[Pure titanium as alternate metal in restorative dentistry. 2. Titanium ceramic].
Explore the source record for details and available documents.
Dental Casting Technique↗
Biomedical subjects
K Bachmann
Publications and source records attributed to K Bachmann.
[ECG changes caused by the effect of static magnetic fields of nuclear magnetic resonance tomography using magnets with a field power of 0.5 to 4.0 Telsa].
ECG-alterations under the influence of static magnetic fields were investigated in phantoms (1.5 Tesla), animals and volunteers (4.0 Tesla), as well as in 12 patients (0.5, 1.0, and 1.5 Tesla). Under the influence of static magnetic fields high- and low-frequency voltages are superimposed on the ECG. Motions of the electrical leads induce high-frequency waves, which can alter the ECG to the extent that only the QRS-complex can be recognized. Electrolytes moved by the blood stream in static magnetic fields also induce voltages (Hall-effect) which, according to the patient's position, result in ST-segment- and partial T-wave-elevations or depressions. All ECG-alterations are reversible after exposition to the static magnetic field. Rhythm disturbances do not occur. The results indicate that static magnetic fields up to 4.0 Tesla do not have permanent adverse effects on the human ECG.
Adult↗
[Quantitative levo-angiography: comparative study of various analysis procedures for detecting regional disorders of myocardial wall motion].
Explore the source record for details and available documents.
Heart Ventricles↗
Circadian investigation of interval therapy with isosorbide dinitrate in coronary heart disease.
One of the most promising concepts in nitrate therapy is interval therapy, a dosage scheme with marked changes of nitrate concentrations in the 24-h interval. In a single-blind, placebo-controlled study in patients with coronary heart disease we investigated the circadian anti-ischaemia and haemodynamic response to interval therapy with isosorbide dinitrate (120 mg sustained release 1 X 1). 10 male patients (46-75 years, mean 60 years) with chronic stable angina and ST-segment depression during exercise entered the trial. At the end of a 10-day placebo period (medication at 8 am) three exercise tests were performed (10 am, 2 pm, 6 pm), recording ST-segment changes, pulmonary capillary wedge pressure (PCP) and cardiac index (CI). Spontaneous ischaemic events were detected by Holter monitoring until 8 am the next day. After three weeks of therapy with isosorbide dinitrate, the protocol was repeated (statistics: paired t-test, *P less than 0.05). PCP was reduced by 8.3 mmHg* at 10 am, 8.0 mmHg at 2 pm, 2.9 mmHg (NS) at 6 pm with a concomitant increase of cardiac index (+0.8,* +0.7*, +0.3 NS l min-1 m-2). While the haemodynamic improvement was maximal in the morning the anti-ischaemia effect (reduction of ST-depression) was constant during the active day (-0.40*, -0.50*, -0.43* mm). Four transient ischaemia episdodes at night were recorded under placebo, none under isosorbide dinitrate. In conclusion, all parameters studied demonstrate the effectiveness of chronic interval therapy with isosorbide dinitrate.
Aged↗
Impact of ciprofloxacin on theophylline clearance and steady-state concentrations in serum.
The effect of a multiple-dose regimen of oral ciprofloxacin (750 mg every 12 h for 11 doses) on the clearance and steady-state concentrations of theophylline in trough (predose) serum was evaluated in nine healthy male subjects, each serving as his own control. Theophylline was taken as a sustained release tablet per os in a dose of 200 mg every 12 h for 19 doses. Theophylline concentrations in serum were measured immediately before each theophylline dose. Ciprofloxacin was administered on study day 4 through the first dose of study day 8. Theophylline concentrations in serum were also measured on study days 3, 6, 8, and 10 at the following times after the first dose of each day: 0, 0.25, 0.50, 1, 2, 4, 6, 8, 10, and 12 h. Steady-state theophylline concentrations in trough serum were significantly higher during ciprofloxacin treatment (day 8) than before (day 3) or after (day 10) ciprofloxacin administration (P less than 0.01). Likewise, theophylline clearance was significantly slower (P less than 0.01) during ciprofloxacin treatment (day 8) than before it (day 3) or after it (day 10). The magnitude of ciprofloxacin-induced changes was approximately 30%. These results suggest that a multidose regimen of ciprofloxacin significantly slows the clearance of theophylline and elevates theophylline concentrations in serum.
Adult↗
Ethosuximide disposition kinetics in rats.
1. Single and multiple dose disposition kinetics of ethosuximide were studied in male Sprague-Dawley rats following intravenous administration. 2. The plasma disappearance of a single 35 mg/kg dose followed for 75 h was not linear. A dose-ranging study suggested that the apparent non-linearity of ethosuximide's plasma disappearance might be due to enzyme induction over time with the drug exhibiting a faster elimination from 24 h onward. 3. Ethosuximide, after only two daily doses of 35 mg/kg/day, shortened pentobarbital-induced sleep in rats. The clearance of ethosuximide was also significantly faster after four daily 35 mg/kg doses than after a single 35 mg/kg dose. 4. Single sample clearance estimates calculated from ethosuximide concentrations prior to enzyme induction, viz. up to 24 h post-dose, were practically identical to multiple sample clearance values. Both single and multiple sample clearances were calculated assuming linear rather than non-linear elimination.
Animals↗
Quantitative comparisons of pharmacokinetic drug interactions: a probabilistic approach.
An empirically-based approach which permits the comparison of changes in plasma clearance caused by pharmacokinetic drug-interactions is described. The analysis is based on the calculation of simple probability ratios for defined ranges of clearance changes that are caused by one of the interacting drugs. Examples of drugs increasing the clearance of a second drug through enzyme induction and of drugs decreasing the clearance of a second drug through enzyme inhibition are given. Data for each pair of interacting drugs is empirically fitted using either exponential or logarithmic functions. For each type of interaction a family of curves is generated which permits quantitative comparisons of both the extent and frequency of changes in plasma clearance caused by the interaction.
Drug Interactions↗
[Antihypertensive effect of once-daily administration of nitrendipine. A placebo-controlled study using non-invasive automatic ambulatory 24-hour blood pressure determination].
Explore the source record for details and available documents.
Adult↗
Theophylline clearance during and after mild upper respiratory infection.
Theophylline clearance was estimated by a single-sample technique in 19 subjects with acute clinical respiratory infections. Mean (+/- SD) theophylline clearance during acute illness was 0.044 +/- 0.011 L X h-1 X kg-1 compared to 0.043 +/- 0.012 L X h-1 X kg-1 1 month later. In a subset of five subjects, single-sample clearance estimates were not different from standard multi-sample clearance estimates. Mild upper respiratory infection does not appear to alter theophylline clearance in adults.
Adult↗
Estimating the clearance of amylobarbitone from a single plasma measurement.
Amylobarbitone sodium (200 mg) was given by intravenous injection to nine healthy, young adults (four males). Subjects were drug-free and nonsmokers. Serial blood samples were drawn for 48 h following the infusion, and multiple sample and single sample estimates of clearance were calculated. The mean (+/- s.d.) values for clearance (CL) and apparent volume of distribution (V) were 0.032 (+/- 0.007) 1 h-1 kg-1 and 1.08 (+/- 0.16) 1 kg-1, respectively. The mean (+/- s.d.) single sample estimate of clearance, CL, based on just the 48 h plasma concentrations of amylobarbitone was 0.033 (+/- 0.006) 1 h-1 kg-1. The 48 h single sample CL value was shown to reliably reflect the value of CL with little bias and good precision. Values of the 48 h CL when compared to CL exhibited a mean prediction error (mpe) of 1.2% with 95% confidence limits of -6.3% to 9.4%, and a root mean squared error (rmse) of 9.4%. It is concluded that amylobarbitone's clearance can be estimated in a single dose, single sample protocol permitting its use as a single dose, single sample probe for studying host factor influences on drug metabolism.
Adult↗
Satisfactory primary tetanus antitoxin responses but markedly reduced germinal centre formation in first draining lymph nodes of ageing mice.
The present report deals with primary antibody responses to tetanus toxoid in 50-54-week-old ('ageing') as compared to 8-9-week-old ('young adult') mice. Antitoxin in the serum appeared 6 days earlier in the older than in the young animals, but in the latter reached 5 times higher titres on day 20. The magnitude of the proliferative response in the paracortex and the medulla of popliteal lymph nodes, as estimated by combined 3H-thymidine autoradiography and planimetry, was 3-7 times greater in the younger than in the older age group, thus approximately reflecting the difference in antibody titres on day 20. In contrast, germinal centre formation in response to the stimulus proved to be about 14 times less in ageing than in young adult mice. The findings demonstrate that, in the model system used, the age-related slopes of decline in humoral antibody responsiveness and proliferative reactivity in paracortex and medulla of first regional lymph nodes tend to be in parallel, while the ability of the immune apparatus to form germinal centres at this site deteriorates at a considerably faster pace. Results are also in line with the notion that centroblasts/centrocytes contribute little, if anything, to the ongoing antibody production elicited by the same stimulus which had triggered germinal centre formation. Finally, the observations made disprove the general validity of the suggestion that immune reactivity is maintained on the same level throughout life if tested with a novel antigen.
Aging↗
Impact of cefaclor on the pharmacokinetics of theophylline.
The influence of cefaclor taken for 8 days (250 mg every 8 h) on the pharmacokinetics of a single intravenous dose of theophylline (2 mg/kg administered on the 8th cefaclor day) was studied in a crossover fashion among 11 healthy adults (10 men and one woman). Theophylline concentrations were measured serially for 12 h by an immunofluorescence polarization technique. No influence of cefaclor was detectable on theophylline clearance, half-life, or volume of distribution. It is concluded that cefaclor and theophylline can be administered together safely.
Adult↗
Screening for the influence of host factors on warfarin clearance using a single dose single sample procedure.
A single dose, single sample procedure for estimating warfarin clearance for screening purposes was evaluated. Single sample estimates of warfarin clearance, CL/F, were closest to actual values for warfarin clearance, CL/F, calculated from multiple sample data when the sample was collected 120 h after warfarin ingestion. An apparent volume of distribution, V/F, of 0.17 l/kg was used in calculating CL/F. After a single dose of warfarin single sample values of CL/F averaged 0.243 l/h +/- 0.042 (N = 12) which compared well with a multiple sample-based value of CL/F which was 0.243 l/h +/- 0.046 (N = 12). When an erythromycin pretreatment was started before warfarin ingestion and continued throughout the period of warfarin elimination CL/F decreased to 0.208 l/h +/- 0.047 while CL/F decreased to 0.210 l/h +/- 0.061. Mean prediction error for CL/F relative to CL/F was -0.001 l/h with a 95% confidence interval of -0.010 to 0.009 l/h. Warfarin is a drug with pharmacokinetic characteristics enabling it to be used in a single dose single sample procedure in screening for host factor influences on its clearance.
Adult↗
Single sample estimate of ethosuximide clearance.
Ethosuximide was administered in single oral doses (ca. 15 mg/kg) to each of 12 healthy, male subjects. Serial blood and salivary ethosuximide concentrations were measured by a polarization immunofluorescence technique. The following parameters were estimated: CL/F, V/F, and plasma disappearance t1/2. Mean (+/- SD) values were 0.0091 (+/- 0.0023) l X h-1 X kg-1, 0.063 (+/- 0.12) l X kg-1, and 48.8 (+/- 9.3) h, respectively. Estimates of CL/F (CL/F) were calculated from single plasma or single salivary measurements. When V/F was set at 0.63 l X kg-1 and the 120-h plasma concentration was used, CL/F was 0.0091 (+/- .0018) l X h-1 X kg-1. CL/F was 0.0089 (+/- .0020) when the 120-h salivary concentration was used. These data demonstrate that under specified conditions ethosuximide clearance (CL/F) can be estimated from a single measurement of ethosuximide in either plasma or saliva, thereby permitting ethosuximide to be used safely and noninvasively as a probe of hepatic mixed function oxidase activity in humans.
Adult↗
[Hemodynamics and coronary dynamics under ISDN long-term therapy].
Although nitrates are among the oldest drugs in cardiology the problem of tolerance is a scientific challenge of today. We examined and compared the effects of initial and chronic therapy (4 weeks) with 1 X 1 ISDN 120 mg sustained release in 9 patients with coronary heart disease and impaired left ventricular function. At intraindividually identical workloads (average 50 +/- 12 watt) there was a reduction of PCWPm from 32.5 +/- 9.5 to 19.7 +/- 9.8 mm Hg. This reduction of PCWPm during bicycle ergometry was fully achieved in long-term therapy. With the first dose of ISDN cardiac index (CI) at maximum workload increased from 6.0 +/- 1.2 to 6.8 +/- 1.3 l/min/m2; during chronic therapy cardiac index improved from 5.3 +/- 1.3 to 6.6 +/- 1.1 l/min/m2. Exercise capacity during bicycle ergometry in the sitting position increased concomitantly from 414 to 686 watt X min. In long-term therapy there was a further significant improvement to 772 watt X min. ST-segment depression, measured as sum of ST-depression in all 12 standard ECG leads decreased from 0.63 mV before medication to 0.11 mV after the first dose and to 0.16 mV in long-term therapy. The investigation of ventricular function during ventriculography and the investigation of coronary vasomotion during coronary angiography after ergonovine maleate i.v. and ISDN s.l. also demonstrated the full nitrate effect in long-term therapy.
Adult↗
Experience with a computer-based technique for estimating pharmacokinetic constants from limited data.
A computer-based approach for estimating pharmacokinetic data and predicting plasma drug concentrations based on two measurements of plasma drug concentrations was compared with a standard two-point method for estimating aminoglycoside (AG) pharmacokinetic parameters. The computer-based technique was also used to predict a theophylline steady-state nadir from two preceding ones. The computer-based and standard two-point methods provided similar estimates for mean (+/- SD) values of elimination rate constant (lambda) (0.172 +/- 0.103 h-1 and 0.179 +/- 0.010 h-1, respectively) and apparent volume of distribution (V) (22.7 +/- 9.9 L and 23.3 +/- 11.5 L, respectively). The mean (+/- SD) of predicted AG troughs was 1.3 +/- 0.5 mg/L for the standard method and 1.3 +/- 0.6 mg/L for the computer-based method. Neither was significantly different from the actual AG trough mean of 1.3 +/- 0.7 mg/L. Both methods exhibited a slightly negative bias in their predictions of actual AG troughs. When applied to theophylline data from patients or subjects receiving multiple-dose theophylline, the computer-based method effectively predicted trough theophylline concentrations for three formulations of theophylline. Mean prediction errors ranged from 0.1 to 0.5 mg/L, and root mean squared error ranged from 1.1 to 1.2 mg/L. This computer-based technique may be useful in dose individualization since relatively few constraints are placed on the type of data required for its application.
Aminoglycosides↗
A new approach to establishing individualized maintenance doses of phenytoin.
A new method for arriving at individualized doses of phenytoin (PHT) is described. This method, designated the eta method, operates on two measurements of unbound plasma PHT. One plasma sample is collected 48 h after a single, oral PHT dose (approximately 4.5 mg/kg). From the single dose, single sample measurements of plasma unbound PHT individual estimates of intrinsic unbound PHT clearance (CLuint) can be made. With the use of CLuint and weight-adjusted mean population values of Vmax predicted plasma concentrations of unbound PHT for 11 subjects exhibited a mean prediction error (mpe) of 0.07 mg/L with 95% confidence limits of -0.11 to 0.26 mg/L and an error coefficient of variation [root mean squared error (rmse)/mean unbound concentration at steady state (Cuss)] of 0.4. The second plasma unbound PHT is collected at steady state. From CLuint and one Cuss measurement, Vmax and Km can be directly calculated. Doses calculated by the eta method to produce plasma unbound PHT concentrations of approximately 1.0 mg/L were identical to those calculated by the Bayesian method to yield plasma total PHT concentrations of approximately 10 mg/L. When those doses were administered to six subjects, the plasma unbound PHT concentrations predicted by the eta method exhibited a mpe of -0.13 mg/L, with 95% confidence limits ranging from -0.33 to 0.06 mg/L and an error coefficient of variation of 0.2. The plasma PHT concentrations predicted by the Bayesian method exhibited an mpe of -1.30 mg/L, with 95% confidence limits of -4.02 to 1.42 mg/L and an error coefficient of variation of 0.3. Values of Vmax and doses of PHT calculated to produce a Cuss of 1.0 mg/L calculated by the eta method were nearly identical to Vmax values and doses of PHT calculated by Bayesian double feedback (based on two different Css values) to produce a Css of 10.0 mg/L.
Adult↗
Theophylline kinetics: dose dependency and single sample prediction of clearance.
Theophylline clearance was measured at 3 doses (2, 4 and 6 mg/kg) in 10 young, healthy adult subjects. Clearance decreased as the dose of theophylline increased going from 0.064 +/- 0.016 to 0.052 +/- 0.011 1.h-1.kg-1 at the 2 and 6 mg/kg doses, respectively (p less than 0.02). A simplified method for estimating theophylline clearance was tested using single plasma concentrations of theophylline and assuming a constant value (0.5 l/kg) for volume distribution of theophylline. This method gave the best results when samples were drawn at 12 or 24 h after a 2 or 4 mg/kg intravenous dose of theophylline, respectively, and was effectively applied in estimating the quantitative impact of cimetidine administration on theophylline clearance.
Adult↗