Determination of nitrates in plasma.

Because of the high efficacy of existing nitrates, alternative dosage formulations have been developed rather than new compounds. These new formulations challenge the analyst to develop analytical methods with lower sensitivity and higher precision. Isosorbide dinitrate is analysed in the presence of its major metabolites isosorbide 2-mononitrate and isosorbide 5-mononitrate. The present method is an improvement over previously published methods. It is not possible to analyse glyceryl trinitrate and its major metabolites 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate with the necessary sensitivity in one chromatogram. A 2-step procedure is therefore applied. The extraction procedures, the gas chromatographic conditions, imprecision and inaccuracy of the methods, the lower limits of quantitation, sample chromatograms and applications of all methods are described in detail. Thus, the possibilities of modern analytical methods in the determination of nitrates in the lower picogram region are demonstrated.

Ultrasonographic resolution time for amebic liver abscess.

Hepatic ultrasonography not only can be used to detect amebic liver abscess, but can follow its resolution. Twenty-five patients with 32 abscesses had hepatic sonography performed repeatedly. Sonography clearly demonstrated abscesses of 1-22 cm; 19 patients (76%) had abscesses only in the right lobe of the liver, and 22 (88%) had solitary abscesses. Resolution time ranged from 2 months for the smallest abscess to 20 months for the largest. Four abscesses initially had a heterogenous partially solidified pattern. All abscesses healed completely, leaving normal hepatic sonographic patterns.

[Studies of the effect of effectors on proteinases from rat liver lysosomes in vitro]. / Untersuchungen zum Einfluss von Effektoren auf die Proteinasen aus Rattenleberlysosomen in vitro.

New test systems using azocasein or double-labelled cytosol proteins from rat livers were developed to test the influence of a lot of possible effectors on lysosomal proteinases from rat liver. All as yet tested inhibitors of serine proteinases did not show substantial inhibition of the sum of all proteinases activity in the soluble part of rat liver lysosomes. Moreover at least 200 different substances were found to be without significant effects against these lysosomal proteinases. These proteinases are only effected by peptide aldehydes and other compounds which influence thiolproteinases. This provides further evidence that mainly the thiolproteinases (cathepsin L, H and B) are responsible for the proteolytic activity in rat liver lysosomes.

Determination of methyldopa in plasma using high-performance liquid chromatography with electrochemical detection. Application to pharmacokinetic/bioavailability studies.

The problem of quantitatively measuring methyldopa (a-methyldopa) in biological matrices after applying therapeutic doses to humans is still challenging. Numerous methods have been published but most of them require a tedious, time-consuming sample preparation, are not specific enough or lack the necessary sensitivity. As the basis of conclusive human pharmacokinetic and bioavailability/bioequivalence studies is a validated analytical method, which is reliable, selective, sensitive and able to proceed hundreds or even thousands of samples in a limited time, an assay to fulfill these needs was developed. The present method employs a hiph-performance liquid chromatographic system consisting of a pump, an ODS column, an autosampler and an electrochemical detector. The assay is sensitive down to 50 ng/ml plasma, the calibration curves are linear in a range of 50-2000 ng/ml, the chromatographic peaks are well resolved and the precision and accuracy are excellent. The assay has been successfully used for the determination of very low methyldopa plasma levels during several clinical studies.

Improved high-performance liquid chromatographic method for the determination of tiotixene in human serum.

The problem of accurate determination of tiotixene in body fluids is still challenging. Several methods have been published but most of them require a tedious, time-consuming sample preparation, are not specific enough and lack the necessary sensitivity or require highly sophisticated analytical devices. As carefully validated analytical methods represent the basis of conclusive clinical trials (e.g. evaluating bioavailability/bioequivalence), an assay was developed to fulfill these needs. The method present employs an HPLC system combined with a UV-detector and uses perazine as an internal standard. The achieved lower limit of detection in serum was 0.05 ng/ml and the calibration curves were linear in the range of 0.5-20 and 0.1-2.0 ng/ml, respectively. The chromatographic peaks were well resolved and the cis-/transisomers well separated. The imprecision and inaccuracy data typically ranged from 2 to 7%; the recovery from serum was always better than 80%. The assay has been successfully used for the determination of very low tiotixene serum levels during several clinical studies.

High-performance liquid chromatographic determination of trans-doxepin and desmethyldoxepin.

An improved high performance liquid chromatographic (HPLC) assay for the quantitative determination of trans-doxepin (I) and desmethyldoxepin (II) in body fluids is presented. This HPLC assay, employing a UV-detector and perazine (III) as an internal standard, provides a very sensitive and selective determination in the low ng/ml range. The lower limit of quantification was 0.426 ng/ml (I) and 0.50 ng/ml (II); respectively. The calibration curve was linear in the measured range of 0.426-34.08 ng/ml (I) and 0.50-40 ng/ml (II). In combination with the excellent precision and accuracy data (c.v. values typically lower than 5%) and a recovery exceeding 90% for both compounds, the method is well suited for quantitative determinations of plasma samples generated during clinical studies, eg. evaluating the pharmacokinetics and/or bioavailability/bioequivalence as well as evaluations of clinical response.

Triple stage quadrupole mass spectrometric determination of bromocriptine in human plasma with negative ion chemical ionization.

A new MS/MS assay for the quantitative determination of bromocriptine in body fluids is presented. The selective reagent gas in combination with the registration of selected, characteristic negative ions (SIM) after collision activated decomposition (CAD) in a Triple-Stage-Quaddrupole-mass spectrometer, provides an exceptional selective and sensitive assay in the low pg/ml range. The lower limit of detection was about 1 pg/ml (at optimal measuring conditions) and the calibration curve was linear in the range of 10-200 pg/ml. The coefficient of variation for the imprecision and inaccuracy data was typically below 10%; the recovery from plasma always exceeded 75%. The sample introduction to the mass spectrometer was done by a direct exposure probe (DEP). Thus, the method is well suited for the reliable, rapid processing of large sample numbers generated e.g. from clinical studies evaluating the pharmacokinetics and/or bioavailability/bioequivalence of different formulations or from drug monitoring/clinical response programs. The assay has been successfully approved in several clinical studies evaluating different bromocriptine preparations.

Determination of flurazepam and its major metabolites N-1-hydroxyethyl- and N-1-desalkylflurazepam in plasma by capillary gas chromatography.

In the present paper we describe a method for the quantitative determination of flurazepam (I) and two of its metabolites, N-1-desalkylflurazepam (II) and N-1-hydroxyethylflurazepam (III), in serum after therapeutic dosings is described. The method is sensitive (lower limit of quantification for I and III: 1 ng/ml, for II: 2 ng/ml), selective and--compared to the analytical approaches already published--simple to handle. Thus this assay is well suitable for determinations during clinical studies (e.g. evaluating the pharmacokinetics, bioavailability/bioequivalence). Following simple extraction- and derivatization steps (the latter being only required for III) the extract is injected directly onto a fused-silica, bonded-phase capillary column of a gas chromatograph and the compounds of interest detected by an electron-capture detector (ECD). The assay has been used successfully during several clinical studies, especially as very low dosages result in also very low blood concentrations.

Gas chromatographic--mass spectrometric determination of haloperidol in plasma. Application to pharmacokinetics.

An improved gas chromatographic-mass spectrometric chemical ionization assay for the quantitative determination of haloperidol in body fluids is presented. A fused silica, bonded phase capillary column, combined with negative ion chemical ionization (NICI), ammonia as a selective reagent gas and the monitoring of preselected characteristic ions (SIM), provide the combined sensitivity and selectivity necessary for reliable measurements in the low ng/ml range. The lower limit of detection was 0.1 ng/ml plasma and the calibration curve linear in the measured range of 0.1-5 ng/ml. In combination with the excellent imprecision and inaccuracy data and a recovery exceeding 90%, the method is very well suited for quantitative determinations of plasma samples generated during clinical studies, e.g. evaluating the pharmacokinetics and/or bioavailability/bioequivalence of haloperidol.

Gas chromatographic/mass spectrometric determination of clonidine in body fluids. Application to pharmacokinetics.

Depending on the very low therapeutic doses of clonidine and the resulting low blood levels (in the pg/ml range), for quantitative determinations in body fluids only methods of necessary selectivity as well as corresponding sensitivity can be employed successfully. Furthermore, the method should also be suited for the rapid processing of large sample numbers generated e.g. during clinical studies evaluating pharmacokinetics and/or the bioavailability/bioequivalence. Thus a gas chromatographic/mass spectrometric assay was developed employing fused-silica, bonded-phase capillary columns, chemical ionization with ammonia as a selective reagent gas in combination with the registration of preselected, characteristic negative ions (SIR, NICI) and a deuterated internal standard. Therefore, the method proves to be exceptionally selective and sensitive: a lower limit of detection of 10 pg/ml plasma is reached, the calibration curve is linear in the 25-1500 pg/ml range and the recovery from blood exceeds 90%. The assay has been successfully approved in several clinical studies, whereby especially the simple sample preparation led to very short times for analysis.

[Studies of the pharmacokinetics and bioavailability of a new trimethoprim/sulfamethoxazole preparation in healthy volunteers]. / Untersuchungen zur Pharmakokinetik und Bioverfügbarkeit einer neuen Trimethoprim/Sulfamethoxazol-Zubereitung an gesunden Freiwilligen.

The objective of this study was to determine both the pharmacokinetic parameters and the bioavailability of a newly developed trimethoprim/sulfamethoxazole preparation (cotrimoxazole, Kepinol forte, 160 mg of trimethoprim/800 mg of sulfamethoxazole) in comparison with a reference preparation customary in trade and registered according to the AMG 1976, after single oral administration. For this purpose the test and the reference preparation were examined in a randomized 2-way crossover design (Latin square) in 12 volunteers each. Both dosage forms led to maximum plasma levels of approx. 1250 ng/ml of trimethoprim and about 40 micrograms/ml of sulfamethoxazole 1.5-2 h after application; the plasma half-lives were about 9 h for trimethoprim and around 8.5 h for sulfamethoxazole. The statistical comparison (ANOVA, confidence intervals according to Westlake, Pratt-Wilcoxon test) of the pharmacokinetic parameters found in the study resulted in bioequivalence of the newly developed trimethoprim/sulfamethoxazole preparation and the reference preparation. Furthermore, after the administration of both preparations no marked side effects worth mentioning were observed, suggesting a good and comparable clinical tolerability of the two preparations.

Endoscopic ultrasonographic study of the azygos vein in patients with varices.

BACKGROUND AND STUDY AIMS: Using EUS in the study of portal hypertensive patients, various divisions of the gastroesophageal collateral circulation can be demonstrated. The azygos vein, which is the main drainage system for varices, can also be scanned endosonographically. We studied the azygos vein in control subjects and portal hypertensive patients using EUS. PATIENTS AND METHODS: Our study included 17 patients with endoscopic evidence of esophagogastric varices and 11 control subjects not suffering from chronic liver disease or varices. EUS and Doppler EUS using a linear scanning echoendoscope were carried out on patients and control subjects with the aim of studying the azygos vein. RESULTS: The azygos vein could be scanned in all subjects and was found to be significantly dilated in patients with varices. Maximal velocity of its blood flow was higher among patients with varices compared to control subjects. Periazygos collaterals could be occasionally observed in portal hypertensive patients. CONCLUSION: EUS can be used both for scanning and hemodynamic studies of the azygos vein. The fact that EUS allows the collection of valuable quantitative and qualitative data from the azygos vein should encourage further studies on the clinical value of this information in the follow up of portal hypertensive patients.

[Comparative studies on the tolerance of bioequivalent doses of intravenous methylxanthine preparations in healthy subjects]. / Vergleichende Untersuchungen zur Verträglichkeit bioäquivalenter Dosen intravenöser Methylxanthin-Zubereitungen bei gesunden Probanden.

In a comparative tolerance study with two different intravenous methylxanthine preparations, a theophylline-ethylendiamine preparation (TE-reference preparation) was tested against a combination of theophylline, proxyphylline (7-(2-hydroxypropyl)-theophylline) and diprophylline (7-(2,3-dihydroxypropyl)-theophylline) (Neobiphyllin; TPD = test preparation) in 10 healthy volunteers by a single blind cross-over design. Both preparations were infused under continuous control of vital parameters (blood pressure, pulse, respiration frequency, heart rhythm) as infusions (1 ampoule with 800 mg TPD or 1 short-infusion with 480 mg of TE for 20 min, each) up to the individual tolerance limit or the pre-defined limit of 3 ampoules/short infusions, respectively. The maximum tolerated infusion time and the serum levels at which the first side-effects appeared, were compared. These maximum doses could be administered to 6 volunteers under TPD, but only to two under medication with the reference preparation. Side-effects under TPD occurred in 5, after infusion of the reference preparation in 9 volunteers. Serum levels of theophylline at the end of the infusion period reached (14.6 +/- 4.21 (TPD) and 23.01 +/- 6.02 mg/l (TE), respectively. The average infusion time for the test preparation was 54.8, for the reference preparation 46.2 min. The average serum theophylline levels of the 5 volunteers with side-effects under TPD reached--when these side-effects occurred --11.26 +/- 4.52 mg/l; the same volunteers showed after administration of TE levels of 14.94 +/- 7.49 mg/l. Our results showed an approx. additive effect of the side-effects together with an--according to literature--over-additive pharmacological effect of the single components of TPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of a high performance liquid chromatography method for the simultaneous measurement of prednisone and prednisolone.

An improved high performance liquid chromatographic assay (HPLC) is presented for the quantitative determination of prednisone and its main metabolite prednisolone. This HPLC assay, employing a UV-detector and dexamethasone as an internal standard, provides a selective and sensitive determination of glucocorticoids in plasma. The advantage of this method is the possibility of simultaneously measuring exogenic and endogenic glucocorticoids. The lower limit of quantification is 5 ng/ml.

Ultrasonography in the diagnosis and management of 52 patients with amebic liver abscess in Cairo.

Clinical characteristics of 52 patients with amebic liver abscess are reported. Forty-two percent had an acute illness, usually with high fever, vomiting, sweating, pain in the abdominal right upper quadrant, and leukocytosis. The other 58% had a more chronic illness, usually with a dull ache in the right upper abdomen, weight loss, fatigue, moderate or low-grade pyrexia, and anemia. Hepatomegaly and hepatic tenderness were present in all patients; fever occurred in 75%. The diagnosis was strongly suggested by amebic antibodies in high titer and hepatic abscesses demonstrated by sonography. Mean abscess diameter was 9.2 cm; 37% were larger than 10 cm. Most abscesses were solitary (81%), in the right lobe (73%), rounded or oval (78%), cystic (57%), and had a well-defined wall (53%). However, 43% were initially solid or heterogeneous. The latter lesions always developed a cystic pattern when ultrasonography was repeated. The diagnosis was confirmed by a good clinical response to metronidazole in 50 patients. Complications included right-sided pleural effusions or empyema (13%), ascites (13%), and jaundice (13%). Drainage of large abscesses was performed in four patients. All 52 patients survived and were cured.

[The pharmacokinetics and bioavailability of a new mexiletine preparation in healthy volunteers]. / Untersuchungen zur Pharmakokinetik und Bioverfügbarkeit einer neuen Mexiletin-Zubereitung an gesunden Freiwilligen.

In the course of this study, both the bioavailability and the most important pharmacokinetic parameters of a newly development mexiletine (CAS 31828-71-4) preparation (Mexiletine-ratiopharm mite, dosage 200 mg of mexiletine) were to be determined in comparison to a commercial reference preparation registered according to the AMG 1976, after single oral administration. For this purpose, the test and the reference preparation were examined in healthy male volunteers according to a randomized, 2-way crossover design. Both preparations entrained maximum plasma levels of approx. 300 ng/ml 3.5-4 h following administration. For the areas under the curve, values around 4000 h x ng/ml were found; the plasma half-life of the test preparation was 7.55, for the reference preparation 7.75 h. The statistical comparison (ANOVA, confidence interval according to Westlake, Pratt-Wilcoxon-Test) of the pharmacokinetic parameters obtained in the study clearly resulted in bioequivalence of the newly developed mexiletine preparation and the reference drug. No side effects worth mentioning were observed after administration of either preparation, thus good and comparable clinical tolerability of both preparations may be presumed.

Quantitative determination of verapamil and metabolites in human serum by high-performance liquid chromatography and its application to biopharmaceutic investigations.

A specific and sensitive high-performance liquid chromatographic method for the quantitative analysis of verapamil and N-desmethylverapamil in human serum is described. The analytes were extracted from serum using diethylether under alkaline conditions, followed by back extraction into dilute hydrochlorid acid for chromatographic analysis on a reversed-phase column with a mobile phase consisting of acetonitrile, water and perchloric acid at a flow rate of 1 l/min. The analytes were detected by fluorescence detection, the influence of temperature on retention is discussed. The method is linear, quantitative and reproducible for two calibration ranges in serum (2.5 ng/ml-100 ng/ml and 12.5 ng/ml-500 ng/ml) using peak area ratios analyte/internal standard for quantification. At ultimate sensitivity, concentrations down to 250 pg/ml could be assayed. The method was selective to 6 other metabolites of verapamil and common exogenous interferences. It was applicated to the serum samples of a comparative 120 mg - verapamil hydrochloride tablet single dose two-way cross-over study comprising 18 volunteers. The pharmacokinetic data for both formulations are presented.

Endoscopic ultrasonographic study of the azygos vein before and after endoscopic obliteration of esophagogastric varices by injection sclerotherapy.

BACKGROUND AND STUDY AIMS: The azygos vein plays an important role as a drainage system for the superior portosystemic collateral circulation in portal hypertensive patients. Endoscopic ultrasonography (EUS) and Doppler EUS allow the performance of hemodynamic studies of the azygos vein. In this study, we observed the changes in the azygos vein which occur with variceal obliteration by endoscopic injection sclerotherapy (EIS). PATIENTS AND METHODS: We recruited patients with portal hypertension and bleeding varices who were not on portal pressure-lowering agents and who were scheduled for the EIS program. EUS was performed in these patients to study the azygos vein at the start of EIS. The azygos vein diameter, maximal velocity (Vmax), and blood flow volume index (BFVI) were measured. After variceal obliteration and within 1 week, another EUS study of the azygos vein was carried out. RESULTS: Out of 40 patients recruited into the study variceal obliteration and EUS assessment of the azygos vein, within 1 week of obliteration, was achieved in 33. We noticed a significant increase in azygos vein diameter (P<0.001) and BFVI (P=0.001) following variceal obliteration. No significant change was observed in Vmax (P>0.05). In one patient, marked caliber irregularities were observed in the azygos vein after variceal obliteration. CONCLUSIONS: Using EUS and Doppler EUS, hemodynamic studies of the azygos vein blood flow can be performed, allowing the monitoring of the effects of EIS and variceal obliteration on the superior portosystemic collateral circulation. The clinical significance of the observed changes in azygos blood flow that occur with variceal obliteration should be investigated in further studies and correlated with short-term and long-term outcome.

The value of combined use of N-butyl-2-cyanoacrylate and ethanolamine oleate in the management of bleeding esophagogastric varices.

BACKGROUND AND STUDY AIMS: Recently, tissue adhesive material has been used to improve the initial control of bleeding from huge esophagogastric varices, and to prevent them from rebleeding, in contrast to the conventional sclerotherapy. The present study assessed the value of the combined use of the tissue adhesive substance: N-butyl-2-cyanoacrylate and ethanolamine oleate 5% for management of bleeding esophagogastric varices. PATIENTS AND METHODS: One hundred and fourteen patients with documented active variceal bleeding at the time of endoscopy were alternatively randomized into two groups. The combined therapy group included 58 patients who underwent injection using both cyanoacrylate for large esophageal and gastric varices and a sclerosant agent for remaining varices. The sclerosis, or control, group included 56 patients, who underwent injection with ethanolamine oleate. RESULTS: This study proved the value of the combined therapy for the initial control of all bleeders (the follow-up period ranged from 12 to 32 months). In the sclerosis group, failure of the initial control of bleeding was reported in two cases (3.6%). Recurrent bleeding occurred in 8.6% in the combined therapy group compared to 25% in the sclerosis group (p < 0.01). Two months of therapy was required to achieve complete eradication of varices in 56.5% and 21.4% in the combined therapy and the sclerosis group, respectively. The mean number of sessions needed until the time of evaluation was 2.4 +/- 1.1 in the combined therapy group versus 5.1 +/- 2.3 sessions in the sclerosis group. The difference showed high statistical significance (p < 0.01). Minor complications occurred less frequently in the combined therapy group. Only one patient in the combined therapy group developed portal pyemia after extension of the tissue adhesive material from the site of injection into the portal vein. This patient died of hepatic failure. The mortality in the combined therapy group was lower than that in the sclerosis group (3.5% and 8.8% respectively, p > 0.05). CONCLUSION: The combined use of tissue adhesive and sclerosant materials seems to be the best plan for rapid eradication of esophagogastric varices within a short time, requiring the lowest number of injection sessions and involving minor complications and low mortality.

Distal splenorenal shunts (Warren's operation) B-mode and real time ultrasonographic assessment.

B mode and real time ultrasonography have been used in a trial to demonstrate the patency of distal splenorenal shunt done in Warren's operation. Thirty seven patients with portal hypertension, and bleeding oesophageal varices were the subject of this study. Using B-mode ultrasonography in 70% of cases (26 patients), the splenic, left renal vein and the site of anastomosis were demonstrated. In 8% (3 patients), both splenic and left renal veins were seen patent, but the site of anastomosis was not detected. In the remaining 22% (8 patients), neither the left renal vein nor the site of anastomosis could be demonstrated. Using the Real-time two dimensional ultrasound, 9 of the 37 patients were examined. The patency of both veins and the site of the shunt was demonstrated in 90% (8 patients).