HPLC-MS/MS analysis of peramivir in rat plasma: Elimination of matrix effect using the phospholipid-removal solid-phase extraction method.

A simple HPLC-MS/MS method has been developed for the determination of peramivir in rat plasma in the present study. The analytes were separated on a C18 column (50 × 2.1 mm, 1.7 µm) and a triple-quadrupole mass spectrometer equipped with an electrospray ionization source was applied for the detection. A phospholipid-free cartridge solid-phase extraction was used to pretreat the plasma and eliminate the endogenous phospholipid. The in-source collision-induced dissociation approach showed that this pretreatment could result in negligible ion suppression from the extracted sample and could produce cleaner samples when compared with the protein precipitation. The method was linear over the concentration range of 0.12-1200.0 ng/mL for peramivir. The method was validated and successfully applied to a pharmacokinetic study after peramivir was orally and intravenously administered to Sprague-Dawley rats.

Population pharmacokinetics of peramivir in healthy volunteers and influenza patients.

UNLABELLED: Peramivir is an intravenous anti-influenza agent that inhibits viral growth by selectively inhibiting neuraminidase in human influenza A and B viruses. To characterize its pharmacokinetics, a population pharmacokinetic analysis of peramivir was performed using 3,199 plasma concentration data samples from 332 subjects in six clinical studies in Japan and the United States, including studies with renal impairment subjects, elderly subjects, and influenza patients. A three-compartment model well described the plasma concentration data for peramivir, and creatinine clearance was found to be the most important factor influencing clearance. Age and body weight were also found to be covariates for clearance and the volume of distribution, respectively. No difference in pharmacokinetics was found between genders or between Japanese and U.S. SUBJECTS: Small differences in pharmacokinetics were observed between uninfected subjects and influenza patients (clearance was 18% higher and the volume of distribution was 6% lower in influenza patients). Monte Carlo simulations indicated that single adjusted doses of 1/3- and 1/6-fold for patients with moderate and severe renal impairment, respectively, would give areas under the curve comparable to those for patients with normal renal function. The population pharmacokinetic model developed for peramivir should be useful for understanding its pharmacokinetic characteristics and for dose adjustment on the basis of renal function.

Pharmacokinetics of peramivir after single intravenous doses in healthy Chinese subjects.

1.The aim of the study was to evaluate the pharmacokinetics of peramivir after single intravenous (i.v.) doses in healthy Chinese subjects. 2.In a cross-over study, 12 subjects were given 300 and 600 mg peramivir by i.v. infusion. Blood and urine samples were collected at 17 designated time points and 7 designated intervals up to 36 h post-dose. Plasma and urine concentrations of peramivir were quantified by LC-MS/MS. 3.After single i.v. doses of 300 and 600 mg peramivir, Cmax and AUC0-t of peramivir were 21.4 ± 3.7, 41.1 ± 5.3 mgcL(-1) and 55.90 ± 10.62, 112.1 ± 13.2 mgch L(-1), respectively. Cmax and AUC increased in proportion to the dose. Within 12 h, accumulative urinary recoveries of peramivir after single i.v. doses of 300 and 600 mg peramivir were 84.31 ± 11.75% and 88.10 ± 7.39%, respectively. 4.In healthy Chinese subjects, peramivir displayed linear pharmacokinetics in the range of 300-600 mg, and was primarily excreted via urine as unchanged drug.

Enhanced anti-amnestic effect of donepezil by Ginkgo biloba extract (EGb 761) via further improvement in pro-cholinergic and antioxidative activities.

ETHNOPHARMACOLOGICAL RELEVANCE: EGb 761 is a standardized dry extract of Ginkgo biloba L. leaves traditionally used by Eastern Asia and has been associated with beneficial effects on neurodegeneration disorders, including Alzheimer's disease. AIM OF THE STUDY: Since beneficial interactions between EGb 761 and donepezil have been observed in previous clinical studies, the current study was proposed aiming to further explore related mechanisms from both pharmacokinetics and pharmacodynamics aspects. MATERIALS AND METHODS: Pharmacodynamic interactions were studied in scopolamine-induced cognitive impairment rats received two-weeks treatment of vehicle, EGb 761 and/or donepezil by the Morris water maze test and ex vivo evaluation of biomarkers of cholinergic transmission and oxidative stress in rat brain. In the meantime, pharmacokinetic profiles of donepezil and bilobalide were obtained and compared among all treatment groups. In addition, impact of the bioavailable EGb 761 components on donepezil brain penetration was evaluated with the hCMEC/D3 cell monolayer model. RESULTS: Scopolamine-induced rats with co-treatment of EGb 761 and donepezil had significantly improved cognitive function in the Morris water maze test with increased brain levels of superoxide dismutase and decreased brain levels of acetylcholinesterase and malondialdehyde than that with treatment of only EGb 761 or donepezil. Despite such beneficial pharmacodynamics outcomes, the two-week co-treatment of EGb 761 and donepezil did not alter the plasma pharmacokinetics and brain uptake of donepezil or bilobalide, which was further verified in the hCMEC/D3 monolayer model. CONCLUSION: Co-administration of EGb 761 and donepezil exerted better anti-amnestic effect via further enhanced pro-cholinergic and antioxidative effects of EGb 761 or donepezil in scopolamine-induced cognitive impairment rat without alteration in their systemic/brain exposure.

A sensitive liquid chromatography-electrospray ionization-mass spectrometry method for the simultaneous determination of pentoxyverine citrate and guaifenesin in human plasma---application to pharmacokinetic and bioequivalence studies.

A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry method for the identification and quantification of pentoxyverine citrate and guaifenesin in human plasma has been developed. After extraction from plasma samples by ethyl acetate, the internal standard and analytes were separated by high-performance liquid chromatographic on a Shim-pack VP-ODS C(18) column (150 x 2.0 mm) using a mobile phase consisting of A (methanol) and B (0.4% glacial acetic acid and 4 mmol/L ammonium acetate) (A:B, 43 : 57). Analysis was performed on a Shimadzu LC/MS-2010A in selected ion monitoring mode with a positive electrospray ionization interface. The method was linear in the concentration range of 1.0-640.0 ng/mL for pentoxyverine citrate and 0.025-6.4 microg/mL for guaifenesin. The inter- and intra- precision were all within 12% and accuracy ranged from 85 to 115%.The lower limits of quantification were 1.0 ng/mL for pentoxyverine citrate and 25.0 ng/mL for guaifenesin. The extraction recovery was on average 81.95% for pentoxyverine citrate and 89.03% for guaifenesin. This is the first assay method reported for the simultaneous determination of pentoxyverine citrate and guaifenesin in plasma using one chromatographic run.

[Quantification of pentoxyverine citrate in human plasma by LC-ESI/MS method and its application].

A rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/ MS) method for quantification of pentoxyverine citrate in human plasma has been developed and applied for the bioequivalence and pharmacokinetics study. After extracted from plasma samples with ethyl acetate, analysis was performed in selected ion monitoring (SIM) mode with a positive electrospray ionization (ESI) interface with a mobile phase consisted of methanol and water (0.4% glacial acetic acid and 4 mmol x L(-1) ammonium acetate, 43 : 57, v/v). The linear concentration range of the calibration curves was 1.0-160.0 ng x mL(-1) for pentoxyverine citrate, inter- and intra-precision (RSD) was less than 12.5%, accuracy (RE) was in +/- 13.5% and absolute recovery was more than 80%. The method was proved simple, rapid, sensitive, specific and suitable for pharmacokinetic and bioequivalence study of Yufenweilin capsule containing pentoxyverine citrate.

Extraction-free spectrophotometric assay of the antitussive drug pentoxyverine citrate using sulfonephthalein dyes.

Pentoxyverine citrate (PEN-citrate) is an antitussive (cough suppressant) drug used for cough associated with illnesses like common cold. In this work, PEN-citrate is quantified by applying a simple, direct and accurate spectrophotometric method in pure form, pharmaceutical formulation (Cabella®, 2.13 mg/mL) and human serum samples. The formation of a stable yellow ion-pair with sulfonephthalein dyes; bromocresol green (BCG), bromophenol blue (BPB), bromothymol blue (BTB), bromocresol purple (BCP), bromochlorophenol blue (BChPB) and bromoxylenol blue (BXB), in three nonpolar solvents (chloroform, dichloromethane, acetonitrile) is used as the basis for this method. This is the first assay method reported for the quantification of PEN-citrate using the sulfonephthaleins as coloring agents. Diverse parameters were investigated in order to optimize the calibration curve conditions. The strategy was validated with respect to linearity range, precision, accuracy, specificity, robustness and limits of detection (LOD) and quantification (LOQ). In addition, solvents of different polarities were utilized to investigate the color reaction, light absorption and to allow for increasing the method sensitivity. Beer's law is obeyed over a wide concentration range (up to 42.05 µg/mL in case of BTB method). LOD and LOQ values reached 0.22 and 0.72 µg/mL, respectively, upon using BChPB. The relative standard deviation (%RSD) was ≤1.91% while correlation coefficient values (r) were ≥ 0.9974. High molar absorptivity values and low values of Sandell's sensitivity were obtained indicating that the proposed methods are highly sensitive. The validated methods were applied to the analysis of PEN-citrate in the dosage form and human serum samples where the drug was successfully resolved from the pharmaceutical additives and serum components with recoveries ≥98.98%.

Influence of organic anion transporter 1/3 on the pharmacokinetics and renal excretion of ginkgolides and bilobalide.

ETHNOPHARMACOLOGICAL RELEVANCE: The major terpene lactones of ginkgo biloba extract (GBE) include ginkgolide A, B, C and bilobalide are used for the protection of cardiovascular, cerebrovascular and neurodegenerative diseases. Terpene lactones are orally bioavailable and predominantly eliminated via the renal pathway. However, information on the transporters involved in the pharmacokinetics (PK) and renal excretion of terpene lactones is limited. AIM OF THE STUDY: The objective of this study is to assess the role of OAT1/3 which are important transporters in the human kidney in the PK and renal excretion ginkgolide A, B, C and bilobalide. MATERIALS AND METHODS: Uptake of ginkgolide A, B, C and bilobalide in Madin-Darby Canine Kidney (MDCK) and human embryonic kidney 293 (HEK293) cells overexpressing OAT1 or OAT3, respectively were studied. To verify the result from in vitro cell models, the studies on PK, kidney accumulation and urinary excretion of ginkgolide A, B, C and bilobalide were carried out in rats. RESULTS: The result showed that ginkgolide A, B, C and bilobalide are low-affinity substrates of OAT1/3. Following co-administration with probenecid, a typical inhibitor of OAT1/3, the rat plasma concentrations of ginkgolide A, B, C and bilobalide increased significantly. AUC showed a significant increase in the probenecid-treated rats compared to control rats (893.48 vs. 1123.85, 314.91 vs. 505.74, and 2724.97 vs. 3096.40 µg/L*h for ginkgolide A, B and bilobalide, respectively), while the clearance of these compounds significantly decreased. The accumulation of ginkgolide A, B and bilobalide in the kidney of the probenecid-treated rats was reduced by 1.8, 2.4, and 1.5-fold, respectively; further reducing the cumulative urinary recovery of these compounds. CONCLUSION: The findings indicated that ginkgolide A, B and bilobalide are excreted via OAT1/3-mediated transport in the kidney and OAT1/3 inhibitor significantly influence the PK ginkgolides and bilobalide.

Development and validation of a high-throughput zwitterionic hydrophilic interaction liquid chromatography solid-phase extraction-liquid chromatography-tandem mass spectrometry method for determination of the anti-influenza drug peramivir in plasma.

An assay for the analysis for the quantification of the anti-influenza drug peramivir in human plasma using high-throughput zwitterionic (ZIC) hydrophilic interaction liquid chromatography (HILIC) solid-phase extraction (SPE) in a 96-wellplate format and liquid chromatography coupled to positive tandem mass spectroscopy has been developed and validated. The ZIC-HILIC SPE efficiently removed sources of interference present in the supernatant after protein precipitation of plasma proteins. The main advantage of the ZIC-HILIC SPE sample preparation step was that it allowed load and elution conditions to be optimised to extract only peramivir and minimize co-extraction of lipophilic phospholipids. The method was validated according to published US Food and Drugs Administration guidelines and showed excellent performance. The assay was validated over two calibration ranges (0.952-500 and 50-50,000 ng/mL) to support analysis of peramivir after intra-venous administration. The lower limit of quantification for peramivir in plasma was 1 ng/mL and the upper limit of quantification was 50,000 ng/mL. The within-day and between-day precisions expressed as RSD, were lower than 8% at all tested quality control concentrations and below 11% at the lower limit of quantification. Validation of over-curve samples ensured that it would be possible with dilution if samples went outside the calibration range.

Simultaneous determination of ginkgolides A, B, C and bilobalide in plasma by LC-MS/MS and its application to the pharmacokinetic study of Ginkgo biloba extract in rats.

A new liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of ginkgolides (includes ginkgolide C for the first time) and bilobalide in plasma is presented. Ketoprofen was used as an internal standard, and sample pre-treatment consisted of a liquid-liquid extraction. Chromatographic separation was achieved on a 5 microm Shiseido C8 column (150 mm x 2.0 mm i.d., particle size 5 microm) with a mobile phase consisting of methanol/ 6 mM ammonium acetate (60/40, v/v) at a flow rate of 0.3 ml/min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring (MRM) under negative ionization mode with an atmospheric pressure chemical ionization (APCI) interface. The method was validated in terms of intra- and inter-day precision (<12.7%), accuracy (within +/- 7.0%), linearity, specificity and stability. In addition, matrix effects of ginkgolides and bilobalide in plasma were evaluated in different reconstitution solvents. Smaller matrix effects were observed for reconstitution solvents containing less organic solvent. The method has been successfully applied to a pharmacokinetic study of Ginkgo biloba extract in rats after intravenous administration. This is the first report of pharmacokinetic data for ginkgolide C.

F15063, a potential antipsychotic with dopamine D(2)/D(3) antagonist, 5-HT(1A) agonist and D(4) partial agonist properties: (IV) duration of brain D2-like receptor occupancy and antipsychotic-like activity versus plasma concentration in mice.

F15063 (N-[(2,2-dimethyl-2,3-dihydro-benzofuran-7-yloxy)ethyl]-3-(cyclopent-1-enyl)-benzylamine fumarate salt) is a novel potential antipsychotic with dopamine D(2)/D(3) blocking properties and agonist activity at 5-HT(1A) and D(4) receptors. The pertinent parameter for pharmacological activity of antipsychotics appears to be central D2-like receptor occupancy. However, its duration is not necessarily correlated with drug plasma levels, on which clinical dosing regimens are often based. Thus, we compared in mice the duration of actions of F15063 and haloperidol to (1) inhibit apomorphine-induced climbing and sniffing (behavioural measures of D2-like receptor antagonism) and (2) occupy D2-like receptors in vivo in the striatum and olfactory tubercles (inhibition of [(3)H]nemonapride binding). Finally, we measured plasma levels of F15063. D2-like receptor occupancy in the striatum remained elevated at 1, 4 and 8 h postadministration, with both F15063 (ID(50): 7.1, 3.6 and 16.5 mg/kg p.o., respectively) and the typical antipsychotic, haloperidol (ID(50): 1.4, 0.52 and 0.53 mg/kg p.o., respectively). This was paralleled by a protracted inhibition of apomorphine-induced climbing (ED(50): 0.9, 2.8 and 3.6 mg/kg p.o., and 0.21, 0.37 and 0.87 mg/kg p.o., respectively, for F15063 and haloperidol). In contrast, after administration of 10 mg/kg p.o. of F15063, its plasma levels decreased rapidly: 15.2, 2.1 and 0.6 ng/ml, 1, 4 and 8 h after administration, respectively. A similar pattern of results was observed when F15063 and haloperidol were administered i.p. and s.c., respectively. To summarise, the time-course of D2-like receptor occupancy and inhibition of apomorphine-climbing (and sniffing) behaviours was similarly long lasting with F15063 and haloperidol. In addition, the durations of action of F15063 and haloperidol in a behavioural model of antipsychotic-like activity were closely correlated to their occupancy of central D2-like receptors, and much longer than their presence in plasma.

Pharmacokinetics and safety of intravenous peramivir, neuraminidase inhibitor of influenza virus, in healthy Japanese subjects.

BACKGROUND: Intravenous peramivir is a potent neuraminidase (NA) inhibitor with activity against influenza A and B viruses. The early use of NA inhibitors has been shown to reduce mortality in influenza patients. METHODS: To evaluate the pharmacokinetics of peramivir and confirm the safety and tolerability of multiple infusions of peramivir in healthy Japanese subjects, two Phase I, single-centre, randomized, double-blind and placebo-controlled studies consisting of a multiple-dose study and a high-dose study were conducted. RESULTS: Multiple intravenous infusions of peramivir were well tolerated up to 800 mg once a day and 400 mg twice daily for 6 days. Dose proportionalities for maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) were established up to the 800 mg dose. Approximately 90% of unchanged peramivir was excreted into urine within 12 h after treatment with 800 mg of peramivir. The peramivir plasma and upper respiratory tract fluid levels were significantly higher than the 50% inhibition concentrations for NA enzyme activity (IC50) of epidemic influenza viruses, including those harbouring the H274Y mutation. CONCLUSIONS: The pharmacokinetic properties obtained here for intravenous peramivir are consistent with the previously reported clinical efficacy and safety of this antiviral.

Determination of Ginkgolides A, B, C, J and Bilobalide in Plasma by LC-ESI (-)/MS/MS (QQQ) and its Application to the Pharmacokinetic Study of Ginkgo Biloba Extract in Rats.

A simple, rapid, and specific high-performance liquid chromatograph coupled with a tandem mass spectrometry method has been developed and validated for the quantification of ginkgolides in rat plasma, and the main pharmacokinetic parameters of ginkgolides after oral administration of Ginkgo biloba extract (GBE) was acquired. Methods: Plasma samples were pretreated with ethyl acetate extraction. Sulfamethoxazole was used as the internal standard (IS). Chromatographic separation was achieved on an Eclipse XDB-C18 column (2.1 mm×150 mm, 5 µm) with a mobile phase consisting of methanol/0.1% formic acid water (gradient elution: 0~25 min (77:23)→(60:40), V/V) at a flow rate of 0.3 mL·min-1. The detection was performed on a triple quadruple tandem mass spectrometer using an electrospray ionization (ESI) source for 25 min. The detection was operated by multiple reaction monitoring(MRM) under negative ionization mode of the transitions of m/z 325→163 for BB, 469→423 for GJ, 439→125 for GC, 453→351 for GA, 423→367 for GB and of m/z 252→156 for sulfamethoxazole (IS) respectively. Results: The pharmacokinetic properties of BB, GJ, GA, GB and GC were in line with the open 2-compartment model after oral administration of GBE in rats; The pharmacokinetic parameters of various lactones were calculated, and drugs-time curve and the curve fitting diagram of 5 ginkgolides were drew; The absorption and distribution rate of BB, GJ, GA, GB and GC were fast in rats in vivo, and half-life of absorption was less than 3 h. Conclusion: The developed LC-ESI (-)/MS/MS (QQQ) method was successfully applied to assess the pharmacokinetic parameters and oral bioavailability of ginkgolides in rats after administration of GBE, which can provide basis for further clinical efficacy studies.

A rapid LC-MS/MS quantification of peramivir using a simple and inexpensive sample precipitation: application to PK.

AIM: Peramivir is a newly approved selective neuraminidase inhibitor designed to inhibit influenza virus infection. METHODOLOGY/RESULTS: We report a robust and sensitive method utilizing simple precipitation extraction with LC-MS/MS for the high-throughput quantification. Addition of 0.06 M of ammonium formate and 0.1% formic acid in mobile phase could help reduce the matrix effect. This method uses 100 µl of plasma and covers a linear concentration range from 5 to 10,000 ng/ml. Other validation parameters are also evaluated and meet regulatory expectations by US FDA guidelines. CONCLUSION: The developed HPLC-MS/MS method has been successfully applied to support a clinical pharmacokinetic study. The strategy presented here can be applied elsewhere and may be useful for other amphiphilic drugs.

Caramiphen-induced block of sodium currents and spinal anesthesia.

The underlying mechanisms for the action of caramiphen used in local anesthesia are not well understood. The purpose of this study was to evaluate the block of caramiphen on voltage-gated Na⁺ channels and in spinal anesthesia. We investigated the effect of caramiphen on voltage-gated sodium channels in differentiated neuronal NG108-15 cells as well as on rat motor function, proprioception, and pain behavior (when administered intrathecally). In in vitro experiments, lidocaine produced concentration- and state-dependent effects on tonic block of voltage-gated Na⁺ currents (IC50 of 66.2 and 212.9 µM at holding potentials of -70 and -100 mV, respectively). Caramiphen exhibited a milder state-dependence of block (IC50 of 52.1 and 99.5 µM at holding potentials of -70 and -100 mV, respectively). Lidocaine showed a much stronger frequency-dependence of block than caramiphen: with high frequency stimulation (3.33 Hz), 50 µM caramiphen elicited an additional 20% blockade, whereas the same concentration of lidocaine produced 50% more block. In in vivo experiments, caramiphen with a more sensory-selective action over motor blockade was more potent than lidocaine (P<0.05) in spinal anesthesia. On an equipotent basis (25% effective dose (ED25), ED50, and ED75), the duration of caramiphen at producing spinal anesthesia was longer than that of lidocaine (P<0.01). Our data revealed that caramiphen had a more potent, prolonged spinal blockade with a more sensory/nociceptive-selective action over motor blockade in comparison with lidocaine. Spinal anesthesia with caramiphen could be through the suppression of voltage-gated Na⁺ currents.

Plasma level studies of penbutolol after oral dose in man.

Plasma levels of penbutolol (HOE 893d) were determined in eight healthy adult male subjects after oral administration of 50-mg capsules. Fast absorpiton of the drug from the gastrointestinal tract was indicated by the rapid increase in plasma levels during the absorption phase, with a peak time at about 1 hour after dosing in all subjects. After the peak level, plasma concentrations declined biexponentially, with an average half-life of 2.5 and 27 hours for the fast and slow disposition phases, respectively. These values were in good agreement with data previously found for this drug. Cumulative excretion of intact drug in the urine of the eight subjects during 72 hours after dosing was less than 4 per cent, except for one subject who excreted 9.82 per cent of the dose. Large individual variations were found for area under the plasma level curves, disposition rates, and amounts of intact drug excreted in the urine. Significant pharmacologic effects were noted in all eight subjects at the 50-mg dose level, and mild side effects were evident in one half of these subjects. The average drop in blood pressure and pulse rate for all subjects was 26/18 mm Hg and 19 beats per minute, respectively.

Fluorescence properties of albumin blue 633 and 670 in plasma and whole blood.

We have determined the fluorescence characteristics of two long wavelength dyes, albumin blue 633 (AB633) and 670 (AB670), in plasma and blood to evaluate the possibility of making direct fluorescence sensing measurements in blood. Using binding and lifetime measurements we were also able to show that these dyes bind selectively to human serum albumin (HSA) in plasma and blood. By measuring changes in the mean lifetime of AB670 with changes in the HSA concentration, we showed that lifetime-based sensing can be used to monitor HSA concentrations using these albumin blue dyes. Anisotropy measurements for AB633 and AB670 in plasma and blood revealed high anisotropy values for these dyes in these media. Exploiting these high anisotropies, we were also able to determine HSA concentrations in plasma and blood mimics using changes in AB670 anisotropy with HSA concentration. These results show that, apart from being able to make fluorescence measurements directly in plasma and blood, it is possible to sense directly for specific plasma/blood components using fluorescent probes that bind preferentially to them.

Quantitative determination of N-(trans-2-dimethylaminocyclopentyl)-N-(3',4'-dichlorophenyl) propanamide and its N-demethyl metabolite in dog serum by gas chromatography.

A gas chromatographic-electron capture (GC-EC) method has been developed for the determination of N-(trans-2-dimethylaminocyclopentyl)-N-(3',4'-dichlorophenyl)pr opanamide, a potential antidepressant drug, and its N-demethyl metabolite in serum. The GC-EC system employed a 3% OV-17 on 100/120 mesh Supelcoport, 2-m X 2-mm i.d. glass column and an isothermal temperature of 195 degrees C. The parent drug and metabolite were extracted from alkalinized serum (pH approximately 13) with toluene, back-extracted into an acidic solution (pH approximately 1), and finally, after adjusting to pH 13, extracted again with toluene. The extensive sample cleanup was necessary to remove serum components which interfered with the analysis. The analytical method was shown to give quantitative recovery of the drug and metabolite, to be linear over a 100-fold concentration range, and to have the necessary precision and sensitivity to detect and quantify as little as 1 ng/mL of the drug or its metabolite. The method has been employed to determine the serum level of drug and metabolite in dogs receiving a single oral dose and to determine the possible correlation between the administered dose and serum levels.

Use of nitrogen-specific detector for GLC determination of caramiphen in whole blood.

A sensitive GLC determination of caramiphen in whole blood was developed using a nitrogen-specific detector. The method permits the determination of levels of caramiphen as low as 2.5 ng/ml of blood and provides sufficient sensitivity and reproducibility for clinical use.

Influence of pharmaceutical quality on the bioavailability of active components from Ginkgo biloba preparations.

To be effective, herbal medicinal products are expected to meet comparable standards concerning the assessment of efficacy, safety and biopharmaceutical quality as chemically defined synthetic drugs as food supplements. However, these requirements are often not fulfilled, particularly regarding the characterization of biopharmaceutical properties such as in-vitro dissolution and in-vivo bioavailability. With respect to the relevance of biopharmaceutical quality of herbal medicinal products, two different Ginkgo biloba brands (test product: Ginkgo biloba capsules; reference product: Ginkgold) were analysed for dissolution rates and bioavailability of the most relevant active ingredients. Dissolution rates at pH 1 and 4.5 were determined according to the USP 23. The relative bioavailability of ginkgolide A, ginkgolide B and bilobalide was investigated after single oral administration of 120 mg Ginkgo biloba extract as tablets or capsules. Bioavailability data (area under the curve and peak concentration in plasma) were clearly different and did not show bioequivalence of test and reference products. The slow in-vitro dissolution of the test product resulted in a large decrease in bioavailability. These results indicate for the first time that the pharmaceutical properties of a herbal medicinal product have a significant impact on the rate and extent of drug absorption, and very likely on efficacy in humans.