Cardiac troponin I and cardiac troponin T increases in pigs during ischemia-reperfusion damage.

In this study we addressed the question of whether the measurement of cardiac Troponin T (cTnT) and cardiac Troponin I (cTnI) is able to detect myocardial cell damage in an ischemia-reperfusion model in pigs. To answer the question 3 pigs were anaesthesized and a cardiac arrest was induced by electric fibrillation. After 5 minutes of global ischemia the cardiac arrest was reversed by electric defibrillation until normal perfusion was restored. We could clearly demonstrate an increase of cTnT and cTnI 30 minutes after reperfusion indicating myocardial injury during ischemia and subsequent reperfusion. The cTnT as well as the cTnI serum levels increased till 180 minutes after reperfusion. This ischemia-reperfusion injury is likely induced by oxygen radicals generated during hypoxia and subsequent reperfusion We conclude from our first results that troponin measurements with commercial available test kits may also reflect myocardial cell damage in pigs as it was recently demonstrated in rats. Further studies are needed for correlation of troponin serum levels and histopathological damage in this model especially if it is used to test beneficial or toxicological effects of radical neutralizing drugs.

Bioequivalence of two oral immediate release formulations of pindolol in healthy volunteers assessed by ratio analysis.

The objective of this study was to test bioequivalence and therapeutic equivalence of two oral formulations of pindolol (ViskenR = Vs = Ref.; Nonspi 5R = Np = Test). Twenty one healthy volunteers (11 females; 10 males; aged 18-55 years) participated in the single-dose (10 mg), single-blind, randomised crossover study. Blood samples were taken up to 24 hs after intake and pindolol in serum was determined using HPLC. Key criteria for ratio analysis to assess bioequivalence were log-transformed AUC (0, last) and Cmax. Blood pressure and heart rate vs. time data were subjected to ANOVA according to Friedman. Vital signs did not show significant differences. Ratios of log-transformed data and 90%-confidence intervals were within the predefined limits of 0.8 to 1.25 or 0.7 and 1.43, respectively. We conclude that both formulations of pindolol are equivalent with regard to extent and rate of absorption as well as pharmacodynamic effect.

Compatibility of plastics with cytotoxic drug solutions-comparison of polyethylene with other container materials.

In this study low density polyethylene (LDPE)-containers were compared to glass bottles and polyvinyl chloride (PVC) bags in view of adsorption effects with antineoplastic drugs. The infusion containers were supplemented with therapeutic doses of the nine common cytotoxic drugs carboplatin, carmustine, cytarabine, dacarbazine, fluorouracil, gemcitabine, melphalan, methotrexate and vinorelbine. 0.9% isotonic sodium chloride solution and 5% dextrose served as infusion solutions. The containers were stored at room temperature or at 4 degrees C, protected from light, for periods of up to 168 h. Turbidity, change of colour and visible crystallization were not observed. Samples were collected at different time intervals and drug contents were determined with high-performance liquid chromatography (HPLC). Preparations of carmustine showed no adsorption phenomena when stored in LDPE or in glass at 4 degrees C. At room temperature in LDPE, a slight decrease in concentration due to adsorption was monitored. However the drug loss in PVC bags was greater. Dacarbazine and melphalan showed decreases in concentration, which were independent on the type of container material. The remaining analyzed agents showed no drug loss at all. In conclusion, investigated drugs were stable in all three container types, with the best stability in glass bottles, followed by LDPE and PVC.

Comparability of a new turbidimetric digoxin test with other immunochemical tests and with HPLC--a multicenter evaluation.

A new turbidimetric inhibition immunoassay for digoxin (Tina-quant [a] Digoxin, Boehringer Mannheim) was evaluated in seven laboratories. It can be performed without sample pretreatment with ready-to-use reagents on nondedicated analyzers in combination with routine clinical chemistry. The studies revealed a good analytical performance: lower limit of detection 0.12 microg/L (3 SD from mean of blank); linearity up to 7.5 microg/L; median between-run CVs 8.1% (0.6 microg/L), 2.8% (1.5 microg/L), 1.9% (3 microg/L); mean analytical recovery in control sera 98-102%; slopes from 0.97 to 1.09 and intercepts from -0.28 to 0.10 microg/L in comparison with four immunoassays; and a high resistance to common interferents. The test was more resistant to digoxin-like immunoreactive factor (DLIF) interference than other methods, showing cross-reactivity only in some intensive care patient samples. Among 192 patients in whom DLIF is expected (e.g., pregnant women, patients with renal failure, newborns), 90% of results were < or =0.26 microg/L digoxin. Cortisol showed no cross-reactivity and digoxigenin had a low reactivity. An interlaboratory survey revealed a good comparability of the Tina-quant [a] test with the median of all methods (slope 0.99, intercept -0.06 microg/L). An HPLC method for digoxin based on isocratic separation of samples on an RP-18 column followed by detection by an immunoassay yielded a reasonable comparability with the immunochemical tests with noncritical samples. Divergent results of immunoassays caused by DLIFs or different cross-reactivities with digoxin metabolites or derivatives can be explained by the use of this HPLC method.

Effects of amphotericin B incorporated into liposomes and in lipid suspensions in the treatment of murine candidiasis.

The effects of similar amounts of amphotericin B (CAS 1397-89-3, AmB) in different preparations either as conventional amphotericin B (des-AmB), or liposomal AmB (lipos-AmB), or des-AmB dissolved in a lipid emulsion (lipid-AmB) on Candida albicans and other Candida species were compared in several in vitro and in vivo models. The minimal inhibitory concentration (MIC) of des-AmB was equal to the MIC of lipid-AmB when determined after 24 h. In contrast, the MIC of lipos-AmB was 4-8 times the MIC of des-AmB. When tested at 4 times the MIC of the respective preparations suspension of lipid-AmB led to a reduced ability to kill the fungi whereas des-AmB reduced the inoculum by 99% within 6 h. Four times the MIC of lipos-AmB failed completely to kill the fungi in the same time, but was only fungistatic. At 24 h all preparations had killed the yeasts at concentrations 4 times the MIC. In contrast to the in vitro data, lipos-AmB was more active in the treatment of murine candidiasis than lipid-AmB and des-AmB. Lipos-AmB but not lipid-AmB or des-AmB was able to significantly reduce the amount of Candida albicans in the liver when given in the same dosage. Concomitantly, AmB measured by HPLC was highly concentrated in the livers of the mice treated with lipos-AmB. It is concluded that even when given in the same dosage as des-AmB and lipid-AmB, lipos-AmB is more effective in the treatment of murine candidiasis, although it is less effective in vitro. Lipid-AmB is no alternative to lipos-AmB in this model of systemic infection of mice with Candida albicans.

Stepwise binary gradient high-performance liquid chromatographic system for routine drug monitoring.

Drug therapy is usually optimized by concentration measurement in patient serum. High-performance liquid chromatography (HPLC) is one of the most important analytical techniques used for therapeutic drug monitoring (TDM) of drugs for which no immunoassay kits are available. HPLC has been frequently used for screening purposes in toxicology, too. The Merck Tox Screening System (MTSS) has been developed for the identification of substances by a combination of gradient HPLC with diode-array detection and identification with a database system. For routine TDM an isocratic HPLC system is more suitable because of shorter analysis time, better reproducibility of retention index and better precision of results. Therefore we defined a set of methods in steps of 10% of the two MTSS eluents. Three examples are shown: Amiodarone, Indometacine and Thiopental. New applications to test for other substances can be transferred to an isocratic system after a complete MTSS gradient run.

The metabolization of carbamazepine to CBZ-10,11-epoxide in children from the newborn age to adolescence.

CBZ-10,11-epoxide is a major metabolite of CBZ. It has anticonvulsive properties and may be responsible for side-effects of CBZ treatment. Fifty-two children between the age of 2 weeks and 15 years were treated with CBZ (mean dosage 17 mg/kg body weight) either as mono- (n = 36) or in polytherapy (n = 16). The drug was delivered as an oral solution, as a nonretarded tablet or, most frequently, as a retarded tablet. The duration of treatment ranged from 1 to 94 months with 23 patients being on treatment for less than 3 months. Blood samples were taken with random timing after the last ingestion of the drug. The relative concentration of CBZ epoxide (expressed in % of CBZ) was higher in infants (median 48.9%) than in older children (median 14.9% in the 12-15-year-old group). A significant linear correlation with age was found (p < 0.001). In addition to young age, polytherapy (p < 0.01) and administration as a nonretarded formulation rather than as a retarded tablet (p < 0.05) induced a higher relative concentration of the epoxide. The relative concentration of the epoxide did not correlate with the serum CBZ concentration and the duration of treatment. Although in our study high epoxide levels were not related to clinical side effects, we recommend that in very young children polytherapy treatment with carbamazepine should be performed with caution and in difficult cases a determination of the epoxide level should be considered.

Liquid chromatographic analysis of phenobarbital, phenytoin, and theophylline.

Sera from the routine of therapeutic drug monitoring were assayed for phenobarbital, phenytoin, and theophylline with three different methods: fluorescence polarization immunoassay as the standard procedure, the new CEDIA assays within a multicenter evaluation and HPLC which is known to yield results with a high specificity. CVs for between-day imprecision ranged from 2.6-8.6%, depending on the concentration of the drugs. There was a tendency to lower CVs for the HPLC procedure. Accuracy was verified with commercial control materials and spiked sera and proved to be satisfactory for all three methods and parameters. The linear range was approx. twice as wide for the HPLC compared with the other methods. The method comparisons were quite favorable. Deviations occurred mainly in the subtherapeutic concentration range.

Results of the multicenter evaluation of the CEDIA Theophylline assay.

We report on the results of the multicenter evaluation of the CEDIA Theophylline assay on Boehringer Mannheim/Hitachi analyzers in 15 clinical laboratories in Europe and U.S.A. Main items of investigation were imprecision, recovery of control sera, interlaboratory survey and method comparisons using patient samples. Imprecision was found to be comparable to other routine methods. An advantage of the CEDIA assay can be seen in the good interlaboratory transferability of results. The new test has been shown to measure very accurately particularly by comparison with HPLC procedures revealing highly correspondent results. The reagent can be used up to one month using multiple recalibration. Due to its high practicability and reliability the CEDIA Theophylline assay can be recommended as a very suitable routine method for therapeutic drug monitoring on random access analyzers like Boehringer Mannheim/Hitachi analysis systems.

Results of the multicenter evaluation of the CEDIA Phenytoin assay.

Thirteen clinical evaluation sites in Europe and U.S.A. investigated the CEDIA Phenytoin assay on Boehringer Mannheim/Hitachi analyzers with respect to imprecision, recovery of control sera, interlaboratory survey, linearity and method comparisons using patient samples. The linear dose-response relationship up to 40 micrograms/mL was confirmed by all participants. Imprecision at therapeutic analyte concentrations equalled that of other routine methods. Recovery of controls was found in a +/- 6% range for target values assigned by the CEDIA assay. The good interlaboratory transferability of the CEDIA assay was confirmed with control material and human samples. The reconstituted reagent can be used up to one month using weekly recalibration. In method comparison studies good correlations to other routine methods were obtained. Results in analyte-free human sera did not deviate systematically from the zero-point. Thus, the accuracy in patient sera has been shown for the CEDIA Phenytoin assay.

[Risk indicators of urinary calculus formation: value of oxalate and citrate excretion in comparison with the oxalate tolerance value]. / Risikoindikatoren der Harnsteinbildung: Aussagekraft von Oxalat- und Zitrat-Ausscheidung im Vergleich zum Oxalat-Toleranz-Wert.

Several methods for the measurement of crystallization conditions in urine, the so-called whole urine systems, have recently been of considerable interest in urolithiasis research. The diagnostic accuracy of the oxalate tolerance value (OTV) was therefore compared with the daily excretion of oxalate and citrate in normal persons and patients with urinary calculi. With the aid of the oxalate/citrate ratio, 77% of the patients could be classified correctly. After standardization of the experimental conditions (24-h urine sample, constant pH value, consideration of endogenous oxalate) we succeeded in correctly classifying 82% of patients using the OTV. These results favour the introduction of the OTV as a clinical chemical tool for the follow-up of patients with urinary calculi and for the screening of normal persons at risk.

Acetate formation after short-term ethanol administration in man.

The effect of an acute oral load of 0.5 g ethanol/kg body weight was studied in a group of 10 healthy male and one of 10 healthy female individuals. The following parameters were measured in the blood between 0 and 7 h after the start of the experiment: ethanol, acetate, glucose, free fatty acids, free glycerol, lactate, pyruvate, 3-hydroxybutyrate, acetoacetate. While the elimination of ethanol followed zero-order kinetics between 2 and 5 h, a steady-state concentration of 0.4 to 0.6 mM acetate in the serum was observed during the same time interval. Concomitantly, a significant decrease of free fatty acid and free glycerol concentrations was observed.

Increased CSF cortisol levels after neuroleptic treatment in schizophrenia.

The cerebrospinal fluid (CSF) concentration of cortisol was determined in schizophrenic patients drug-free and on neuroleptics, compared to healthy controls, and in schizophrenics before and during neuroleptic treatment. Neuroleptics significantly increased the CSF concentrations of cortisol in these patients.