Quantification of (-)doxazosin at very low concentration in rat plasma samples by SPE-LC-MS/MS / 药学学报

Previous publications showed that the value of LLOQ (lowest limit of quantification) for doxazosin and its enantiomers in biological samples were above 0.1 ng·mL-1. The present study was designed to establish a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification at very low concentration of (-)doxazosin in rat plasma after intravenous administration of (-)doxazosin (3.0 mg·kg-1). The plasma samples containing prazosin as an internal standard were extracted by solid-phase extraction (SPE) and separated on Acquity BEH C18(50 mm×2.1 mm, 1.7 μm) column under alkaline conditions of the mobile phase. (-)Doxazosin was monitored under positive ionization condition by multiple reaction monitoring (MRM) with an ESI source. The good linear range of (-)doxazosin varied from 10.4 pg·mL-1 to 13 ng·mL-1(r=0.9922), and the lowest limit of quantification was 10.4 pg·mL-1. An assessment of the matrix effect using post-extraction spiking method and post-column infusion method demonstrated that co-eluting matrix components did not significantly influenced the ionization of (-)doxazosin and prazosin (IS). Using the new method, we accurately measured (-)doxazosin concentration at 48 h after intravenous administration in the rats, and the concentration was 0.0344±0.0102 ng·mL-1. The method is specific, sensitive, and suitable for determining (-)doxazosin at very low concentration in rat plasma samples.

An overview of effects of traditional medicine on pharmacokinetics of western medicine / 药学学报

Traditional medicine (herb medicine) began to prevail again over last two decades, and it is about 70% of the world population taking herb medicine as supplement or alternative medicine according to a recent survey. The consumption of herb medicine increased exponentially in Canada, Australia and Europe during last 10 years. Since concomitant administration of herbal and western medicine has become a trend, it requires paying close attention to the problem. Herb-drug interactions have been extensively investigated worldwide, and there is an increasing concern about the clinical herb-drug interaction. In this review we introduced the current progress in the herb-drug interactions including evidence-based clinical studies and establishment of levels of evidence for herb-drug interaction; and in the related mechanisms including the induction and inhibition of metabolic enzymes, inhibition and induction of transport and efflux proteins, alteration of gastrointestinal functions, and alteration in renal elimination. We also analyzed both the achievements and the challenges faced in the concomitant administration of traditional Chinese medicine and western medicine.

Determination of doxazosin enantiomers in rat plasma and investigation of their chiral inversion / 药学学报

The study is to establish an HPLC method using fluorescence detector for the determination of doxazosin enantiomers and investigate their chiral inversion in vitro and in vivo. Ultron ES-OVM was taken as the chiral chromatographic column, and the column temperature was 30 degrees C. Isocratic elution using a mobile phase of phosphate buffer-acetonitrile (85 : 15, v/v) at a flow rate of 0.8 mL x min(-1) was done. The fluorescence detection was set at lambda(Ex) = 255 nm and lambda(Em) = 385 nm. Prazosin was used as the internal standard. (-) Doxazosin or (+) doxazosin added into rat plasma in vitro was determined after incubating in 37 degrees C water bath for 2, 5 and 10 days. (-) Doxazosin or (+) doxazosin was administered orally to the rats for one months. Plasma samples were taken at 8 h after the last administration. A good linear relationship was achieved when the concentration of doxazosin enantiomers was within the range of 4 - 2 000 ng x mL(-1). The average recovery for (-) doxazosin was 99.5% with RSD 3.6%, and for (+) doxazosin was 99.3% with RSD 4.3%. Chiral inversion was observed neither in vitro nor in vivo studies. The method is selective, accurate and reproducible, which is suitable for the detection of doxazosin enantiomers in rat plasma. The in vitro and in vivo studies indicate that chiral inversion occurs uneasily between (-) doxazosin and (+) doxazosin in the rat.

Effects of doxazosin and its enantiomers on serum lipid levels in rabbits fed by an atherogenic diet / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To observe the effects of (-)doxazosin(DOX), (+)DOX and (+/-)DOX on serum lipid levels and the mortality rates of the rabbits fed by an atherogenic diet.</p><p><b>METHODS</b>Male white New Zealand rabbits were fed by an atherogenic diet for 4 weeks. 8 rabbits whose serum TC <10 mmol/L were confirmed as normal diet group and were fed normally. 40 rabbits whose serum TC >10 mmol/L were randomly divided into 4 groups (n=10): atherogenic diet group, atherogenic diet with (-)DOX group, atherogenic diet with (+)DOX group and atherogenic diet with (+/-)DOX group, which were intraperitoneally injected with (-)DOX, (+)DOX and (+/-)DOX for 9 weeks respectively. Normal and atherogenic diet group were intraperitoneally injected with double distilled water. After 9 weeks administration of (+/-)doxazosin and its enantiomers, effects of the three agents on serum levels of total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C) were observed.</p><p><b>RESULTS</b>The mortality rate of the rabbits fed by an atherogenic diet for 13 weeks was 40%, and it was much higher than that of the rabbits fed by a normal diet (10%). The mortality rates in the rabbits treated with (-)DOX and (+/-)DOX were lower than that in the rabbits fed by a normal diet (10%). Serum LDL-C level of the rabbits was increased markedly after 4 weeks of atherogenic diet, and it was further increased significantly (P < 0.05 and P < 0.01) during the continued 9 weeks of atherogenic diet. However, serum LDL-C levels were not further increased significantly (P > 0.05) during the continued 9 weeks of atherogenic diet in the rabbits treated with (-)DOX, (+)DOX and (+/-)DOX, respectively.</p><p><b>CONCLUSION</b>(-)DOX and (+/-)DOX increase the survival rate and improve LDL-C disorder mildly in the rabbits fed by an atherogenic diet. The improvements in LDL-C induced by (-)DOX and (+/-)DOX, however, might not be the reason for exploration about the increased survival rate in the rabbits fed by an atherogenic diet.</p>

Pharmacological characteristics of contractile responses regulated by P2Y receptors in circular smooth muscle of the rat gastric body / 药学学报

This study is to observe the difference in pharmacological characteristics between circular smooth muscles of rat isolated gastric body and gastric fundus, and to investigate the effects of nucleoside and nucleotide on circular smooth muscle of the rat gastric body and the involved receptors. Circular muscle strips of the rat gastric body and gastric fundus were prepared, and contractile responses to agonists were investigated with a technique of drug-receptor interaction in functional system. There was no significant difference between the circular muscle strips of the gastric body and gastric fundus in the responses to KCl, and no difference in EC50 values of contractile responses for 5-HT and His between the two kinds of preparations (P > 0.05). However, Emax values of contractile responses to 5-HT and His [(0.81 +/- 0.26) and (0.88 +/- 0.27) g] in gastric body were significantly smaller than those in gastric fundus [(2.67 +/- 0.61) and (1.90 +/- 0.68) g, P < 0.01], and EC50 value of CCh produced contractile response [(0.45 +/- 0.15) micromol x L(-1)] in gastric body was significantly higher than that in gastric fundus [(0.20 +/- 0.09) micromol x L(-1), P < 0.01]. In precontracted circular muscle strips of the gastric body, ATP (0.1-3000 micromol x L(-1)) produced only a contractile response concentration-dependently, but the same concentration of ATP induced a biphasic response (relaxation followed by a contraction) in precontracted circular muscle strips of the gastric fundus. ATP, UTP, ADP, 2-MeSATP and alpha,beta-MeATP produced contractile responses concentration-dependently in circular muscle strips of the rat gastric body. The EC50 value for 2-MeSATP [(7.2 +/- 5.2) nmol x L(-1)] was about 500 times lower than that for Ach [(3.47 +/- 1.20) micromol x L(-1)]. The rank order of potency for the contraction was 2-MeSATP>ADP>ATP=UTP>alpha,beta-MeATP>adenosine. The contractile responses to ATP and UTP were not significantly affected by phentolamine, propranolol, atropine or tetrodotoxin. In conclusion, there is a significant difference in pharmacological characteristics between the circular smooth muscles of the rat gastric body and gastric fundus and nucleotides might be important mediators responsible for the contraction via a specific P2Y receptor in circular smooth muscle of the rat gastric body.

Effect of isosorbide-5-mononitrate on sympathetic purinergic vasoconstriction of the rabbit saphenous artery / 药学学报

The aim of this study is to investigate the effect of isosorbide-5-mononitrate (ISMN) on the electric field stimulation induced sympathetic purinergic vasoconstriction of the rabbit saphenous arterial rings. Isometric vasoconstrictive responses to electric field stimulation and to exogenous noradrenaline and adenosine triphosphate were recorded. We found that the vasoconstrictive responses to electric field stimulation (15 V, 1 ms pulse duration, 2 - 16 Hz) were frequency-dependant in the rabbit saphenous arterial rings, and abolished by tetrodotoxin (0.1 micromol x L(-1)). The alpha1-adrenoceptor antagonist prazosin (1 micromol x L(-1)) did not affect the vascular responses to the electric field stimulation (2 -8 Hz). After a combination treatment with both alpha,beta-meATP (3 micromol x L(-1), desensitizing P2X1 receptors) and prazosin (1 micromol x L(-1)), the vasoconstrictive responses to electric field stimulation were abolished. When the arterial preparation was treated with ISMN (one preparation was exposed to only one concentration of ISMN), ISMN at 0.1 mmol x L(-1) significantly inhibited the vasoconstriction induced by electric stimulation at 8 Hz, 0.3 and 1.0 mmol x L(-1) significantly inhibited the vasoconstrictive responses to electric stimulation at 2 - 16 Hz. The highest concentration of ISMN (1.0 mmol x L(-1)) reduced the vasoconstrictive responses by 46% (2 Hz), 47% (4 Hz), 34% (8 Hz) and 22% (16 Hz), separately. ISMN (0.3 and 1.0 mmol x L(-1)) did not affect the vascular responses to exogenous noradrenaline (0.01-100 micromol x L(-1)) and adenosine triphosphate (1 mmol x L(-1)). It is reasonable to suggest that ISMN inhibits the purinergic vasoconstriction induced by sympathetic nerve stimulation via a prejunctional mechanism.

Effects of doxazosin enantiomers on alpha-adrenoceptors of isolated rabbit blood vessels / 药学学报

Doxazosin, a high selective alpha1-adrenoceptor antagonist, is considered as the first-line therapy for the patients with benign prostatic hyperplasia (BPH) and also produce several side effects in cardiovascular system. In this study, we observed the isometric vasoconstrictive responses of the rabbit isolated arterial rings to electric field stimulation and noradrenaline ( NA ) to study the effects of R-doxazosin ( R-DOX ) and S-doxazosin ( S-DOX ) on the alpha1-adrenoceptor-regulated vasoconstrictive responses in the rabbit isolated ear artery, mesenteric artery and pulmonary artery, and the effects of higher concentration of S-DOX and R-DOX on presynaptic alpha2-adrenoceptor-regulated purinergic vasoconstriction in the rabbit isolated saphenous artery. We found that R-DOX and S-DOX competitively inhibited the vasoconstriction induced by NA in the rabbit isolated ear artery, mesenteric artery and pulmonary artery. The pA2 values of R-DOX and S-DOX against NA in the rabbit isolated ear artery, mesenteric artery and pulmonary artery were 7. 91 +/- 0. 03 and 7. 53 +/- 0. 05, 7. 80 +/- 0. 05 and 7. 29 +/-0. 07, 8. 32 +/- 0. 06 and 7. 97 +/- 0. 07, respectively. The pA2 values of R-DOX in the three arterial preparations were significantly higher than those of S-DOX (P < 0. 01). R-DOX and S-DOX at the concentrations of 0. 1 - 10 micromol x L (-1) did not affect the vasoconstriction induced by electric stimulation in the rabbit isolated saphenous artery. R-DOX and S-DOX at 100 micromol x L(-1) in the rabbit isolated saphenous artery completely inhibited the vascular responses to exogenous NA, but did not affect the vascular responses to exogenous adenosine triphosphate (1 mmol x L(-1) ). It is reasonable to suggest that R-DOX and S-DOX competitively inhibit the vasoconstriction induced by NA in the rabbit ear artery, mesenteric artery and pulmonary artery, and the pA2 values of S-DOX are significantly lower than those of R-DOX. The higher concentration (10 micromol x L(-1)) of R-DOX and S-DOX does not affect the presynaptic alpha2-adrenoceptors at sympathetic nerve terminals of the rabbit saphenous artery.

Relation between adenosine A1 receptor and NMDA receptor on synaptic transmission in dentate gyrus of hippocampus / 药学学报

<p><b>AIM</b>To observe the effect of adenosine A, receptor antagonist on synaptic transmission in the dentate gyrus of hippocampus and its relations with NMDA receptor.</p><p><b>METHODS</b>Using electrophysiological technique to record the long-term potentiation (LTP), the relation between selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and NMDA receptor agonist/antagonist, in both basic synaptic transmission and 200 Hz high-frequency stimulation (HFS) induced LTP of the dentate gyrus of hippocampus in anesthetized rats, was studied.</p><p><b>RESULTS</b>DPCPX (6 mg x L(-1), 5 microL, icv) or NMDA (0.2 mg x L(-1), 5 microL, icv) was shown not to affect the synaptic transmission in the dentate gyrus in rats. DPCPX was found not to affect the keeping of LTP induced by HFS after icv NMDA. But the basic synaptic transmission and the magnitude of LTP induced by HFS in the dentate gyrus after icv NMDA could be enhanced significantly by icv DPCPX in advance. DPCPX could not affect the magnitude of LTP inhibited by AP5 (0.5 mg x L(-1), 5 microL) NMDA receptor antagonist, but the inhibitory effect of AP5 on LTP could be antagonized by icv DPCPX in advance.</p><p><b>CONCLUSION</b>The selective adenosine A1 receptor antagonist DPCPX could not affect the synaptic transmission in the dentate gyrus of hippocampus, but could significantly enhance the effect of NMDA receptor in both basic synaptic transmission and HFS induced LTP in the dentate gyrus of hippocampus in anesthetized rats.</p>

Effect of adenosine A1 receptor antagonist on learning and memory and analysis of its mechanism / 药学学报

<p><b>AIM</b>To study the effect of blocking adenosine A1 receptors on learning and memory and the relation with cholinergic and aminoacidergic nerve.</p><p><b>METHODS</b>Using step through test, spectrophotometry and HPLC method, the effect of selective adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 0.3, 0.15, 0.075, 0.03, 0.015 microgram, icv) on memory impairment by scopolamine (Scop, 3 mg.kg-1 i.p.) or 2-amino-5-phosphonovaleric (AP5, 2.5 ng, icv), acetylcholinesterase (AChE) activity and aminoacid level in brain of mice was studied.</p><p><b>RESULTS</b>DPCPX was shown to significantly improve scopolamine-induced memory impairment, but not AP5-induced. The activity of AChE in mouse brain was significantly inhibited by large doses of DPCPX in vitro and in vivo test. DPCPX(0.3 microgram, icv) was shown to significantly increase the content of glutamate and aspartic acid in brain of mice. DPCPX (0.3, 0.15 microgram, icv) significantly decrease GABA and increase Glu/GABA in brain of mice.</p><p><b>CONCLUSION</b>The selective adenosine A1 receptor antagonist DPCPX was shown to significantly improve scopolamine but not AP5-induced memory impairment. Large doses of DPCPX was shown to influence the AChE activity and the changes in aminoacid level in brain, especially increase Glu/GABA.</p>

Studies on pharmacokinetics of loganin and morroniside in Cornus officinalis injection in mice / 中国中药杂志

<p><b>OBJECTIVE</b>To establish a revered-phase HPLC method for the study of pharmacokinetics of loganin and morroniside in Cornus officinalis injectionin mice after a single oral and intravenous administrations.</p><p><b>METHOD</b>The Diamonsil C18 column (4.6 mm x 250 mm, 5 microns) was used as the analytical column and the mobile phase consisted of acetonitrile-methanol-0.2% formic acid (12:8:80) with the flow rate at 1.0 mL.min-1. The UV detection was set at 237 nm.</p><p><b>RESULT</b>The calibration curves of loganin and morroniside were linear in the range from 0.38 to 68.25 mg.L-1(r = 0.9999), and from 0.66 to 117.22 mg.L-1(r = 0.9999), respectively. The lowest determination concentrations of loganin and morroniside were 0.10 and 0.16 mg.L-1, respectively. The recoveries and relative standard deviations of loganin were 99.6% (2.0%), 102.0% (1.0%), 87.9% (7.2%), and those of morroniside were 99.2% (2.5%), 104.1% (1.2%), 92.7% (4.2%), respectively. The relative standard deviations of within-day and between-day precision for the method were all less than 6.8%. After a single intravenous administration of Cornus officinalis injection to mice, the mean plasma concentration-time courses were found to fit a two-compartment open model, the main pharmacokinetic parameters of loganin were as follows: T1/2(alpha), T1/2(beta), K21, K12, K10, V(c), AUC, CL were 3.2 min, 25.1 min, 5.997 h-1, 4.981 h-1, 3.564 h-1, 0.551 L.kg-1, 13.59 mg.L-1.h, 1.965 L.kg-1.h-1, respectively and those of morroniside were 3.6 min, 21.5 min, 5.926 h-1, 3.833 h-1, 3.797 h-1, 0.647 L.kg-1, 27.15 mg.L-1.h, 2.457 L.kg-1.h-1, respectively.</p><p><b>CONCLUSION</b>It is the first time to establish the revered-phase HPLC method to determine concentrations of loganin and morroniside in plasma and to obtain their pharmacokinetic parameters and characteristics.</p>

Chiral separation and preparation of three new antagonists of alpha 1-adrenoceptors by chiral mobile phase HPLC / 药学学报

<p><b>AIM</b>To establish new methods for the chiral separation and preparation of three new drugs, alfuzosin, terazosin and doxazosin.</p><p><b>METHODS</b>By optimizing factors which affect the chiral separation, modifier of solvent, chiral additive, pH of mobile phase, modifier of organic base and stationary phase, the optimum condition for chiral separation were selected. The preparation of enantiomers was carried out on semi-preparative reverse phase column (7.8 mm x 250 mm C4 5 microns). Acetonitrile-water modified by the addition of carboxymethyl-beta-cyclodextrin (2%-5%, w/v) was applied as chiral mobile phase.</p><p><b>RESULTS</b>The enantiomers of three new drugs were base-line-separated and milligram-scale samples of enantiomer were obtained.</p><p><b>CONCLUSION</b>The newly established method can be used in research and development of the enantiomers of three new drugs.</p>