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Biomedical subjects

P Weiss

Publications and source records attributed to P Weiss.

At least 181 records · Page 10Linked to original sources
PubMed1986

The negative impact of biological variation in the effect and clearance of warfarin on methods for prediction of dose requirements.

Within-individual variation over time in the clearance (Cl) and effect (PT%) of warfarin, was measured in 25 inpatients (group I) studied after standard single or individualized split loading doses and 1-3 times (n = 16) 8-16 weeks later during maintenance. Mean Cl (2.5 +/- 0.9 ml/min) was similar in both phases but significant changes occurred in 6/16 patients, exceeding those expected from within-individual variation alone (defined by its 95% tolerance limits -24% to +62%). Initial PT% (21 +/- 5) was unaffected by dosing schedule, total or free plasma warfarin, varying between patients by only 18-24%. Mean initial and maintenance dose-PT% ratios (8.2 mg/d: 21% and 4.1 mg/d: 40%) were similar but significant changes in sensitivity to warfarin occurred in 4/16 patients. In group I and 64 other outpatients on maintenance therapy, between-individual variability was 36-52% for Cl and 49-56% for effect. PT% correlated best (r = 0.56) with free and total plasma warfarin but poorly with dose (r = 0.29), with only 30% of PT% variance explained at best, due to high between patient variability. Warfarin dose prediction whether based on extrapolation from initial effects to the maintenance phase, or on iterative methods not allowing for between- or within-patient variation in warfarin clearance or effect which may occur independently over time, have not improved on empirical therapy. This, due to the elements of biological variability as well as the intricacy of the warfarin-prothrombin complex interaction not captured by any kinetic-dynamic model used for prediction to date.

Biological Availability↗
PubMed1986

Multiplanar (MPR) imaging of the hip.

Multiplanar CT expands the ability of the radiologist to define the extent of disease, to suggest appropriate surgery, and to offer a probable prognosis.

Acetabulum↗
PubMed1986

Metallic hip implants: CT with multiplanar reconstruction.

Thirty consecutive patients with metallic implants in the hip were evaluated with both standard transaxial computed tomography (CT) and multiplanar reconstruction (MPR) to assess the contribution of MPR. The metallic devices included total hip replacements (n = 6), one or more surgical plates with screws (n = 9), acetabular pins or screws (n = 9), and Knowles pins (n = 6). The metallic implants were on the side of interest in 25 hips and in the contralateral hip in five cases. One patient had bilateral hardware. MPR reformats axially acquired data into other planes. The reconstruction program weights the true signal over the randomly distributed artifacts by integrating adjacent axial images. Examination using standard transaxial imaging was graded as excellent in five cases, adequate in 15 cases, and inadequate in ten cases. After MPR, 19 studies were classified as excellent, 11 were classified as adequate, and none were classified as inadequate. It is concluded that MPR significantly reduced artifacts caused by metal present in transaxial images.

Acetabulum↗
PubMed1986

[Organic nitrates and prostaglandins in the cardiovascular system].

The beneficial effect of organic nitrates in acute myocardial ischemia is commonly explained by their hemodynamic actions, especially the dilatation of venous capacitance vessels. Recent studies have shown an inhibition of platelet function by organic nitrates ex vivo but not in vitro. Antiplatelet activities of organic nitrates might represent an additional mechanism, independent of vascular actions which might eventually involve stimulation of prostacyclin formation by the vessel wall. In vitro experiments on isolated coronary artery preparations have demonstrated stimulation of PGI2 as well as inhibition of platelet thromboxane synthesis by a number of organic nitrates. Optimal stimulation requires the presence of a free nitro group in the molecule at a particular steric position and can be suppressed by a number of inhibitors, including corticosteroids, indomethacin and methylene blue. Administration of the organic nitrate teopranitol to healthy volunteers is associated with depressed platelet secretion ex vivo which is not seen with the compound in vitro. It is concluded that further clinical elucidation of the PGI2-related mechanism in the action of organic nitrates in patients appears to be both necessary and useful.

Adenosine Triphosphate↗
PubMed1985

[The supply of iodine in the province of Vorarlberg].

For evaluation of iodine supply in Vorarlberg, Austria, iodine urine excretion was measured in 299 patients. The Mean was 74,3 +/- 53,6 micrograms J/g Cr, the Median 61 micrograms J/g Cr. 79% of the patients showed an iodine deficiency I according to WHO classification and 41% an iodine deficiency II. In this patient group were included 44 subjects with no thyroid disease who showed an iodine excretion of 70.8 +/- 56,5 micrograms J/g Cr and a Median of 50,5 micrograms J/g Cr. There was no statistical difference to the values of the patient group. Regional evaluation of iodine supply showed an iodine deficiency I in 78% and an iodine deficiency II in 38% in the industrial region of the Rheintal. In the region Walgau with mixed industrial-rural population an iodine deficiency I was found in 81% and an iodine deficiency II in 45%. In the rural areas of Bregenzerwald and deep valleys an iodine deficiency I could be demonstrated in 81% and 83% respectively and an iodine deficiency II in 47 and 57% respectively. This moderate but statistically not significant differences show the minor influence of alimentation in iodine supply. Assuming a constant table salt consumption the results support the common belief that iodine supply in iodine deficient areas is strongly connected to incorporation of iodinated table salt. Therefore an increase of the iodination of table salt in Austria seems to be necessary to guarantee sufficient iodine supply.

Adolescent↗
PubMed1985

Mechanism of warfarin potentiation by amiodarone: dose--and concentration--dependent inhibition of warfarin elimination.

Potentiation of the anticoagulant-effect of warfarin by amiodarone was studied in 30 patients. Thirteen received both drugs concurrently, and 17 received warfarin alone and the combination sequentially. Warfarin doses were adjusted to maintain the prothrombin time between 25-30% of control and its kinetics were compared to those in 20 control patients who received warfarin alone. Potentiation occurred in 28/30 patients, presenting as a 35%-65% reduction in the required dose of warfarin, and was correlated with the dose of amiodarone (r = 0.77, p less than 0.01). The free warfarin fraction was not affected by amiodarone (1.8% vs 1.6% in the controls). Warfarin clearance was lower in amiodarone-treated patients than in the controls (1.4 vs 3.1 ml/min, p less than 0.01) with similar plasma concentrations (1.5 vs 1.2 micrograms/ml) despite administration of lower doses (23.3 vs 39 mg/week respectively). The amiodarone concentration was significantly correlated with the warfarin concentrations independent of the effect of amiodarone on the dose of warfarin. Amiodarone hat no effect on prothrombin other than through its actions on the dose and plasma concentration of warfarin. The mechanism of the amiodarone-warfarin interaction is pharmacokinetic through dose - and concentration - dependent inhibition of warfarin elimination.

Adult↗
PubMed1985

Safety of thymopentin. Data from European clinical studies.

The safety data collected from 196 patients treated with thymopentin during the clinical development of this compound in Europe are reviewed and compared with the incidence of adverse drug reactions experienced when using a commercial nonsteroid anti-inflammatory drug. Quantitatively side effects are reported in the same range for both drugs, however, they appear to be quite different when classified by body systems. Some patients complained about somnolence, and it is speculated whether this symptom might be related to thymopentin's known effect on the neuromuscular junction. The general conclusion is that thymopentin is an extremely well tolerated drug when used according to the dose regimens recommended.

Animals↗
PubMed1984

Stereospecific stimulation of coronary vascular PGI2 by organic nitrates--studies with the new compound teopranitol (KC-046).

PGI2 release of bovine coronary arteries (BCA) was studied in vitro (bioassay) under control conditions and in presence of the new isoidide-nitrate teopranitol (2-(gamma-theophylline-7-ylpropylamino)-2-desoxy-L-isoidide- 5-nitrate- bifumarate) (KC-046). Teopranitol dose-dependently stimulated (2-200 nmoles/1) PGI2 release 2-3-fold. This action was inhibited by both methylene blue (150 mumoles/1) and indomethacin (11 mumoles/1). The 5-[endo] stereoisomere (KC-144) was inactive, although both compounds produced an equally potent relaxation of isolated BCA strips. Similar stereospecificity was found for isosorbide nitrates. It is suggested that stimulation of coronary vascular PGI2 by organic nitrates is critically determined by the steric position of the free nitrate group(s), whereas the vasodilation is a more general property.

Animals↗