Development of antibody-mediated extraction followed by GC/MS (antibody/GC/MS) and its application to iloprost determination in plasma

A high performance liquid radiochromatographic assay for the simultaneous analysis of iloprost and misoprostol

A high-performance liquid chromatographic (HPLC) method utilizing ultraviolet absorbance coupled with radioisotove detection was developed for the precise and simultaneous determination of iloprost and misoprostol. This assay allows complete resolution of iloprost diastereoisomers and has a total run time of approximately twenty minutes. Samples were prepared for chromatographic analysis by extracting a mixture of tritiated drugs from rat plasma with acetonitrile. The resulting solutions were chromatographed on a reversed phase Zorbax Rx-C8 column using 0.02M potassium phosphate (pH 3.0), acetonitrile, and methanol (46:30:24, v/v) at a flow rate of 1.7 mL/min. 2-Naphthoic acid was employed as an internal standard. The correlation coefficient for varying concentrations of tritiated iloprost (12.7 Ci/mmol specific activity) from 2.18 ng/mL to 21.8 ng/mL was 0.995, and the correlation coefficient for concentrations of tritiated misoprostol (50 Ci/mmol specific activity) from 0.617 ng/mL to 6.17 ng/mL was 0.993. The high selectivity and sensitivity of this assay make it useful for the simultaneous quantitation of iloprost and misoprostol.

Measurement of canine urinary thromboxanes by GC-MS and HPLC-RIA

Immunoaffinity extraction/gas chromatography-mass spectrometry (IA/GC-MS) and high-performance liquid chromatography-radioimmunoassay (HPLC-RIA) methods were developed to analyse a major human urinary thromboxane metabolite, 2,3-dinor thromboxane B2, in the urine of dogs, a species commonly used for functional studies of thromboxane pharmacology. The beta-metabolite 2,3-dinor TXB2 was unequivocally identified in pooled normal canine urine by IA/GC-MS, and its excretion measured in 6 anesthetized dogs over a 7h period as 2001 +/- 132 pg 2,3-dinor TXB2/mg creatinine (range 624-4493 pg/mg). Thromboxane immunoreactivity co-eluting with synthetic 2,3-dinor TXB2 was also identified by HPLC-RIA and similarly determined (2585 +/- 276 pg/mg creatinine). Exogenous 2,3-dinor TXB2 could be quantitatively recovered by both methodologies over a wide range of concentrations (50-5000 pg/mL), although with better precision by IA/GC-MS (added vs recovered; m = 1.05, r = 0.99) compared with HPLC-RIA (added vs recovered; m = 0.89, r = 0.89). The cyclooxygenase inhibitor indomethacin given by infusion in anaesthetized dogs (2.5, 8 and 25 micrograms/kg/min) dose-dependently inhibited 2,3-dinor TXB2 excretion measured by IA/GC-MS, with maximal inhibition (83.0 +/- 4.2%) being achieved after 6h (25 micrograms/kg/min). Similar results were obtained by HPLC-RIA, with a correlation of 0.88 (slope = 0.9) between the methodologies in samples after drug treatment. These data suggest that the profile of metabolism and excretion of thromboxanes in dogs resembles that of man, and provide a useful animal model for the non-invasive in vivo assessment of inhibitors of thromboxane biosynthesis.

Application of an alpha-sidechain length-specific monoclonal antibody to immunoaffinity purification and enzyme immunoassay of 2,3-dinor-6-keto-prostaglandin F1 alpha from human urine

2,3-Dinor-6-keto-prostaglandin F1 alpha (2,3-dinor-6-keto-PGF1 alpha) is a major urinary metabolite of PGI2 (prostacyclin) and one of the most reliable parameters of PGI2 production in vivo. A mouse was immunized with 2,3-dinor-6-keto-20-carboxy-PGF1 alpha conjugated to bovine serum albumin for preparation of a monoclonal antibody which recognized the difference in the alpha-sidechain length of 6-keto-PGF1 alpha and its 2,3-dinor-metabolite. A sensitive and specific enzyme immunoassay was developed by the solid-phase competition method with 2,3-dinor-6-keto-20-carboxy-PGF1 alpha labeled with peroxidase protein. The detection range of the assay was 14-1200 fmol (IC50 = 120 fmol). The cross-reactivities of the antibody with 6-keto-PGF1 alpha, 6,15-diketo-13,14-dihydro-PGF1 alpha, and other arachidonate metabolites were less than 0.01%. An immunoaffinity column was prepared by coupling the anti-2,3-dinor-6-keto-PGF1 alpha antibody to BrCN-activated Sepharose 4B. Human urine was applied to an octadecylsilyl silica cartridge, and the extract was applied to the immunoaffinity column. This procedure allowed an efficient separation of 2,3-dinor-6-keto-PGF1 alpha from unidentified urinary substances which interfered with immunoassay. Validity of the results obtained by the enzyme immunoassay was confirmed by GC/MS employing selected ion monitoring for quantification.

Immunoaffinity purification of prostaglandin E2 and leukotriene C4 prior to radioimmunoassay: application to human synovial fluid

When human synovial fluid as such was subjected to radioimmunoassays of prostaglandin E2 (PGE2) and leukotriene C4 (LTC4), there was no linear increase in PGE2 and LTC4 as the amount of synovial fluid was raised. For removal of substances thus disturbing the assay we developed a method of immunoaffinity purification of PGE2 and LTC4. A monoclonal antibody against PGE2 or LTC4 was coupled to BrCN-activated Sepharose 4B. When synovial fluid mixed with radiolabelled PGE2 or LTC4 was applied to the column of immobilized antibody, the ligand was adsorbed to the column and eluted with a mixture of methanol/water in a recovery of about 80%. The purified material showed a linearity between the amount of the sample and the value of radioimmunoassay. The one-step method was applied to synovial fluid from patients with rheumatoid arthritis, osteoarthritis and other joint diseases.

Pharmacokinetics of tissue-type plasminogen activator during acute myocardial infarction in men. Effect of a prostacyclin analogue

BACKGROUND

Coronary reocclusion complicates the thrombolytic therapy of acute myocardial infarction despite the routine use of aspirin. This is consistent with experimental studies demonstrating that multiple agonists, in addition to thromboxane A2, mediate the platelet activation underlying reocclusion. Consequently, a more potent antiplatelet therapy with a broader spectrum of activity than aspirin may be required in this setting. Prostacyclin and its more stable analogue, iloprost, inhibit platelet aggregation to all known agonists and exert an additional effect over aspirin alone. Experiments in animal models have demonstrated, however, that iloprost increases the clearance of tissue-type plasminogen activator (t-PA) and impairs thrombolysis in vivo. This study examines whether a similar interaction occurs in humans.

METHODS AND RESULTS

Twelve patients with acute myocardial infarction received t-PA intravenously, 60 mg in the first hour and a maintenance infusion of 13.3 mg/hr for 3 hours. Patients were assigned in a double-blind fashion to iloprost (2 ng/kg/min) or placebo following the initial 90 minutes of the maintenance infusion of t-PA. Iloprost decreased mean arterial blood pressure (-10 +/- 2.9 mm Hg, p less than 0.05) but did not alter heart rate. Steady-state plasma iloprost concentration was 591 +/- 64 pmol/l. At this concentration, iloprost markedly inhibited platelet aggregation in vitro, particularly in the presence of aspirin. Steady-state clearance of t-PA was unchanged by iloprost (454 +/- 65 versus 443 +/- 136 ml/min in controls, p = NS). Furthermore, neither elimination kinetics nor plasma protein binding of t-PA was altered by iloprost.

CONCLUSIONS

At plasma levels that exert a potent antiplatelet effect, iloprost did not alter the pharmacokinetics of t-PA in men. Prostacyclin analogues may prove useful as an adjunct to plasminogen activators, particularly in patients at high risk for thrombotic reocclusion.

Characterization of oral sustained release preparations of iloprost in a pig model by plasma level monitoring

Iloprost (5-[(E)-1S,5S,6R,7R)-7-hydroxy-6-[(E)-3S,4RS)-3-hydroxy-4- methyl-octen-6-inyl]-bicyclo[3.3.0]-oct-3-ylidene)-pentanoic acid) is a chemically stable PGI2-mimetic with high pharmacological potency. Therapeutic efficacy in various disease stages (e.g. peripheral arterial occlusive disease, M. Raynaud and thromboangiitis obliterans) was shown after repeated once-a-day infusion treatment over several weeks. In order to facilitate drug therapy an oral dosage form is desirable. As a first step, a suitable animal model was needed to screen several formulation variants prior to characterization of promising candidates in man. After intravenous infusion treatment, the pig exhibited - similar to man - strictly dose-dependent steady state plasma levels and a total iloprost clearance of approximately 26 ml/min/kg (man approximately 20 ml/min/kg). Partial similarity of physiology and anatomy of the GI-tract and the possibility to administer intact capsule dosage forms led to a series of screen experiments with several sustained release preparations (pellets and matrix tablets) of iloprost exhibiting different in-vitro drug release profiles. A good correlation of in-vitro dissolution and in vivo plasma level data was obtained for all preparations containing the pellet neutral polymer. For the other formulations slight differences between duration of liberation and plasma level or time of maximum dissolution rate and tmax of plasma levels was observed. In the case of ionized polymers or matrix tablets, in vitro dissolution profiles were slightly different from in vivo data. This might be due to different dissolution behaviour in the gastro-intestinal tract. The pig seems to be a model that is suitable for verifying drug liberation profile in-vivo. Based upon plasma levels obtained in animals, selection of a formulation for characterization in man can be made.

Autocrine control of adipose cell differentiation by prostacyclin and PGF2 alpha

The mitogenic-adipogenic effect exerted by arachidonic acid, which leads to terminal differentiation of Ob1771 mouse preadipocytes, has been shown to be (i) blocked by cyclooxygenase inhibitors, (ii) mimicked by a stable analogue of prostacyclin (carbaprostacyclin) and (iii) potentiated by PGF2 alpha. Since these prostanoids are known to be synthesized and secreted by preadipocytes, we have proposed that both prostacyclin as the key mediator and PGF2 alpha as a modulator control the expression of terminal events of adipose conversion by means of an autocrine mechanism (Gaillard, D. et al. and Negrel, R. et al. Biochem. J. (1989) 257, 389-397 and 399-405). In order to test this hypothesis, the release of prostacyclin, characterized under the form of its stable degradation product 6-keto-PGF1 alpha, and that of PGF2 alpha have been studied in the culture medium of Ob1771 cells. A striking increase in the release of 6-keto-PGF1 alpha and to a minor degree of PGF2 alpha was observed when cells were exposed to arachidonic acid as shown by using [3H]arachidonic acid prelabelled cells or by radio-immunoassays. Since antagonists of PGF2 alpha and PGI2 receptors were not available, specific antibodies directed against PGF2 alpha and 6 beta-PGI1, another stable analogue of prostacyclin, were added as neutralizing agents in the culture medium. These antibodies were able to counteract the mitogenic-adipogenic effect of arachidonic acid. Prostacyclin and PGF2 alpha thus appear as autocrine mediators in the process of adipose conversion.

Synthesis of a deuterated analogue and development of antibody/GC/MS for the determination of nocloprost in plasma

An analytical method for the determination of the PGE derivative nocloprost in plasma was developed combining the features of both radioimmunoassay and GC/MS. The antibody usually employed in nocloprost radioimmunoassay was coupled to Sepharose 4B and used as a stationary phase for the extraction of the drug. After appropriate derivatisation, nocloprost was determined by GC/MS in the negative ion-chemical ionisation mode. As an internal standard deuterated nocloprost was synthesized and added to the plasma samples before extraction. The extraction recovery was 94% and the limit of detection was 5 pg/ml. Intra- and interassay precision at 100 pg/ml was calculated as 3.3 and 4.0%, respectively.

Immunoaffinity purification of 11-dehydro-thromboxane B2 from human urine and plasma for quantitative analysis by radioimmunoassay

11-Dehydro-thromboxane B2 is now considered to be a reliable parameter of thromboxane A2 formation in vivo. An immunoaffinity purification method was developed for radioimmunoassay of this compound contained in human urine and plasma. Monoclonal anti-11-dehydro-thromboxane B2 antibody was prepared and coupled to BrCN-activated Sepharose 4B. Human urine or plasma was applied to a disposable column of the immobilized antibody. After the column was washed with water, 11-dehydro-thromboxane B2 was eluted with methanol/water (95/5) with a recovery of more than 90%. The purified extract was subjected to a radioimmunoassay utilizing 11-[3H]dehydro-thromboxane B2 methyl ester and the monoclonal anti-11-dehydro-thromboxane B2 antibody. The detection range of the assay was 10-600 fmol (IC50 = 90 fmol). The cross-reactivities of the antibody with thromboxane B2, 2,3-dinor-thromboxane B2, and other arachidonate metabolites were less than 0.05%. These compounds were efficiently separated from 11-dehydro-thromboxane B2 by the immunoaffinity purification. This procedure also allowed the separation of 11-dehydro-thromboxane B2 from unidentified urinary and plasma substances which interfered with the radioimmunoassay. Validity of the results obtained by the radioimmunoassay was confirmed by GC/MS employing selected ion monitoring for quantification.

Intraoperative management of patients with heparin-induced thrombocytopenia

For 11 patients with confirmed heparin-induced thrombocytopenia, we used reversible platelet inhibition with iloprost, a stable prostacyclin analogue, to permit safe heparin administration for cardiac (n = 9) or vascular (n = 2) operations. In vitro, iloprost (0.01 mumol/L) prevented both heparin-induced platelet aggregation and 14C-serotonin release in all patients. Therefore, intraoperatively, a continuous infusion of iloprost was started before administration of heparin and was continued until 15 minutes after administration of protamine. For cardiac patients, after heparin administration, the whole blood platelet count did not change (171,000 +/- 29,000/microL versus 174,000 +/- 29,000/microL, mean +/- standard error of the mean); no spontaneous platelet aggregation was observed, and plasma levels of the alpha-granule constituents platelet factor 4 and beta-thromboglobulin increased from 38 +/- 14 and 140 +/- 18 ng/mL to 591 +/- 135 and 235 +/- 48 ng/mL, respectively. Fibrinopeptide A levels actually decreased from 287 +/- 150 to 27 +/- 6 ng/mL. Furthermore, adenosine diphosphate-induced platelet activation was preserved, postoperative bleeding times were unchanged, and no heparin-related deaths occurred. Similar results were obtained in both vascular patients. We conclude that temporary platelet inhibition with iloprost now permits safe heparin administration in all patients with heparin-induced thrombocytopenia who require a cardiac or vascular operation.

Quantitative profiling of 6-ketoprostaglandin F1 alpha, 2,3-dinor-6-ketoprostaglandin F1 alpha, thromboxane B2 and 2,3-dinor-thromboxane B2 in human and rat urine by immunoaffinity extraction with gas chromatography-mass spectrometry

A rapid and simple method based on immunoaffinity extraction, stable isotope dilution and gas chromatography-mass spectrometry has been developed for profiling urinary metabolites of prostacyclin and thromboxane. 6-Ketoprostaglandin F1 alpha (6-keto-PGF1 alpha), 2,3-dinor-6-ketoprostaglandin F1 alpha (2,3-dinor-6-keto-PGF1 alpha), thromboxane B2 (TXB2) and 2,3-dinor-thromboxane B2 (2,3-dinor-TXB2) were quantitatively extracted from human or rat urine spiked with deuterated internal standards using mixed-bed columns containing immobilized anti-6-keto-PGF1 alpha and anti-TXB2 antibodies (cross-reacting with 2,3-dinor-6-keto-PGF1 alpha and 2,3-dinor-TXB2, respectively). The extract was directly derivatized to form pentafluorobenzyl ester, methyloxime, trimethylsilyl ether derivatives. Quantitation was performed by stable isotope dilution assay and high-resolution gas chromatography-negative ion chemical ionization mass spectrometry, by monitoring the carboxylate anions (M-181) of the derivatized metabolites. The method was applied to evaluate the urinary excretion of 6-keto PGF1 alpha, 2,3-dinor-6-keto-PGF1 alpha, TXB2 and 2,3-dinor-TXB2 in humans and rats. Results were in accordance with previously reported data obtained by other methods. Novel data on the urinary excretion of 2,3-dinor-6-keto-PGF1 alpha in rats under basal conditions are presented. This sensitive and selective method represents a significant advance in terms of rapidity and simplicity over other immunoaffinity-gas chromatography-mass spectrometry methods for measuring single prostanoids, such as 6-keto-PGF1 alpha or TXB2, since it allows profiling of a group of metabolites whose balance is important in several physiopathological conditions.

Cigarette smoking: profiles of thromboxane- and prostacyclin-derived products in human urine

Thromboxane (TX) B2, 2,3-dinor-TXB2, 11-dehydro-TXB2, 6-oxoprostaglandin (PG)F1 alpha and 2,3-dinor-6-oxo-PGF1 alpha were measured in 24 h urine samples obtained from 30 apparently healthy chronic cigarette smokers and 37 closely matched non-smoking control subjects. Samples were analysed using a newly developed assay based on immunoaffinity chromatography and capillary column gas chromatography/electron capture negative ion chemical ionisation mass spectrometry. There were significant and comparable increases in the excretion rates of both 2,3-dinor-TXB2 and 11-dehydro-TXB2 in the smoking compared with the non-smoking group (2P less than 0.001). Excretion rates of 2,3-dinor-TXB2 were 418 +/- 35 and 265 +/- 26 pg/mg creatinine in the two groups, respectively. 11-Dehydro-TXB2 excretion rates were 440 +/- 54 and 221 +/- 18 pg/mg creatinine, respectively (mean +/- S.E.). There were significant (2P less than 0.05) positive correlations between average reported cigarette consumption and excretion of both thromboxane metabolites. There were small but significant (2P less than 0.02) increases in the excretion rates of both 6-oxo-PGF1 alpha and 2,3-dinor-6-oxo-PGF1 alpha in the smoking compared with the non-smoking group. There was no significant difference in the rates of excretion of TXB2 in the two groups. The effects of acute cigarette smoke exposure (five cigarettes in 2 h) was also studied in four normally non-smoking healthy volunteers. There was no significant change in the excretion rate of any of the eicosanoids measured during control and smoking periods (at least 2 weeks apart), indicating that increased TXA2 biosynthesis in chronic smokers is unlikely to be a consequence of acute platelet activation.

Simultaneous determination of the primary prostanoids prostaglandin E2, prostaglandin F2 alpha and 6-oxoprostaglandin F1 alpha by immunoaffinity chromatography in combination with negative ion chemical ionization gas chromatography-tandem mass spectrometry

The simultaneous determination of prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) and 6-oxoprostaglandin F1 alpha (6-oxo-PGF1 alpha) in urine using immunoaffinity chromatography in combination with negative ion chemical ionization gas chromatography-tandem mass spectrometry (NICI-GC-MS-MS) is described. Monoclonal antibodies against PGE2 (100% cross-reactivity with 6-oxo-PGF1 alpha) and PGF2 alpha were both coupled to a derivatized agarose matrix. After extraction with a C18 cartridge the sample was applied to the immunoaffinity column. The prostaglandins with eluted with acetone-water and the methoxime-pentafluorobenzyl-trimethylsilyl (MO-PFB-TMS) derivatives (PGE2 and 6-oxo-PGF1 alpha) and the PFB-TMS derivative (PGF2 alpha) were quantified by GC-MS-MS. For reproducibility experiments, spiked urine samples were analysed several times. The correlation coefficients were 0.997 (6-oxo-PGF1 alpha) and 0.999 (PGE2 and PGF2 alpha) and the slopes were 0.99 and 1.03, respectively. The inter-assay coefficient of variation ranged from 8.6 to 9.5% for the unspiked urine samples and from 2.0 to 5.2% for the spiked samples. This method offers several advantages, e.g., high specificity and sensitivity, good reproducibility and an increase in sample throughput.

High performance liquid chromatographic determination of thromboxane B2 in human serum as a methoxime-panacylester derivative

A high performance liquid chromatographic (HPLC) method was developed to measure thromboxane B2 (TxB2) levels in human serum. Serum samples (2 mL) were extracted using solid phase extraction columns in a C 18/silica mode sequencing approach. The internal standard, 6-ketoprostaglandin F1 alpha, was added to the serum extracts. The eicosanoids were doubly derivatized, first with panacyl bromide, then with methoxyamine to form methoxime-panacyl ester derivatives. The eicosanoid derivatives were chromatographed using a reverse phase HPLC system with UV detection (254 nm). Assay linearity was demonstrated with fortified TxB2 standards in 3% bovine serum albumin over a range of 25 to 500 ng/mL (r greater than or equal to 0.994). There was no significant interday difference or bias in assay results for pooled standards at 75, 226 and 376 ng/mL concentrations (p greater than 0.05). Pooled estimates of precision at these levels indicate an assay relative standard deviation 6-9%. The HPLC assay was used to quantitate TxB2 levels in human serum. Results were consistent with previously published values when drug-free serum was analyzed to assess ex vivo TxB2 formation.

Pharmacokinetics and pharmacodynamics of radio-labeled iloprost in elderly volunteers

The plasma levels and excretion of tritium-labeled iloprost in healthy elderly male and female volunteers have been measured after i.v. infusion of 2 ng X kg-1 X min-1 for 4 h and oral administration of 0.1 and 0.48 microgram/kg. During infusion, a steady-state of labeled compounds in the plasma was not achieved. Total radioactivity declined from a mean of 408 pg equiv/ml in three phases, with half-lives of 24 min, 1.7 h and 5.0 h, respectively. A steady-state of unchanged iloprost was reached rapidly with a peak of 81 pg/ml. Plasma levels declined biphasically with half-lives of 6 min and 31 min. Total clearance was 24 ml X min-1 X kg-1. Maximum concentrations of labeled substances after oral administration were 307 and 1,051 pg equiv/ml after 29 and 39 min, respectively. The peak of unchanged iloprost (116 pg/ml) was observed 7.5 min after an oral dose of 0.48 microgram/kg. Bioavailability was 16%. Iloprost was totally metabolized and the metabolites were mainly excreted in urine. The main biotransformation products in plasma and urine were tentatively identified by cochromatography as dinor- and tetranoriloprost and their glucuronides. ADP-induced platelet aggregation was reduced by 60% during the i.v. infusion and 15 min after oral administration of 0.48 microgram/kg. Heart rate and blood pressure were virtually unaffected. Common side-effects were facial flush, headache and nausea.

Antibody-mediated extraction/negative-ion chemical ionization mass spectrometric measurement of thromboxane B2 and 2,3-dinor-thromboxane B2 in human and rat urine

An antibody-mediated extraction method for gas chromatographic-mass spectrometric analysis of thromboxane A2 (TXA2) urinary metabolites is reported. An antibody (Ab) raised against thromboxane B2 (TXB2) (35% cross-reacting with 2,3-dinor-TXB2) was coupled to CNBr-activated Sepharose 4B (Se) and used as stationary phase for simultaneous extraction of both compounds from urine. After addition of deuterium-labeled TXB2 as internal standard, rat or human urine was percolated through a small Ab-Se column. After being washed, the eluate was directly derivatized to the pentafluorobenzyl ester, methyloxime, and trimethylsilyl ether. Quantitation was performed by high-resolution gas chromatography-negative-ion chemical ionization mass spectrometry, monitoring the carboxylate anions. This method was applied to evaluate the urinary excretion of TXB2 and 2,3-dinor-TXB2 in humans and rats. We report on the excretion of 2,3-dinor-TXB2 in the rat. This novel approach to the extraction of urinary thromboxanes is more convenient than currently available methods in terms of simplicity, rapidity, and recovery. This method could be extended to any other prostanoid for which an antibody could be obtained.

Development of a selective clean-up method using immobilized antibody and its application to HPLC and GC/MS determination of a carbacyclin derivative, CS-570, in plasma

Methods for the determination of CS-570, a chemically stable prostacyclin analogue, in plasma were developed by using an immobilized antibody column followed by fluorescence HPLC and GC/MS. The CS-570 antibody, obtained from rabbit plasma by giving CS-570-BSA for a few months, was coupled to Sepharose 4B and used as extraction phase for sample clean-up and extraction of the drug. A plasma sample was applied to this column, washed with water and the drug was eluted with 90% acetonitrile. 0.02% (w/v) 9-anthryldiazomethane (ADAM) was added to the extract to form a fluorescent derivative. The CS-570-ADAM adduct exhibited high sensitivity when applied to HPLC with fluorescence detection and column switching. The detection limit was 1 ng/mL when 1 mL of plasma was available. Additionally, a pentafluorobenzyltrimethylsilyl derivative of CS-570 showed excellent sensitivity when determined by capillary GC interfaced to negative ion chemical ionization MS using a stable isotope labelled analogue as an internal standard.

Limitation of myocardial unperfused area and necrotic zone 24 hours and 7 days after coronary artery ligation in rats by the stable prostacyclin analogue iloprost

Protective effects of prostacyclin (PGI2) and Iloprost in experimental cardiac ischemia are reported by several authors. However, the effects of continuous administration on the final outcome of myocardial infarction are not yet known. We investigated the effects of Iloprost on cardiac unperfused area (UA) and necrotic zone (NZ) as assessed by Evans blue perfusion and extraction and nitrobluetetrazolium staining, respectively, using osmotic minipumps for continuous intravenous drug administration. Starting 3-4 hours after left descending coronary artery-ligation (LAD-L) Iloprost was infused at doses of 0.1 microgram and 0.5 microgram X kg-1 X min-1. While the lower dose is below pharmacological effect level, the higher dose in rats slightly lowered blood pressure and effectively inhibited platelet aggregation. LAD-L in control rats resulted in UA and NZ extending to 34.2 and 16.9%, respectively, of total ventricular mass (VM) after 24 hours and 28.3 and 21.3% of VM, respectively, after 7 days. At the dose of 0.1 micrograms X kg-1 X min-1 Iloprost was ineffective in reducing UA 24 hours after LAD-L. However, at 0.5 microgram X kg-1 X min-1 Iloprost with UA and NZ of 16.3 and 8.4% of VM, respectively, after 24 hours and 8.5 and 5.2% of VM, respectively, after 7 days reduced the extension of myocardial infarction by approximately 50% after 24 hours and 70% after 7 days, as compared to controls. As assessed in unperfused ventricular tissue after LAD-L and normal myocardium of sham-operated rats following 24 hours of Iloprost infusion, myocardial tissue concentrations of Iloprost amount to approximately half of the plasma levels irrespective of LAD-L.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of the prostacyclin analogue iloprost in man

Plasma levels of the prostacyclin analogue, iloprost, were measured by antibody/GC/MS in healthy male volunteers given 1 and 3 ng/kg per min i.v. for 45 min, and 1 microgram/kg p.o. Following i.v. infusion, the steady-state plasma levels of iloprost were strictly dose-dependent (46 +/- 8 pg/ml and 135 +/- 24 pg/ml). The disposition was biphasic with half-lives of 3-4 min and 0.5 h. After oral administration, absorption of the drug was extremely rapid, the maximum plasma level of 251 +/- 32 pg/ml being achieved after 10 +/- 6 min. The bioavailability was 16 +/- 4%. Platelet aggregation induced by 2 microM ADP was reduced by 53% and 68% at the end of the two different infusions, and by 68% 15 min after p.o. administration. The ex-vivo inhibition of platelet aggregation by iloprost was not affected by preceding drug treatment. The cAMP content of platelets was increased by a factor of 2.5 at the end of the infusions and to a lesser extent 15 min after oral dosing. A slight increase in heart rate occurred during the infusion and within 30 min after oral administration; blood pressure was virtually unaffected. Except for transient side-effects (facial flush and headache) no adverse reactions were observed.

Determination of prostaglandin E1 in plasma with picogram per millilitre sensitivity by double antibody extraction and column switching high-performance liquid chromatography

Prostaglandin E(1) (PGE(1)) is a vaso- and arteriodilator that is used for the experimental treatment of a variety of vascular diseases. A high-performance liquid chromatography (HPLC) method was developed for the purpose of quantifying PGE(1) in the plasma of patients undergoing constant infusion therapy. Plasma (0.5 ml) was extracted with a double antibody precipitation technique and the PGE(1)-immunoprecipitate was isolated and washed by repeated resuspension and centrifugation. PGE(1) was recovered from the precipitate by extraction with acetonitrile and derivatized with panacyl bromide for determination on a heteromodel column switching HPLC system with fluorescence detection. The content of PGE(1) in immunoextracts was determined by HPLC peak height comparison against a standard curve of PGE(1) peak height vs amount derivatized. The result was corrected for the plasma extraction efficiency (determined with radiolabelled PGE(1)) to obtain the plasma concentration. Standard curves were linear from 25 to 400 pg (r > 0.99) and the y-intercepts were not significantly different from zero (p < 0.05). The immunoextraction recovery from six human donors was 63.5 +/- 2.0% (S.D., n = 18). The quantification limit of the method was 50 pg ml(-1) (signal-to-noise ratio 3:1), at which the estimated assay relative standard deviation was 18%. The utility of the method for the measurement of PGE(1) plasma levels during constant intravenous infusion was demonstrated in a dog study.