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Biomedical subjects

Z Svoboda

Publications and source records attributed to Z Svoboda.

At least 19 recordsLinked to original sources
PubMed2003

Comparative biotransformation and disposition studies of nabumetone in humans and minipigs using high-performance liquid chromatography with ultraviolet, fluorescence and mass spectrometric detection.

The disposition of the non-steroidal anti-inflammatory drug (NSAID) nabumetone after a single oral dose administration of nabumetone tablets to humans and minipigs was investigated. Nabumetone is a prodrug, which is metabolized in the organism to the principal pharmacodynamically active metabolite -- 6-methoxy-2-naphthylacetic acid (6-MNA), and some other minor metabolites (carbonyl group reduction products, O-desmethylation products and their conjugates with glucuronic and sulphuric acids). Standards of the above-mentioned metabolites were prepared using simple synthetic procedures and their structures were confirmed by NMR and mass spectrometry. A simple HPLC method for the simultaneous determination of nabumetone, 6-MNA and the other metabolites was developed, validated and used for xenobiochemical and pharmacokinetic studies in humans and minipigs and for distribution studies in minipigs. Naproxen was chosen as the internal standard (I.S.), both UV (for higher concentrations) and fluorescence detection (for very low concentrations) were used. The identity of the nabumetone metabolites in biological samples was confirmed using HPLC-MS experiments. Pharmacokinetics of nabumetone, 6-MNA and 6-HNA (6-hydroxy-2-naphthylacetic acid) in human and minipig plasma was evaluated and compared. The concentration levels of nabumetone metabolites in urine, bile and synovial fluid were also evaluated.

Adult↗
PubMed2002

High-performance liquid chromatographic determination of tramadol and its O-desmethylated metabolite in blood plasma. Application to a bioequivalence study in humans.

Simultaneous HPLC determination of the analgetic agent tramadol, its major pharmacodynamically active metabolite (O-desmethyltramadol) in human plasma is described. Simple methods for the preparation of the standard of the above-mentioned tramadol metabolite and N1,N1-dimethylsulfanilamide (used as the internal standard) are also presented. The analytical procedure involved a simple liquid-liquid extraction of the analytes from the plasma under the conditions described previously. HPLC analysis was performed on a 250x4 mm chromatographic column with LiChrospher 60 RP-selectB 5-microm (Merck) and consists of an analytical period where the mobile phase acetonitrile-0.01 M phosphate buffer, pH 2.8 (3:7, v/v) was used, and of a subsequent wash-out period where the plasmatic ballast compounds were eluted from the column using acetonitrile-ultra-high-quality water (8:2, v/v). The whole analysis, including the equilibration preceding the initial analytical conditions lasted 19 min. Fluorescence detection (lambda(ex) 202 nm/lambda(em) 296 nm for tramadol and its metabolite, lambda(ex) 264 nm/lambda(em) 344 nm for N1,N1-dimethylsulfanilamide) was used. The validated analytical method was applied to pharmacokinetic studies of tramadol in human volunteers.

Analgesics, Opioid↗
PubMed2001

High-performance liquid chromatographic determination of ursodeoxycholic acid after solid phase extraction of blood serum and detection-oriented derivatization.

Ursodeoxycholic acid (3 alpha,7 beta-dihydroxy-5 beta-cholanoic acid, UDCA) is a therapeutically applicable bile acid widely used for the dissolution of cholesterol-rich gallstones and in the treatment of chronic liver diseases associated with cholestasis. UDCA is more hydrophilic and less toxic than another therapeutically valuable bile acid, chenodeoxycholic acid (CDCA), the 7 alpha-epimer of UDCA. Procedures for sample preparation and HPLC determination of UDCA in blood serum were developed and validated. A higher homologue of UDCA containing an additional methylene group in the side chain was synthetized and used as an internal standard (IS). Serum samples with IS were diluted with a buffer (pH=7). The bile acids and IS were captured using solid phase extraction (C18 cartridges). The carboxylic group of the analytes was derivatized using 2-bromo-2'-acetonaphthone (a detection-oriented derivatization), and reaction mixtures were analyzed (HPLC with UV 245 nm detection; a 125--4 mm column containing Lichrospher 100 C18, 5 microm; mobile phase: acetonitrile--water, 6:4 (v/v)). Following validation, this method was used for pharmacokinetic studies of UDCA in humans.

Adult↗
PubMed1999

Study of the biotransformation of benfluron using the isolated perfused rat liver.

The isolated perfused rat liver method (IPRL) was used to find, isolate and identify further metabolites of Phase I and Phase II biotransformation of the potential cytostatic agent benfluron with special regard to the conjugation processes. Its pharmacokinetic profile during the perfusion was also estimated. The rat liver was isolated from the body and perfused in vitro using a recirculating perfusion system. Benfluron was added to the reservoir as a bolus in doses of 200, 100, 30 mg/kg of body weigh and 1 mg/perfusate volume and also as a continual infusion in a dose of 0.1 mg/min in separate series of experiments. The following metabolites formed during Phase I biotransformation were found in the perfusion liquid as well as in the bile: benfluron N-oxide, 9-hydroxy benfluron, demethylated 9-hydroxy benfluron, demethylated benfluron, and reduced benfluron. The major Phase II metabolite found in the bile samples was the glucuronide of 9-hydroxy benfluron. The pharmacokinetic profile of benfluron in IPRL indicated its main disposition and metabolic pathway, i.e. its rapid extraction from perfusate by the liver (t1/2 alpha = 3.76 min), 9-hydroxylation followed up O-glucuronidation and excretion to the bile. It was revealed that 12% of the total dose of the parent compound was excreted to the bile in the form of conjugates during the first hour of perfusion, 32% during 1.5 hour, and 70% during 2 hours after the administration of benfluron. The conjugates with glucuronic acid represented 96-98% of all metabolites found in the bile.

Animals↗
PubMed1999

Experimental Goettingen minipig and beagle dog as two species used in bioequivalence studies for clinical pharmacology (5-aminosalicylic acid and atenolol as model drugs).

Due to proven similarities in biotransformation between man and minipig, minipig seems to be the experimental animal of choice for preclinical pharmacokinetic studies when an experiment with a drug exhibiting a great first pass bioelimination (like 5-aminosalicylic acid) is to be realised. On the other hand, both minipig and dog may be suitable species for a pharmacokinetic study with a drug characterized by a small extent of first pass biotransformation (like atenolol).

Animals↗
PubMed1998

Presence and activity of cytochrome P450 isoforms in minipig liver microsomes. Comparison with human liver samples.

Cytochrome P450 (CYP) of the 3A family (CYP3A) has been detected in minipig liver microsomes by immunochemical screening (Western blotting), revealing bands that co-migrate with human CYP3A4 and 3A5. The nifedipine oxidase activity and testosterone 6beta-hydroxylating activity (specific markers for CYP3A enzymes) of the human liver microsomal and minipig liver microsomal samples were comparable, as were the results of specific inhibition of this activity by triacetyloleandomycin. The presence of CYP1A, 2A, 2C, 2D, and 2E1 marker activities in minipig liver microsomes was found by testing with the respective specific substrates (7-ethoxyresorufin, coumarin, tolbutamide, bufuralol, and chlorzoxazone). 7-Pentoxyresorufin O-depentylase activity (indicative of CYP2B) was absent from minipig as well as human liver microsomal samples. The results indicate that minipigs might be, in many cases, the most suitable experimental animals to predict biotransformation pathways in humans, because the activity of the most important CYP isoform in humans (CYP3A, metabolizing the majority of known drug substrates) is present in minipigs, with comparable levels and activities. Moreover, there is no need to induce CYP enzyme levels.

Animals↗
PubMed1997

Preclinical comparison of bis-diketopiperazine-propane (dexrazoxane) and bis-diketopiperazine-ethane (antimet) on the adriamycin-cardiotoxic effect.

A cardiotoxic effect induced by adriamycin (by repeated i.v. administration to experimental rats in 7-day intervals of administration) begins to be manifested in the ECG record by prolongation of the S alpha T segment between days 14 and 20, on day 30 it is statistically significant. By means of this index, the known protective effect of dexrazoxane (the preparation Cardioxan) against adriamycin cardiotoxicity has been successfully confirmed in a four-week experiment. A comparative study (using the identical frequency of the dosing scheme and S alpha T segment as the decisive parameter) has revealed that antimet-as another original substance of the diketopiperazines group-also involves (though less significantly) protective effects against the toxic action of adriamycin.

Administration, Oral↗
PubMed1996

Study of the biotransformation of a potential benzo[c]fluorene antineoplastic using high-performance liquid chromatography with high-speed-scanning ultraviolet detection.

As the sum of benfluron metabolites found was only a part of the total amount applied, a search for undiscovered metabolites was undertaken in the extracts from isolated rat hepatocytes and in the bile and perfusate in the experiments with an isolated perfused rat liver. To identify the metabolites, high-performance liquid chromatography with UV spectral analysis was used, as benfluron derivatives exhibit characteristic absorption spectra. Administration of known metabolites to experimental animals and selective induction of certain metabolic pathways led to the finding of new metabolites and of the respective conjugates. Fast atom bombardment-mass spectrometry analysis was used to identify the newly found metabolites and conjugates.

Animals↗
PubMed1991

[Medical informatics and health care in Subotica yesterday, today and tomorrow].

The application of information systems in health care throughout the world has begun ten years after the first generation of computers. Computers are a tool for doing business in all segments of health care. After a presentation of the development of informatics in the world and in our surroundings, a survey of events related to the health-care informatics in Subotica is given, as well as the perspective which is expected.

Health Services↗
PubMed1990

[An unusual case of prolonged hypoglycemia].

The author described a case of protracted hypoglycaemia in a young type I insulin treated diabetic, associated at first with neurological symptomatology imitating a cerebrovascular attack. After three days, when it was necessary to administer repeatedly glucose by the i.v. route on account of low blood sugar levels, the carbohydrate metabolism deteriorated and called for administration of similar insulin doses as before. In the discussion the author deals with pathogenetic possibilities of the described condition.

Adult↗
PubMed1989

[Evaluation of glycosuria in normal glucose tolerance].

In 52 subjects where after 10.6 +/- 7 years after detection of glycosuria on fasting normal glucose tolerance persists some risk factors and early biochemical changes indicating possible later development of diabetes were evaluated. 73% of the subjects had a positive family-history of diabetes and 61% were obese. In 42% of the subjects during the present examination glucose in urine was detected only after a glucose load. In 35% of the subjects pathological serum values of glycoproteins were found and their mean fasting blood sugar levels and levels 60 minutes after a glucose load were significantly higher, although in the range of normal oGTT, as compared with the group with normal glycoprotein levels. 21% had pathological values of N-acetyl-beta-D-glucosaminidase levels in serum and urine and concurrently significantly higher IRI values 60 and 120 minutes after a glucose load, than the group with a normal value. In obese subjects, as compared with those with a normal body weight, there were significantly higher mean blood sugar levels on fasting and 60 minutes after a glucose load and the same applies to IRI levels on fasting and after 60 minutes following stimulation. The authors discuss the causes and interrelations of the assembled results.

Adult↗