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W Siegmund

Publications and source records attributed to W Siegmund.

At least 19 recordsLinked to original sources
PubMed2006

Determination of propiverine and its metabolites in rat samples by liquid chromatography-tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed and validated for the determination of the anticholinergic and antimuscarinc drug propiverine and eight of its metabolites in serum, urine, faeces and different tissue samples of rats. Samples containing propiverine and its metabolites in serum and urine and in the supernatants of faeces and tissue homogenates were extracted and cleaned up using an automated solid phase extraction (SPE) method. An external calibration was used. The analytes were measured employing the multiple reaction monitoring mode (MRM). A sufficient response over the range of 10-1000 ng/ml was demonstrated. The lower limit of quantification of the nine substances was 10 ng/ml. The presented method is suitable for pharmacokinetic or toxicokinetic studies. To look for additional unknown metabolites, the LC-MS-MS system operated in the precursor ion mode using typical product ions of propiverine and of its metabolites. With the help of the chromatographic behaviour and typical fragment ions of the unknown metabolites, it was possible to elucidate their structure. Five until now unknown metabolites were found in the urine and faeces samples. However, without reference substances, a quantification of these analytes was not possible.

Animals↗
PubMed2006

Influence of polymorphisms of ABCB1 and ABCC2 on mRNA and protein expression in normal and cancerous kidney cortex.

There is increasing evidence that polymorphisms of the adenosine 5' triphosphate membrane transporters ABCB1 (P-glycoprotein, MDR1) may affect expression and function, whereas less information is available about the impact of ABCC2 (multidrug resistance-associated protein (MRP2)) single-nucleotide polymorphisms . Particularly, their role in human kidney for drug elimination and in the etiology of renal cell carcinoma is poorly understood. ABCB1 and ABCC2 mRNA and protein expression levels were determined by real-time polymerase chain reaction or immunohistochemistry in kidney cancer and adjacent unaffected cortex tissue of 82 nephrectomized renal cell cancer (RCC) patients (63 clear-cell RCC (CCRCC), 19 non-CCRCC). The DNA of all patients was genotyped for ABCB1 -2352G>A, -692T>C, 2677G>T/A (Ala893Ser/Thr), and 3435C>T, and ABCC2 -24C>T, 1249G>A (Val417Ile) and 3972C>T. ABCB1 and ABCC2 were less expressed in CCRCC than in normal cortex on mRNA as well as on protein level. Although the overall genotype frequency distribution did not differ between the patients and a matched control group, ABCB1 2677T/A and 3435T genotypes were associated with higher (P=0.02 and P=0.04) and ABCC2 -24 T with lower mRNA levels in normal tissues (0.03). The expression of ABCB1 and ABCC2 was not related to genetic variants in RCC tissue. In a reporter gene assay in HepG2 cells, the ABCC2 -24T construct showed an 18.7% reduced activity (P=0.003). In conclusion, ABCB1 and ABCC2 genotypes modulate the expression in the unaffected renal cortex of RCC patients, possibly contributing to inter-individual differences in drug and xenobiotics elimination. Their role in RCC cancer susceptibility or chemotherapy resistance needs further elucidation.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2006

Roflumilast, a once-daily oral phosphodiesterase 4 inhibitor, lacks relevant pharmacokinetic interactions with inhaled salbutamol when co-administered in healthy subjects.

OBJECTIVE: Roflumilast is an oral, once-daily phosphodiesterase 4 inhibitor under investigation for the treatment of chronic obstructive pulmonary disease and asthma. In clinical practice, the drug is likely to be co-administered with inhaled bronchodilating beta2-adrenoceptor agonists. Therefore, this study investigated the pharmacokinetic characteristics of roflumilast and its pharmacodynamically active metabolite roflumilast N-oxide when co-administered with orally inhaled salbutamol in healthy subjects. METHODS: In this open, randomized clinical study, 12 healthy male subjects received repeated doses of oral roflumilast 500 microg once daily, orally inhaled salbutamol 200 microg 3 times daily, and a combination of both drugs over 7 days according to a 3-period, changeover design with 14 days washout between treatments. RESULTS: Co-administration of roflumilast and salbutamol did not markedly change roflumilast or roflumilast N-oxide disposition. Point estimates (90% confidence intervals) of area under the curve from 0-24 h (AUC 0-24) and maximum plasma concentration in steady state (Cmax,ss) for roflumilast with salbutamol versus roflumilast alone were 1.05 (0.94, 1.17) and 0.97 (0.84, 1.10); the respective point estimates (90% confidence intervals) for AUC 0-24 and Cmax,ss of roflumilast N-oxide were 0.98 (0.91, 1.06) and 0.98 (0.92, 1.03). Roflumilast co-administration did not alter the pharmacokinetics of steady state salbutamol. The respective point estimates (90% confidence intervals) for AUC 0-6 and Cmax,ss of salbutamol with roflumilast versus salbutamol alone were 1.10 (0.99, 1.21), 1.08 (0.91, 1.28). The combination of both drugs was well tolerated. CONCLUSION: There were no relevant pharmacokinetic interactions between roflumilast and salbutamol at therapeutically effective doses.

Adrenergic beta-Agonists↗
PubMed2006

The classification of antiseptic products to be administered to wounds--another borderline case between medicinal products and medical devices?

The importance of a correct demarcation between a Medicinal Product (MP) and a Medical Device (MD) is undisputedly one of the major topics related to the development and launch of a new healthcare product. However, for some products the correct demarcation between MPs and MDs can turn out to be somewhat complicated. This article aims to provide an overview on the existing legislation and its adequate application based on a suitable example at hand. Article 2 (2) of the European Directive 2001/83/EC as amended by Directive 2004/27/EC on the Community code relating to medicinal products for human use stipulates that the respective Medicinal Products Legislation must be applied whenever a product can be covered by both the definitions for MPs and for products regulated by other legal provisions enacted by the European Community, e.g. Cosmetic Products (CPs) or MDs. This basic principle implies that the decision to base the risk-benefit assessment of the product in question on the Medical Device Directive (MDD) would contradict the aforementioned constitutional principle, pursuant to which the stricter of the regulatory procedures theoretically possible is to apply in cases of doubt. In contrast to the approval procedure established for MPs, the MDD requires a Conformity Assessment Procedure to be performed by the manufacturer himself and a "Notified Body". Thus, in the majority of cases the responsibility for the risk assessment of MDs lies solely with the manufacturer and is prior to launch not subject to further scrutiny by regulators. Only in specific cases, i.e. for the Conformity Assessment Procedure of Class III MDs which contain an Active Pharmaceutical Ingredient one of the Member States competent authorities designated in accordance with Directive 65/ 65/EEC has to be involved before taking a decision. It is therefore important that the classification of the product is carried out carefully in full compliance with existing legal provisions, also taking into account the related guidance documents issued by the European Commission. The adequate application of these rules is explained using the example of the antiseptic compound polihexanide, which is used both in approved medicinal products (wound antiseptics) and wound irrigation solutions labelled as medical devices.

Animals↗
PubMed2005

Intestinal fluid volumes and transit of dosage forms as assessed by magnetic resonance imaging.

AIM: The gastrointestinal transit of sequentially administered capsules was investigated in relation to the availability of fluid along the intestinal lumen by magnetic resonance imaging. METHODS: Water-sensitive magnetic resonance imaging was performed on 12 healthy subjects during fasting and 1 h after a meal. Specifiable non-disintegrating capsules were administered at 7, 4 and 1 h prior to imaging. RESULTS: While food intake reduced the mean fluid volumes in the small intestine (105 +/- 72 mL vs. 54 +/- 41 mL, P < 0.01) it had no significant effect on the mean fluid volumes in the colon (13 +/- 12 mL vs. 18 +/- 26 mL). The mean number of separated fluid pockets increased in both organs after meal (small intestine: 4 vs. 6, P < 0.05; large intestine: 4 vs. 6, P < 0.05). The distribution of capsules between the small and large intestine was strongly influenced by food (colon: 3 vs. 17 capsules, P < 0.01). CONCLUSIONS: The results show that fluid is not homogeneously distributed along the gut, which likely contributes to the individual variability of drug absorption. Furthermore, transport of fluid and solids through the ileocaecal valve is obviously initiated by a meal-induced gastro-ileocaecal reflex.

Adult↗
PubMed2005

The anticholinergic drug propiverine inhibits the protein kinase C activity in the rat urinary bladder.

UNLABELLED: There is ample evidence that non-cholinergic protein kinase C (PKC) mediated signal transduction pathways are involved into regulation of bladder smooth muscle contractions. To evaluate whether the anticholinergic and calcium modulating drug propiverine exerts intracellular effects by inhibition of the PKC, male inbred LEW 1A rats were pretreated with 0.6, 2, 6 and 60 mg/kg body weight for 5 days. Furthermore, competition assays with partially purified PKC were performed with propiverine in vitro. The activities of the membrane-bound and soluble PKC were assessed by 32P enrichment of lysine-rich histone. RESULTS: The active, membrane-bound PKC decreased by about 60% accompanied by increase of the soluble form after propiverine in doses above 0.6 mg/kg. 100 nM of the drug inhibited the PKC also in vitro whereas the propiverine metabolites M5 and M6 and atropine were without any effect. CONCLUSIONS: Propiverine was identified to be an inhibitor of the protein kinase C. Its contribution to the noncholinergic control of hyperactive detrusor smooth muscle cells needs further investigation.

Animals↗
PubMed2004

Replacement therapy with levothyroxine plus triiodothyronine (bioavailable molar ratio 14 : 1) is not superior to thyroxine alone to improve well-being and cognitive performance in hypothyroidism.

OBJECTIVES: There is evidence from recent controlled clinical studies that replacement therapy of hypothyroidism with T4 in combination with a small amount of T3 may improve the well-being of the patients. As the issue is still the subject of controversial discussion, our study was assigned to confirm the superiority of a physiological combination of thyroid hormones (absorbed molar ratio 14 : 1) over T4 alone with regard to mood states and cognitive functioning. DESIGN AND PATIENTS: After a run-in period with the T4 study medication for 4 weeks, a controlled, randomized, double-blind, two-period (each 12 weeks), cross-over study without washout between the treatment periods was performed in 23 hypothyroid patients (three males, 20 females, age 23-69 years, 21 subjects after surgery/radioiodine, two with autoimmune thyroiditis) to compare the effects of the previous individual T4 dose (100-175 micro g) with a treatment in which 5% of the respective T4 dose was substituted by T3. MEASUREMENTS: Standard hormonal characteristics and standardized psychological tests to quantify mood and cognitive performance were measured after the run-in period and at the end of each treatment period. In 12 subjects, the concentration-time profiles of fT3 and fT4 were compared after the last administration of the respective study medication. TSH, fT3 and fT4 were measured with immunological assays. CLINICAL RESULTS: Replacement therapy with T4 and T4/T3 was not different in all steady-state hormonal, metabolic and cardiovascular characteristics except for TSH, which was more suppressed after T4/T3. The efficacy of replacement therapy with the T4/T3 combination was not different from the T4 monotherapy with regard to all psychological test scores describing mood and cognitive functioning of the patients. Mood was even significantly impaired by the T4/T3 combination in eight subjects, with TSH < 0.02 mU/l, compared to patients with normal TSH (Beck Depression Inventory: 8.25 +/- 5.01 vs. 4.07 +/- 5.60, P = 0.026). PHARMACOKINETIC RESULTS: The area under the concentration-time curve (AUC(0-8h)) of fT3 was significantly higher after T4/T3 compared to the T4 monotherapy (42.8 +/- 9.03 pmol x h/l vs. 36.3 +/- 8.50 pmol x h/l, P < 0.05) and was significantly correlated to serum TSH (r(s) = -0.609, P < 0.05). After T4/T3, patients with a history of Graves' disease or autoimmune thyroiditis had significantly higher serum trough levels of fT3 whereas the fT4 concentrations were significantly lower in patients with a nonautoimmune background. CONCLUSION: Replacement therapy of hypothyroidism with T4 plus T3 does not improve mood and cognitive performance compared to the standard T4 monotherapy. There is even a higher risk of signs of subclinical hyperthyroidism associated with impaired well-being of the patients, which is clearly caused by significant fluctuations in the steady-state fT3 serum concentrations.

Adult↗
PubMed2003

Influence of propiverine on hepatic microsomal cytochrome p450 enzymes in male rats.

The bladder spasmolytics propiverine was shown to induce hepatic cytochrome P450 (P450) and aminopyrine and aniline oxidation in rats. To characterize the type of enzyme induction and its dose dependence, activities of seven hepatic microsomal P450-dependent monooxygenases were measured in 72 male LEW1A albino rats (body weight 236-295 g) after oral treatment with 0.5, 2, 6, and 60 mg/kg of propiverine hydrochloride for 5 days and compared with the effects of 40 mg/kg beta-naphthoflavone, 10 mg/kg phenobarbital, and 20 mg/kg dexamethasone (each group, n = 8). CYP2B expression was measured by Western blotting. Furthermore, the inhibitory potency of propiverine on P450 enzymes was evaluated in competition assays with three most specific monooxygenases. Results show that Propiverine induced several monooxygenases and CYP2B expression dose dependently. The effects were well comparable with a phenobarbital-type inducer with 60 mg/kg being equipotent to 10 mg/kg phenobarbital. Furthermore, propiverine in low concentrations inhibited pentylresorufin O-dealkylase (for CYP2B) in vitro. In conclusion, propiverine is a phenobarbital-type inducer on hepatic P450 enzymes in rats in doses about 100-times above the therapeutic doses in man.

Animals↗
PubMed2001

Endocrine effects of dopexamine vs. dopamine in high-risk surgical patients.

OBJECTIVES: To compare the endocrine effects of dopexamine and dopamine on prolactin (PRL), dihydroepiandrosterone sulfate (DHEAS), cortisol, thyrotropin (TSH), and peripheral thyroid hormone serum concentrations in surgical patients at risk of developing postoperative complications because of hypoperfusion of various organ systems. DESIGN AND SETTING: A prospective, randomized, placebo-controlled, blinded clinical trial in an adult surgical intensive care unit in a university hospital. PATIENTS: Thirty-two male surgical risk patients undergoing elective major abdominal surgery. INTERVENTIONS: Patients were randomized to receive placebo ( n=8), dopexamine (0.5 microg kg(-1) min(-1), n=8), dopexamine (1 microg kg(-1) min(-1), n=8) or dopamine (5 microg kg(-1) min(-1), n=8) on the first postoperative day. MEASUREMENTS AND RESULTS: All patients received either a placebo or catecholamine infusion for 24 h. Blood samples were obtained every 2 h for the next 2 days. PRL, DHEAS, cortisol, TSH, triiodothyronine, thyroxin, free triiodothyronine, and free thyroxin serum concentrations were determined by radioimmunoassay or luminescence immunoassay. Dopexamine (0.5 microg kg(-1) min(-1)) had no effects on serum concentrations of PRL or TSH. Higher doses of dopexamine (1 microg kg(-1) min(-1)) suppressed PRL secretion significantly, but not TSH. In contrast, infusion of dopamine (5 microg kg(-1) min(-1)) completely inhibited PRL and TSH secretion. DHEAS, cortisol, and thyroid hormone serum concentrations were not affected by either dopexamine or dopamine infusion. Measurements of hemodynamic parameters, peripheral oxygen saturation, diuresis, blood gases, and standard laboratory parameters were repeated hourly. Significant differences were not found between placebo, dopexamine (0.5 microg kg(-1) min(-1)) and dopamine (5 microg kg(-1) min(-1)) group. Dopexamine at 1 microg kg(-1) min(-1) increased the heart rate significantly. CONCLUSIONS: Routine postoperative optimizing of men undergoing abdominal surgical procedures with dopexamine at higher doses or dopamine induces at least partial hypopituitarism, which may possibly affect postoperative morbidity.

Abdomen↗
PubMed2001

Prediction of metabolic activity from genotype: the gene-dose effect of N-acetyltransferase.

Metabolic activity of the polymorphic N-acetyltransferase (NAT2) is determined by the mutation pattern of the NAT2 gene. This results in interindividual differences in the metabolic capacity (the phenotype), with continuous distribution of the activities rather than qualitative distinction between rapid and slow acetylators. To determine whether the phenotype might be predicted solely from the mutation pattern of NAT2, quantitative relationships were calculated between mutation patterns of the NAT2 gene and the phenotype of NAT2 assessed either in vitro or in vivo. Healthy volunteers were examined for the velocity at which they metabolized sulfamethazine, and human liver cytosols were measured for NAT2 enzymatic activity, obtaining in vivo and in vitro metabolic phenotype, respectively. Typing of the NAT2 gene was performed by polymerase chain reaction, restriction fragment length analysis, or allele-specific polymerase chain reaction. Multiple linear regression analysis provided quantitative relationships between allelic pattern and the NAT2 activities measured in vivo and in vitro. Estimates showed the influence of particular allelic configurations on enzyme activity in vitro and the extent of acetylation of the probe drug in vivo, resulting in a strict gene-dose effect. Comparison of in vitro results with in vivo phenotyping figures showed a high degree of correspondence, indicating that the one is the reflection of the other.

Adult↗
PubMed2000

Polymorphism of the N-acetyltransferase (NAT2), smoking and the potential risk of periodontal disease.

Periodontal disease is a common multifactorial process that leads to bone destruction and tooth loss. Interactions of environmental and genetic factors determine the extent and severity of periodontal disease. Smoking is one of the risk factors for periodontal disease, and the risk may be influenced by the polymorphism of N-acetyltransferase (NAT2) via metabolism of smoke-derived xenobiotics. We therefore hypothesized that a NAT2 genotype would be a risk factor for periodontal disease. A total of 154 Caucasian subjects were assigned to one of two groups (1) no or mild and (2) severe periodontal disease based on radiographic (bone destruction) and clinical criteria (probing depth, attachment loss) and the number of teeth. In all subjects genotyping for mutations on NAT2 was performed by means of PCR and RFLP analysis. In the less-affected group genotyping showed a fraction of predicted slow and rapid acetylators (53.6% and 46.4%, respectively) corresponding to the normal distribution in Caucasians. Severely affected patients were predominantly slow acetylators, the odds ratios being between 2.38 and 5.02 for the NAT2-related risk depending on the outcome parameters chosen. Adjustment for age had no influence on these findings. Our data indicate that the slow acetylator phenotype is associated with a higher risk of periodontitis, especially with respect to the severity of the disease. Possible implications with respect to the risk associated with smoking are discussed.

Acetylation↗
PubMed2000

The effect of rifampin treatment on intestinal expression of human MRP transporters.

The importance of the ATP-dependent transporter P-glycoprotein, which is expressed in the brush border membrane of enterocytes and in other tissues with excretory function, for overall drug disposition is well recognized. For example, induction of intestinal P-glycoprotein by rifampin appears to be the underlying mechanism of decreased plasma concentrations of P-glycoprotein substrates such as digoxin with concomitant rifampin therapy. The contribution of transporter proteins other than P-glycoprotein to drug interactions in humans has not been elucidated. Therefore, we tested in this study the hypothesis whether the conjugate export pump MRP2 (cMOAT), which is another member of the ABC transporter family, is inducible by rifampin in humans. Duodenal biopsies were obtained from 16 healthy subjects before and after nine days of oral treatment with 600 mg rifampin/day. MRP2 mRNA and protein were determined by reverse transcription-polymerase chain reaction and immunohistochemistry. Rifampin induced duodenal MRP2 mRNA in 14 out of 16 individuals. Moreover, MRP2 protein, which was expressed in the apical membrane of enterocytes, was significantly induced by rifampin in 10 out of 16 subjects. In summary, rifampin induces MRP2 mRNA and protein in human duodenum. Increased elimination of MRP2 substrates (eg, drug conjugates) into the lumen of the gastrointestinal tract during treatment with rifampin could be a new mechanism of drug interactions.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2000

Oral bioavailability of digoxin is enhanced by talinolol: evidence for involvement of intestinal P-glycoprotein.

OBJECTIVE: Recent data indicated that disposition of oral digoxin is modulated by intestinal P-glycoprotein. The cardioselective beta-blocker talinolol has been described to be secreted by way of P-glycoprotein into the lumen of the gastrointestinal tract after oral and intravenous administration. We therefore hypothesized that coadministration of digoxin and talinolol may lead to a drug-drug interaction based on a competition for intestinal P-glycoprotein. METHODS: Pharmacokinetics of digoxin (0.5 mg orally), talinolol (30 mg intravenously and 100 mg orally), and digoxin plus talinolol orally, as well as digoxin plus talinolol intravenously, were assessed in five male and five female healthy volunteers (age range, 23 to 30 years; body weight, 60 to 95 kg) in a changeover study with at least a 7-day washout period. Digoxin and talinolol were analyzed by fluorescence polarization immunoassay and HPLC, respectively. RESULTS: Oral coadministration of 100 mg talinolol increased the area under the concentration-time curve (AUC) from 0 to 6 hours and the AUC from 0 to 72 hours of digoxin significantly by 18% and 23%, respectively (5.85+/-1.49 versus 7.22+/-1.29 ng x h/mL and 23.0+/-3.3 versus 27.1+/-3.7 ng x h/mL, for both P<.05) and the maximum serum levels by 45%. Renal clearance and half-life of digoxin remained unchanged. Coinfusion of 30 mg talinolol with oral digoxin had no significant effects on digoxin pharmacokinetics. Digoxin did not affect the disposition of talinolol after both oral and intravenous administration. CONCLUSION: We observed a significantly increased bioavailability of digoxin with oral coadministration of talinolol, which is most likely caused by competition for intestinal P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Induction of P-glycoprotein by rifampin increases intestinal secretion of talinolol in human beings: a new type of drug/drug interaction.

BACKGROUND: P-Glycoprotein is an efflux pump in many epithelial cells with excretory function. It has been demonstrated that rifampin (INN, rifampicin) induces P-glycoprotein, particularly in the gut wall. We therefore hypothesized that rifampin affects pharmacokinetics of the P-glycoprotein substrate talinolol, a beta1-blocker without appreciable metabolic disposition but intense intestinal secretion in human beings. METHODS: Pharmacokinetics of talinolol (a single dose of 30 mg administered intravenously or 100 mg administered orally for 7 days) and duodenal expression of the MDR1 gene product P-glycoprotein as assessed by reverse transcriptase-polymerase chain reaction of the MDR1-messenger ribonucleic acid, by immunohistochemistry and Western blot analysis were analyzed before and after coadministration of rifampin (600 mg per day for 9 days) in 8 male healthy volunteers (age 22 to 26 years). RESULTS: During rifampin treatment, the areas under the curve of intravenous and oral talinolol were significantly lower (21% and 35%; P < .05). Treatment with rifampin resulted in a significantly increased expression of duodenal P-glycoprotein content 4.2-fold (2.9, 6.51) (Western blot) and messenger RNA was increased in six of the eight volunteers. P-Glycoprotein expression in biopsy specimens of gut mucosa correlated significantly with the systemic clearance of intravenous talinolol (rs = 0.74; P < .001). CONCLUSIONS: Rifampin induces P-glycoprotein-mediated excretion of talinolol predominantly in the gut wall. Moreover, clearance of talinolol from the blood into the lumen of the gastrointestinal tract may be predicted by the individual intestinal P-glycoprotein expression. Thus we describe a new type of steady-state drug interaction affecting compounds that are subject to transport rather than metabolism.

ATP Binding Cassette Transporter, Subfamily B, Mem↗