered bioequivalent and interchangeable in medical practice.     

Bioequivalence study of sultamicillin suspensions

Sultamicillin (CAS 76497-13-7) is a prodrug combination of ampicillin (CAS 69-53-4) and sulbactam (CAS 68373-14-8), with the antibiotic ampicillin and the beta-lactamase inhibitor sulbactam chemically linked as double ester. The present study was performed to investigate the relative bioavailability and to assess the bioequivalence of two different sultamicillin suspensions (Devasid 250 mg/5 ml as test preparation and 375 mg/7.5 ml of the originator product as reference preparation). Twenty-four healthy male volunteers received equal doses of the sultamicillin preparations according to an open, randomised, single-dose, two-period cross-over design with a wash-out phase of 7 days. Blood samples for pharmacokinetic profiling were taken up to 8 h post-dose, and ampicillin and sulbactam plasma concentrations were determined with a validated LC-MS/MS method. Maximum plasma concentrations (C(max)) of 11,267.4 ng/ml (ampicillin, test), 10,864.4 ng/ml (ampicillin, reference), 6,360.6 ng/ml (sulbactam, test and 6,410.7 ng/ml (sulbactam, reference) were achieved. Areas under the plasma concentration-time curve (AUC(0-infinity) of 17,512.9 ng x h/ml (ampicillin, test), 18,388.0 ng x h/ml (ampicillin, reference), 10,971.7 ng ng x h/ml (sulbactam, test) and 11,181.2 ng x h/ml (sulbactam, reference) were calculated. The median t(max) was 0.69 h (ampicillin, test), 0.85 h (ampicillin, reference), 0.72 h (sulbactam, Devasid) and 0.83 h (sulbactam, reference). Plasma elimination half-lives (t(1/2)) of 1.04 h (ampicillin, test), 1.03 h (ampicillin, reference), 1.26 h (sulbactam, Devasid) and 1.00 h (sulbactam, reference) were determined. Both primary target parameters AUC(0-infinity) and C(max) of ampicillin and sulbactam were tested parametrically by analysis of variance (ANOVA) and the 90% confidence intervals were between 84.58%-117.80% (AUC(0-infinity), ampicillin), 92.37%-119.93% (C(max), ampicillin), 85.81%-120.50% (AUC(0-infinity), sulbactam) and 88.41%-117.57% (C(max), sulbactam). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and C(max) the 90% confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80%-125%.     

Pharmacokinetics and comparative bioavailability of two vinpocetine tablet formulations in healthy volunteers by using the metabolite apovincaminic acid as pharmacokinetic parameter

The objective of this study was to evaluate the pharmacokinetics of apovincaminic acid, the main metabolite of vinpocetine ((3alpha, 16alpha) -eburnamenine-14-carboxylic acid ethyl ester, CAS 42971-09-5), and to assess the average bioequivalence of two immediate release formulations of 10 mg vinpocetine tablets in 24 healthy male volunteers. The relative bioavailability of the test (generic) product (Vimpocetina) with respect to the reference product was determined in a single dose, randomized, crossover study. A simple, rapid specific and reliable high performance liquid chromatographic method coupled with mass spectrometry detection has been developed and validated for vinpocetine and apovincaminic acid. However, only the concentrations of the metabolite could be used for bioequivalence determinations because the concentrations of the parent drug were too low to be accurately measured in the biological matrix. The compartmental analysis of the metabolite's appearance-disappearance in blood shows similarity with first-order kinetics of a drug extravascularly administered. The apparent pharmacokinetic constants were determined. The mean values for the Cmax were 49.5 (+/- 16) ng/ml for test and 51.4 (+/- 14) ng/ml for the reference product. The mean values for the AUC0-infinity were 95 (+/- 29) ng/ml x h for test and 96.9 (+/- 26) ng/ml x h for reference, respectively. The 90 % confidence intervals for test/reference mean ratios of the plasma pharmacokinetic variables Cmax and AUC0-infinity lie between 0.83-1.08 and 0.88-1.08, respectively, which is within the conventional bioequivalence range of 80-125 % (Schuirman test). The difference between Tmax of the test and reference products was statistically non-significant (Friedman test). The test product is therefore bioequivalent to the reference product with respect to the rate and extent of apovincaminic acid pharmacokinetics.     

Pharmacokinetic and bioequivalence study of meloxicam tablets in healthy male subjects

Meloxicam (CAS 71125-38-7), a non-steroidal anti-inflammatory drug (NSAID), is used for the treatment of osteoarthritis and rheumatic arthritis. In the present study, two different oral meloxicam formulations (Melcam 15 mg tablets as test preparation and tablets of a reference preparation) were investigated in 24 healthy male subjects in order to prove bioequivalence between both preparations. A single 15 mg oral dose was administered according to an open, randomised, two-period cross-over design in the fasted state. Blood samples for the determination of meloxicam plasma concentrations were collected at pre-defined time points up to 96 h following drug administration. A wash-out period of 7-8 days separated both treatment periods. Meloxicam plasma concentrations were determined by means of a validated HPLC method with UV-detection. Maximum plasma concentrations (C(max)) of 1,146.9 ng/ml (test) and 1,064.8 ng/ml (reference) were achieved. Areas under the plasma concentration-time curve (AUC(0-infinity) of 34,499.0 ng x h/ml (test) and 33,784.3 ng x h/ml (reference) were determined. The results showed nearly identical rate and extent of drug absorption. Also further pharmacokinetic parameters were well comparable. Thus, t(max) showed values of 5.00 h for both test and reference. The plasma elimination half-life (t1/2) was 18.29 h (test) und 18.94 h (reference). Both primary target parameters C(max). and AUC(0-infinity, were tested parametrically by analysis of variance (ANOVA) and the 90% confidence intervals were between 99.46%-105.24% (AUC0-infinity)) and 103.37%-112.46% (C(max)). Bioequivalence between test and reference preparation was demonstrated since for both parameters AUC and C(max) the 90% confidence intervals of the T/R ratios of logarithmically transformed data were in the generally accepted range of 80%-125%.     

Bioavailability study of drotaverine from capsule and tablet preparations in healthy volunteers

The bioavailability of drotaverine (CAS 14009-24-6) was investigated after oral administration of a drotaverine capsule preparation (20 mg Droxa mite) and compared to that of a reference tablet preparation. The preparations were investigated in 23 healthy volunteers, aged between 20 and 27 years, according to a randomised two-way, cross-over design in the fasted state. Blood samples for determination of drotaverine plasma concentrations were collected at pre-defined time points up to 30 h following drug administration. A washout period of two weeks separated both treatment periods. Drotaverine plasma concentrations were determined by means of a validated HPLC method (UV detector, imipramine HCl salt as an internal standard). The limit of detection was 6 ng/ml. Values of 1593.92 +/- 949.70 ng x h/l (95% confidence interval (CI): 1183.20-2004.60) for the test and 1705.48 +/- 737.78 ng x h/l (95% CI: 1386.40-2024.50) for the reference preparation AUC(0-infinity) demonstrate a nearly identical extent of drug absorption. Maximum concentrations--Cmax of 121.89 +/- 37.03 ng/ml (95% CI: 104.05-139.80) and 121.85 +/- 37.97 ng/ml (95% CI: 107.09-135.74) and time to reach maximum plasma concentration--Tmax of 1.29 +/- 0.42 h (95% CI: 1.11-1.48) and 1.14 +/- 0.34 h (95% CI: 0.99-1.29) achieved for the test and reference preparations did not differ significantly. The relative bioavailability (AUC(0-infinity) ratio test/reference) and Cmax ratio test/reference were 103.15% (90% CI: 81.68-124.60) and 103.74% (90% CI: 94.10-113.38), respectively. AUC was calculated using two different methods. There were no significant differences between the obtained values. Since the 90% CI for both, AUC and Cmax ratios were within the 80-125% interval proposed by the European Agency for the Evalution of Medicinal Products (CPMP) and the Food and Drug Administration, it is concluded that the new drotaverine capsule formulation is therapeutically equivalent to the conventional formulation for both, the extent and the rate of absorption after single dose administration in healthy volunteers.     

盐酸特比萘芬片在中国健康受试者体内的生物等效性研究

目的 研究盐酸特比萘芬片在中国健康受试者中的药代动力学,评价国产受试制剂与原研参比制剂的生物等效性.方法 采用空腹/餐后、随机、开放、单剂量、两周期、两序列、双交叉试验设计.空腹试验和餐后试验各入组36例健康受试者,随机分为2组,每周期单次空腹或餐后口服盐酸特比萘芬片受试制剂或参比制剂125 mg.用液相色谱-串联质谱...     

Comparative bioavailability study of two ibuprofen preparations after oral administration in healthy volunteers

The bioavailability of a new ibuprofen (2-(p-isobutylphenyl)propionic acid, CAS 15687-27-1) preparation was compared with a reference preparation of the drug in 23 healthy male volunteers, aged between 19 and 27. A single dose of 400 mg was given orally in the fasted state, using a randomized two-way crossover study. A washout period of two weeks separated both treatment periods. Ibuprofen plasma levels were determined by means of a validated HPLC method (UV detector). Values of 154.48 +/- 53.27 microg x h/ml (95 % confidence interval CI: 133.50-177.03) for the test, and 140.86 +/- 44.82 microg x h/ml (95% CI: 122.53-159.16) for the reference preparation AUC(0-infinity) demonstrate a nearly identical extent of drug absorption. Maximum plasma concentrations Cmax of 39.53 +/- 7.11 microg/ml (95 % CI: 35.97-41.78) and 37.71 +/- 8.67 microg/ml (95% CI: 33.37-40.46) achieved for the test and reference preparations did not differ significantly. AUC(0-infinity) and Cmax ratios (90% CI) were within the 80-125% interval required for bioequivalence as stipulated in the current international regulations of the European Agency for the Evalution of Medicinal Products and the Food and Drug Administration. Therefore it is concluded that the new ibuprofen preparation is therapeutically equivalent to the reference preparation for both, the extent and the rate of absorption, after single dose administration in healthy volunteers.     

Bioavailability investigation of a new tilidine/naloxone liquid formulation compared to a reference formulation.

An oral solution available as ethanol-free droplets of the fixed drug combination tilidine-HCl 50 mg/naloxone-HCl 4 mg (CAS 27107-79-5 and CAS 465-65-6, respectively; Tilidin-ratiopharm plus Tropfen) was investigated in 12 healthy volunteers together with an ethanol-containing reference preparation for comparable bioavailability. The study was conducted in an open, randomized, two-way cross-over design applying single doses of 20 droplets (equivalent to 50 mg tilidine-HCl/4 mg naloxone-HCl) of either formulation in the fasting state. The drug plasma profiles were monitored for a period of 48 h by means of LC-MS/MS for tilidine and its active metabolite nortilidine, whereas GC-MS was employed in order to determine naloxone and its phase I metabolite, 6-beta-naloxole. Maximum concentrations (Cmax) achieved were 22.28 ng/ml (tilidine) and 92.78 ng/ml (nortilidine) for the test preparation. Corresponding values for the reference preparation were 24.95 ng/ml (tilidine) and 100.73 ng/ml (nortilidine). The extent of drug absorption (AUC0-infinity) amounted to 38.83 ng h/ml and 467.63 ng h/ml for the prodrug tilidine and the metabolite nortilidine of the test preparation and corresponded well to 43.81 ng h/ml and 493.85 ng h/ml of the reference. Regarding the rate of drug absorption, essentially identical tmax and Rabs values for both tilidine and nortilidine of either preparation in addition pointed to well comparable liquid formulations and equipotent analgesia may be inferred from opioid pharmakokinetic profiles. Pharmacokinetics of the opioid antagonist naloxone and 6-beta-naloxole were also determined and resulted in well coinciding profiles for both preparations. Thus despite the fact that only minimum oral naloxone bioavailabilities were observed, plasma level monitoring of naloxone and 6-beta-naloxole allowed for demonstration of systemic exposure of opioid antagonistic compounds throughout a period of 2-3 h after oral drug administration. Due to the limited number of subjects involved, the primary aim of the study did not consist in demonstration of drug bioequivalence. Rather a comparable bioavailability between preparations was assumed if AUC and Cmax point estimators of 90% confidence intervals would be contained within a 0.80-1.20 range. The study outcome revealed that all four investigated analytes met this requirement, whilst nortilidine pharmacokinetic parameters even fulfilled commonly accepted bioequivalence criteria, i.e. inclusion of 90% confidence intervals of AUC- and Cmax-ratios within acceptance limits of 80% and 125%. Increased data variation observed with bioavailability parameters of tilidine, naloxone and 6-beta-naloxole prevented their bioequivalence demonstration based on only 12 study participants. In conclusion, single doses of two different tilidine/naloxone 50 mg/4 mg liquid formulations revealed well comparable bioavailability for all 4 analytes investigated. Both treatments were fairly well tolerated. Most frequently reported adverse events were dizziness, headache and nausea, which all recovered without sequelae and necessity of concomitant treatment.     

Pharmacokinetics and comparative bioavailability of two terbinafine hydrochloride formulations after single-dose administration in Chinese healthy subjects

The bioavailability of a new terbinafine (CAS 91161-71-6) preparation was compared with a commercially available original preparation (reference) of the drug in 19 Chinese healthy male volunteers. The study was performed in an open, randomized, single blind two-sequence, two-period crossover design. Under fasting conditions, each subject received a single oral dose of 250 mg terbinafine as a test or reference formulation with a 7-day washout period between the two preparations. The plasma concentrations of terbinafine were analyzed by a sensitive liquid chromatography-ultraviolet spectrometry method. The pharmacokinetic parameters included AUC(0-t) AUC(0-infinity), C(max), t1/2, and T(max). The values of AUC(0-t) demonstrated nearly identical bioavailability of terbinafine from the examined formulations. The AUC(0.48) of terbinafine was 5982.85 +/- 2449.17 and 6761.63 +/- 3140.33 ng x h/ml for the test and reference formulation, respectively. The maximum plasma concentration (C(max)) of terbinafine was 1656.25 +/- 623.18 ng/ml for the test and 1552.07 +/- 660.35 ng/ml for the reference product, respectively. No statistical differences were observed for C(max) and the area under the plasma concentration time curve for terbinafine. The 90% confidence limits calculated for C(max) and AUC from zero to infinity (AUC(0-infinity)) of terbinafine were within the bioequivalence range (80%-125% for AUC). This study shows that the test formulation is bioequivalent to the reference formulation of terbinafine.     

A model study of bioequivalence of dissolved nifedipine from soft gelatin capsules

Oral absorption of nifedipine determined from plasma concentrations was studied in 20 healthy subjects aged 19 to 40 years following application of a single soft gelatin capsule as a generic preparation (P) and a reference preparation (R) containing 10 mg nifedipine. Nifedipine was measurable in plasma 15 min after application and maximal concentrations occurred after 0.44 and 0.64 h (mean), respectively. Maximal concentrations Cmax varied between 46.4 and 251.0 ng/ml (median 100.7, mean 112.6) after P and between 35.5 and 279.7 ng.h/ml (median 115.8, mean 125.2) after R. Mean areas under the curves (AUC0-infinity) were 173.6 (median 151.4 P) and 188.6 ng.h/ml (median 163.1, R). The minor differences in the AUC values and Cmax values were not statistically significant. The shorter tmax after the generic preparation (p less than 0.05) is clinically unimportant. Since the bioavailability of P is 97% the two preparations are bioequivalent.     

Bioequivalence study of finasteride. Determination in human plasma by high-pressure liquid chromatography coupled to tandem mass spectrometry

Two different finasteride (CAS 98319-26-7) tablet formulations were evaluated for their relative bioavailability (Flaxin tablets 5 mg, as the test formulation vs reference formulation, tablets 5 mg) in 23 healthy male volunteers who received a single 5 mg oral dose of each preparation. The study was open, randomized with a two-period crossover design and a 7-day washout period. Plasma samples were obtained over a 48-h interval. The finasteride concentrations were determined by high-pressure liquid chromatography (HPLC) coupled to tandem mass spectrometry (LC-MS-MS). The analytical method developed has a limit of quantitation (LOQ) of 0.50 ng/ml in plasma. For the quality control the measured concentration was 2.05 +/- 0.14 ng/ml (mean +/- SD, n = 30) with a precision of 6.9% and an accuracy of 2.55% at a concentration of the starting solution of 2.00 ng/ml, while with 20.00 ng/ml starting solution the measured concentrations were 20 +/- 0.80 ng/ml (n = 30) with a precision of 3.81% and an accuracy of 0.09%. From the plasma finasteride concentration vs time curves the following pharmacokinetics parameters were obtained: AUC0-48, AUC0-infinity, Cmax, Cmax/AUC0-48, Ke, elimination half-life and tmax. Geometric mean test/reference formulations individual percent ratio was 95.71 for AUC0-48 h and 88.70% for Cmax. The 90% confidence interval for the geometric mean of the individual ratio test/reference formulations was 95.70-120.20% for AUC0-48 h, 94.60-121.30 for AUC0-infinity and 88.70-108% for Cmax. Since for both Cmax or AUC the 90% Cl values are within the interval proposed by the Food and Drug Administration, the test formulation is bioequivalent to the reference formulation for both the rate and extent of absorption after single dose administration.     

Pharmacokinetics and bioequivalence study of two digoxin formulations after single-dose administration in healthy Chinese male volunteers

The pharmacokinetics and relative bioavailability/bioequivalence of two formulations of digoxin (CAS 20830-75-5) were assessed in this paper. The study was conducted in 20 healthy Chinese male volunteers according to an open, randomized, single-blind, 2-way crossover study design with a wash-out phase of 14 days. Blood samples for pharmacokinetic profiling were taken up to 72 h post-dose and digoxin plasma concentrations were determined by a validated liquid chromatography-tandem mass spectrometry (LCMS/MS) method. Based on the plasma concentration-time data of each individual during two periods, pharmacokinetic parameters, Cmax, AUC0-tau, AUC0-infinity and t1/2, were calculated by applying noncompartmental analysis. Pharmacokinetic data for test and reference formulations were analyzed statistically to evaluate bioequivalence of the two formulations. After oral administration, the values of Cmax Tmax, t1/2, AUC0-tau, AUC0-infinity for test and reference formulations were 2.61 +/- 0.98 and 2.68 +/- 1.09 ng/ mL, 1.0 +/- 0.4 and 1.0 +/- 0.4 h, 27.94 +/- 3.14 and 27.56 +/- 3.86 h, 28.57 +/- 4.99 and 28.77 +/- 6.53 ng x h/mL, 33.44 +/- 4.85 and 33.63 +/- 7.57 ng x h/mL, respectively. Both primary target parameters, AUC0-infinity and AUC0-tau, were tested parametrically by analysis of variance (ANOVA). Relative bioavailabilities were 102.5 +/- 19.2% for AUC0-infinity, 102.0 +/- 19.3% for AUC0-tau. Bioequivalence between test and reference formulations was demonstrated for both parameters, AUC0-infinity and AUC0-tau. The 90% confidence intervals of the T/R-ratios of logarithmically transformed data were in the generally accepted range of 80%-125%, which means that the test formulation is bioequivalent to the reference formulation of digoxin.