Development and Validation of an LC-MS/MS Assay to Quantitate 2',4',6'-Trihydroxyacetophenone in Rat and Dog Plasma and its Application to a Pharmacokinetic Study

In the present study, a simple, rapid, and reliable bioanalytical method was developed using liquid chromatography with tandem-mass spectrometry (LC-MS/MS) to quantify 2',4',6'-trihydroxyacetophenone (THAP) in rat and dog plasma with 2',4',6'-trihydroxybenzaldehyde as an internal standard (IS). The LC-MS/MS instrument was operated in the multiple reaction monitoring (MRM) mode to detect THAP at m/z transition 166.89 > 82.8 and IS at 152.89 > 82.8, respectively. A simple, one-step protein precipitation (PP) method was employed with acetonitrile for sample preparation. Utilizing a Gemini C18 column, THAP and IS were separated with an isocratic mobile phase consisting of 10 mM ammonium acetate and methanol (10:90, v/v) at a flow rate of 0.2 mL/min. Total chromatographic run time was 2.5 min per sample injection. The standard calibration curve for THAP was linear (r2 ≥ 0.9987) over the concentration range of 0.1 to 100 µg/mL with the lower limit of quantitation (LLOQ) of 0.1 µg/mL (S/N ratio > 10). According to the regulatory guidelines from the U.S. Food and Drug Administration (FDA) and the Korea Ministry of Food and Drug Safety (MFDS), our newly developed biomedical analytical method was fully and adequately validated in terms of selectivity, sensitivity, linearity, intra- and inter-day precision and accuracy, recovery, matrix effect, stability, and dilution integrity. Our validated assay was successfully utilized in a nonclinical pharmacokinetic study of THAP in rats and dogs.

In vivo and in silico characterization of apocynin in reducing organ oxidative stress: A pharmacokinetic and pharmacodynamic study

Apocynin has been widely used in vivo as a Nox2-contaninig nicotinamide adenine dinucleotide phosphate oxidase inhibitor. However, its time-dependent tissue distribution and inhibition on organ reactive oxygen species (ROS) production remained unclear. In this study, we examined apocynin pharmacokinetics and pharmacodynamics (PKPD) after intravenous (iv) injection (bolus, 5 mg/kg) of mice (CD1, 12-week). Apocynin was detected using a HPLC coupled to a linear ion-trap tandem mass spectrometer. Apocynin peak concentrations were detected in plasma at 1 minute (5494 ± 400 ng/mL) (t1/2  = 0.05 hours, clearance = 7.76 L/h/kg), in urine at 15 minutes (14 942 ± 5977 ng/mL), in liver at 5 minutes (2853 ± 35 ng/g), in heart at 5 minutes (3161 ± 309 ng/g) and in brain at 1 minute (4603 ± 208 ng/g) after iv injection. These were accompanied with reduction of ROS production in the liver, heart and brain homogenates. Diapocynin was not detected in these samples. Therapeutic effect of apocynin was examined using a mouse model (C57BL/6J) of high-fat diet (HFD, 16 weeks)-induced obesity and accelerated aging. Apocynin (5 mmol/L) was supplied in drinking water during the HFD period and was detected at the end of treatment in the brain (5369 ± 1612 ng/g), liver (4818 ± 1340 ng/g) and heart (1795 ± 1487 ng/g) along with significant reductions of ROS production in these organs. In conclusion, apocynin PKPD is characterized by a short half-life, rapid clearance, good distribution and inhibition of ROS production in major organs. Diapocynin is not a metabolite of apocynin in vivo. Apocynin crosses easily the blood-brain barrier and reduces brain oxidative stress associated with metabolic disorders and aging.

Pharmacokinetics and Metabolism of Liposome-Encapsulated 2,4,6-Trihydroxygeranylacetophenone in Rats Using High-Resolution Orbitrap Liquid Chromatography Mass Spectrometry

2,4,6-trihydroxy-3-geranylacetophenone (tHGA) is a bioactive compound that shows excellent anti-inflammatory properties. However, its pharmacokinetics and metabolism have yet to be evaluated. In this study, a sensitive LC-HRMS method was developed and validated to quantify tHGA in rat plasma. The method showed good linearity (0.5–80 ng/mL). The accuracy and precision were within 10%. Pharmacokinetic investigations were performed on three groups of six rats. The first two groups were given oral administrations of unformulated and liposome-encapsulated tHGA, respectively, while the third group received intraperitoneal administration of liposome-encapsulated tHGA. The maximum concentration (C_max), the time required to reach C_max (t_max), elimination half-life (t_1/2) and area under curve (AUC_0–24) values for intraperitoneal administration were 54.6 ng/mL, 1.5 h, 6.7 h, and 193.9 ng/mL·h, respectively. For the oral administration of unformulated and formulated tHGA, C_max values were 5.4 and 14.5 ng/mL, t_max values were 0.25 h for both, t_1/2 values were 6.9 and 6.6 h, and AUC_0–24 values were 17.6 and 40.7 ng/mL·h, respectively. The liposomal formulation improved the relative oral bioavailability of tHGA from 9.1% to 21.0% which was a 2.3-fold increment. Further, a total of 12 metabolites were detected and structurally characterized. The metabolites were mainly products of oxidation and glucuronide conjugation.

Apocynin and catalase prevent hypertension and kidney injury in Cyclosporine A-induced nephrotoxicity in rats

Oxidative stress is involved in the pathogenesis of a number of diseases including hypertension and renal failure. There is enhanced expression of nicotinamide adenine dinucleotide (NADPH oxidase) and therefore production of hydrogen peroxide (H2O2) during renal disease progression. This study investigated the effect of apocynin, an NADPH oxidase inhibitor and catalase, an H2O2 scavenger on Cyclosporine A (CsA) nephrotoxicity in Wistar-Kyoto rats. Rats received CsA (25mg/kg/day via gavage) and were assigned to vehicle, apocynin (2.5mmol/L p.o.), catalase (10,000U/kg/day i.p.) or apocynin plus catalase for 14 days. Renal functional and hemodynamic parameters were measured every week, and kidneys were harvested at the end of the study for histological and NADPH oxidase 4 (NOX4) assessment. Oxidative stress markers and blood urea nitrogen (BUN) were measured. CsA rats had higher plasma malondialdehyde (by 340%) and BUN (by 125%), but lower superoxide dismutase and total antioxidant capacity (by 40%, all P<0.05) compared to control. CsA increased blood pressure (by 46mmHg) and decreased creatinine clearance (by 49%, all P<0.05). Treatment of CsA rats with apocynin, catalase, and their combination decreased blood pressure to near control values (all P<0.05). NOX4 mRNA activity was higher in the renal tissue of CsA rats by approximately 63% (P<0.05) compared to controls but was reduced in apocynin (by 64%), catalase (by 33%) and combined treatment with apocynin and catalase (by 84%) compared to untreated CsA rats. Treatment of CsA rats with apocynin, catalase, and their combination prevented hypertension and restored renal functional parameters and tissue Nox4 expression in this model. NADPH inhibition and H2O2 scavenging is an important therapeutic strategy during CsA nephrotoxicity and hypertension.

Kinetics and metabolism of apocynin in the mouse brain assessed with positron-emission tomography

BACKGROUND

Apocynin is a constituent of the medicinal herb Picrorhiza kurroa. It is an inhibitor of nicotinamide adenine dinucleotide phosphate oxidase. This compound shows potential anti-inflammatory and antioxidant effects and has been tested as a neuroprotectant in many animal models of brain disease. In such studies, understanding the brain kinetics of apocynin would be important for interpreting its in vivo efficacy; however, little has been reported on the kinetics of apocynin in the brain.

PURPOSE

The purpose of this study is to investigate the kinetics and metabolism of apocynin in the brain of mice.

STUDY DESIGN

The kinetics and metabolism of apocynin were examined using [¹¹C]apocynin and positron-emission tomography (PET).

METHODS

In vivo PET scanning was performed in mice for 20min after intraperitoneal administration of an apocynin solution containing [¹¹C]apocynin. Metabolites in the brain were analyzed using high-performance liquid chromatography. The doses of apocynin used ranged from <1.5 µg/kg (tracer dose) to 100mg/kg.

RESULTS

Brain radioactivity during the period of 0 to 20min after administration was negligible at the tracer dose and extremely low at the dose of 10mg/kg. Moderate radioactivity was observed in the brain a few minutes after administration at the doses of 25 and 50mg/kg and rapidly decreased thereafter. At a dose of 100mg/kg, [¹¹C]apocynin resulted in a high uptake of radioactivity followed by a gradual washout. In contrast to the brain, a clear dose-dependent increase in radioactivity was not observed in the blood. The fraction of the unchanged form in the brain decreased with time, and the degree of the reduction depended on apocynin doses: apocynin was rapidly metabolized in the brain at lower doses, whereas it was slowly decomposed at higher doses. On the basis of these data, the maximum apocynin concentrations in the brain were calculated to be 10 µM (10mg/kg), 49 µM (25mg/kg), 150 µM (50mg/kg), and 380 µM (100mg/kg). A metabolite observed in the brain was found to be apocynin glucuronide but not diapocynin, an active metabolite.

CONCLUSION

These results would be useful for an evaluation of the potential efficacy of apocynin as a neuroprotective agent.

[Study on in vitro release and percutaneous absorption of Huoxue Zhitong gel]

To evaluate in vitro release and transdermal behaviors of Huoxue Zhitong gel, modified Franz diffusion cell methods was applied to investigate in vitro transdermal absorption of Huoxue Zhitong gel and the content of paeonolan in receptor fluid composed of PEG400%-95% ethanol-water (l:3:6)were determined by HPLC. The results were processed and different equations were fitted. The release law were in accordance with Weibull equation and the fitting equation was In[-1/(1 - Q)] = -0.790 51nt - 1.7012 (r = 0.9809). In 8 hours, cumulative release of paeonol was 85. 18% and the release rate was 2.827 µg . cm-2 h-1. Transdermal actions were consistent with zero-level model fit and the fitting equation was Q(t) = 1.7579t + 0. 7213 (r = 0.9991). In 8 hours, cumulative transdermal rate and transmission rate of paeonol was 54. 85%, 1. 820 µg . cm-2 h-1. So the Huoxue Zhitong gel had a good release and transdermal properties.

Discovery, synthesis and characterization of a highly muscarinic acetylcholine receptor (mAChR)-selective M5-orthosteric antagonist, VU0488130 (ML381): a novel molecular probe

Of the five G-protein-coupled muscarinic acetylcholine receptors (mAChRs; M1-M5), M5 is the least explored and understood due to a lack of mAChR subtype-selective ligands. We recently performed a high-throughput functional screen and identified a number of weak antagonist hits that are selective for the M5 receptor. Here, we report an iterative parallel synthesis and detailed molecular pharmacologic profiling effort that led to the discovery of the first highly selective, central nervous system (CNS)-penetrant M5-orthosteric antagonist, with sub-micromolar potency (hM5 IC50=450 nM, hM5 Ki=340 nM, M1-M4 IC50>30 μM), enantiospecific inhibition, and an acceptable drug metabolism and pharmacokinetics (DMPK) profile for in vitro and electrophysiology studies. This compound will be a powerful tool and molecular probe for the further investigation into the role of M5 in addiction and other diseases.

[Preparation of paeonol transdermal delivery systems based on proniosomes-based ointment and its pharmacokinetics characters]

The paeonol proniosomes ointment and ordinary ointment were administered to rats. Physiological saline served as perfused solution. The perfusion rate was 5 mL x L(-1) and the microdialysis samples were collected every 20 min intervals. The paeonol concentration in perfused solution was determined by HPLC. Investigation of the pharmacokinetics of paeonol proniosomes ointment and ordinary ointment by the skin-blood synchronous microdialysis coupled with HPLC is reported in this study. The results show that the recovery was (54.80 +/- 1.50)% in vitro and (54.58 +/- 4.61)% in vivo. The results showed that paeonol proniosomes ointment significantly raised the drug concentrations in skin more than the paeonol ordinary ointment. The paeono proniosomes ointment has less drugs into the blood as the ordinary ointments in blood, but its blood drug concentrations were steadier. The paeonol proniosomes ointment may be developed into a new preparation.

Evaluation of paeonol skin-target delivery from its microsponge formulation: in vitro skin permeation and in vivo microdialysis

The aim of the present study was to design a novel topical skin-target drug-delivery system, the paeonol microsponge, and to investigate its drug-release patterns in dosage form, both in vitro and in vivo. Paeonol microsponges were prepared using the quasi-emulsion solvent-diffusion method. In vitro release studies were carried out using Franz diffusion cells, while in vivo studies were investigated by microdialysis after the paeonol microsponges were incorporated into a cream base. In vitro release studies showed that the drug delivered via microsponges increased the paeonol permeation rate. Ex vivo drug-deposition studies showed that the microsponge formulation improved drug residence in skin. In addition, in vivo microdialysis showed that the values for the area under the concentration versus time curve (AUC) for the paeonol microsponge cream was much higher than that of paeonol cream without microsponges. Maximum time (Tmax) was 220 min for paeonol microsponge cream and 480 min for paeonol cream, while the half-life (t1/2) of paeonol microsponge cream (935.1 min) was almost twice that of paeonol cream (548.6 min) in the skin (n = 3). Meanwhile, in the plasma, the AUC value for paeonol microsponge cream was half that of the paeonol cream. Based on these results, paeonol-loaded microsponge formulations could be a better alternative for treating skin disease, as the formulation increases drug bioavailability by lengthening the time of drug residence in the skin and should reduce side-effects because of the lower levels of paeonol moving into the circulation.

Improvement of pharmacokinetics behavior of apocynin by nitrone derivatization: comparative pharmacokinetics of nitrone-apocynin and its parent apocynin in rats

Apocynin, a potent inhibitor of NADPH-oxidase, was widely studied for activities in diseases such as inflammation-mediated disorders, asthma and cardiovascular diseases. In our recent study, a novel nitrone derivative of apocynin, AN-1, demonstrated potent inhibition to oxidative injury and to high expression of gp91^phox subunit of NADPH-oxidase induced by tert-butyl hydroperoxide (t-BHP) in RAW 264.7 macrophage cells, and displayed promising preclinical protective effect against lipopolysaccharide (LPS)-induced acute lung injury in rats. In this work, the pharmacokinetic behaviors of AN-1 in Sprague-Dawley rats with single intravenous and intragastric doses were investigated for further development. Furthermore, apocynin’s pharmacokinetics remain lacking, even though its pharmacological action has been extensively evaluated. The pharmacokinetics of parent apocynin were also comparatively characterized. A simple HPLC method was developed and validated to determine both AN-1 and apocynin in rat plasma. The chromatographic separation was achieved on an Agilent HC-C18 column (250 mm×4.6 mm, 5 µm) at an isocratic flow rate of 1.0 mL/min, with the mobile phase of methanol and water (53∶47, v/v) and the UV detection set at 279 nm. Good linearity was established over the concentration range of 0.1–500 µg/mL for AN-1 and 0.2–100 µg/mL for apocynin. The absolute recovery, precision and accuracy were satisfactory. Compared with the parent compound apocynin, AN-1 yielded a much longer T_1/2 (AN-1 179.8 min, apocynin 6.1 min) and higher AUC_0–t (AN-1 61.89 mmol/L·min, apocynin 2.49 mmol/L·min) after equimolar intravenous dosing (0.302 mmol/kg). The absolute bioavailability of oral AN-1 was 78%, but that of apocynin was only 2.8%. The significant improvement of pharmacokinetic behavior might be accounted for the effective pharmacodynamic results we documented for the novel nitrone derivative AN-1.

[Study on stability and cutaneous permeation kinetics in vitro of positive-ionized liposome gel containing paeonol]

OBJECTIVE

To prepare positive-ionized liposome gel containing paeonol and study its stability and cutaneous permeation kinetics in vitro.

METHODS

Prepared the liposome gel by dispersion-ultrasonic and gridding method, and studied the stability with the impact factor experiments. Compared the permeation rate of liposome gel with conventional gel in vitro using the Franz-diffusion cell.

RESULTS

Mean diameter of the liposome was (132.7 +/- 14.1) nm with Zeta potential of (+33.54 +/- 1.95) mV and mean entrapment efficiency of (73.04 +/- 1.24)% (n=3), and the content of paeonol was (3.17 +/- 0.13) mg/g (n=3). The liposome gel had a promising appearance. It was stable at the humidity and the room temperature while was sensitive at the light and the temperature from 40 degrees C to 60 degrees C. The cumulative penetration amounts of the liposome gel was higher than that of the conventional gel (P < 0.05). Its cutaneous penetration rate and cumulative amounts in skin were higher than those of the conventional gel (P < 0.05).

CONCLUSION

The positive-ionized liposome gel containing paeonol is stable and feasibly prepared. It can enhance the cutaneous permeation efficiency and guarantee the persistent release rate.

[The preparation of paeonol transdermal delivery systems based on the microemulsion-based gels and its pharmacokinetics characters]

Investigation of the pharmacokinetics of paeonol microemulsion, microemulsion-based gels and marketed paeonol ointments by the skin-blood synchronous microdialysis coupled with LC/MS is reported in this study. The microdialysis systems were established by linear probes and concentric circles probes. In vivo recovery of paeonol in skin is (69.7 +/- 4.8) % and in blood is (51.6 +/- 7.2)%. The paeonol microemulsion, microemulsion-based gels and marketed paeonol ointments were administered to rats. PBS (pH 7.4) served as perfused solution. The perfusion rate was 5 microL x mL(-1) and the microdialysis samples were collected every 20 min intervals. The paeonol concentration in perfused solution was determined by LC/MS. The results showed that paeonol microemulsion and microemulsion-based gels significantly raised the drug concentrations in skin more than that of paeonol ointments. The paeonol microemulsion-based gels has similar bioavailability as the paeonol ointments in blood, but its blood drug concentrations were steadier. The paeonol microemulsion-based gels may be developed into a new preparation for dermis eczema. The skin-blood synchronous microdialysis technique proved to be a new method for the pharmacokinetics study of transdermal delivery systems.

Influence of co-administered danshensu on pharmacokinetic fate and tissue distribution of paeonol in rats

Cortex Moutan (root bark of Paeonia suffruticosa Andrew) and Radix Salviae miltiorrhizae (root and rhizome of Salvia miltiorrhiza Bunge) are two herbs widely used in traditional Chinese medicine (TCM) to treat cerebrovascular and cardiovascular diseases. In clinical practice, these two herbs are prescribed together. Studies on the pharmacokinetic interaction between the active constituents of these two herbs (paeonol and danshensu, respectively) can provide substantial foundation for understanding its mechanism and empirical evidence to support the clinical practice. A simple and sensitive high-performance liquid chromatographic (HPLC) method coupled with ultraviolet detector was developed for determination of paeonol in plasma and different tissues (heart, liver, spleen, lung, kidney, and brain) of male Sprague-Dawley rats. When co-administering danshensu, the peak plasma concentration of paeonol was decreased (p < 0.01), the mean residence time (MRT) was prolonged (p < 0.001), the volume of distribution (Vd/F) was increased (p < 0.001), and the concentrations of paeonol in heart, brain, and lung were dramatically increased (p < 0.01 or p < 0.001), compared with these values for rats administered paeonol alone. The results showed that the co-administration of danshensu could alter pharmacokinetic fate and tissue distribution of paeonol in rats, especially in heart and brain, providing substantial foundation for the investigation of the impact of danshensu on paeonol in clinical applications.

[Preparation of paeonol-beta-cyclodextrin inclusion complex loaded colon specific delivery tablets]

OBJECTIVE

To prepare paeonol-beta-cyclodextrin inclusion complex (Pae-beta-CYD) loaded colon-specific release tablets.

METHOD

The core tablets were prepared with the mixture of Pae-beta-CYD inclusion complex, peotin and calcium acetate, and coated with ethanolic solution of Eudragit S100. The effects of coating weight, amount of plasticizer, curing time and temperature on the release of drug from tablets were investigated in vitro.

RESULT

About 5-6 h retarded release of paeonol in the dissolution media of pectinase or rats colon contents were obtained by 12% coating weight gain and 20% Dibutyl phthalate (DBP) was used as plasticizer, and subsequently curing the tablets at 45 degrees C for 12 h.

CONCLUSION

Pae-beta-CYD loaded colon-specific release tablets showed pH environment and enzyme dependant release properties.

In situ and in vivo study of nasal absorption of paeonol in rats

The objective of this work was to study the in situ and in vivo nasal absorption of paeonol. A novel single pass in situ nasal perfusion technique was applied to examine the rate and extent of nasal absorption of paeonol by rats. Various experimental conditions, such as perfusion rate, pH, osmotic pressure and drug concentration, were investigated. The in situ experiments showed that the nasal absorption of paeonol was not dependent on drug concentration, and fitted a first order process. The absorption rate constant, Ka, increased with an increase in perfusion speed. Paeonol was better absorbed in acidic solutions than in neutral or alkaline solutions. The value of Ka was higher in a hypertonic environment than under isotonic or hypotonic conditions. In vivo studies of paeonol absorption were carried out in rats and the pharmacokinetics parameters of intranasal (i.n.) and intragastric (i.g.) administration were compared with intravenous (i.v.) administration. The bioavailabilities of paeonol were 52.37% and 15.81% for i.n. and i.g, respectively, while T_max values were 3.05 ± 1.46 min and 6.30 ± 0.70 min. MRT (Mean Residence Time) were 23.19 ± 6.46 min, 41.49 ± 2.96 min and 23.09 ± 5.88 min for i.n., i.g. and i.v. methods, respectively. The results demonstrate that paeonol could be absorbed promptly and thoroughly by i.n. administration in rats.

[Determination of paeonol in rat plasma by HPLC and pharmacokinetic study]

OBJECTIVE

To establish a sensitive HPLC method for determining the concentrations of paeonol in rat plasma and to evaluate its pharmacokinetic characteristics.

METHOD

The paeonol from eortex Moutan was distilled by the way of water-vapor. A single i.v. dose of 4 mg x kg(-1) paeonol injection was given to 5 health rats. Paeonol was separated on a Diamonsil -C18 column with methanol-water (60: 40)as mobile phase. The plasma concentrations of paeonol were determined and its pharmacokinetic parameters were calculated and evaluated by using kinetica 4.0.

RESULT

The linear range of the method for paeonol was 0.204-20.4 mg x L(-1) and the determination limit was 0.204 mg x L(-1). The main pharmacokinetic parameters, such as AUC, MRT, C(max), Kel, t(1/2kel), after a single dose of paeonol injection were (111.88 +/- 14.44) mg x L(-1) x min(-1), (23.25 +/- 5.86) min, (8.99 +/- 0.84) mg x L(-1), (0.082 +/- 0.015) min(-1) and (8.73 +/- 1.54) min, respectively.

CONCLUSION

The HPLC method for determining paeonol concentration in plasma is simple, rapid, sensitive and suitable for pharmacokinetic studies.

[Dermatopharmacokinetic studies of liangfu cream in mice skin]

OBJECTIVE

To study the relationship between deposition content and time of the active ingredients in rat skin, and investigate the dermatopharmacokinetics of Liangfu Cream.

METHOD

The contents of paeonol, dictamnine, fraxinellone and glycyrrhetinic acid in rat skin were determined by HPLC. The dermatopharmacokinetics parameters were calculated by DAS software.

RESULT

The dermatopharmacokinetics of paeonol and glycyrrhetinic acid were two compartment model, while that of dictamnine and fraxinellone were one compartment model: T(1/2Ka) of four active ingredients were 0.307, 0.112, 0.146, 0.216 h, respectively; T(lag) of them were 0.006, 0.123, 0.136, 0.109 h, respectively; all the Tmax of them was 0.5 h; the Cmax, were 40.163, 1.607, 6.725, 100.553 microg x cm(-3), respectively; the t(1/2beta), were 14.719, 1.262, 0.838, 234.807 h, respectively; the AUC(0-infinity), were 16.987, 2.713, 9.345, 697.000 microg x cm(-3) x h(-1), respectively; and the MRT(0-infinity) were 3.662, 1.67, 1.585, 10.897, respectively.

CONCLUSION

The skin pharmacokinetics characteristic of four ingredients in Liangfu cream is lined with the cataplasm long time.

Pharmacokinetics, disposition, and metabolism of [14C]-nebicapone in humans

OBJECTIVE

This study investigated the absorption, distribution, metabolism and excretion (ADME) of nebicapone [BIA 3-202; 1-(3,4-dihydroxy-5-nitrophenyl)-2-phenyl-ethanone], a reversible catechol-O-methyltransferase (COMT) inhibitor, in 4 healthy male subjects.

METHODS

This was a single center, open, non-placebo-controlled, single-group, and a single 200 mg dose study of [(14)C]-nebicapone (2.5 MBq). Blood, urine and faeces were collected up to 264 hours post-dose.

RESULTS

Collectively more than 22 metabolites were identified in plasma, urine and faeces, with 3-O-nebicapone-glucuronide (BIA 3-476) identified as the major metabolite. Plasma concentration-time profiles of [(14)C]-nebicapone demonstrated T(max) (h) 1.25+/-0.65, t(1/2) (h) 134.55+/-25.67, C(max) (ng-eq/g) 19647.02+/-4930.20, AUC(0-t) (h.ng-eq/g) 161735.51+/-9224.66, AUC(0-infinity) (h.ng-eq/g) 199603.30+/-16854.08, and for whole blood T(max) 1.00+/-0.41, t(1/2) 32.98+/-22.82, AUC(0-t) 35539.23+/-13664.87, AUC(0-infinity) 36970.64+/-14559.17. Plasma pharmacokinetics of nebicapone demonstrated T(max) (h) 1.00+/-0.41, t(1/2) (h) 2.34+/-0.51; C(max) (ng-eq/g) 12650.00+/-2898.85, AUC(0-t) (h.ng-eq/g) 18719.96+/-734.18, AUC(0-infinity) (h.ng-eq/g) 18392.12+/-753.81; BIA 3-476 demonstrated T(max) 1.25+/-0.50, t(1/2) 3.47+/-0.68; C(max) 15250+/-2563.20, AUC(0-t) 53810.61+/-7358.81, AUC(0-infinity) 54541.21+/-7135.70; 3-O-methyl-nebicapone (BIA 3-270) demonstrated T(max) 21.01+/-6.01, t(1/2) 103.43+/-6.01; C(max) 286.25+/-20.48, AUC(0-t) 27641.89+/-4569.99, AUC(0-infinity) 36968.12+/-4294.42.

CONCLUSIONS

Nebicapone and BIA 3-476 accounted for most early phase circulating nebicapone-derived moieties, have limited circulating cell association, peak concentrations shortly after dosing, and short body residence. In longer terminal half-life phases low concentrations of BIA 3-270 predominate. While about 70% of the dose was eliminated in the urine as BIA 3-476, < 1% of the dose was excreted as unchanged nebicapone. Faecal excretion accounted for 17.3% administered dose. On average, the total recovery of 88.6% of the radioactivity suggested no worrisome retention of drug derived material following a single 200 mg administration of nebicapone to healthy volunteers. The treatment was very well tolerated with no reported adverse events.

[Preparation of paeonol microemulsion gel its and transdermal characterization in vitro]

OBJECTIVE

To prepare paeonol microemulsion and microemulsion gel, and investigate its content, physical and chemical properties. Their transdermal properties in vitro were studied as well.

METHOD

IPM acted as oil phase, lecithin/APG as surfactant, 1,2-propanediol as cosurfactant, water was added dropwise to the oil phase to prepare paeonol microemulsion at room temperature using magnetic stirring. HPLC method were used to determine the content of paeonol in paeonol microemulsion. Transmission electron microscopy and laser particle size analyzer were used to determine the shape and size of the microemulsion. Carbopol 940 was uesd as substrate to prepare paeonol microemulsion gel. Franz diffusion cell was used for characterizing the microemulsion and gel transdermal properties in vitro.

RESULT

The paeonol microemulsion was O/W microemulsion. Its uniform particle size was 32 nm and was with roundness appearance and stable content. The steady-state permeation rates of paeonol saturated aqueous solution, microemulsion, and microemulsion gel were 47.846, 103.760, 70.401 microg x cm(-2) x h(-1), and their 12 h cumulative amount of infiltration were 657.179, 1 266.484, 881.217 microg x cm(-2), respectively.

CONCLUSION

The 12 h cumulative infiltration and infiltration rate of paeonol microemulsion and microemulsion gel are better than the saturated aqueous solution. Paeonol microemulsion gel is a new dosage form for transdermal drug delivery.

Bioavailability of apocynin through its conversion to glycoconjugate but not to diapocynin

Apocynin (4-hydroxy-3-methoxyacetophenone) is a major active ingredient from the rhizomes of Picrorhiza kurroa, a botanical plant used as an herbal medicine for treatment of a number of inflammatory diseases. Recently, apocynin is regarded as a specific inhibitor for NADPH oxidase in cell and animal models. In vitro studies indicated conversion of apocynin to diapocynin in the presence of peroxidases, e.g., myloperoxidase, posing the possibility that diapocynin also contributes to the anti-oxidative action of apocynin. The objectives of this study are to examine the bioavailability of apocynin to plasma, liver and brain tissue after intraperitoneal (i.p.) injection, and to examine whether apocynin is converted to diapocynin in vivo. Diapocynin was chemically synthetized and characterized by NMR and IR. Apocynin (5mg/kg body wt) was injected i.p. to adult male Sprague-Dawley rats and plasma, liver and brain were collected at different times (30min, 1 and 2h) after injection. Samples were treated with beta-glucuronidase to hydrolyze the glycosyl linkage and analyzed by HPLC/MS. At 30min and 1h after injection, approximately 50% of apocynin was converted to its glycosyl derivative and was distributed in plasma, liver and brain. No diapocynin was detected in any samples. These results indicate rapid glycosylation of apocynin and its transport to blood and other organs but no apparent conversion to diapocynin in vivo.

Fast determination of paeonol in plasma by headspace solid-phase microextraction followed by gas chromatography–mass spectrometry

Paeonol is the active component in the traditional Chinese medicines (TCMs), such as Cynanchum paniculatum, which has been used to treat many diseases, such as eczema. In this work, a simple, rapid and sensitive method was developed for the determination of paeonol in rabbit plasma, which was based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). The extraction parameters of fiber coating, sample temperature, extraction time, stirring rate and ion strength were systemically optimized; the method linearity, detection limit and precision were also investigated. It was shown that the proposed method provided a good linearity (0.02-20 microg mL(-1), R(2)>0.990), low detection limit (2.0 ng mL(-1)) and good precision (R.S.D. value less than 8%). Finally, GC/MS following HS-SPME was applied to fast determination of paeonol in rabbit plasma at different time point after oral demonstration of Cynanchum paniculatum essential oil. The experimental results suggest that the proposed method provided an alternative and novel approach to the pharmacokinetics study of paeonol in the TCMs.

A liquid chromatographic-mass spectrometric method to evaluate the distribution kinetics of 1,2-diethylbenzene and its metabolite 1,2-diacetylbenzene in the F344 male rat

Diethylbenzene (DEB) is a moderately volatile, colorless liquid found in gasoline, kerosene, and fuel oils. Exposure to DEB has been shown to produce peripheral neuropathy in rats, and the ortho isomer of DEB (1,2-DEB) is generally believed to be the isomer responsible. 1,2-DEB is assumed to be metabolized primarily by direct oxidation of the ethyl side chain to form two enantiomers of 1-(2-ethylphenol) ethanol and their glucuroconjugates, which are the main 1,2-DEB metabolites, and 1,2-diacetylbenzene (1,2-DAB), a minor metabolite. The metabolite 1,2-DAB appears to be a chromogenic neurotoxin. A liquid chromatographic-mass spectrometric (LC-MS) method using atmospheric pressure photoionization (APPI) for quantifying 1,2-DEB and 1,2-DAB in blood, urine, and brain tissues from animals treated with an intraperitoneal injection of 1,2-DEB was developed. Calibration curves were prepared using matrix-specific standards with concentrations ranging from 0.068 to 402 microM. Results indicate that the concentration of 1,2-DEB in blood peaked at 2 h post intraperitoneal injection and rapidly declined thereafter. In contrast, 1,2-DAB levels in blood were fairly constant up to 24 h postinjection. Urine concentrations of 1,2-DEB were highest at the first collection interval (0-12 h postinjection), and dropped rapidly thereafter; concentrations at 24 h were similar to concentrations observed at 48 h postexposure. Urine concentrations of 1,2-DAB, however, showed the reverse, with peak concentrations observed at 24 h postinjection and only a slight decrease in concentration by 48 h.

Human Metabolism of Nebicapone (BIA 3-202), a Novel Catechol-O-Methyltransferase Inhibitor: Characterization of in Vitro Glucuronidation

Nebicapone (BIA 3-202; 1-[3,4-dihydroxy-5-nitrophenyl]-2-phenylethanone), a novel catechol-O-methyltransferase inhibitor, is mainly metabolized by glucuronidation. The purpose of this study was to characterize the major plasma metabolites of nebicapone following p.o. administration of nebicapone to healthy volunteers, and to determine the human UDP-glucuronosyltransferase (UGT) enzymes involved in nebicapone glucuronidation. Plasma samples were collected as part of a clinical trial at different time points postdose and were analyzed for nebicapone and its metabolites using a validated method consisting of a solid-phase extraction, followed by high-performance liquid chromatography/mass spectrometry detection. The primary metabolic pathways of nebicapone in humans involve mainly 3-O-glucuronidation, the major early metabolite, and 3-O-methylation, the predominant late metabolite. Of the nine commercially available recombinant UGT enzymes studied (UGT1A1, UGT1A3, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15), only UGT1A9 exhibited high nebicapone glucuronosyltransferase specific activity (24.3 +/- 1.3 nmol/mg protein/min). UGT1A6, UGT1A7, UGT1A8, UGT1A10, UGT2B7, and UGT2B15 exhibited low activity (0.1-1.1 nmol/mg protein/min), and UGT1A1 and UGT1A3 showed extremely low activities (less than 0.03 nmol/mg protein/min). The results show that nebicapone is mainly glucuronidated in humans and that multiple UGT enzymes are involved in this reaction.

Benzazoles as allosteric potentiators of metabotropic glutamate receptor 2 (mGluR2): efficacy in an animal model for schizophrenia

Metabotropic glutamate receptor 2 (mGluR2) has been implicated in a variety of CNS disorders, including schizophrenia. Disclosed herein is the development of a new series of allosteric potentiators of mGluR2. Structure-activity relationship studies in conjunction with pharmacokinetic data led to the discovery of indole 5, which is active in an animal model for schizophrenia.

Pharmacokinetic-pharmacodynamic interaction between BIA 3-202, a novel COMT inhibitor, and levodopa/carbidopa

This study investigated the tolerability and the pharmacokinetic and pharmacodynamic interactions between single oral administration of BIA 3-202 (50 mg, 100 mg, 200 mg, and 400 mg), a novel catechol-O-methyltransferase (COMT) inhibitor, and standard carbidopa/levodopa 25 mg/100 mg (Sinemet 25/100) in healthy adult volunteers. This was a single-center, double-blind, placebo-controlled, randomized, crossover study with 5 single-dose treatment periods with a washout period of 2 weeks between doses. During each treatment period, a different dose of BIA 3-202 or placebo was administered concomitantly with Sinemet 25/100. Tolerability was assessed by recording adverse events, vital signs, continuous EKG, and clinical laboratory parameters. Pharmacokinetic parameters of levodopa and 3-O-methyl-levodopa (3-OMD) were determined. The activity of soluble COMT in erythrocytes was also measured. Eighteen subjects (10 men and 8 women) participated in the study. The drug combination was well tolerated, with the adverse events reported being transient and generally mild in severity. Mean levodopa Cmax values were attained at 0.8 to 1.8 hours postdose. Thereafter, plasma levodopa levels declined with a mean t1/2 that increased in a manner that depended on the dose of BIA 3-202. The increase in systemic exposure to levodopa (AUC0-infinity) occurred at all doses of BIA 3-202, attaining its maximum at 200 mg BIA 3-202 (95% conficence interval, 1.43-1.73). The mean Cmax and AUC0-infinity values of 3-OMD decreased dose proportionally in BIA 3-202-treated subjects, with differences being statistically significant for all the doses tested. Maximum COMT inhibition occurred between 0.8 and 2.0 hours postdose, and ranged from 56 (50 mg) to 85% (400 mg). Time to return to baseline COMT activity ranged from 6 (50 mg) to 18 hours (400 mg), following the same dose-dependent tendency. In conclusion, the novel COMT inhibitor BIA 3-202 increased the bioavailability of levodopa and reduced the formation of 3-OMD when administered with standard levodopa/carbidopa.

Pharmacokinetic and pharmacodynamic profiles of BIA 3-202, a novel catechol-O-methyltransferase (COMT) inhibitor, during multiple-dose administration to healthy subjects

The tolerability, pharmacodynamics, and pharmacokinetics of BIA 3-202 (50 mg, 100 mg, and 200 mg twice daily and 200 mg thrice daily), a novel catechol-O-methyltransferase (COMT) inhibitor, were investigated in healthy volunteers. BIA 3-202 was administered to four sequential groups of 8 healthy male subjects under a double-blind, randomized, placebo-controlled design. Within each group, 2 subjects were randomized to treatment with placebo. Treatment duration was 9 days: single dose on the first and last days and twice or thrice daily on days 3 to 8. BIA 3-202 was well tolerated at all dose regimens tested. Median maximum plasma BIA 3-202 concentrations were attained at 0.5 to 2.5 hours postdose. Thereafter, concentrations declined with a t1/2 of approximately 2 to 4 hours. The increase in the extent of systemic exposure, as measured by AUC0-tau, was approximately proportional to the administered dose. Steady state of plasma BIA 3-202 concentrations occurred by day 4 in all dose groups. Less than 1% of the total dose administered was excreted in urine up to 48 hours postdose. BIA 3-202 markedly reduced soluble COMT (S-COMT) activity in erythrocytes, with maximum inhibition occurring at 1 to 2 hours postdose; enzyme activity returned to baseline levels by approximately 8 hours. Inhibition of S-COMT activity appeared to increase with increasing doses of BIA 3-202 on both day 1 and day 9. In conclusion, BIA 3-202 was well tolerated in all the oral multiple-dose regimens tested. BIA 3-202 was shown to inhibit S-COMT activity in erythrocytes, and its pharmacokinetics appeared to be linear (i.e., dose independent and time invariant).

Pharmacokinetics and pharmacodynamics of BIA 3-202, a novel COMT inhibitor, during first administration to humans

OBJECTIVE

To determine the tolerability, pharmacodynamics and pharmacokinetics of single oral doses of BIA 3-202, a novel catechol-O-methyltransferase (COMT) inhibitor, in healthy male volunteers.

METHODS

Single increasing oral doses of BIA 3-202 (10, 30, 50, 100, 200, 400 and 800mg) were administered under fasting conditions to seven sequential groups of nine subjects, under a double-blind, randomised, placebo-controlled design. In an additional group of eight subjects (group 8), a single dose of BIA 3-202 400mg was administered on two occasions, once under fasting conditions and once with a high-fat meal, under an open-label, two-way crossover design.

RESULTS

BIA 3-202 was well tolerated at all doses tested. Most adverse events were mild in severity and their incidence was similar between BIA 3-202 and placebo. Maximum plasma concentrations (C(max)) of BIA 3-202 were attained at 0.5-2.5h (t(max)) and thereafter declined with an apparent terminal half-life (t(1/2)) of 1.5-5h. Over the dose range of 10-800mg, there was an approximately dose-proportional increase in the area under the plasma concentration-time curve (AUC) values of BIA 3-202: for a dose level increase in the ratio 3.0:1.7:2.0:2.0:2.0:2.0, AUC increased in the ratio 3.1:1.7:1.9:2.2:2.1:1.7. Plasma concentrations of the O-methylated derivative, BIA 3-270, increased markedly less than predicted from a proportional relationship: for a dose level increase in the ratio 1:80, AUC(0-t )increased in the ratio 1:5. In most subjects, the t(max) of BIA 3-270 was attained at the last sampling time and, therefore, t(1/2 )could not be estimated. Urine assays showed that less than 1% of the total dose administered was excreted in urine as BIA 3-202. Urine concentrations of BIA 3-270 were below the limit of quantification. In group 8, the rate and extent of systemic availability (t(max), AUC and C(max)) of BIA 3-202 and BIA 3-270 after a high-fat meal were similar to those under fasting conditions. Inhibition of COMT activity in erythrocytes reached maximum levels at 2-2.5h post dose, with sustained inhibition up to approximately 4-6 hours, returning to baseline by about 16 hours.

CONCLUSION

BIA 3-202 was well tolerated at single 10-800mg oral doses and presented dose-proportional kinetics. It effectively inhibited COMT activity and the presence of food did not affect its pharmacokinetics or COMT inhibitory activity. The results provide a basis for further clinical studies with BIA 3-202.

Pharmacokinetic-pharmacodynamic interaction between BIA 3-202, a novel COMT inhibitor, and levodopa/benserazide

BIA 3-202 is a novel catechol-O-methyltransferase (COMT) inhibitor being developed for use as a levodopa-sparing agent in Parkinson's disease. This study investigated the effect of four single oral doses of BIA 3-202 (50 mg, 100 mg, 200 mg, and 400 mg) compared with placebo on plasma concentrations of levodopa and its metabolite 3- O-methyl-levodopa (3-OMD) and on inhibition of erythrocyte COMT in healthy subjects receiving 100 mg of levodopa and 25 mg of benserazide (Madopar 125). This was a single-centre, double-blind, placebo-controlled, randomised, crossover study with five single-dose treatment periods. The washout period between doses was 2 weeks. On each treatment period, a different dose of BIA 3-202 or placebo was administered concomitantly with Madopar 125. Tolerability was assessed by recording adverse events, vital signs, continuous electrocardiogram and clinical laboratory parameters. In the study, 18 subjects (12 male and 6 female) participated. The drug combination was well tolerated. All doses of BIA 3-202 significantly increased the area under the concentration-time curve (AUC) versus placebo, ranging from 39% (95% confidence intervals, 1.06-1.69) with 50 mg to 80% (95% confidence intervals, 1.42-2.22) with 400 mg. No significant change in mean maximum plasma concentrations (C(max)) of levodopa was found. Mean C(max) and AUC of 3-OMD significantly decreased for all doses tested. BIA 3-202 caused a rapid and reversible inhibition of S-COMT activity, ranging from 57% (50 mg) to 84% (400 mg). In conclusion, the novel COMT inhibitor BIA 3-202 was well tolerated and significantly increased the bioavailability of levodopa and reduced the formation of 3-OMD when administered with standard release levodopa/benserazide.

Determination of paeonol in rat plasma by high-performance liquid chromatography and its application to pharmacokinetic studies following oral administration of Moutan cortex decoction

Quantification of paeonol, the principal bioactive component of Moutan cortex, in rat plasma following oral administration of Moutan cortex decoction was achieved by using a simple and sensitive high-performance liquid chromatographic method. The calibration curves for paeonol were linear in both the low (25-200 ng/mL) and the high concentration range (200-4000 ng/mL) with r(2) values of 0.9928 and 0.9993, respectively. The coefficients of variation of intra- and inter-day assays were 14.36, 6.52, 1.76, 1.25, 5.36, 3.30 and 1.42% and 12.70, 1.19, 2.98, 1.91, 1.75, 1.78 and 0.96% at concentrations of 25, 50, 100, 200, 500, 1000 and 2000 ng/mL, respectively. The recoveries of paeonol from rat plasma were found to be 101.9, 104.5, 105.4 and 101.2% for concentrations of 50, 500, 1000 and 2000 ng/mL, respectively. The paeonol plasma concentrations were fitted to two-compartment model with fi rst order absorption. The mean terminal half-lives (t(1/2)) of paeonol was 80.9 min.

Metabolism of paeonol in rats

As a part of our studies on the metabolism of active components from traditional Chinese medicines, paeonol was orally administered to rats. The urinary metabolites were analyzed by 3D HPLC, and their structures were determined to be 2, 4-dihydroxyacetophenone-5-O-sulfate (P1), resacetophenone-2-O-sulfate (P2), 2-hydroxy-4-methoxyacetophenone-5-O-sulfate (P3), paeonol-2-O-sulfate(P4), resacetophenone (P5), and unchanged paeonol, on the basis of their chemical and spectral data. Among these metabolites, P2-P4 and paeonol were detected in the plasma after the oral administration of paeonol. Furthermore, the bile of rats given paeonol orally was found to contain P3, suggesting the enterohepatic circulation of paeonol.

Virological and immunological analysis of a triple combination pilot study with loviride, lamivudine and zidovudine in HIV-1-infected patients

OBJECTIVE

To compare two antiretroviral regiments, loviride plus lamivudine (3TC) plus zidovudine (ZDV) (triple combination) and loviride plus ZDV (double combination) in terms of pharmacokinetic interactions, tolerability, safety, and immunological and virological efficacy.

STUDY DESIGN

An open, case-controlled, pharmacokinetic and 24-week continuous treatment pilot study.

PATIENTS

Twenty p24 antigen-positive patients, 10 per treatment group, were matched according to p24 antigenaemia less or more than 100 pg, CD4 count less or more than 150 x 10-(6)/l, and gender. Eight out of 10 cases and seven out of 10 controls had received previous antiretroviral therapy.

RESULTS

No clinically relevant pharmacokinetic interactions were observed. Both treatment combinations were well tolerated. Median absolute and percentage CD4 count increases above baseline were more pronounced in the triple combination arm than in the double combination arm. Median p24-antigen and plasma viraemia level decreases below baseline were more pronounced in the triple combination arm. The M(184)I/V mutation was detected in all plasma samples of triple combination patients examined at week 12. Mutations conferring resistance to loviride and ZDV were found in a significant subset of patients in both treatment arms.

CONCLUSIONS

Both combination regimens have an excellent safety/tolerability profile, but a higher level of in vivo efficacy is achieved by the triple combination, despite genotypic changes conferring resistance to one or all of these agents. The conclusions drawn are limited by small population size and the heterogenous pretreatment history. However, they support the validity of and strongly encourage a rationally designed multidrug combination approach to HIV therapy.

Pharmacokinetics and pharmacodynamics of the acetylcholinesterase inhibitor 2,2,2-trifluoro-1-(3-trimethylsilylphenyl) ethanone in dog. Potential for transdermal patch delivery

MDL 73,745 (2,2,2-trifluoro-1-(3-trimethylsilylphenyl) ethanone, CAS 132236(18-1) is a novel tight-binding inhibitor of acetylcholinesterase (AChE), which is in development as a potential therapeutic compound in the symptomatic treatment of Alzheimer's disease. Pharmacokinetics and pharmacodynamics of the compound were studied in the dog after single intravenous (i.v. 2 mg/kg), oral p.o. 10 mg/kg) and sub-cutaneous (s.c., 10 mg/kg) administrations of [14C]-MDL 73,745. Plasma concentrations of total radioactivity were much higher than those of parent drug after i.v., p.o. and s.c. administration, indicating extensive metabolism of the compound, although this was less after, s.c. administration than after p.o. administration. The bioavailability (F) was 34% after s.c. administration, compared with 4% after p.o. administration. The low bioavailability after p.o. administration was not due to poor drug absorption, as over 64% of the dose was absorbed. Pharmacokinetic parameters, calculated after i.v. administration, showed a terminal elimination half-life of 24 h, total body plasma clearance of around 70 ml/min/kg and apparent volume of distribution of 150 l/kg. AChE activity was almost 100% inhibited after i.v. administration, and over 80% inhibited 1 h after p.o. administration. In both cases, AChE activity returned to baseline levels by 12 h. AChE was around 80% inhibited 4 h after s.c. administration, and did not return to baseline levels until 36 h after drug administration. A combined pharmacokinetic-pharmacodynamic (PK-PD) effect model demonstrated that the extent of AChE inhibition could be correlated with plasma levels of the parent compound. As s.c. administration increased F, and led to longer AChE inhibition, transdermal (t.d.) delivery was assessed in the same animals. Patches, corresponding to a dose of 50 mg/kg, were applied to the shaved lateral abdominal skin for a period of 96 h. Sustained plasma concentrations of the parent drug were observed over the 96 h period of t.d. application. Mean (+/- SD) maximum plasma concentrations (Cmax) of 26.9 +/- 4.3 ng/ml were found 3.7 +/- 2.5 h after t.d. patch application und F was around 13%. AChE inhibition reached a maximum of 72% at 6 h after t.d. application and was still 35% at 96 h. The rate of release from the delivery system, per unit surface area, (ko) was calculated to be 7.7 micrograms/cm2. Transdermal delivery of MDL 73,745 thus decreased the important hepatic first-pass effect, and led to sustained plasma concentrations of drug, thus avoiding peaks and troughs which could lead to side-effects or poor efficacy.

Acetylcholinesterase inhibition by zifrosilone: pharmacokinetics and pharmacodynamics

OBJECTIVE

To determine the pharmacokinetics, pharmacodynamics and safety of the acetylcholinesterase inhibitor zifrosilone in healthy male volunteers.

METHODS

Pharmacokinetics, pharmacodynamics, and tolerance of zifrosilone were studied in a double-blind, sequential, single-escalating-dose, randomized panel design. Each panel consisted of six subjects, with four subjects receiving zifrosilone (10, 30, 60, 90, 120, 150, 200, 250, and 300 mg orally) and two subjects receiving matching placebo. Serial blood samples were obtained for zifrosilone plasma concentrations and red blood cell acetylcholinesterase and butyrylcholinesterase activities. Participating subjects (n = 54) were men between the ages of 18 and 45 years. Each subject had a normal physical examination, electrocardiogram, serum chemistries, hematology, urinalysis, and test for human immunodeficiency virus at screening.

RESULTS

A greater than proportionate increase in mean plasma concentration values for area under the curve from time zero to infinity was observed over the 200 to 300 mg dose range groups. Red blood cell acetylcholinesterase showed a dose-inhibition relationship, with a mean maximum inhibition of 20.9% at 10 mg that increased to 62.1% at 300 mg. Butyrylcholinesterase activity was relatively unaffected by zifrosilone (< 20% inhibition at 300 mg). For doses > or = 200 mg, an Emax pharmacodynamic model was used to describe the relationship between zifrosilone plasma concentration and red blood cell acetylcholinesterase inhibition (Emax = 83.8%; EC50 = 0.65 ng/ml).

CONCLUSIONS

Zifrosilone showed dose-dependent pharmacokinetics after oral administration and was effective in causing selective inhibition of red blood cell acetylcholinesterase.

The effect of food on the absorption of 14C-SDZ FOX 988, an antidiabetic agent, in healthy human volunteers

The objective of this study is to examine the effect of food on oral absorption of SDZ FOX 988 (FOX 988), an antidiabetic agent, and circulating levels of its active metabolite, SDZ 53-450 (53-450). Sixteen normal volunteers received a single 10 mg dose of 14C-FOX 988, either as gelatin capsules or in a suspension (0.5% CMC). For subjects receiving each formulation, four subjects received a meal, consisting of 50% fat by calories, immediately following dosing, while the other four received the same meal at 2 h post-dose. Serial blood, urine, and fecal samples were collected for 120 h and analyzed for total radioactivity. Blood concentrations of 53-450 were analyzed using an HPLC-UV method. Concomitant administration with food increased the extent of FOX 988 absorption from either suspension or capsule, as shown by an increase in AUC and in urinary recovery of radioactivity. Blood concentrations of 53-450 were only detected in subjects receiving food at dosing. No difference in absorption was observed between the capsule and the suspension. Results from this study showed that oral absorption of FOX 988 is enhanced by co-administration of food in normal volunteers.

The effect of the fat content of food on the pharmacokinetics and pharmacodynamics of SDZ FOX 988, an antidiabetic agent, in the dog

SDZ FOX 988 (FOX 988) is being developed for the treatment of type II diabetes. The objective of this study was to examine the effect of the fat content of food on the pharmacokinetics and pharmacodynamics of FOX 988 following oral administration in the dog. In a randomized, cross-over design, four dogs received a single 10 mg kg-1 dose of 14C-FOX 988 suspension concomitantly with food containing 10% fat or 40% fat, or with the 10% fat food at 4 h post-dose. Serial blood, urine, and fecal samples were collected for 96 h and analyzed for total radioactivity. Blood concentrations of 53-450, the active metabolite of FOX 988, were also determined. Serum concentrations of beta-hydroxybutyrate and glucose, pharmacological markers for the antidiabetic effects, were measured serially for 24 h after dosing. The animals receiving the low-fat meal at dosing and at 4 h post-dose exhibited similar extents of absorption, as shown by similar AUC values and urinary radioactivity recovery. Administration of the high-fat meal at dosing significantly enhanced the absorption of FOX 988 and resulted in high blood concentrations of 53-450. However, no significant differences in the pharmacological activity of the drug were observed among the three treatments.

Pharmacokinetics of paeonol after intravenous administration in rats

A simple high-performance liquid chromatography methodology was developed to study the pharmacokinetics of paeonol in the rat after intravenous (iv) bolus administration of various doses (2.5, 5, or 10 mg/kg). The pharmacokinetics of paeonol in rat plasma at each dose were well described by a two-compartment model. The area under the curve increased proportionally with dose and consequently total body clearance was independent of dose. There was no dose-related difference in the elimination half-life or volume of distribution. These results indicate that the pharmacokinetics of paeonol after iv administration are linear over the 2.5-10 mg/kg dose range.

Potent and highly selective human immunodeficiency virus type 1 (HIV-1) inhibition by a series of alpha-anilinophenylacetamide derivatives targeted at HIV-1 reverse transcriptase

In vitro evaluation of a large chemical library of pharmacologically acceptable prototype compounds in a high-capacity, cellular-based screening system has led to the discovery of another family of human immunodeficiency virus type 1 (HIV-1) inhibitors. Through optimization of a lead compound, several alpha-anilinophenylacetamide (alpha-APA) derivatives have been identified that inhibit the replication of several HIV-1 strains (IIIB/LAI, RF, NDK, MN, HE) in a variety of host cell types at concentrations that are 10,000- to 100,000-fold lower than their cytotoxic concentrations. The IC50 of the alpha-APA derivative R 89439 for HIV-1 cytopathicity in MT-4 cells was 13 nM. The median 90% inhibitory concentration (IC90) in a variety of host cells was 50-100 nM. Although these alpha-APA derivatives are active against a tetrahydroimidazo [4,5,1-jk][1,4]benzodiazepin-2(1H)-thione-(TIBO)-resistant HIV-1 strain, they do not inhibit replication of HIV-2 (strains ROD and EHO) or simian immunodeficiency virus (strains Mac251, mndGB1, and agm3). An HIV-1 strain containing the Tyr181-->Cys mutation in the reverse transcriptase region displayed reduced sensitivity. alpha-APA derivative R 89439 inhibited virion and recombinant reverse transcriptase of HIV-1 but did not inhibit that of HIV-2. Reverse transcriptase inhibition depended upon the template/primer used. The relatively uncomplicated synthesis of R 89439, its potent anti-HIV-1 activity, and its favorable pharmacokinetic profile make R 89439 a good candidate for clinical studies.

Deimidazolation of antimycotic croconazole through epoxide formation in rabbit liver microsomes

Incubation of croconazole with rabbit microsomes in the presence of NADPH + 18O2 produced the major metabolite, 2-(3-chlorobenzyloxy)phenacyl alcohol (M2) containing one 18O atom. Also detected in the ethyl acetate extracts from the incubation mixture was the remainder of the product, imidazole. These results indicate that the deimidazolation process from croconazole involves the intermediate, croconazole epoxide, which is hydrolyzed immediately to M2 and imidazole. This reaction is mediated by cytochrome P-450 as indicated by the requirement of NADPH, the incorporation of 18O, and inhibition by 10 mM metyrapone, 0.1 mM SKF 525-A, and CO/O2 (50/50, 80/20). Double reciprocal plots of M2 formation give a straight line, suggesting that the reaction may be mediated by an isozyme of cytochrome P-450 families.

The disposition of the hypolipidemic agent, o-(N-phthalimido)acetophenone, in Sprague-Dawley rats

Disposition studies of the potent experimental hypolipidemic agent, o-(N-phthalimido)acetophenone, were conducted in the laboratory rat. Intravenous administration of the drug demonstrated a declining biphasic plasma concentration-time curve suggesting a rapid distribution into tissues. Less than 5% of the intravenous dose was recovered in urine and feces after 5 days. Oral administration of the drug showed that the maximum blood levels were attained within 15 min. After 48 hr, 92% of the orally administered 14C dose was eliminated either via urine (60%) or feces (40%). 14C in a 0-24-hr urine collection after oral administration showed that urinary radioactivity was composed of 22% of the parent compound o-(N-phthalimido) acetophenone, a benzoic acid metabolite (22%) o-(N-phthalimido)benzoic acid, and an amic acid metabolite (56%) N-(o-acetophenone)phthalamic acid. The two metabolites were unconjugated and possessed less hypolipidemic activity than the parent drug.

Metabolism of aromatic plant ketones in rats: acetovanillone and paeonol

1. The metabolism of the plant ketones acetovanillone (4-hydroxy-3-methoxyacetophenone) and paeonol (2-hydroxy-4-methoxyacetophenone), was studied in rats. Identification and quantification of metabolites was carried out by g.l.c.-mass spectometry and g.l.c., respectively, following intragastric doses of 1 mmol/kg. 2. Acetovanillone was rapidly excreted in the urine, mainly unchanged but also as the demethylated compound and three ring-hydroxylated metabolites. Minor additional metabolic pathways produced the para-methoxy derivative, acetoisovanillone, a dimethoxy-hydroxy derivative and two 1-phenylethanol derivatives formed by ketone reduction of acetovanillone and 3,4-dihydroxyacetophenone. 3. Paeonol was metabolized more extensively and larger amounts of the demethylated (resacetophenone) and hydroxylated (mainly 2,5-dihydroxy-4-methoxyacetophenone and a trihydroxyacetophenone) metabolites were excreted. Paeonol was not found to undergo ketone reduction, however, small amounts of the hydroxymethyl derivative formed by omega-oxidation were detected. 4. The metabolites were excreted mainly as glucuronide and/or sulphate conjugates. Faecal recoveries of metabolites were very small and the urinary excretion (48 h) was 97% (acetovanillone) and 61% (paeonol).