Quantitative determination of spinosin in rat plasma by liquid chromatography-tandem mass spectrometry method

A sensitive method for the quantitative determination of spinosin in rat plasma was developed and validated using high-performance liquid chromatographic separation with tandem mass spectrometric detection. The analytes of interest were extracted from rat plasma samples by methyl tert-butyl ether (MTBE) after acidification with 1.0% acetic acid aqueous solution. Chromatographic separation was achieved on an Agilent Zorbax SB-C(18) (50 mm x 4.6 mm, 5 microm) using a isocratic mobile phase consisting of acetonitrile-water (30:70, v/v) with 1% isopropyl alcohol and 0.01% heptafluorobutyric acid. The flow rate was 0.2 ml/min. The column temperature was maintained at 25 degrees C. Detection was performed on a triple quadrupole tandem mass spectrometer by selected reaction monitoring (SRM) mode via electrospray ionization (ESI). The calibration curve was linear over the range of 1.00-400 ng/ml in rat plasma, with 1.00 ng/ml of the lower limit of quantification (LLOQ). The inter- and intra-day precisions and accuracy for all samples were satisfactory. The validated method was successfully applied for the pharmacokinetic study of spinosin in rat. After oral administration of 20mg/kg spinosin to rats, the main pharmacokinetic parameters of T(max), C(max), T(0.5) and AUC(0-T) were 5.33+/-0.58 h, 132.2+/-10.6 ng/ml, 4.89+/-0.37 h, 1.02+/-0.09 microg h/l, respectively.     

Bioequivalence assessment of two formulations of spironolactone in Chinese healthy male volunteers

The bioavailability of a new spironolactone ((7alpha,17alpha)-7-(acetylthio)-17-hydroxy-3-oxopregn-4-ene-21-carboxylic acid gamma-lactone, CAS 52-01-7) formulation (test) was compared with a commercially available original formulation (reference) of the drug in 20 Chinese healthy male volunteers, aged between 21 and 27. 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 100 mg spironolactone as a test or reference formulation with a 7-day washout period between the two formulations. The plasma concentrations of spironolactone and its active metabolite canrenone (CAS 976-71-6) were analyzed by a sensitive liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) method. The pharmacokinetic parameters included AUC(0.t), AUC(0-infinity), C(max), t1/2, and T(max). Values of AUC(0-t) demonstrate nearly identical bioavailability of spironolactone from the examined formulations. The AUC(0.12) of spironolactone was 148.35 +/- 39.5 and 144.39 +/- 53.02 ng x h/ml for the test and reference formulation, respectively. The AUC(0-60) of the metabolite canrenone was 1873.36 +/- 318.10 and 1911.28 +/- 355.60 ng h/ml for test and reference formulation, respectively. The maximum plasma concentration (C(max)) of spironolactone was 48.34 +/- 21.16 ng/ml for the test and 47.40 +/- 23.40 ng/ml for the reference product and the C(max) of the metabolite was 122.90 +/- 27.70 and 123.35 +/- 27.29 ng/ml for the test and reference product, respectively. No statistical differences were observed for C(max) and the area under the plasma concentration-time curve for both spironolactone and its active metabolite canrenone. 90% confidence limits calculated for C(max) and AUC from zero to infinity (AUC(0-infinity)) of spironolactone and its metabolite were included in the bioequivalence range (80%-125% for AUC). This study shows that the test formulation is bioequivalent to the reference formulation for spironolactone and its main active metabolite canrenone.     

A pharmacokinetic study of intramuscular administration of bulleyaconitine A in healthy volunteers

The pharmacokinetics of bulleyaconitine A (BLA) after a single dose of 0.2 mg intramuscular injection was evaluated in healthy volunteers. Physical exam, vital signs, clinical laboratory tests and electrocardiogram measurements were monitored to assess the safety and tolerance of the drug. The plasma levels of BLA in serial samples, collected over 15 h, were measured by a validated high-performance liquid chromatography (HPLC)-electrospray ionization tandem mass spectrometry (MS-MS) method. It was demonstrated that BLA was absorbed rapidly after intramuscular injection. The pharmacokinetic parameters were as follows: the t(max) value was 0.90+/-0.68 h, the C(max) value was 1.13+/-0.76 ng/ml, the AUC(0-t) was 5.16+/-2.05 ng.h/ml, and t(1/2) was found to be 4.88+/-0.97 h. No subject showed any drug-related clinically significant changes on physical examination, vital signs or laboratory tests. Eight of ten subjects reported a distinct feeling of pain at the site of injection starting approximately at the time of their peak plasma concentration and lasting for 2-6 h. The pain was tolerable, and no subject required additional 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.     

Determination and pharmacokinetic study of oxymatrine and its metabolite matrine in human plasma by liquid chromatography tandem mass spectrometry

There is little information about the pharmacokinetics of oxymatrine (OMT) and its metabolite matrine (MT) after i.v. administration of OMT in human. Therefore a specific and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was established for the determination and pharmacokinetic study of OMT and its metabolite MT in human plasma after i.v. infusion administration of 600 mg of OMT in 100 ml of 5% glucose injection in 0.5 h. The analysis was carried out on a Lichrospher-CN column (250 mmx4.6 mm, i.d., 5 microm, Merck) with mobile phase of methanol-ammonium acetate (20 mmol/l; 85:15, v/v) pumped at a flow rate of 1.0 ml/min. The tandem mass detection was made with electrospray ionization in positive ion selected reaction monitoring mode, with argon collision-induced dissociation ion transitions m/z 265.2 to m/z 265.2 for OMT at 25 eV, m/z 249.2 to m/z 249.2 for MT at 25 eV and m/z 340.2 to m/z 324.0 at 35 eV for the internal standard (papaverine), respectively. The assay was validated to be accurate and precise for the analysis in the concentration range of 1.0-40,000 ng/ml for both OMT and MT with the LOD being 0.5 and 0.2 ng/ml, respectively, when 0.25 ml of human plasma sample was processed with papaverine as internal standard. The pharmacokinetic study was made with 10 healthy male Chinese subjects. The plasma concentration time profiles of OMT and MT obtained were best fitted with two-compartment and one-compartment models, respectively. The main pharmacokinetic parameters found for OMT and MT after i.v. infusion were as follows: Cmax (20,519+/-7581) and (247+/-45) ng/ml, Tmax (0.5+/-0.1) and (5.6+/-1.7) h, AUC0-t (20,360+/-5205) and (3817+/-610) ng h/ml, AUC0-infinity (20,436+/-5188) and (3841+/-615) ng h/ml, t1/2 (2.17+/-0.49) and (9.43+/-0.62) h, respectively. The CL/F and Vd/F of OMT were (43.8+/-10.8) l h-1 and (70.1+/-26.6) l, respectively. Therefore only a small amount of OMT was reduced to MT following i.v. administration of OMT judged by the AUCs.     

Pharmacokinetics of lovastatin extended-release dosage form (Lovastatin XL) in healthy volunteers

The purpose of this study was to evaluate pharmacokinetics and dose proportionality of lovastatin extended-release dosage form (ER-lovastatin) in the dosage levels of 10, 20 and 40 mg in 9 healthy male subjects. Each subject was randomized to receive a single oral dose of ER-lovastatin either 10, 20 or 40 mg in a three-way crossover design with a washout period of 7 days between the treatments. Subjects were served dinner at approximately 5:30 PM followed by dosing at approximately 10:00 PM in each study period. Serial plasma samples were collected up to 48 h after dosing and assayed for lovastatin and its active metabolite lovastatin acid using an LC/MS/MS method. The plasma concentration-time profiles of lovastatin and its active metabolite lovastatin acid exhibited delayed- and extended-release characteristics at each dose. Mean (+/-) values for the C(max) of lovastatin were 1.04+/-0.43, 2.03+/-0.65 and 4.03+/-3.02 ng/ml for the 10, 20 and 40 mg dosage, respectively. The corresponding values for the AUC(0-48 h) of lovastatin were 14.6+/-7.8, 34.1 +/-13.7, and 53.9+/-35.6 ng h/ml. The same tendency was also found for C(max) and AUC(0-48 h) values of lovastatin acid. Results from this study demonstrated as the dose of ER-lovastatin increased from 10 to 40 mg, the C(max) and AUC(0-48 h) values of lovastatin as well as lovastatin acid appeared to increase linearly.     

LC-MS determination and pharmacokinetic studies of ursolic acid in rat plasma after administration of the traditional chinese medicinal preparation Lu-Ying extract

Sambucus chinensis L. is a native perennial herb distributed throughout China. In traditional Chinese medicine (TCM), this herb is known as Lu-Ying. Ursolic acid is the major effective constituent of Lu-Ying. A rapid, sensitive, and accurate liquid chromatography-mass spectrometry (LC-MS) method for the determination of ursolic acid in rat plasma was developed and validated. Plasma samples taken from rats that had received Lu-Ying extract orally were acidified with acetic acid and then extracted with a mixture of hexane-dichloromethane-2-propanol (20:10:1, v/v/v). Separation of ursolic acid was accomplished on a C(18) column interfaced with a single quadrupole mass spectrometer. The mobile phase consisting of methanol and water (95:5, v/v) was delivered at a flow rate of 1.0 ml/min. Atmospheric pressure chemical ionization was operated in negative-ion mode. Using selected ion-monitoring mode, the deprotonated molecules [M-H](-) at m/z 455 and 469 were used to quantify ursolic acid and glycyrrhetic acid (internal standard), respectively. The assay was shown to be linear over the range of 10-1000 ng/ml (r> or =0.9960) with a lower limit of quantification of 10 ng/ml. The method was shown to be reproducible and reliable with intraday precision below 7.8%, interday precision below 8.1%, accuracy within +/-4.3%, and mean extraction recovery excess of 83.6%, which were all calculated from the blank plasma sample spiked with ursolic acid at three concentrations of 20, 200, and 800 ng/ml. The LC-MS method has been successfully applied to pharmacokinetic studies of ursolic acid after oral administration of Lu-Ying ethanolic extract (at a dose containing 80.32 mg/kg ursolic acid) to rats. The main pharmacokinetic parameters were: t(1/2), 4.3 h; K(e), 0.16 1/h; t(max), 1.0 h; C(max), 294.8 ng/ml; AUC(0-t) and AUC(0-infinity), 1007.1 ng.h/ml and 1175.3 ng.h/ml, respectively.     

Variable omeprazole kinetics in healthy Jordanian adults

OBJECTIVES: The objective of this study was to examine the pharmacokinetics of orally administered omeprazole in healthy adult Jordanian men. METHOD: Plasma concentrations of omeprazole were measured over a 12 h period after administration of a single oral dose of 40 mg omeprazole (Losec), AstraZeneca, UK). Subjects were healthy adult Jordanian men age 18-38 (24 +/- 4, mean +/- SD). The pharmacokinetic parameters were derived from the plasma concentration-time profiles for AUC(0-t), AUC(0-inf), C(max), t(max), t(1/2e) and K(e). RESULTS: The pharmacokinetic of omeprazole were scattered over a wide range. The median AUC(0-inf) was 784.86 +/- 1182.88 (ng.h/ml), and the median C(max) was 521 +/- 354 (ng/ml) (median +/- SD). In general, most subjects showed normal distribution (approximately 90%). Some subjects (10%) did show very high AUC and C(max) compared with the reported AUC and C(max) levels. These subjects had higher half-lives and lower rates of elimination. CONCLUSION: Significant difference in the pharmacokinetics of omeprazole after a single dose administration was noted. Approximately 10% of the study group showed very high omeprazole plasma levels and AUCs. Differences in the pharmacokinetics might be due to differences in the genetic make-up of subjects.     

Pharmacokinetics of telmisartan in healthy Chinese subjects after oral administration of two dosage levels

To study the pharmacolkinetics of telmisartan in healthy Chinese male subjects after oral administration of two dosage levels, 36 healthy subjects were divided into two groups and given a single oral dose of 40 or 80 mg telmisartan (CAS 144701-48-4, MicardisPlus). A sensitive liquid chromatography-tandem mass spectrometry method (LC-MS-MS) was used for the determination of telmisartan in plasma. Both, a non-compartmental and compartmental method were used for analysis of parameters of kinetics. The main pharmacokinetic parameters of the 40 mg and 80 mg regimen group were as follows: t(max) (1.76 +/- 1.75) h, (1.56 +/- 1.09) h, C(max) (163.2 +/- 128.4) ng/mL, (905.7 +/- 583.4) ng/mL, t1/2 (23.6 +/- 10.8) h, (23.0 +/- 6.4) h, AUC(o-t) (1456 +/- 1072) ng x h/mL, (6759 +/- 3754) ng x h/mL, AUC(o-infinity (1611 +/- 1180) ng x h/mL, (7588 +/- 4661) ng x h/mL, respectively. After dose normalization, there was significant difference for main pharmacokinetic parameters C(max) AUC(o-t) and AUC(o-infinity) between two dosage level groups. The plasma concentration-time profile of telmisartan was characterized by a high degree of inter-individual variability and the disposition of telmisartan in healthy Chinese subjects was dose-dependent. The pharmacokinetic parameters C(max) and AUC(o-inifinity) of the 80 mg regimen group increased to about 5-fold compared to that of the 40 mg regimen group, but there was no significant difference for t(max) and t1/2 between the two dose groups.     

Pharmacokinetics of liposomal amphotericin B in neutropenic cancer patients

This study was conducted to characterise the pharmacokinetics of a liposomal pharmaceutical product of amphotericin B (LAB) in three neutropenic cancer patients complicated by suspected fungal infections. LAB was administered at a constant dose of 50 mg/day over 1--6 h by intravenous infusion, and blood samples were obtained between two infusion intervals without complicating the systemic therapy of the patients. Quantitative analysis of amphotericin B (AB) in plasma was established by a validated reversed-phase high-performance liquid chromatographic (HPLC) assay. Model independent pharmacokinetic parameters were estimated using area and moment analysis. Administration of LAB to the first patient (day 1) diagnosed as malignant melanoma resulted in a mean maximum concentration (C(max)) of 679+/-6 ng/ml and a mean minimum concentration (C(min)) of 139+/-9 ng/ml of AB. Pre-dose, C(max) and C(min) values of AB, after multiple LAB dosing to the other two patients both having acute myeloblastic leukemia were found to be 440+/-6, 1140+/-10, 409+/-11 ng/ml (day 19) and 408+/-3, 1180+/-10, and 283+/-1 ng/ml (day 9), respectively. The area under the plasma concentration-time curve (AUC) and the mean residence time (MRT) calculated between the two infusion intervals were 6180 ngh/ml, 7.79 h (day 1) for the first patient; 13,700 ng.h/ml, 10.5 h (day 19) and 14,000 ng.h/ml, 9.93 h (day 9) for the other two patients, respectively. The pharmacokinetic profiles and non-compartmental parameters calculated were comparable for both patients diagnosed with acute myeloblastic leukemia after multiple dosing at steady state, which also demonstrated a twofold increase in their AUC values compared with the AUC of the first patient. Although C(min) values supported the assumption that there was AB accumulation in plasma and this accumulation could be increased at high doses, LAB was administered safely to these patients and well tolerated at the doses given.     

In vivo evaluation of risperidone-SAIB in situ system as a sustained release delivery system in rats.

The objective of this study was to evaluate a sustained release sucrose acetate isobutyrate (SAIB) in situ system formulation of risperidone (RSP) in vivo. The formulation contained SAIB, ethanol, and polylactic acid (PLA) as a release regulator. In vivo pharmacokinetics (PK) studies have shown that PLA is effective in reducing the burst effect. After a 12.5mg/kg IM injection of a 25mg/g RSP-SAIB in situ system, the C(max) was markedly reduced from 944.1+/-80.2 to 330.4+/-33.6ng/ml by increasing PLA from 1% to 10% (w/w), the T(max) were prolonged from 2 to 4.3+/-2.0h, and the area under the curve from day 0 to 2 (AUC(0-2day)) was reduced significantly from 16294.8+/-3946.4 to 7025.3+/-1979.2ngh/ml. For the RSP-SAIB in situ system including 10% PLA, the high release rates over a short period allowed therapeutic plasma concentrations to be achieved in the initial stages after activation, and sustained release of the drug led to a stable plasma concentration (by day 25, the plasma concentration was 8% of the C(max)). These initial in vivo studies suggest that RSP-SAIB in situ system is effective as a sustained delivery system.     

Effect of roxithromycin on the pharmacokinetics of lovastatin in volunteers

OBJECTIVE: To investigate the influence of concomitant administration of roxithromycin on the plasma pharmacokinetics of lovastatin. METHODS: In an open, randomized, crossover study, 12 healthy volunteers received 80 mg lovastatin orally either alone or concomitantly with 300 mg roxithromycin after 5-day pretreatment with roxithromycin 300 mg daily. Plasma concentrations of lovastatin (lactone and acid) were determined using high-performance liquid chromatography, and the pharmacokinetic parameters were estimated. RESULTS: The mean (+/- SD) pharmacokinetic parameters of lovastatin lactone with and without roxithromycin were maximum concentration (Cmax) 8.49+/-6.80/16.3+/-9.4 ng ml(-1), time to Cmax (tmax) 1.8+/-0.4/1.7+/-0.6 h, terminal plasma half-life (t1/2) 4.3+/-2.0/3.7+/-2.5 h, area under the plasma concentration-time curve from zero to infinity (AUC0-infinity) 53+/-60/85+/-67 ng ml(-1) h. The respective parameters of lovastatin acid were Cmax 24.6+/-13.4/17.8+/-11.0 ng ml(-1), tmax 3.7+/-1.1/4.1+/-0.7 h, t1/2 3.2+/-2.5/4.3+/-2.8 h, AUC0-infinity 149+/-123/105+/-58 ng ml(-1) h. Mean bioavailability of lovastatin lactone was lower and that of lovastatin acid was higher with concomitant treatment. However, the differences were significant only with respect to lovastatin lactone (AUC and Cmax) and Cmax of lovastatin acid. CONCLUSION: Roxithromycin does not influence the pharmacokinetics of lovastatin in such a way that dosage adjustment of lovastatin seems to be necessary during co-administration.     

Development and validation of a gas chromatography-mass spectrometry method for the determination of phenazopyridine in rat plasma: application to the pharmacokinetic study

Phenazopyridine hydrochloride is a strong analgesic used in the treatment of urinary tract infections. The aim of the present study was to develop a procedure based on gas chromatography-mass spectrometry (GC-MS) for the analysis of phenazopyridine in rat plasma. The method was set up and adapted for the analysis of small biological samples taken from rats. Biological samples were extracted by liquid-liquid extraction. The extraction agent was ethyl acetate. The samples were separated by GC on a DB-5MS analytical column and determined by a quadrupole mass spectrometer detector operated under selected ion monitoring mode. Excellent linearity was found between 0.01 and 1.00 microg/ml (r = 0.9991, n = 9) for plasma samples. The limit of detection (LOD) was 0.3 ng/ml. Within-day and between-day precisions expressed as the relative standard deviation (RSD) for the method were 1.83-4.91% and 2.12-4.76%, respectively. The recoveries for all samples were >90%. The main pharmacokinetic parameters obtained were T(max) = (0.35+/-0.01) h, C(max) = (0.396+/-0.079) microg/ml, AUC = (0.373+/-0.065) h microg/ml and CL = (94.2+/-5.9) ml/g/h. The results presented here clearly indicate that this proposed method could be applicable to investigate the pharmacokinetic of phenazopyridine in rats after administration. (c)     

The bioavailability of griseofulvin from microsized and ultramicrosized tablets in nonfasting volunteers

Tablets of either microsized or ultramicrosized griseofulvin (2 x 125 mg), were administered to 6 healthy volunteers of either sex just before a breakfast containing 4o g. of butter. The plasma concentration of griseofulvin were determined 1, 3, 5, 7, 9, 24, and 32 h. after dosing using a spectrofluorometric method, and pharmacokinetic parameters (Cp max, t max, AUC 0 - greater than 32) were calculated. These parameters were found to be; Cp max = 0.0.681 +/- 0.1 mu/ml, t max. = 2.51 +/- 0.33 h. and AUC = 14.14 +/- 2.33 micrograms h/ml for microsized tablets and Cp max = 0.80 +/- 0.08 +/- g/ml, t max = 2.44 +/- 0.54 and AUC = 16.25 +/- 1.16 microgram h/ml for ultramicrosized tablets. Our results show that mean peak plasma level and AUC (0 - greater than 32) are only slightly higher for the ultramicrosized preparation and the time to peak plasma level is similar in two preparations. Therefore, it is concluded that coadministration of griseofulvin with food will tend to reduce the difference between the bioavailability of the two type of preparations.     

Enhanced bioavailability of atenolol by transdermal administration of the ethylene-vinyl acetate matrix in rabbits.

The pharmacokinetics and bioavailability of atenolol, a antihypertensive, were studied to determine the feasibility of enhanced transdermal delivery of atenolol from the ethylene-vinyl acetate (EVA) matrix system containing polyoxyethylene-2-oleyl ether as an enhancer in rabbits. The atenolol-EVA matrix (20 mg/kg) was applied to abdominal skin of rabbits. Blood samples were collected via the femoral artery for 32 h and the plasma concentrations of atenolol were determined by high-performance liquid chromatography. Pharmacokinetic parameters was calculated using Lagran computer program. The area under the curve (AUC) was significantly higher in the enhancer group (12,402+/-3061 ng/ml.h) than that in the control group (8507+/-2092 ng/ml.h), showing about 46% increased bioavailability (P<0.05). The average C(max) was increased in the enhancer group (1361+/-340 ng/ml) compared with the control group (1168+/-293 ng/ml), but not significantly. The T(max) was significantly decreased in the enhancer group (1.3+/-0.36 h) compared with the control group (2.0+/-0.51 h). The elimination time (t(1/2)) and mean residence time were significantly increased in the transdermal group compared with the IV group. The absolute bioavailability was 19.7% in the control group, 28.6% in the enhancer group and 77.4% in the oral administration group compared with IV the group. As the atenolol-EVA matrix containing polyoxyethylene-2-oleyl ether as an enhancer and tributyl citrate as a plasticizer was administered to rabbits via the transdermal routes, the relative AUC% increased about 1.46-fold compared to the control group, showing a relatively constant, sustained blood concentration with minimal fluctuation. The results of this study show that atenolol-EVA matrix could be developed as a transdermal delivery system providing sustained plasma concentration.     

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%.     

Bioeqivalence assessment of two domperidone 1 tablet formulations

A randomized, single-dose, crossover study was conducted to assess the bioavailability of two domperidone (CAS 57808-66-9) tablet formulations, Domperidone (test) and a commercially available original preparation (reference) under fasting conditions. A 10 mg dose of each formulation was administered to 36 healthy male volunteers with a one-week washout period, 17 blood samples were collected over 48 h, plasma concentrations of domperidone were analyzed by a locally validated LC-MS-MS assay, and the pharmacokinetic parameters were determined by the standard non-compartmental method. Mean +/- SD maximum concentration (C(max)), time to reach maximum concentration (T(max)), areas under the curve (AUC(0 --> t and AUC(0 --> infininty)), and elimination constant (K(el)) were 17.13 +/- 9.62 and 17.67 +/- 7.97 ng/ml, 0.87 +/- 0.58, and 0.89 +/- 0.33 h, 73.12 +/- 43.37 and 71.45 +/- 35.41 ng x h/ml, 90.32 +/- 48.55 and 87.08 +/- 40.29 ng x h/ml, and 0.069 +/- 0.046 and 0.068 +/- 0.048 h(-1) for the test and reference formulation, respectively. The parametric 90% confidence intervals on the mean difference between log-transformed values of the two formulations were within the acceptable bioequivalence range for AUC(0 --> t) (87.84% to 109.60%), AUC(0 --> infinity) (89.05% to 111.67%) and C(max) (83.28% to 107.50%). ANOVA revealed significant subject's effect for AU4C(0 --> t), AUC((0 -->infinity), C(max), and t1/2 with a ratio of the inter-subject to intra-subject coefficient of variation of 2.10, 1.55, 1.10, and 1.02, respectively. The results indicate that the two formulations are equivalent in relation to the extent and rate of absorption and confirm the previously reported marked intra-individual variations in the pharmacokinetics of domperidone.     

Pharmacokinetics of diphenhydramine in healthy volunteers with a dimenhydrinate 25 mg chewing gum formulation

This pharmacokinetic study evaluated diphenhydramine in the plasma of healthy volunteers after a single 25 mg oral dose of dimenhydrinate (diphenhydramine theophyllinate), corresponding to 12.7 mg diphenhydramine, in a chewing gum formulation. Seven volunteers (4 men, 3 women; age: 26.3 +/- 1.2 years; body weight: 63.1 +/- 4.1 kg; height: 172.4 +/- 4.6 cm) chewed the gum for 1 h. Blood samples (10 ml) were collected at different time intervals up to 24 h. Blood plasma was subsequently processed and analyzed for diphenhydramine content using a GLC method and an NPD detector. Analytical data revealed the following kinetic parameters: AUC(0-24h): 155.2h x ng x ml(-1); AUC(0-infinity): 195.3 h x ng x ml(-1); Mean resident time: 16 h; t(1/2): 10 h; C(max): 14.5 ng x ml(-1); t(max): 2.6 h; and plasma clearance: 9.0 ml x min(-1) x kg(-1). This study indicates that the pharmaceutical formulation employed provided sustained plasma concentrations of diphenhydramine, presumably sufficient to support its clinical efficacy towards motion sickness owing to the almost complete (> 95%) release by the formulation of the active principle. Moreover, the maximal concentrations of diphenhydramine attained in plasma were much lower than the concentration threshold needed to produce drowsiness.     

Study on bioavailability difference between clopidogrel bisulfate form I and form II using liquid chromatography/tandem mass spectrometry

The bioavailability of clopidogrel bisulfate (CAS 135046-48-9) form I was compared with that of clopidogrel bisulfate form II in 12 male Sprague-Dawley rats. The rats, randomly divided into two groups, received a single oral dose of 8 mg/kg clopidogrel (CP) bisulfate form I and form II, respectively, under fasting condition. The plasma concentrations of CP and its inactive carboxylic acid metabolite (CAS 144457-28-3, IM) were simultaneously determined by a sensitive, specific LC-MS/MS method. The pharmacokinetic parameters included C(max), T(max), t1/2, AUC(0-t), AUC(0-infinity). The AUC(0-infinity) of CP was 13.78 +/- 0.67 and 11.46 +/- 1.98 ng/ mL x h for CP form I and form II, respectively. The AUC(0-infinity) of IM was 33.08 +/- 5.76 and 21.67 +/- 8.95 microg/mL x h for CP form I and form II, respectively. The maximum plasma concentration (C(max)) of CP was 3.81 +/- 0.54 ng/mL for CP form I and 3.18 +/- 0.31 ng/mL for CP form II, the C(max) of IM was 3.42 +/- 0.41 and 2.08 +/- 0.68 microg/ mL for the CP form I and form II, respectively. There was an obvious difference between form I and form II for C(max) and the area under the plasma concentration time curve for both CP and IM after a t-test. This study shows that CP form I has better bioavailability in rats than CP form II.     

Dose-linear pharmacokinetics of oleanolic acid after intravenous and oral administration in rats

The pharmacokinetics of oleanolic acid was evaluated in vitro and in vivo. From Caco-2 cell permeation studies, oleanolic acid was a low permeability compound with no directional effects, suggesting a low in vivo absorption mediated by a passive diffusion. Oleanolic acid was metabolically unstable following incubation with rat liver microsomes in the presence of NADPH. After intravenous injection at doses of 0.5, 1 and 2 mg/kg doses, oleanolic acid showed dose-linear pharmacokinetics as evidenced by unaltered CL (28.6-33.0 ml/min/kg), Vss (437-583 ml/kg), dose-normalized AUC (16.0-17.9 microg min/ml based on 1 mg/kg) and t1/2 (41.9-52.7 min). Following oral administration of oleanolic acid at doses of 10, 25 and 50 mg/kg, Tmax, t1/2, dose-normalized Cmax (66-74 ng/ml based on 25 mg/kg) and dose-normalized AUC (5.4-5.9 microg min/ml based on 25 mg/kg) were comparable between 25 and 50 mg/kg dose, but the plasma concentrations at 10 mg/kg dose were not measurable as they were below the limit of quantitation (2 ng/ml). The absolute oral bioavailability was 0.7% for oral doses of 25 and 50 mg/kg. The extent of urinary excretion was minimal for both i.v. and oral doses. The very low oral bioavailability of oleanolic acid could be due to a poor absorption and extensive metabolic clearance.