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Biomedical subjects

N Pozet

Publications and source records attributed to N Pozet.

At least 55 records · Page 3Linked to original sources
PubMed1991

[Renal function during stress in hypertensive patients].

In this study, the measurement of blood pressure values, glomerular filtration rate (GFR, inulin clearance), renal plasma flow (RPF, PAH clearance), the filtration fraction (GFR/RPF), natiuresis and proximal sodium resorption (measured by lithium clearance), was performed at rest and during a computerised psychological stress test (Stroop word color conflict test) in 12 normotensive and 10 hypertensive subjects. The stress induced in the normotensives induced a significant increase of the filtration fraction and proximal tubule sodium resorption. The hypertensive kidney, submitted to a basal vasoconstriction greater than that of the normotensive kidney, does not react to stress. In the hypertensives, proximal sodium resorption occurs but is not significantly greater than at rest. In the long-term, the increased sodium resorption during stress could contribute to the development and the persistence of essential hypertension.

Adult↗
PubMed1991

[Treatment of cystine calculi using intra-urologic methods and extracorporeal lithotripsy].

The hardness and frequent recurrence of cystine stones represent a special challenge for the urologist. Fifteen cystinuric patients were treated in our department and followed over a mean period of 30 months. Most patients had a previous history of open surgery (1.5 pyelolithotomy/patient). Diagnosis of cystinuria was confirmed by metabolic studies and stone analysis. Over the follow-up period recurrence was observed in 23 instances in 11 patients thus leading to 38 stone treatments on 74 cystine stones. Stone size was less than 10 mm: 35 (47%); 10-20 mm: 21 (28%); 20-30 mm: 14 (19%); 30 mm: 4 (staghorn stones). A percutaneous approach was used in 9 cases as monotherapy (55% success) and in association with ESWL in 10 cases (50% success). ESWL was employed 18 times as monotherapy (39% success). Medical treatment included high fluid intake, alkalinisation and thiola in 6 patients. In conclusion, results obtained are poor in terms of stone clearance when compared to non-cystine stones. Recurrence rate is very high. Instrumental treatment should not be used excessively and is only indicated in symptomatic stones or refractory to intensive medical therapy.

Adolescent↗
PubMed1990

Predictive value of phase I studies: relevant criteria.

Phase I studies cannot predict the therapeutic efficacy of a new drug. However, they can lead to important information concerning: i), the undersirable effects and their mechanisms of occurrence; and ii), the pharmacokinetics and the metabolism of the drug as well as their possible alterations in renal or hepatic diseases. When considering the therapeutic effects, 3 cases have to be considered which are, in order of decreasing predictive value: i), when a direct relationship is expected between the drug concentration in the body and its therapeutic effects (eg, antibiotics); ii), when the drug has a known molecular or cellular target which is directly involved in the pathophysiology of the disease (eg, renin inhibitors); and iii), when the drug does not have a known target or is directed toward a precise target which is not directly involved in the disease. In all these cases, a phase I study in healthy volunteers should be able to describe, at least qualitatively, the pharmacodynamic effects of the drug which are relevant to its therapeutic goal.

Drug Evaluation↗
PubMed1990

Cardiovascular reactivity to and renal impact of stress and exercise: effects of bisoprolol.

The orthosympathetic nervous system is involved in the pathogenesis of essential hypertension. In this study, we carried out tests of sympathetic stimulation using successfully an isometric exercise and a psychological stress. The efficacy of the two tests in 10 normotensive patients (NTs) was assessed by a significant increase in blood pressure and heart rate and a significant increase in metanephrine urinary excretion. These tests, repeated 2 months later, were perfectly reproducible in NTs. The cardiovascular response during exercise and stress was significantly higher in 10 hypertensive patients (HTs) than in NTs. At rest, urinary norepinephrine excretion was significantly higher in HTs. In contrast to NTs, stress in HTs significantly increased urinary excretion of epinephrine and norepinephrine, whereas exercise failed to increase urinary catecholamine excretion in both groups. In HTs, both tests induced an increase in microalbuminuria. Among functional renal parameters, only proximal sodium reabsorption (measured by lithium clearance) was significantly lower in HTs than in NTs, compensated by a higher distal reabsorption. In HTs, 2 months of treatment with bisoprolol reduced rest and peak heart rate and blood pressure, but failed to reduce blood pressure reactivity to the orthosympathetic stimulation. Proximal sodium reabsorption at rest was normalized by the treatment. Bisoprolol was also able to reduce microalbuminuria during the 24 h and in the rest period preceding the test, but the same percent increase was observed during tests.

Adrenergic beta-Antagonists↗
PubMed1990

[Is it possible to use creatinine for following the development of renal insufficiency?].

Accurate methods of measuring glomerular filtration rate are usually considered as expansive and time consuming. Therefore, alternative methods (creatinine clearance, either calculated or measured, reciprocal plasma creatinine, slopes of creatinine vs time) have frequently been used to assess the rate of progression of renal failure and predict the time of dialysis. The present review underlines the limitations of such techniques frequently underestimated in recent trials intending to evaluate the potential benefit of protein restriction. It delimitates the restrictive conditions in which such methods could be used for clinical but not research purposes.

Creatinine↗
PubMed1989

The influence of renal insufficiency and haemodialysis on the kinetics of ciprofibrate.

1. The kinetics of the hypolipidaemic drug, ciprofibrate, were studied after a single oral dose (100 mg) in subjects with normal renal function (n = 6), patients with mild (n = 6) and severe (n = 6) renal insufficiency as well as in haemodialysed patients (n = 5). 2. Under fasting conditions, ciprofibrate, was absorbed rapidly in subjects with normal renal function, and its apparent elimination half-life was approximately 81 h. Both renal clearance (0.15 ml min-1) and cumulative renal excretion (less than 7% of the administered dose) were low. 3. Mild renal insufficiency did not alter the pharmacokinetics of ciprofibrate, but severe renal impairment significantly reduced both its renal clearance and cumulative urinary excretion and increased the apparent elimination half-life. 4. A 5 h haemodialysis session did not lower the plasma concentrations of ciprofibrate. 5. It is concluded that, from a pharmacokinetic point of view, a reduction in the dosage of ciprofibrate should be considered in patients with a glomerular filtration rate below 30 ml min-1/1.73 m2.

Adult↗
PubMed1989

Effects of xamoterol on sodium excretion in volunteers.

Xamoterol has been shown to reduce the frequency of oedema and lung crepitations in heart failure. We examined its effects on blood pressure and renal function in healthy volunteers. Systolic blood pressure rose, sodium and chloride excretion increased and there was a strong correlation in individual subjects between rises in systolic blood pressure and in sodium excretion. Although no changes in glomerular filtration rates were seen, changes sufficient to explain the observed rise in sodium excretion are well within the experimental error of this study. Xamoterol may increase sodium excretion by an action on renal haemodynamics.

Adrenergic beta-Agonists↗
PubMed1989

Restrictions on use of creatinine clearance for measurement of renal functional reserve.

The increase of glomerular filtration rate after a 90-gram oral protein load was determined in 9 healthy individuals by simultaneous measurements of both creatinine (Ccr) and inulin (Cin) clearances, performed before and every 30 min during 4 h after the meat meal. This protein load resulted in a short 26% increase of Cin at 90 min, and a sustained 29% increase of Ccr from 90 to 240 min after load. Individual peak values of Ccr occurred later than those of Cin (Ccr: 189 +/- 19 vs. Cin: 127 +/- 19 min; p = 0.023). These discrepancies were related to an increase of serum creatinine, and a subsequent increase of the net tubular excretion of creatinine which accounted for up to 15% of the urinary creatinine. The creatinine content of red meat could lead to overestimation of renal functional reserve when measured by creatinine clearance only.

Adult↗
PubMed1989

[Clinicobiological study of drug-induced renal diseases].

The kidney is the main organ involved in drugs elimination and thereby is particularly liable to their toxic effect. The determination of renal function is thus of importance, before and during treatment with a potentially nephrotoxic drug or during trial of new drugs. In this general review, the main methods to measure renal function are briefly analysed. They consist either of simple dosages in blood and urine which allow to roughly evaluate renal functional value and its variations, or more sophisticated investigations which allow a more precise analysis of various nephron functions: glomerular filtration rate and renal plasma flow with measurement of clearances of exogenous markers, determination of basal or maximal tubular activities. The interest of these specific tests is illustrated by the results of a study performed in patients receiving streptozotocin, an antineoplastic nephrotoxic drug. In conclusion, nephrotoxicity of drugs may be in most cases prevented owing to an accurate knowledge of their pharmacokinetics and of risk factors inherent in patients, and to survey of renal function with suitable methods which may lead to modify drug dosage and/or to choose a therapy considering the own evolution of the disease and the possible occurrence of irreversible renal impairment.

Adult↗
PubMed1989

[The prevention of recurrence of calculus: results of a regional study].

The frequency of measures of prevention of stone recurrence was evaluated in 250 patients treated in one center by extra corporeal shock wave lithotripsy (ESWL). Half were recurrent stone formers (RSF). Only two thirds admitted a previous 24 h urinary analysis and less than 30% knew the result as abnormal while hypercalciuria and or hyperuricuria was later evidenced in 63%. These figures were similar in first stone and recurrent stones formers. Dietary or drug based regimen were followed by only 27.5% of RSF irrespective of the activity of the disease. This percentage was the highest (40%) in RSF known as having abnormal urinary values and the lowest (13%) in those without previous analysis. Only 17% of RSF admitted having received dietary advise after ESWL.

Adult↗
PubMed1988

Pharmacokinetics of rilmenidine.

Rilmenidine, an alpha 2-adrenoceptor agonist, was studied (1 mg single dose) in order to determine the effects of pathology on its basic pharmacokinetic parameters. Because of the mainly renal elimination of rilmenidine, studies involved hypertensive, elderly hypertensive, renal insufficient and hepatic insufficient patients. Hypertension was found to influence neither the absorption, the distribution nor the elimination processes; the linearity in the range of 1 to 2 mg and the absence of accumulation in long-term treatment were confirmed. In contrast, in the elderly, the absorption phase was delayed. The slight decrease in the apparent volume of distribution (-12%), with a notable decrease in the apparent total clearance (-50%) led to a prolonged elimination half-life (+50%). In renal failure, linear relations between the degree of renal impairment and the elimination parameters were shown. These relations allow the evaluation of the predicted steady-state level of rilmenidine for a given degree of renal failure. In hepatic insufficiency, the modification of rilmenidine disposition concerned exclusively the elimination phase in which apparent clearance was decreased approximately 20%. In conclusion, these results lead to a decreased dosage regimen in patients with severe renal failure.

Absorption↗
PubMed1988

Influence of renal insufficiency on the pharmacokinetics of cicletanine and its effects on the urinary excretion of electrolytes and prostanoids.

1. The kinetics of a single oral dose (300 mg) of cicletanine a new antihypertensive drug with diuretic properties, and its effects on the urinary excretion of electrolytes and of the major stable metabolites of prostacyclin and thromboxane A2 were studied in patients with normal renal function (n = 6), mild (n = 9) and severe (n = 10) renal insufficiency. 2. In normotensive subjects with normal renal function, cicletanine was rapidly and regularly absorbed, its apparent elimination half-life established around 7 h, and both its renal clearance (0.4 ml min-1) and its cumulative renal excretion (0.85% of the administered dose), were low. Mild renal insufficiency did not significantly alter these parameters, while severe renal impairment reduced the renal clearance and the cumulative urinary excretion of cicletanine and increased its apparent elimination half-life (31 h). However the area under the plasma curve was not changed due to reduced plasma concentrations in these patients. 3. Cicletanine induced a rapid and marked (four fold as a mean) increase in the urinary excretion of water, sodium and potassium which lasted for 6 to 10 h, in subjects with normal renal function. Renal insufficiency did not alter the slope of the calculated plasma concentration-effects curves but reduced the maximum effect observed for water, sodium and potassium. 4. A single oral dose of cicletanine did not change the urinary excretion of 6-keto-prostaglandin F1 alpha and thromboxane B2 in the three groups of patients studied, the basal values of which being found to be closely related to the creatinine clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗