Biomedical subjects

H Laufen

Publications and source records attributed to H Laufen.

At least 55 records · Page 3Linked to original sources

PubMed1991

Slow release isosorbide-5-mononitrate therapy in angina pectoris. Effects of exercise performance and hemodynamics.

The possibility of maintaining preload reduction and enhancement of exercise tolerance during an interval treatment with 100 mg/day of slow-release isosorbide-5-mononitrate (IS-5-MN) was investigated in 12 patients (aged 57 +/- 5.0 years) with angiographically confirmed coronary artery disease and chronic stable angina pectoris. The effects of a single dose (acute test) were compared with those following an 8-day (chronic) regimen of mononitrate administration. Two hours after administration of 100 mg sustained-release IS-5-MN, mean resting pulmonary artery pressure (PAP), measured with a Swan-Ganz catheter, was reduced by 32% (p less than 0.001) and at submaximal exercise level (50 W, 3 min) by 37% (p less than 0.001). At individually highest comparable work loads mean PAP was reduced by 37% (p less than 0.001), and at maximal work load the PAP reduction was 14% (p less than 0.05). At the end of 1 week of therapy with sustained-release IS-5-MN a slight, clinically irrelevant reduction of hemodynamic effect was recorded. Work capacity increased after 1 h by 79% (264 +/- 154 vs. 472 +/- 180 W x min, p less than 0.01), still significantly above base-line 10 h after nitrate administration. No difference from baseline was demonstrable 24 h after medication. During interval therapy the improved work capacity was fully maintained (chronic, 1 h: 280 +/- 119 vs. 532 +/- 160 W x min, p less than 0.001). There was no significant difference between the plasma IS-5-MN levels at acute and chronic therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1991

[Interactions of fluconazole and phagocytic cells].

Fluconazole is a triazole compound with a coefficient of distribution P at pH 7.4 of 1.6 (log P = 0.2), and has thus both hydrophilic and lipophilic properties. The physicochemical and pharmacokinetic profiles of fluconazole are clearly different from those of other azole antimycotics. 3H-labelled fluconazole penetrates very rapidly into granulocytes and monocytes (macrophages) isolated from volunteers. The concentrations of the triazole in the granulocytes are about 28% and in the macrophages about 63% higher than in the extracellular milieu. At the concentrations examined (5, 10 and 20 micrograms ml-1) fluconazole damages cells of Candida albicans which have been phagocytized by granulocytes or by macrophages. A clear synergy between fluconazole and the phagocytes can be demonstrated.

Candida albicans↗

PubMed1990

Interaction of fluconazole and human phagocytic cells. Uptake of the antifungal agent and its effects on the survival of ingested fungi in phagocytes.

3H-labelled fluconazole (CAS 86386-73-4) very rapidly penetrated into polymorphonuclear leucocytes (PMNLs) and macrophages (monocytes) isolated from volunteers. The concentration of the antimycotic in the PMNLs was about 28% and in the macrophages even 63% above that in the extracellular medium. At the concentrations examined (5, 10 and 20 micrograms/ml) fluconazole damaged cells of Candida albicans which had been phagocytized by PMNLs or macrophages. There is an evident synergism between therapeutically attainable concentrations of fluconazole and phagocytic cells and this militates against the intracellular survival of the fungus.

Candida albicans↗

PubMed1990

Mechanism of azithromycin uptake in human polymorphonuclear leucocytes.

The new antibiotic azithromycin (CP-62.993) is enriched in human polymorphonuclear leucocytes by up to 300-fold the extra-cellular concentrations. To approach an understanding of the underlying mechanism of this unique behavior of azithromycin, some characteristics of the uptake process were investigated in vitro. The speed of the uptake in human polymorphonuclear leucocytes was found to be independent of the extracellular starting concentrations of azithromycin. There was no indication of saturation up to extracellular concentrations of 100 micrograms/ml. The uptake was largely determined by incubation temperatures. At 4 degrees C no penetration into the cells could be observed. The activation energy of azithromycin uptake came to 144 kJ mol-1, twice the value of erythromycin uptake. The presence of various inhibitors of cell metabolism did not change the intracellular accumulation compared to control, nor did the presence of some agents which interfere with certain transport channels. These findings suggest that passive diffusion is an essential mechanism of azithromycin transport through the phagocyte membrane, while active transport is less important. The high cellular enrichment of azithromycin and the relatively high activation energy of the uptake process could be explained by accumulation of the drug in phagocytic lysosomes and this would also be in keeping with pH partition considerations.

Adult↗

PubMed1989

Effective treatment of chronically progressive multiple sclerosis with low-dose cyclophosphamide with minor side-effects.

Twenty-one multiple sclerosis (MS) patients with a chronically progressive course were treated with a low dose of cyclophosphamide (CY). The control group consisted of 21 MS patients with a chronically progressive course who received the standard treatment (ACTH or cortisone). The control group consisted of patients who preferred the standard therapy because of its beneficial effects. In contrast, the patients of the CY group wanted to try a new therapy because the standard therapy was not effective. Thus before starting the study the progression of the disease was faster in the CY group than in the standard therapy group. As regards age, sex and degree of disability, the two groups were comparable. For 20 of the 21 patients in the CY group the degree of disability (Kurtzke scale) remained stable over 1 year; for 2 of the 20 stable patients there was even an improvement. In the standard therapy group, 7 out of 21 patients were stable over 1 year, while 14 showed progressive disability. A quantitative neurological score at the beginning and 1 year after the therapy showed a nearly identical difference between the CY group and the control group. The changes of the patients' abilities in daily-life activities (which were observed and recorded by the nurses) were similar to the Kurtzke scale data obtained by the physicians. The beneficial effect of CY in chronically progressive MS was thus highly significant (P less than 0.001). The side-effects of low-dose CY were fewer than those of ACTH.

Adult↗

PubMed1989

Interaction of azithromycin and human phagocytic cells. Uptake of the antibiotic and the effect on the survival of ingested bacteria in phagocytes.

14C-labeled azithromycin, a new macrolide antibiotic, was accumulated by various phagocytic cells isolated from volunteers or patients. The concentration of the antibiotic in monocytes, polymorphonuclear leucocytes (PMNLs), and alveolar macrophages was greater than that in the surrounding medium by a factor of between 200 and 668. Azithromycin penetrated somewhat more rapidly into PMNLs and monocytes than into alveolar macrophages. On the other hand the final concentration in the alveolar macrophages was greater by a factor of about 3 than that in the other two phagocytic cells. Staphylococcus aureus, Legionella pneumophila and Haemophilus influenzae previously taken up by the phagocytes were rapidly inactivated by low (0.031-0.5 micrograms/ml) concentrations of the antibiotic, which in the presence of the cells were subinhibitory. There is thus a clear synergism between azithromycin and the phagocytic cells which leads to increased intracellular killing of the bacteria.

Azithromycin↗

PubMed1989

Kinetics of the uptake of antimicrobial agents by human polymorphonuclear leucocytes.

The in-vitro rate constants of the cellular uptake and elimination of the antimicrobial agents josamycin (Wilprafen), erythromycin and tetracycline were measured in normal human polymorphonuclear leucocytes (PMNs) using the velocity gradient centrifugation technique with radiolabelled drugs at extracellular concentrations corresponding to therapeutically effective serum levels. The rate of antibiotic uptake increased stepwise in the order tetracycline less than erythromycin less than josamycin. The half-lives of the uptake came to 0.8 min for josamycin, 4.7 min for erythromycin, and 14.8 min for tetracycline. The extraordinarily rapid uptake of josamycin by PMNs corresponds to the high lipophility of the drug. The accumulation of the three tested antibiotics in PMNs occurred much faster than their elimination from the cells, suggesting directional transport of the molecules through the leucocyte membrane and/or rate limiting dissociation from intracellular binding sites. Significant differences between the drugs tested were observed in the temperature dependence of their rates of uptake. The apparent activation energies of cellular uptake amounted to 114.2 kJ mol-1 (josamycin), 68.6 kJ mol-1 (erythromycin) and 52.2 kJ mol-1 (tetracycline). There is experimental support for a contribution of the nucleoside carrier system to the membrane transport of josamycin.

Adult↗

PubMed1988

Piroxicam in breast milk after long-term treatment.

The presence of piroxicam in breast milk was determined by HPTLC during initial and long term dosing in 4 women treated for arthritis. Piroxicam appeared in breast milk at about 1-3% of the maternal plasma concentration. No accumulation of piroxicam occurred in milk relative to that in plasma up to 52 days of treatment. Neither piroxicam nor its conjugates were detectable in the urine of one breast-fed infant. The daily dose ingested by the infant was calculated to average 3.5% (maximum 6.3%) of the weight-related maternal dose of piroxicam. It is concluded that a breast-fed infant will be exposed to a very small amount of piroxicam.

Adult↗

PubMed1988

The pattern of glyceryl nitrates after oral administration of glyceryl trinitrate.

An oral dose of 20 mg sustained release glyceryl trinitrate (GTN, Nitro Mack Retard) was administered to 6 healthy human subjects. In the plasma of all subjects the metabolically generated glyceryl nitrates glyceryl 1,2-dinitrate (G-1,2-DN), glyceryl 1,3-dinitrate (G-1,3-DN), glyceryl 2-nitrate (G-2-N) and glyceryl (G-1-N) could be identified, but no intact GTN was found. The nitrate metabolites showed sustained plasma profiles which can be explained by a slow release of GTN with subsequent complete first-pass denitration. The plasma concentrations of the mononitrates were generally higher than those of the dinitrates. G-1,2-DN and G-2-N, the metabolites which contain a nitrate group in the central position, showed higher concentrations than the respective isomeric compounds. The combined glyceryl dinitrates reached concentrations between 10.2 and 21.7 ng/ml, the combined mononitrates varied from 70.4 to 106.8 ng/ml. The ratios of the areas under the curve G-1,3-DN:G-1,2-DN:G-1-N:G-2-N were 1:4:19:64, on average. Taking into consideration the relative vasodilator potencies of glyceryl nitrates in the animal, our results give rise to the hypothesis that the glyceryl dinitrate metabolites participate in the clinical efficacy of large oral doses of sustained release GTN.

Administration, Oral↗

PubMed1988

Comparative pharmacokinetics of isosorbide nitrates after repeated doses of sustained release isosorbide dinitrate.

The plasma kinetics of isosorbide dinitrate (ISDN), isosorbide-5-nitrate (IS-5-N) and isosorbide-2-nitrate (IS-2-N) were investigated in 20 healthy male and female volunteers, after b.i.d. administration over 2 days of sustained release ISDN 20 mg and 40 mg capsules (Iso Mack Retard 20 mg and 40 mg) and of a 40 mg sustained release ISDN tablet as reference formulation. The means of the individual maximum ISDN concentrations during the complete 2-day treatment amounted to 10.4 ng/ml after the 40 mg capsule, 5.3 ng/ml after the 20 mg capsule and 5.3 ng/ml after the reference tablet. The corresponding figures of the metabolically generated IS-5-N were 355.5 ng/ml, 168.8 ng/ml and 161.5 ng/ml, respectively. The measured amounts of IS-5-N are expected to contribute to the overall antianginal effect of at least the 40 mg capsule. According to the b.i.d. schedule, ISDN and the two mononitrates accumulated in the plasma after all three tested formulations. However, during the treatment with the 20 mg and the 40 mg capsules, accumulation was practically completed at the second day, while it was found to be more extended during treatment with the reference product. In terms of areas under the curve, the mean bioavailability of the 40 mg sustained release capsule relative to the reference formulation was 198% with respect to ISDN, and 197% both with respect to IS-2-N and IS-5-N. On the other hand, perfect dose-linearity of all relevant pharmacokinetic parameters of all three measured isosorbide nitrates was observed for the 20 mg and the 40 mg dose of the capsule.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

[Functions of intrinsic defense against anaerobic bacteria in healthy probands and patients with chronic-septic granulomatosis].

Different strains of Bacteroides fragilis exhibit great differences in sensitivity towards serum from healthy volunteers. In the presence of 10% autologous serum, neutrophilic granulocytes and monocytes (macrophages) caused significant killing of B. fragilis. The measured phagocytic and killing activity of the cells is comparable to their activity against aerobic bacteria (S. aureus). In four patients with chronic granulomatous disease of childhood, phagocytosis was normal but killing of B. fragilis and S. aureus in granulocytes or monocytes (macrophages) was appreciably lowered. This malfunction of the cells was accompanied by a disturbance in oxidative metabolism and inadequate iodination after phagocytosis of B. fragilis. The results suggest that granulocytes and monocytes play an important role in host defense against endogenous infections with anaerobes.

Abscess↗

PubMed1987

Gas chromatographic assay of glycerol mononitrates in biological samples.

A new gas chromatographic analysis of glycerol 1-nitrate and glycerol 2-nitrate is described. The method is suitable for a variety of biological samples and can detect down to the low nanogram range. An extract of the sample to be analysed is treated with phenylboronic acid. The glycerol mononitrates rapidly form cyclic boronates, with five- and six-membered rings, respectively, which can then be separated by gas chromatography and detected by an electron-capture detector.

Animals↗

PubMed1987

Glyceryl-1-nitrate pharmacokinetics in healthy volunteers.

The plasma kinetics and urinary excretion of glyceryl-1-nitrate (G-1-N), a metabolite of glyceryl trinitrate with antianginal potential, were investigated in 10 healthy male volunteers, after intravenous infusion and oral administration of 20 mg G-1-N. The apparent volume of G-1-N distribution was 601 corresponding to 0.761 kg-1 body weight, on average. It is suggested that total body water is the principal biological correlate of the hydrophilic drug. Mean intravenous clearance was 283 ml min-1 or 3.61 ml min-1 kg-1. The average of elimination half-lives were 2.50 +/- 0.36 (s.d.) h after the intravenous and 2.54 +/- 0.40 (s.d.) h after the oral dose. Inter-subject variances of pharmacokinetic parameters were low compared to variances reported for glyceryl trinitrate. The coefficient of intra-subject variation of the elimination half-lives was 8.8%. 5.5% (i.v.) and 5.4% (p.o.) of the administered dose were excreted into urine up to 48 h after the administration. 1% (i.v.) and 1.5% (p.o.) were in the conjugated form. The oral dose was rapidly and almost completely absorbed. The oral bioavailability on the basis of areas under the curve amounted to 88.6% on the average. For clinical use, owing to its high oral bioavailability, long residence in the body, inactivation by metabolic conversion, and good predictability of kinetic parameters, G-1-N offers advantage over glyceryl trinitrate.

Adult↗

PubMed1987

[The pharmacology and pharmacokinetics of glycerol-2-nitrate].

Glyceryl 2-nitrate (G-2-N), which is the major metabolite of glyceryl trinitrate (GTN, Nitro Mack, glyceryl 1-nitrate (G-1-N) and isosorbide-5-nitrate (IS-5-N, Mono Mack) were examined in a comparative study. The haemodynamic and antianginal properties and the spasmolytic activity on blood vessels were investigated in the rat and dog. Also examined were the pharmacokinetics of G-2-N in the rat and of oral GTN in the dog. Strips of rat aorta contracted with potassium chloride or with norepinephrine were relaxed by G-2-N, but somewhat more weakly than with IS-5-N or G-1-N. After oral administration to the anaesthetized rat or to the conscious dog G-2-N exhibited antianginal and hypotensive activity for 6 h. The duration of action of orally administered GTN in the dog depended on the concentration used and was between 15 and 360 min. The half-life of elimination of G-2-N in the rat came to 2 h, and the substance was 100% bioavailable. The concentrations of G-2-N found in the walls of rat vena cava caudalis and rat aorta abdominalis were twice as high as those in blood or plasma. After oral administration of GTN to the conscious dog, G-2-N is the main metabolite, followed by G-1-N, glyceryl 1,2-dinitrate (1,2-GDN), and glyceryl 1,3-dinitrate (1,3-GDN). After a large oral dose of GTN (30 mg/kg), G-2-N contributes to the pharmacodynamic effect from the 3rd h or earlier.

Angina Pectoris↗

PubMed1987

The effect of antibiotics on the intracellular survival of bacteria in human phagocytic cells.

[14C]-labeled josamycin (Wilprafen) readily enters several types of human phagocytic cells-polymorphonuclear leucocytes (PMNLs), adherent monocytes and alveolar macrophages - and is accumulated by these cells to a concentration about 20 times that in the extracellular medium. Similar studies using [14C]-benzyl penicillin revealed that the beta-lactam antibiotic penetrated these cells very poorly. Low concentrations of josamycin and the various phagocytes acted synergistically to inhibit the intracellular proliferation of L. pneumophila or H. influenzae. In contrast, penicillin G was not effective against legionellae ingested by PMNLs, monocytes or alveolar macrophages, even at high concentrations. The uptake of the antibiotics apparently correlates well with its efficacy against the intracellular survival of bacterial pathogens in human phagocytic cells.

Erythrocytes↗

PubMed1986

Pharmacokinetics of oral glycerol-1-nitrate.

The plasma kinetics and urinary excretion of glycerol-1-nitrate (G-1-N), a water soluble metabolite of glycerol trinitrate with anti-anginal potential, have been investigated in healthy human volunteers following oral doses of 10, 20 and 40 mg tablets and 20 mg as drops. In all volunteers G-1-N was rapidly absorbed. The mean concentration-time curves peaked 40 min after administration of tablets at 144 ng/ml (10 mg), 308 ng/ml (20 mg) and 573 ng/ml (40 mg). After the drops the peak of 324 ng/ml occurred at 1 h. The areas under the G-1-N concentration-time curve and the G-1-N peak heights were linear with dose. Tablets and drops can be regarded as bioequivalent with respect to area under the curve and elimination half-life. The bioavailability of the 20 mg tablet relative to the 20 mg drops was 98.6% in terms of area under the curve. The mean apparent half-life of G-1-N elimination from plasma was 2.69 +/- 0.67 h (n = 46). The mean residence time of G-1-N in the body was 4.65 h compared to 0.28 h for glycerol trinitrate after buccal administration. Female volunteers were found to have significantly lower areas under the curve than male volunteers. The difference was probably due to differences in body weight. Renal excretion does not play an important role in the elimination of oral G-1-N from the body. An overall average of 5.42% of the G-1-N dose was excreted in the urine; free drug accounted for 4.02% and conjugated drug for 1.40%.

Adult↗

PubMed1986

Isosorbide dinitrate in plasma and dialysate during haemodialysis.

In 10 patients with end stage renal disease on regular haemodialysis the plasma concentrations and dialyzer clearance of isosorbide dinitrate (ISDN) were determined after an oral dose of a retarded release formulation of 60 mg ISDN. The maximal plasma concentration of ISDN 2-7 h after oral administration was higher (14 ng/ml) than has been reported in healthy volunteers. The haemodialyzer clearance of ISDN was 92.4 ml/min at a blood flow of 200 ml/min and dialysate flow of 500 ml/min. During a 5-h haemodialysis an average of 0.3 mg ISDN was removed from the patient's circulation, representing about 0.5% of the administered dose and about 3% of the available drug in the circulation. No influence of haemodialysis on the plasma level of ISDN was found.

Aged↗

PubMed1986

Preliminary study of the pharmacokinetics of desmethyldiazepam administered as drops or tablets.

Desmethyldiazepam (Vegesan) was administered in the form of 5-mg and 10-mg tablets and of 10-mg drops to 4 male and 4 female young healthy volunteers. The plasma levels of desmethyldiazepam were measured over 168 h. The time courses could be fitted to the one- or to the two-compartment model. The mean half-lives of elimination came to 75.3 +/- 32.0 (SD) h (5-mg tablets), 66.5 +/- 21.0 (SD) h (10-mg tablets) and 78.4 +/- 33.2 (SD) h (10-mg drops). The bioavailability of desmethyldiazepam from tablets and from drops was practically the same. The bioavailability appeared to be independent of dose in this range. A significantly higher total plasma clearance was calculated for the male than for the female volunteers after all three dosage forms (p less than 0.05). The total plasma clearance lay between 4.8 and 13.0 ml/min for the female and 12.4 and 24.3 ml/min for the male volunteers. Ingestion of the contraceptive pill is suggested as a possible cause of the sex differences.

Adult↗