Transfer of epinastine to infants through human breast milk

The purpose of this study was to develop an analytical method for analyzing epinastine in breast milk and maternal plasma samples to determine the safety of epinastine in breastfed infants. Six nursing mothers took epinastine hydrochloride (20 mg) once a day for 7 days, while a nursing mother took it for 30 days. Breast milk and blood samples were collected 2, 4, and 10 h after administration from the volunteers. A liquid chromatography-mass spectrometry system was used to analyze samples pretreated by liquid-liquid extractions. The concentration of epinastine in human milk was 10.3-33.5 ng/mL after 2 h, 9.1-63.8 ng/mL after 4 h, and 8.3-28.9 ng/mL after 10 h. The increase achieved 4 h after administration indicates that epinastine was transferred into human breast milk. However, the milk-to-plasma ratio had a wide range (0.82-3.39), while the relative infant dose at 4 h was 0.36-2.49%, which is lower than the safety level of transferability (10%). Moreover, the plasma levels of epinastine in two infants were slightly below the quantification limit. Overall, our results suggested that epinastine can safely be used by nursing mothers without affecting their infants.

Development and validation of a specific and sensitive LC-MS/MS method for determination of eslicarbazepine in human plasma and its clinical pharmacokinetic study

In this work, we developed and validated the specific, sensitive and simple LC-MS/MS method for quantification of eslicarbazepine in human plasma. The analyte samples were prepared through a simple one-step protein precipitation method by acetonitrile. The chromatographic separation was operated on an economical Hanbon ODS-2 C18 column (150 mm × 2.1 mm, 10 μm) with isocratic elution using 10 mM ammonium acetate containing 0.01% formic acid and acetonitrile (72:28, v/v) as the mobile phase at the flow rate of 0.5 mL/min. The mass quantification was carried on the multiple reaction monitoring (MRM) of the transitions of m/z 255.1 → 194.1 for eslicarbazepine and m/z 446.1 → 321.1 for glipizide (the internal standard), respectively. The established method was validated with acceptable specificity, linearity, accuracy, precision, extraction recovery, matrix effect and stability in accordance with FDA regulations. At last, the validated method was successfully applied to determination of eslicarbazepine in human plasma obtained from clinical study.

Safety, Tolerability, and Pharmacokinetic Profile of BIA 2-093, a Novel Putative Antiepileptic, in a Rising Multiple-Dose Study in Young Healthy Humans

This was a double-blind, randomized, placebo-controlled study to investigate rising oral doses of BIA 2-093 (S-(-)-10-acetoxy-10,11-dihydro-5H-dibenz/b,f/azepine-5-carboxamide), a putative new antiepileptic drug. Within each of 4 dosage groups of 8 healthy male adult subjects, 2 subjects were randomized to receive placebo, and the remaining 6 subjects were randomized to receive BIA 2-093 (200 mg bid, 400 mg qd, 800 mg qd, and 1200 mg qd) for 8 days. Concentrations of BIA 2-093 in plasma or urine were generally not measurable. Median maximum plasma concentrations of the major metabolite (licarbazepine, (+/-)-10,11-dihydro-10-hydroxy-5H-dibenz/b,f/azepine-5-carboxamide) were attained (t(max)) at 2 to 3 h postdose; thereafter, plasma concentrations declined with a mean apparent terminal half-life of 9 to 13 h following repeated dosing. The extent of systemic exposure to licarbazepine increased in an approximately dose-proportional manner following single and repeated administration. Licarbazepine accumulated in plasma following repeated administration of BIA 2-093; the mean extent of accumulation (R(O), calculated from AUC(0-tau) (day 8)/AUC(0-tau) (day 1)) was 3.0 after repeated, twice-daily dosing and 1.4 to 1.7 after once-daily dosing. Steady-state plasma licarbazepine concentrations were attained at 4 to 5 days of once- or twice-daily dosing, consistent with an effective half-life on the order of 20 to 24 h. The mean renal clearance of licarbazepine from plasma was approximately 20 to 30 mL/min, which is low compared with the glomerular filtration rate. The total amount of licarbazepine recovered in urine was approximately 20% within 12 h postdose and 40% within 24 h postdose. All adverse events were mild in severity, except for 1 case of somnolence of moderate severity, which occurred in a subject receiving 1200 mg BIA 2-093. The incidence of adverse events was similar between all treatment groups, including placebo. There were no serious adverse events. In conclusion, BIA 2-093 was well tolerated and appeared to be rapidly and extensively metabolized to licarbazepine following single and repeated administration to healthy young subjects.

TLN-4601 peripheral benzodiazepine receptor (PBR/TSPO) binding properties do not mediate apoptosis but confer tumor-specific accumulation

TLN-4601 is a farnesylated dibenzodiazepinone isolated from Micromonospora sp. with an antiproliferative effect on several human cancer cell lines. Although the mechanism of action of TLN-4601 is unknown, our earlier work indicated that TLN-4601 binds the PBR (peripheral benzodiazepine receptor; more recently known as the translocator protein or TSPO), an 18 kDa protein associated with the mitochondrial permeability transition (mPT) pore. While the exact function of the PBR remains a matter of debate, it has been implicated in heme and steroid synthesis, cellular growth and differentiation, oxygen consumption and apoptosis. Using the Jurkat immortalized T-lymphocyte cell line, documented to have negligible PBR expression, and Jurkat cells stably transfected with a human PBR cDNA, the present study demonstrates that TLN-4601 induces apoptosis independently of PBR expression. As PBRs are overexpressed in brain tumors compared to normal brain, we examined if TLN-4601 would preferentially accumulate in tumors using an intra-cerebral tumor model. Our results demonstrate the ability of TLN-4601 to effectively bind the PBR in vivo as determined by competitive binding assay and receptor occupancy. Analysis of TLN-4601 tissue and plasma indicated that TLN-4601 preferentially accumulates in the tumor. Indeed, drug levels were 200-fold higher in the tumor compared to the normal brain. TLN-4601 accumulation in the tumor (176 μg/g) was also significant compared to liver (24.8 μg/g; 7-fold) and plasma (16.2 μg/mL; 11-fold). Taken together our data indicate that while PBR binding does not mediate cell growth inhibition and apoptosis, PBR binding may allow for the specific accumulation of TLN-4601 in PBR positive tumors.

Simultaneous multiresponse optimization applied to epinastine determination in human serum by using capillary electrophoresis

Experimental design and optimization techniques were implemented for the development of a rapid and simple capillary zone electrophoresis method (CZE) for the determination of epinastine hydrochloride in human serum. The effects of five factors were studied on the resolution between the peaks for the target analyte (epinastine hydrochloride) and lidocaine hydrochloride, used as internal standard, as well as on the analysis time. The factors were the concentration and pH of the buffer, the injection time, the injection voltage and the separation voltage. The separation was carried out by using an uncoated silica capillary with 50 microm i.d. and total length 64.5 cm (150 microm of path length) and UV detection (200 nm). Multiple response simultaneous optimization by using the desirability function was used to find experimental conditions where the system generates desirable results. The optimum conditions were: sodium phosphate buffer solution, 16.0 mmol L(-1); pH 8.50; injection voltage, 20.0 kV; injection time, 30 s; separation voltage, 26.7 kV. The method was confirmed to be linear in the range of 2.0-12 ng mL(-1). The injection repeatability of the method was evaluated by six injections at three concentration levels, while intra-assay precision was assessed by analysing a single concentration level, yielding a CV's of ca. 1% for standard and 2% for serum samples. Accuracy was evaluated by recovery assays and by comparing with an HPLC method, the results being acceptable according to regulatory agencies. The rudgeness was evaluated by means of an experimental Plackett-Burman design, in which the accuracy was assessed when small changes were set in the studied parameters. Clean-up of human serum samples was carried out by means of a liquid-liquid extraction procedure, which gave a high extraction yield for epinastine hydrochloride (93.00%).

Simultaneous and enantioselective liquid chromatographic determination of eslicarbazepine acetate, S-licarbazepine, R-licarbazepine and oxcarbazepine in mouse tissue samples using ultraviolet detection

Herein is reported, for the first time, a simple and reliable chiral reversed-phase liquid chromatographic method coupled to ultraviolet (UV) detection for simultaneous determination of eslicarbazepine acetate (ESL) and its metabolites, S-licarbazepine (S-LC), R-licarbazepine (R-LC) and oxcarbazepine (OXC), in mouse plasma and brain, liver and kidney tissue homogenates. All analytes and the internal standard were extracted from plasma and tissue homogenates by a solid-phase extraction procedure using Waters Oasis hydrophilic-lipophilic balance cartridges. The chromatographic separation was performed by isocratic elution with water/methanol (88:12, v/v), pumped at a flow rate of 0.7 mL min(-1), on a LichroCART 250-4 ChiraDex (beta-cyclodextrin, 5 microm) column at 30 degrees C. The UV detector was set at 225 nm. Calibration curves were linear (r2 > or = 0.996) in the ranges 0.4-8 microg mL(-1), 0.1-1.5 microg mL(-1) and 0.1-2 microg mL(-1) for ESL and OXC and in the ranges 0.4-80 microg mL(-1), 0.1-15 microg mL(-1) and 0.1-20 microg mL(-1) for R-LC and S-LC in plasma, brain and liver/kidney homogenates, respectively. The overall precision not exceeded 11.6% (%CV) and the accuracy ranged from -3.79 to 3.84% (%bias), considering all analytes in all matrices. Hence, this method will be a useful tool to characterize the pharmacokinetic disposition of ESL in mice.

A Novel Enantioselective Microassay for the High-Performance Liquid Chromatography Determination of Oxcarbazepine and Its Active Metabolite Monohydroxycarbazepine in Human Plasma

A simple and innovative assay is described that allows the determination of the antiepileptic drug oxcarbazepine and the chiral separation of the two enantiomers of its active metabolite monohydroxycarbazepine (licarbazepine). The assay requires liquid-liquid extraction of the sample (200 microL) into tert-butyl methyl ether and dichloromethane, drying of the organic phase under a nitrogen stream, reconstitution with the mobile phase, and injection in the high-performance liquid chromatography system after filtering. Separation of oxcarbazepine, R-(-)-monohydroxycarbazepine, S-(+)-monohydroxycarbazepine, and the second-step metabolite 10,11-trans-dihydroxycarbamazepine (racemate) is achieved with a Chiralcel ODR column and potassium hexafluorophosphate/acetonitrile as mobile phase. Detection is by ultraviolet absorbance at 210 nm. Standard curves are linear (r2 > or = 0.999) over the range of 0.1 to 25 microg/mL for each analyte with a limit of quantification of 0.1 microg/mL (1 ng injected) for all compounds. Within-day and between-day precision is better than 12% and within-day and between-day accuracy is between 99% and 116% for each compound. These performance characteristics are adequate for pharmacokinetic studies and for therapeutic drug monitoring. However, because the two enantiomers of monohydroxycarbazepine exhibit similar pharmacologic activity, nonenantioselective assays are likely to be more cost-effective for therapeutic drug monitoring purposes.

Enantioselective HPLC-UV method for determination of eslicarbazepine acetate (BIA 2-093) and its metabolites in human plasma

Eslicarbazepine acetate (BIA 2-093) is a novel central nervous system drug undergoing clinical phase III trials for epilepsy and phase II trials for bipolar disorder. A simple and reliable chiral reversed-phase HPLC-UV method was developed and validated for the simultaneous determination of eslicarbazepine acetate, oxcarbazepine, S-licarbazepine and R-licarbazepine in human plasma. The analytes and internal standard were extracted from plasma by a solid-phase extraction using Waters Oasis HLB cartridges. Chromatographic separation was achieved by isocratic elution with water-methanol (88:12, v/v), at a flow rate of 0.7 mL/min, on a LichroCART 250-4 ChiraDex (beta-cyclodextrin, 5 microm) column at 30 degrees C. All compounds were detected at 225 nm. Calibration curves were linear over the range 0.4-8 microg/mL for eslicarbazepine acetate and oxcarbazepine, and 0.4-80 microg/mL for each licarbazepine enantiomer. The overall intra- and interday precision and accuracy did not exceed 15%. Mean relative recoveries varied from 94.00 to 102.23% and the limit of quantification of the assay was 0.4 microg/mL for all compounds. This method seems to be a useful tool for clinical research and therapeutic drug monitoring of eslicarbazepine acetate and its metabolites S-licarbazepine, R-licarbazepine and oxcarbazepine.

Effect of gender on the pharmacokinetics of eslicarbazepine acetate (BIA 2-093), a new voltage-gated sodium channel blocker

PURPOSE

To determine the effect of gender on the pharmacokinetics of eslicarbazepine acetate, a novel voltage-gated sodium channel blocker in the development for the treatment of epilepsy and bipolar disorder.

METHODS

Single-centre, open-label, parallel-group study in 12 female and 12 male healthy subjects. The study consisted of a single-dose (600 mg) period and a multiple-dose (600 mg, once-daily, for 8 days) period, separated by 4 days.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolized to eslicarbazepine (S-licarbazepine), the main active metabolite. Following a single-dose, arithmetic mean eslicarbazepine maximum plasma concentrations (C(max)) and area under the plasma concentration-time curve over 24 h (AUC(0-24)) and from 0 to infinity (AUC(0-infinity)) were, respectively, 9.3 microg/ml, 128.5 microg h/ml and 171.9 microg h/ml in male subjects and 10.1 microg/ml, 150.1 microg h/ml and 205.0 microg h/ml in female subjects. At steady-state, C(max), AUC(0-24) and AUC(0-infinity) were 15.5 microg/ml, 207.8 microg h/ml and 295.8 microg h/ml in male subjects, and 16.8 microg/ml, 214.5 microg h/ml and 295.2 microg h/ml in female subjects. Steady-state plasma concentrations were attained at 4 to 5 days of administration in both groups. Eslicarbazepine C(max), AUC(0-24) and AUC(0-infinity) female:male geometric mean ratios (90%CI) were, respectively, 1.09 (0.94; 1.24), 1.16 (1.00; 1.33) and 1.17 (0.99; 1.38) following single-dose, and 1.10 (0.97; 1.25), 1.04 (0.92; 1.17) and 1.01 (0.88; 1.16) at steady-state.

CONCLUSION

At steady-state, the pharmacokinetic profile of eslicarbazepine acetate was not affected by gender.

Optimization of the SPME Parameters and Its Online Coupling with HPLC for the Analysis of Tricyclic Antidepressants in Plasma Samples

Solid-phase microextraction (SPME)-liquid chromatography (LC) is used to analyze tricyclic antidepressant drugs desipramine, imipramine, nortriptyline, amitriptyline, and clomipramine (internal standard) in plasma samples. Extraction conditions are optimized using a 2(3) factorial design plus a central point to evaluate the influence of the time, temperature, and matrix pH. A Polydimethylsiloxane-divinylbenzene (60-mum film thickness) fiber is selected after the assessment of different types of coating. The chromatographic separation is realized using a C(18) column (150 x 4.6 mm, 5-microm particles), ammonium acetate buffer (0.05 mol/L, pH 5.50)-acetonitrile (55:45 v/v) with 0.1% of triethylamine as mobile phase and UV-vis detection at 214 nm. Among the factorial design conditions evaluated, the best results are obtained at a pH 11.0, temperature of 30 degrees C, and extraction time of 45 min. The proposed method, using a lab-made SPME-LC interface, allowed the determination of tricyclic antidepressants in in plasma at therapeutic concentration levels.

Simultaneous liquid chromatographic determination of lamotrigine, oxcarbazepine monohydroxy derivative and felbamate in plasma of patients with epilepsy

A very simple and fast method has been developed and validated for simultaneous determination of the new generation antiepileptic drugs (AEDs) lamotrigine (LTG), oxcarbazepine's (OXC) main active metabolite monohydroxycarbamazepine and felbamate in plasma of patients with epilepsy using high-performance liquid chromatography (HPLC) with spectrophotometric detection. Plasma sample (500 microL) pre-treatment was based on simple deproteinization by acetonitrile. Liquid chromatographic analysis was carried out on a Synergi 4 microm Hydro-RP, 150 mm x 4 mm I.D. column, using a mixture of potassium dihydrogen phosphate buffer (50mM, pH 4.5) and acetonitrile/methanol (3/1) (65:35, v/v) as the mobile phase, at a flow rate of 1.0 mL/min. The UV detector was set at 210 nm. Calibration curves were linear (mean correlation coefficient >0.999 for all the three analytes) over a range of 1-20 mg/mL for lamotrigine, 2-40 microg/mL for monohydroxycarbamazepine and 10-120 microg/mL for felbamate. Both intra and interassay precision and accuracy were lower than 7.5% for all three analytes. Absolute recoveries ranged between 100 and 104%. The present procedure describes for the first time the simultaneous determination of these three new antiepileptic drugs. The simple sample pre-treatment, combined with the fast chromatographic run permit rapid processing of a large series of patient samples.

Effect of Food on the Pharmacokinetic Profile of Eslicarbazepine Acetate (BIA 2-093)

OBJECTIVE

To investigate the effect of food on the pharmacokinetics of eslicarbazepine acetate (BIA 2-093), a new voltage-gated sodium channel antagonist.

MATERIAL AND METHODS

Single-centre, open-label, randomised, two-way crossover study in 12 healthy subjects. The study consisted of two consecutive treatment periods separated by a washout of 14 days or more. In each of the study periods subjects were administered a single dose of eslicarbazepine acetate 800 mg following either a standard high-fat content meal or 10 hours of fasting.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolised to BIA 2-005. Maximum BIA 2-005 plasma concentrations (C(max)) in fed (test) and fasting (reference) conditions were, respectively, 12.8 +/- 1.8 microg/mL and 11.3 +/- 1.9 microg/mL, and the areas under the plasma concentration time curve from 0 to infinity (AUC(infinity)) were, respectively, 242.5 +/- 32.1 microg.h/mL and 243.6 +/- 31.1 microg.h/mL (arithmetic mean +/- SD). The point estimate (PE) and 90% confidence interval (90% CI) of the test/reference C(max )geometric mean ratio were 1.14 and 1.04, 1.25, respectively; for the AUC(infinity) ratio, the PE and 90% CI were 1.00 and 0.95, 1.04, respectively. Bioavailability of eslicarbazepine acetate administered in fed and fasting conditions was similar and bioequivalence is accepted for both AUC(infinity) and C(max) because the 90% CI lies within the acceptance range of 0.80-1.25. No statistically significant differences were found in time of occurrence of C(max).

CONCLUSION

The presence of food had no significant effect on the pharmacokinetics of eslicarbazepine acetate and therefore this new voltage-gated sodium channel antagonist may be administered without regard to meals.

Eslicarbazepine Acetate (BIA 2-093)

PURPOSE

To investigate the bioavailability and bioequivalence of three different formulations of eslicarbazepine acetate (BIA 2-093): 50 mg/mL oral suspension (test 1), 200mg tablets (test 2) and 800mg tablets (reference).

DESIGN, SUBJECTS AND METHODS

Single-centre, open-label, randomised, three-way crossover study in 18 healthy subjects. The study consisted of three consecutive periods separated by a washout period of 7 days or more. Each subject received a single dose of eslicarbazepine acetate 800mg on three different occasions: 16mL of oral 50 mg/mL suspension, four 200mg tablets or one 800mg tablet.

RESULTS

Eslicarbazepine acetate was rapidly and extensively metabolised to BIA 2-005. Maximum BIA 2-005 plasma concentrations (Cmax) and area under the plasma concentration-time curve from time 0 to infinity (AUCinfinity) were, respectively (arithmetic mean +/- SD), 18.0 +/- 4.6 microg/mL and 325.7 +/- 64.9 microg x h/mL for test 1, 16.0 +/- 4.0 microg/mL and 304.2 +/- 66.0 microg x h/mL for test 2, and 17.0 +/- 4.1 microg/mL and 301.1 +/- 60.0 microg x h/mL for the reference formulation. Point estimate (PE) and 90% confidence intervals (CIs) for AUCinfinity test 1/reference geometric mean ratio were 1.09 and 1.01, 1.15; for Cmax ratio, PE and 90% CI were 1.07 and 0.97, 1.15. When test 2 and the reference formulations were compared, the PE and 90% CI were 0.99 and 0.94, 1.07 for the AUCinfinity ratio, and 0.94 and 0.86, 1.02 for the Cmax ratio. Bioequivalence of test versus reference formulations is thus accepted for both AUCinfinity and Cmax because the 90% CIs lie within the acceptance range of 0.80-1.25.

CONCLUSION

The pharmacokinetic profiles of eslicarbazepine acetate oral 50 mg/mL suspension, 200mg tablet and 800mg tablet formulations were essentially similar, and the formulations can be considered bioequivalent.

Assessment of the bioequivalence of two oxcarbazepine oral suspensions versus a film-coated tablet in healthy subjects

Oxcarbazepine (trileptal) oral suspension has been reformulated and a study was performed to compare the bioavailability after single doses and at steady state of the current and former oral suspension versus the marketed film-coated tablets and to compare the bioavailability of the current and former oral suspension. The results support the switch from the former oral suspension to the current oral suspension and also from both oral suspensions to the film-coated tablet and vice versa. The study was an open-label, single-center, 3-way crossover trial. Each treatment period consisted of a single dose of 600 mg oxcarbazepine on Day 1, 600 mg oxcarbazepine b.i.d. repeated administration from Day 4 up to including Day 7, and a final dose of 600 mg oxcarbazepine administered on the morning of Day 8. Blood samples were taken on Day 1, Day 7 and Day 8 (pre-dose). Plasma concentrations of the main metabolite of oxcarbazepine (MHD) were determined using a validated HPLC assay. The 2 oral suspensions were compared with the film-coated tablet as reference formulation under fasted conditions. Also the current oral suspension was compared with the former oral suspension. These comparisons were made using data following single dose administration and under steady state conditions. Plasma AUC for single dose and AUC(0-12h) at steady state and plasma Cmax, log-transformed (natural base) were used for the assessment of bioequivalence. The 90% confidence interval (CI) approach was used for testing bioequivalence. Bioequivalence was accepted if CI was contained within the region (0.8, 1.25). At steady state, both the former and the current oral suspensions showed bioequivalence with the film-coated tablet with respect to AUC and Cmax. The current oral suspension was also bioequivalent when compared to the former oral suspension with respect to AUC and Cmax. After single dose, the former oral suspension was bioequivalent when compared to the film-coated tablet with respect to both AUC and Cmax. However, the current oral suspension was bioequivalent to both the film-coated tablet and the former oral suspension with respect to AUC but not to Cmax.

Oxcarbazepine final market image tablet formulation bioequivalence study after single administration and at steady state in healthy subjects

A final market image (FMI) tablet formulation of oxcarbazepine was compared with the marketed formulation (current market formulation (CMF)) and with the clinical trial formulation (CTF) tablet used during clinical efficacy and safety studies. The goal of the study was to compare the bioavailability after single doses and at steady state of the FMI versus CMF and CTF as well. Additionally, the effect of food was evaluated on the final market formulation. The study was an open-label, single-center, 4-way crossover trial. Each treatment period consisted of a single dose of 600 mg OXC on Day 1. From Day 4 up to including Day 7, 600 mg b.i.d. were administered. A final dose of 600 mg was administered in the morning on Day 8. Blood samples were taken on Day 1 before and on Day 7 (predose) and on Day 8 (morning dose). Plasma concentrations of MHD (the main metabolite of OXC) were determined by using a validated HPLC assay. FMI as test formulation was compared with the CMF and CTF as reference formulations. FMI under fed conditions was also compared with FMI under fasting conditions. These comparisons were made using data following single-dose administration and steady state conditions. Plasma AUC for single dose or AUC(0-12h) for steady state, and plasma Cmax, log-transformed (natural base), were used for the assessment of bioequivalence. The 90% confidence interval (CI) approach was used for testing bioequivalence. Bioequivalence was accepted if the CI was contained within the region (0.8, 1.25). At steady state under fed conditions, tested formulation (FMI) was bioequivalent to CTF and with the reference marketed formulation (CMF) with regard to AUC and Cmax. After single dose under fed conditions, FMI and CTF were bioequivalent with regard to AUC and Cmax, and FMI and CMF were equivalent with regard to AUC but not Cmax. Food had no effect on the bioavailability of the FMI. These results clearly support the switch from the current market formulation (CMF) to the final market image tablet in the countries where Trileptal is or was already registered.

Metabolism of 10,11-dihydro-10-hydroxyimino-5H-dibenz/b, f/azepine-5-carboxamide, a potent anti-epileptic drug

1. 10,11-Dihydro-10-hydroxyimino-5H-dibenzo/b, f/azepine-5-carboxamide (BIA 2-024) is a new anti-epileptic drug similar to oxcarbazepine (OXC) in structure and efficacy, but with a preferred pharmacodynamic profile. It possesses high in vitro activity, but since oximes are usually metabolized to their corresponding ketones, it is important to know whether its is vivo potency is a result of acting as a prodrug of OXC or if it is acting on its own. 2. The drug was given orally to rats, mice and rabbits, the metabolites identified and pharmacokinetic profiles compared between those species. Furthermore, the pharmacokinetic profile of the main metabolite was established in the rat. The results were compared to in vitro metabolism studies with liver microsomes from different mammalian species and humans. 3. In an atypical reaction for oximes, BIA 2-024 in rats was rapidly (t(max) = 2h) metabolized to the non-active 10-nitro-derivative (BIA 2-254), whereas rabbits and particularly mice oxidized the oxime moiety to a much lower extent. BIA 2-254 was then transformed to OXC and subsequently to the 10-hydroxy derivative and other minor metabolites. 4. In vitro data showed a very similar cross-species behaviour as the in vivo results; human liver microsomes catalysed the oxidation of BIA 2-024 to the nitro metabolite only at a low rate, and the same was observed for the subsequent metabolism to OXC. 5. The results allow prediction of the in vivo metabolism of BIA 2-024 in humans, where this drug is most likely absorbed efficiently and excreted mainly as the parent compound with a relatively low hepatic clearance. With the exception of rat, BIA 2-024 does not act as a prodrug of OXC.

Pharmacokinetics of epinastine and a possible mechanism for double peaks in oral plasma concentration profiles

The pharmacokinetics of epinastine (EPN), an anti-allergic agent, was investigated in rats. The plasma concentration-time profile of EPN after intravenous (i.v.) administration was triexponential. After oral administration of EPN (7.5 and 20 mg/kg), the drug was rapidly absorbed, and Cmax was reached 2 h after dosing. A minor secondary peak was observed in EPN plasma concentration-time profiles at both doses. The bioavailability of EPN after oral dosing was 41 and 40%. The kinetic parameters (T 1/2, AUC and MRT) for unlabeled EPN were much smaller than those for 14C-EPN, which has already been reported. The total biliary excretion of EPN at a 7.5 mg/kg dose was 15.5% of the dose, but the percentage of conjugates in bile was extremely low and about 11% of the total biliary excretion. The increase in the plasma concentration in bile duct-linked rats after oral administration of EPN (20 mg/kg) was not observed, indicating that a secondary increase in drug concentration based on enterohepatic circulation was ruled out. When the gastrointestinal (GI)-transit of phenol red (PR) after oral administration of EPN (20 mg/kg) was estimated, the GI-transit of PR was significantly delayed, and at 3-4 h after dosing half of the PR dose reached the jejunum. The remaining EPN in the small intestine after oral administration (7.5 mg/kg) reached peak levels 2 h after dosing, but then partly increased again at 4 h. As a result, it was clarified that the double peaks observed after oral doses are mainly due to the delayed absorption of a part of EPN, based on the reduction in gastric motility caused by the drug.

Effects of terfenadine, astemizole and epinastine on electrocardiogram in conscious cynomolgus monkeys

We examined the effects of non-sedative histamine H1 receptor antagonists on the electrocardiogram (ECG) in conscious cynomolgus monkeys. Terfenadine (3 mg kg(-1) h(-1), i.v.) and astemizole (0.3 and 1 mg kg(-1) h(-1), i.v.) caused significant time-dependent increases in the QT interval and QTc Bazett (QTc). However, normal ECG forms were found during a 60-min infusion of epinastine (3 mg kg(-1) h(-1) i.v.). A higher dose of epinastine (10 mg kg(-1) h(-1), i.v.) increased the QTc and PR interval only 5 min after the start of the infusion. The minimum plasma concentrations of terfenadine, astemizole and epinastine which caused QTc prolongation were 85, 35 and over than 3600 ng/ml, respectively. These drugs did not alter the PQ and QRS intervals and did not cause arrhythmia or atrioventricular block. Our results are consistent with the clinical observation that prolongation of QTc is caused by terfenadine and astemizole but not by epinastine. Thus, measurement of QTc in cynomolgus monkey appears to be a useful approach for evaluating the potential cardiotoxicity of histamine H1 receptor antagonists.

Quantitative determination of epinastine in plasma by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for the quantitative determination of epinastine, a non-sedating histamine H1 receptor antagonist, in rat plasma, was developed. A 100-microliters volume of plasma sample was spiked with a solution of internal standard (diphenidol) and extracted with dichloromethane under alkaline conditions. The extract was applied onto the HPLC system and detected by ultraviolet absorption at a wavelength of 220 nm. The linearity of the calibration curve was preserved over the concentration range of 20-1000 ng/ml. Both intra-assay variation and relative error were less than 5% for the plasma containing 50 ng/ml or 1000 ng/ml of epinastine hydrochloride. The analytical method presented here should be useful for the investigation of the pharmacokinetic properties of epinastine, which is of clinical significance.

Positron emission tomographic study of central histamine H1-receptor occupancy in human subjects treated with epinastine, a second-generation antihistamine

Histamine H1-receptor occupancy in the human brain was measured in healthy young volunteers by positron emission tomography (PET) using [11C]doxepin. d-Chlorpheniramine, a selective and classical antihistamine, occupied 76.8 +/- 4.2% of the averaged values of available histamine H1 receptors in the frontal cortex after its administration in a single oral dose of 2 mg. Epinastine, a non-sedative antihistamine, occupied 13.2 +/- 18.5% of the available H1 receptors in the human frontal cortex after its administration in a single oral dose of 20 mg. There was significant correlation between H1 receptor occupancy by epinastine and its plasma concentration in each subject. PET data on the human brain were essentially compatible with those on H1-receptor occupancy in the guinea pig brain as determined by an in vivo binding technique, although for the same H1-receptor occupancy, the dose was less in humans than in guinea pigs. Our PET studies demonstrated that receptor occupancy by a second-generation H1 antagonist, epinastine, was less than 20% of the total H1 receptors, and that the low receptor occupancy was closely related to the low incidence of central side effects.

Pharmacokinetics of the antiarrhythmic agent tiracizine: steady state kinetics in comparison with single-dose kinetics

Serum and urine kinetics of unchanged tiracizine (T), a new class I antiarrhythmic agent, and three metabolites (M1, 2, and 3) were assessed in eight healthy extensive metabolizers after a single oral administration of 50 mg tiracizine and during steady state (50 mg b.i.d.). Additionally, tiracizine-induced ECG changes were measured. Considerable accumulation of M1 and M2 was observed during repeated dosing (M1, Cmax,ss = 391.8 ng mL-1 against Cmax,sd = 132.8 ng mL-1; M2, Cmax,ss = 143.2 ng mL-1 against Cmax,sd = 25.8 ng mL-1). However, significant increases of AUC (AUC tau = 261.9 ng h mL-1 against AUC0-infinity,sd = 182.9 ng h mL-1), Cmax (Cmax,ss = 75.9 ng mL-1 against Cmax,sd = 56.9 ng mL-1) and t 1/2 beta (t 1/2 beta,ss = 4.0 h against t 1/2 beta,sd = 2.4 h) of the parent compound indicate non-linear kinetics. The significant decrease in renal clearance of all four substances as well as the decrease of non-renal tiracizine clearance with repeated dosing led to the assumption that non-linearity is due to saturable renal excretion and a fall in intrinsic tiracizine clearance. PQ time was prolonged significantly during steady state and culminated at the tmax of the parent compound, whereas there was no change in any ECG parameter after a single-dose administration of 50 mg tiracizine.

Dose dependent tiracizine disposition in healthy volunteers: serum and urine kinetics and dose related ECG-changes

The pharmacokinetics of tiracizine, a new class I antiarrhythmic agent, and 3 of its metabolites were assessed in serum and urine of 8 healthy extensive metabolisers after single oral administration of 50, 100, and 200 mg tiracizine hydrochloride. Additionally, tiracizine induced ECG-changes were compared between the different doses. With increasing doses enhancement of AUC and Cmax of tiracizine and its metabolites revealed a slight deviation from linearity indicated by exceeding the upper limits of the 95% nonparametric confidence interval set by 0.8-1.2 for the ratio (dose corrected parameters after the 100 and 200 mg dose, respectively)/(parameters after 50 mg). The increase of the dose corrected parameters after the 200 mg dose was about 1.3-fold compared with the 50 mg parameters for the parent compound as well as its metabolites. The significant decrease of the renal clearance of all 4 substances with increasing doses indicates that saturable tubular secretion mainly accounts for non-linearity. Due to the occurrence of non-linear (tubular secretion) as well as linear (glomerular filtration, hepatic metabolism) elimination in parallel, however, it is concluded that saturable tubular secretion is of minor importance at higher doses and should not be overestimated. However, there was some evidence for saturable hepatic tiracizine metabolism in 4 of the 8 participants. Therefore, a fall of apparent intrinsic clearance has also to be taken into consideration, especially at higher doses. PQ- and QRS-intervals were prolonged in a dose dependent manner and culminated at 1 h after drug intake. QTc-time, however, remained unchanged. A log-linear relationship between serum concentrations of the parent compound and PQ- as well as QRS-time is suspected for serum levels about 80 ng/ml, but has to be confirmed by individual pharmacokinetic-pharmacodynamic modelling. PQ- and QRS-intervals might be suitable for tiracizine therapeutic monitoring.

Determination of the tricyclic compound adosupine and its three metabolites in plasma and brain of rat using high-performance liquid chromatography

An analytical method for the detection in biological samples of the novel tricyclic compound adosupine (10-acetoamido-5-methyl-5,6-dihydro-11H-dibenzo[b,e]azepin-6 ,11-dione), which is capable of influencing various forms of urinary bladder hyperreflexia has been developed using high-performance liquid chromatography with UV detection. Liquid-liquid extraction was used to isolate the parent compound, three metabolites and an analogue (added as internal standard) from plasma and brain of rat. Adosupine was well separated from its three metabolites with 0.01 M disodium hydrogenphosphate-acetonitrile-methanol-nonylamine (59.986:38:2:0.014) at pH 4.5 as mobile phase using a C18 reversed-phase column. The standard curves were linear in the range 50-5000 ng/ml (or ng/g) for adosupine and metabolites in both plasma and brain. The between- and within-assay variations for high and low concentrations of the parent compound and the three metabolites were 8.2-14%. In the range 50-5000 ng/ml (or ng/g) the accuracy of the method was satisfactory, with the relative error always lower than 10%. Analytical recoveries of added adosupine and the three metabolites were higher than 82%. The method has been applied successfully, to investigate the pharmacokinetics of the drug and its distribution in the central nervous system of rats.

[The pharmacokinetics and metabolism of bonnecor in rats]

The pharmacokinetics of 14C-bonnecor after intravenous and oral administration was studied. The bioavailability was 70%. It was shown that administration of doses in the range of from 3 to 43 mg/kg as well as the repeated use of bonnecor failed to influence the pharmacokinetic parameters.

[Plasma levels of metapramine and its 3 major metabolites in patients with depression. Results and preliminary interpretations]

Metapramine (Timaxel) and his three major metabolites (19148 RP, 23669 RP, 19749 RP) have been determined in the plasma of 18 depressed inpatients treated by the antidepressant drug (12 women and 6 men; 7 are smokers and 11 non-smokers). In a steady state, interindividual variability is very important, especially for 23669 RP. No significant correlation exists between normalized doses (mg.kg-1) and normalized plasma concentrations (ng.ml-1/dose mg.kg-1) of metapramine or anyone of its metabolites. The plasma metabolic ratios reveal also important intraindividual and interindividual variability. Two populations of patients seem to exist: extensive metabolizers and relatively poor metabolizers, without apparent clinical consequence because 23669 RP shows an antidepressant activity. Women seem, with equal normalized doses, to exhibit higher plasma levels of unchanged metapramine than men, due to a lower protein-binding rather than to a more active metabolism. In patients who received a poly-medication smoking seems not to induce desmethylation of metapramine. The plasma metabolic ratios, compared by the analysis of variance and the Wilcoxon distribution-free test, are significatively influenced by sex and not by tobacco-smoking.

Pharmacokinetics of metapramine and its demethylated metabolites in plasma and brain of mice

Previous studies on pharmacokinetic parameters of tricyclic antidepressants (TCAs) in rodents have shown different results from those obtained for the same drugs in man. The kinetics of metapramine (META) and its major demethylated metabolites (METs) were studied in the SWISS CD 1 mouse after acute administration in order to establish the pharmacokinetic parameters in plasma and brain. The plasma half-life (T1/2) was very short (87 min) compared with the half-life (7 h) in man. The metabolism of META was intensive as was the transfer of META and its metabolites into the brain. The kinetic profiles of the substances were quite similar both in plasma and in brain, namely a bicompartment open model. META was rapidly absorbed (Tmax = 10 min) into and quickly eliminated (T 1/2 = 40 min) from the brain. These parameters were used to schedule sampling (blood and brain) at the appropriate time after acute administration of increased doses. The administered doses were significantly correlated to firstly the plasma or brain levels of META, secondly the plasma levels of the main monodemethylated metabolite (MET I), and thirdly the plasma or brain levels of META + METs. Finally, the evolution of plasma and brain levels of the substances was studied after repeated injections (i.e. every 40 min) and confirmed the high affinity of META and its metabolites for the brain regions.

Determination of clozapine in human serum by capillary gas chromatography

A gas chromatographic method using a fused-silica wide-bore capillary column and a nitrogen-specific detector for the determination of the antipsychotic agent clozapine in human serum is described. This method was found to be suitable for the determination of serum levels down to 1-2 ng/ml. The sensitivity, precision and accuracy of this method are adequate for studies on pharmacokinetics and bioavailability.

Plasma levels and therapeutic response with trimipramine treatment of endogenous depression

In a 6-week, double-blind study involving 34 endogenously depressed patients, plasma trimipramine levels of two dosage groups, 75-mg/day and 150-mg/day, were compared with regard to clinical efficacy as determined by scores on the Hamilton Rating Scale for Depression, the Clinical Global Impressions scale, and the Zung Self-Rating Depression Scale. Both dosage levels of trimipramine produced prompt, consistent, and progressive antidepressant effects. No correlation between plasma levels and clinical efficacy was found.

Determination of clozapine and its N-demethylated metabolite in plasma by use of gas chromatography-mass spectrometry with single ion detection

A gas chromatographic-mass spectrometric method with single ion detection has been developed for determination of clozapine and its N-demethylated metabolite norclozapine in plasma. Propylnorclozapine was used as internal standard and the mass spectrometer was adjusted to record the ion m/z 373 for the compounds analyzed. The precision of the method was found to be high, with a relative standard deviation of 6% or less for replicated samples. The limit of determination was 1.0 ng/ml for clozapine and 5.0 ng/ml norclozapine. A significant correlation was obtained between the daily oral dose of clozapine within the dose interval 100-800 mg/day and the plasma level of clozapine in 22 chronic schizophrenic patients. The plasma levels of clozapine and norclozapine were also significantly correlated. The quotient norclozapine/clozapine showed great interindividual variation and was not correlated to the daily dose of clozapine. The method is rapid and sensitive to allow evaluation of the pharmacokinetic properties of clozapine in the treatment of schizophrenic patients.

A carpipramine related fatality

A fatality following ingestion of the tricyclic antidepressant carpipramine (Prazinil) and ethyl alcohol is described. Carpipramine was quantitated by high performance liquid chromatography. The concentration of carpipramine was 2.0 mg/L in blood and 0.44 mg/L in urine. Ethyl alcohol was measured by headspace gas chromatography and found to be 105 mg/dL in blood and 55 mg/dL in the urine. Quantitative analysis of stomach contents was positive for carpipramine by thin-layer chromatography. To our knowledge, this is the first reported fatality involving carpipramine.

Investigation of the effect of fluperlapine on the EEG in schizophrenic patients

The investigations of the EEG during an open study with the antipsychotic drug fluperlapine in acute schizophrenic patients are reported. Due to ethical and practical considerations some of the common pharmaco-electroencephalographic procedures as well as placebo controlled study designs could not be applied in these patients. To overcome at least partly these limitations, intraindividual as well as interindividual correlations were used. They were computed between plasma concentrations of unchanged fluperlapine as well as its metabolite N-oxide fluperlapine, on one hand, and EEG variables, on the other. The intraindividual correlations can be computed either on the first day of the active treatment over various time points of that day (acute effects) or across several appointed treatment days always taking values at the same time during these days (chronic effects). The intraindividual correlations of a set of subjects were submitted to a sign test to obtain an overall result for the relation between the EEG and blood plasma levels of the drug. In this way an acute and a chronic effect of fluperlapine on the EEG could be shown consisting mainly of an increase in slow waves, a decrease in the alpha-activity and a tendency of beta-activity to decrease. A comparison of the correlations between the plasma levels of fluperlapine and the EEG variables with the correlations between the plasma levels of N-oxide fluperlapine and the EEG gives rise to the hypothesis that unchanged fluperlapine has a stronger effect on the EEG than its metabolite.

Kinetics of metapramine and its demethylated metabolites after single and chronic oral administration in man

The kinetics of metapramine and two of its demethylated metabolites were determined in six normal subjects after oral administration of a single 150 mg dose on day 1 and 3 X 50 mg dose on day 2-6. This study has shown that three demethylated metabolites are found in plasma beside metapramine. The monodemethylated metabolite I appeared to be the predominant one and the mean area under the plasma concentration curve (AUCo24) was 49% of the metapramine value. Its half-life was shorter (5.92 h) than that of metapramine (8.29 h). The kinetic profiles of metapramine and its major metabolites I and II were similar and data over 24 h could be fitted by a tri-exponential equation even though entero-hepatic cycles were observed. A high interindividual variability of data was found for both metapramine and its metabolites. There were no significant differences between men and women. The minimal plasma level (Cmin) seemed in agreement with the half-life of the drug.

Determination of metapramine, imipramine, trimipramine and their major metabolites in plasma by reversed-phase column liquid chromatography

The determination of metapramine, imipramine, trimipramine and their desmethyl metabolites after alkaline diethyl ether extraction from plasma is achieved by column liquid chromatography using two internal standards and mu Bondapak C18 column. Elution is carried out isocratically at 1 or 0.6 ml min-1 with two mixtures of acetonitrile-potassium dihydrogen phosphate-distilled water (45:55:10 for metapramine and its metabolites; 45:50:5 for imipramine, trimipramine and their metabolites). Detection is monitored by absorption at 254 nm. The detection limit is less than 5 ng ml-1 for each compound. The coefficients of variation (within-day and day-to-day) for the eight compounds are less than 11.3%. Interference from several possible co-medications is discussed. The technique can be used for routine therapeutic monitoring of the antidepressants as well as analytical toxicology. However, the three antidepressants cannot be analysed simultaneously by this method because metapramine requires a different elution system and imipramine interferes with monodesmethyltrimipramine (retention times 8.90 and 8.60 min, respectively).

[Pharmacokinetics and metabolism of 3-carbethoxyamino-5-dimethylamino-acetyl-iminodibenzyl hydrochloride (Bonnecor, AWD 19-166, GS 015) in the rat]

Excretion, blood level, distribution, and metabolite samples were studied on the rat after application of GS 015 marked by 14C. The compound is quickly and completely absorbed and metabolized from an aqueous solution. The marked substances form a broad blood level maximum, at the occasion of which a main metabolite distinguishes itself apart from the initial compound at first provable yet. The elimination half-life from the blood is 6 h. An intense influx of radioactive substance into the tissues takes place. The excretion of the marked metabolites occurs mainly renally making appear a second main metabolite. Striking sex differences are partly observed in the parameters tested.

Simultaneous determination of metapramine and its demethylated metabolites in plasma by gas chromatography-mass spectrometry

A capillary column gas chromatography--mass fragmentographic method for metapramine and its three major demethylated metabolites is described. Compounds are extracted from plasma using a double-extraction procedure and transformed into N-trifluoroacetyl derivatives. The detection is performed by monitoring specific ions for metapramine and for its metabolites with a mass detector. In spite of extensive metabolism in the liver and rapid elimination of metapramine, plasma concentrations of both metapramine and its metabolites can be simultaneously followed over 24 h after a single 150-mg oral dose, because of the sensitivity and selectivity of the method. This method has been successfully applied to the analysis of samples obtained from patients who were at steady state with metapramine and to a pharmacokinetic study in a healthy volunteer.

Mianserin protein binding in serum and plasma from healthy subjects and patients with depression and rheumatoid arthritis

Mianserin protein binding was measured in serum from 43 healthy subjects and plasma from 12 elderly depressed patients and 23 patients with rheumatoid arthritis. Free fraction (mean +/- SD) was 5.5 +/- 0.7% in the healthy subjects, 5.0 +/- 0.8% in the elderly subjects and 6.0 +/- 1.0 in the patients with rheumatoid arthritis. In the group of elderly patients treated with mianserin, a high correlation (r = 0.83, P less than 0.001) between total and free concentrations of mianserin was found. In both groups a high linear correlation (r = +0.90, P less than 0.001) between the free fraction of mianserin and that of imipramine was found, the latter being about twice as high as for mianserin. In both healthy subjects and arthritis patients the degree of protein binding was positively correlated to the concentration of alpha 1-acid-glycoprotein and complement C3c, and somewhat more weakly to haptoglobin. In the healthy subjects protein binding was also highly positively correlated to the concentration of apolipoprotein B, whereas no such correlation was found in the rheumatoid arthritis patients. In the rheumatoid arthritis patients protein binding was highly correlated to the concentration of hemopexin and somewhat more weakly to ceruloplasmin and fibrinogen; a weak negative correlation to the concentration of albumin was also found. Since significant intercorrelations between the concentrations of these proteins were found, the correlation to the degree of binding of mianserin may not necessarily represent binding of the drug to the protein.

Determination of trimipramine and metabolites in plasma by liquid chromatography with electrochemical detection

A procedure for the determination of trimipramine, the demethyl, 2-hydroxy, and 2-hydroxy demethyl metabolites in plasma by liquid chromatography with electrochemical detection is described. A 1-mL plasma sample is made alkaline with a carbonate buffer (pH 9.8) and extracted with 20% ethyl acetate in n-heptane. After back-extraction into an acid phosphate buffer, an aliquot is injected onto a reverse-phase trimethylsilyl-packed column and eluted with a phosphate buffer-acetonitrile mobile phase (65:35) containing n-butylamine. The peaks were detected at +1.1 V versus the silver-silver chloride reference electrode. The method provides absolute recoveries of 60-91% and a day-to-day precision of less than 9% for all compounds. The minimum quantifiable level for all compounds was 3 ng/mL. Steady-state plasma concentration data for 29 depressed patients receiving either 75 mg or 150 mg/d is reported.

Liquid-chromatographic determination of two antidepressants, trazodone and mianserin, in plasma

Plasma containing trazodone or mianserin was extracted. The organic phase containing trazodone was evaporated and the residue was reconstituted in dilute acid. Mianserin was back-extracted from the organic phase with dilute acid. Both drugs were chromatographed on mu Bondapak C18 columns, with phosphate/acetonitrile as the mobile phase. Peak-height ratios of drug/internal standard were linearly correlated with concentrations between 25 and 2000 micrograms/L for trazodone, and between 25 and 200 micrograms/L for mianserin, with respective between-run CVs of 4.7% and 7.6%. Detection limits were 5 ng. Of some common drugs and metabolites examined, nortriptyline co-elutes with the internal standard used in the trazodone assay, while flurazepam co-elutes with mianserin. Concentrations of trazodone in 26 patients ranged from 73 to 1678 micrograms/L. For two geriatric patients, concentrations were about 2000 micrograms/L. For two overdose patients, they were about 5000 micrograms/L. The concentration of mianserin was 27 micrograms/L for a volunteer treated with a single 40-mg oral dose.

The pharmacokinetics of mianserin in elderly depressed patients

The pharmacokinetics of mianserin were examined in eight elderly depressed patients following a single oral dose of 60 mg. Plasma concentrations were measured by gas chromatography/mass spectrometry and the data analyzed using a two-compartment open model. Mean (+/- SD) estimates were: absorption half-life 0.8 +/- 1.0h, peak concentration 117 +/- 23 micrograms/l, peak time 2.2 +/- 1.3h, distribution half-life 3.4 +/- 1.2h, elimination half-life 33 +/- 15h, apparent volume of distribution 20.2 +/- 7.9 1/kg, and oral clearance 0.49 +/- 0.21 l/kg/h. These parameters were not significantly different from those found in healthy volunteers. The absorption lag time (0.6 +/- 0.2h) and area under the curve (2009 +/- 566 micrograms/l/h) were significantly different in the elderly. The clinical implications of these differences for the treatment of elderly depressed patients are discussed.

Analysis of blood and tissue for amoxapine and trimipramine

A method for the identification and quantitation of two tricyclic antidepressants, amoxapine (Asendin) and trimipramine (Surmontil) is presented here. Samples were extracted with hexane at pH 10, back-extracted with 1.0N sulfuric acid. The acidic layer was adjusted to pH 10 and re-extracted with hexane. Electron impact mass spectra were obtained. The base peak and molecular ion for amoxapine were at m/z 245 and 313, respectively. The base peak and molecular ion for trimipramine were at m/z 58 and 294, respectively. There were three forensic toxicology cases involving amoxapine in Cook County, IL, in 1980 and 1981. The concentrations of amoxapine in blood for these three cases were 1.66 mg/L, 7.16 mg/L, and 2.95 mg/L, respectively.

Determination of mianserin in human plasma by gas--liquid chromatography

The authors describe a method for the plasma determination of mianserin by gas--liquid chromatography (GLC), using cyproheptadine as an internal standard. After extraction from 2 ml of plasma by a hexane:isoamyl alcohol (99:1, vol/vol) mixture and its purification by reextraction, the mianserin is determined by GLC, using a glass column packed with 3% OV1 on Gas-Chrom Q, and a nitrogen-sensitive detector. Since the between-day coefficient of variation (n = 15) is less than 8%, this technique appears to be sufficiently reproducible for routine determination in therapeutic concentrations (detection limit with accuracy = 2.5 microgram/L). As an example, the authors describe the time variations of the plasma concentration of mianserin after a first-dose ingestion of 30 mg. Preliminary studies of kinetic parameters are determined in 11 adult patients following a single oral dose (30 mg of mianserin).

Homogeneous substrate-labeled fluorescent immunoassay for carbamazepine

Carbamazepine is an anticonvulsant drug useful in the management of epilepsy. Because of the narrow therapeutic range, serum carbamazepine monitoring is useful for ensuring adequate drug therapy without toxicity. We report the development of a homogeneous substrate-labeled fluorescent immunoassay for carbamazepine in human serum. A carbamazepine fluorogenic reagent (FR) has been synthesized. Upon hydrolysis by beta-galactosidase, the nonfluorescent FR produces a fluorescent product. This enzymic hydrolysis sin inhibited when the FR binds with antibody against carbamazepine. The inhibition is relieved when carbamazepine competes with FR for available antibody binding sites. Thus, increasing levels of carbamazepine result in increasing levels of fluorescence that can be conveniently monitored with any conventional fluorometer. For low, medium, and high control sera (4, 12, and 16 micrograms carbamazepine/ml), the within-run coefficient of variation for the assay is 5.5%, 1.6%, and 2.9%, respectively, while the respective between-run coefficients of variation are 3.5%, 1.9%, and 2.3%. Fifty-three clinical serum samples were assayed by the SLFIA, gas chromatography (GC), high pressure liquid chromatography (HPLC), and an enzyme immunoassay method. The SLFIA method compares favorably with the HPLC technique (r - 0.97, slope = 1.10, y-intercept = 1.21), the enzyme immunoassay (r = 0.98, slope = 1.07, y-intercept = 0.82), and the GC method (r = 0.95, slope = 1.01, y-intercept = -0.03).

Determination of mianserin and metabolites in plasma by liquid chromatography with electrochemical detection

A procedure for the determination of mianserin, desmethylmianserin, and 8-hydroxymianserin in plasma at therapeutic concentrations by liquid chromatography with electrochemical detection is described. Following a multiple-step extraction from alkaline plasma into methyl-tert-butyl ether, the reconstituted extract was injected onto a reversed-phase trimethylsilyl-packed column and eluted with an acetate-acetonitrile mobile phase containing an ion-paired reagent. The method provides an absolute recovery of 71-76% and a day-to-day precision of 5.4-9.1% for each compound at 25 ng/ml. The minimum quantifiable level for all three compounds was 5 ng/ml (RSD greater than 11%), and the detector response was linear up to 500 ng/ml. Fixed-dose steady-state plasma level data for 34 patients are reported.