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A rapid, reliable and sensitive assay for routine determination of ajmaline in plasma by high-performance liquid chromatography with fluorimetric detection is presented. A low limit of detection in plasma (less than 1 ng/ml ajmaline) could be achieved by the extraction of plasma samples and the use of fluorimetric detection. Deproteinization of the plasma sample instead of extraction, or the use of an ultraviolet detector, yielded a higher limit of detection (less than 50 ng/ml). Two different eluents were studied. Eluent 1 allowed clear separation of ajmaline from isoajmaline and sandwicine, but did not separate isoajamaline from sandwicine. With eluent 2, separation of isoajmaline and sandwicine was achieved, but separation of ajmaline from sandwicine was less optimal than with eluent 1. Therefore, eluent 1 was used for further clinical studies. No interference was observed from therapeutic doses of other commonly co-administered drugs, such as acetylsalicylic acid, digoxin, digitoxin, ranitidine, dopamine, dobutamine, furosemide, captopril or glycerol trinitrate. In addition, the chemical stability of ajmaline and a possible rearrangement of ajmaline to its stereoisomers isoajmaline and sandwicine was studied in vivo and in vitro. Ajmaline proved to be unusually stable under both in vivo and in vitro conditions.

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A high-performance liquid chromatographic assay was developed for determination of verapamil, norverapamil (M1) and its N-dealkylated metabolites (M2 and M3) in plasma. Plasma samples were vortex-mixed, deproteinized and centrifuged. The analysis was performed on a C18 reversed-phase column with fluorimetric detection. Since the polarity of verapamil and norverapamil differs considerably from that of M2 and M3, two different eluents were used for rapid high-performance liquid chromatographic separation. The eluent for the separation of verapamil and norverapamil was acetonitrile-0.07% orthophosphoric acid (33:67, v/v), and for M2 and M3 acetonitrile-0.07% orthophosphoric acid (25:75, v/v). The high-performance liquid chromatographic assay allowed rapid, sensitive and reliable quantitation of verapamil and three of its metabolites in plasma without an extraction procedure. The limit of detection was less than 5 ng/ml (plasma) for all compounds. No interferences with other commonly co-administered drugs was observed. Plasma concentrations of verapamil and its metabolites were determined in 21 patients receiving a continuous infusion of verapamil for tachyarrhythmia of acute onset. The steady-state plasma concentration data of verapamil and its three main metabolites in these patients gave evidence that the plasma concentration of verapamil and its active metabolite norverapamil was primarily determined by the extent of the formation of M2.

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Chlormezanone plasma concentrations were determined in 5 volunteers (group 1) after a single oral dose of 200 mg of chlormezanone with high performance liquid chromatography. A plasma elimination half-life of 23 +/- 2.3 h was calculated. The mean peak chlormezanone plasma level was 1.86 +/- 0.2 micrograms/ml, 1 h after ingestion. Additionally, chlormezanone plasma levels were determined after repeated oral doses of chlormezanone recommended for treatment of muscular spasms due to degenerative skeletal disease. After 5 days of repeated daily doses of 3 x 200 mg (group 2; 12 patients) or 3 x 400 mg (group 3; 10 patients) of chlormezanone, mean predose chlormezanone plasma levels were 12.0 +/- 2.0 micrograms/ml (group 2) and 22.7 +/- 4.0 micrograms/ml (group 3), respectively. Comparable plasma concentrations were determined after 10 days of repeated doses of 3 x 200 mg or 3 x 400 mg of chlormezanone in 3 patients from each of these 2 groups. In 7 patients of group 3, chlormezanone had to be discontinued on the 5th day due to increasing muscular weakness, ataxia and exercise-inducible tachycardia. After a loading dose of 800 mg and repeated doses of 3 x 200 mg chlormezanone to 5 patients (group 4), plasma levels of 6.5 +/- 2.1 micrograms/ml, 8.9 +/- 2.2 micrograms/ml, 12.7 +/- 2.0 micrograms/ml, and 10.4 +/- 2.4 micrograms/ml were determined after 2, 8, 16, and 36 h, respectively. Trace amounts of a degradation product of the acid-labile chlormezanone could be detected in plasma besides the unchanged drug after administration of repeated oral doses.(ABSTRACT TRUNCATED AT 250 WORDS)

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The clinical efficacy of different doses of the specific benzodiazepine antagonist flumazenil was studied in a total of 72 patients with benzodiazepine or ethanol overdose. In a randomized double-blind study, 18 patients (group 1) and eight patients (group 2) with suspected benzodiazepine overdose received 5 mg (group 1) or 1 mg (group 2) flumazenil or placebo, respectively. The stage of coma, heart rate, blood pressure and respiratory rate were monitored within the following 15 min. If no change in the stage of coma was observed, 5 mg (group 1) or 1 mg (group 2) flumazenil were given, and the stage of coma, heart rate and blood pressure were again monitored. In a similar way, the effect of 5 and 1 mg flumazenil was investigated in 13 patients (group 3) and four patients (group 4) with ethanol intoxication. In an open trial, the clinical efficacy of flumazenil for the diagnosis of benzodiazepine or ethanol overdose was studied in 29 patients (group 5). In all patients, a toxicological screening confirmed benzodiazepine or ethanol overdose. None of the patients receiving placebo showed effects on stage of coma, heart rate, blood pressure or respiratory rate. Patients with benzodiazepine overdose who received 5 mg flumazenil regained consciousness about 1-2 min after the end of injection. The effect of 1 mg flumazenil (group 2) on benzodiazepine-induced coma was less pronounced. In patients with ethanol overdose (group 3), ethanol-induced coma was reversed after 5 mg flumazenil more slowly than in patients of group 1. No effect of flumazenil on ethanol-induced coma was observed in group 4. In group 5, flumazenil proved to be useful for diagnosing benzodiazepine or ethanol intoxication. In one patient with coma due to carbamazepine overdose, flumazenil was also found to be effective. Additionally, a possible analytical interference of flumazenil and its metabolites with the identification of other benzodiazepines by a toxicological screening procedure was studied. Even after an oral dose of 200 mg flumazenil, no interference with immunological benzodiazepine assays (EMIT, TDX, and RIA) was found. A metabolite and an artifact of flumazenil could be identified in urine by gas chromatography/mass spectrometry.

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21 patients with acute myocardial infarction and ventricular arrhythmia of Lown class II-IIIB of acute onset received a short infusion of (50 mg/5 min) ajmaline (Gilurytmal). 6 of the patients had normal kidney and liver function (Group 1), 4 patients had acute renal failure and hemodialysis treatment (Group 2), 4 patients had impaired hepatic function (Group 3), 3 patients had cardiogenic shock (Group 4), and 4 patients had been pretreated with phenobarbital for seizures for at least 5 days (Group 5). A distribution half-life of 6 +/- 1 min and an elimination half-life of 95 +/- 6 min was determined in Group 1. The total plasma clearance was significantly lower in patients with impaired liver or cardiac function and significantly higher in Group 5, whereas impaired renal function did not affect total plasma clearance. After short infusion, ventricular arrhythmia of Lown II-IIIB completely disappeared for at least 16 to 36 min (mean: 19 min), which was associated with an ajmaline plasma level of 0.1-0.45 micrograms/ml. Additionally, steady-state plasma levels of ajmaline were determined after continuous infusion of 10-50 mg/h to 16 patients (Group 6) with ventricular arrhythmia of acute onset (Lown class IVA-V). Ventricular arrhythmia completely disappeared or at least changed to lower Lown classes at ajmaline plasma levels of 0.4-2.0 micrograms/ml. The ajmaline plasma protein binding was 76 +/- 9%. Ajmaline had a special affinity to alpha 1-acid glycoprotein.

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The metabolism of chlormezanone (Muskel Trancopal) in man was studied by the aid of gas chromatography/mass spectrometry and high performance liquid chromatography after an oral dose of 400 mg. Six metabolites and/or degradation products were identified in the urine. Some of the metabolites are formed at least partially by nonenzymatic hydrolysis in the stomach. In contrast to previous publications, no unchanged drug was detected in plasma and urine. The main metabolite in plasma is generated by cleavage of the amide bond in the six-membered heterocyclic ring. This derivative is easily formed by in vitro hydrolysis at pH 1, too. It structurally resembles baclofene. About 40% of the dose is excreted with the urine. The major metabolite in urine is 4-chlorohippuric acid. Additionally, 4-chloro-benzoyl-N-methylamide, 4-chlorobenzoic acid, N-methylimino-4-chlorobenzaldehyde, 4-chlorobenzaldehyde, and "hydrolized" chlormezanone were identified.

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After ingestion of 2000 mg tiaprofenic acid (Surgam), a 14-year-old girl was admitted to the clinic. The ingested dose was tolerated without signs of systemic intoxication. Tiaprofenic acid, its metabolites, and products of chemical decomposition were identified by gas chromatography/mass spectrometry in the urine sample of the patient. Additionally, a previously unknown decomposition product of a metabolite was detected. For quantitation of the drug in plasma, a rapid and sensitive high-performance liquid chromatography assay was established.

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H. R. Nielsen and H. Remmer described a quantitative method for the estimation of carbamazepin serum levels. The specificity of this method was examined with the result that besides carbamazepin also its metabolites react under the authors' conditions.

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