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Biomedical subjects

N Pozet

Publications and source records attributed to N Pozet.

At least 91 records · Page 5Linked to original sources
PubMed1985

Pharmacokinetics of penbutolol and its metabolites in renal insufficiency.

The pharmacokinetics of penbutolol, its 4-hydroxylated metabolite and of their conjugates was studied in hypertensive patients with various degrees of renal impairment. A single oral dose of penbutolol 40 mg, was rapidly absorbed after a lag-time of 0.34 h. Its plasma concentration reached a maximum after 0.84 h and then declined bi-exponentially, with an apparent elimination half-life of 21.8 h. The hydroxylation of penbutolol was negligible and conjugation was of major importance for its elimination. Consequently, the kinetics of unchanged penbutolol were not altered by renal impairment. The 48 h-urinary excretion of penbutolol and its metabolites reached 13-14% of the administered dose, which is consistent with extensive metabolism of the drug. After treatment for 30 days with penbutolol 40 mg/d there was no accumulation of the parent drug but the concentration of its conjugates was increased. It is concluded that the dose of penbutolol need not be changed in patients with mild renal insufficiency, 4-hydroxypenbutolol is unlikely to participate in the anti-hypertensive effect of the drug, due to its low concentrations, and biotransformation of penbutolol may be enhanced during chronic treatment.

Adult↗
PubMed1985

Separate calculation of glomerular and tubular clearance by means of renal scintigraphy with hippuran and DTPA.

A simplified method of renal scintigraphy carried out with 131I-Hippuran and 99mTc-DTPA diethylenetriaminopentacetate is described in man. Results were expressed as tubular clearance (with Hippuran) and glomerular clearance (with DTPA) per kidney, and compared to PAH and inulin clearances measured in the same patients. There was a close positive correlation between clearances calculated by means of renal scintigraphy and those measured by standard procedure for studying renal function. This study showed that a simple calculation allowed to express scintigraphical findings in terms of clearance.

Female↗
PubMed1984

Renal glucose transport after kidney transplantation.

Tubular maximal transport of glucose (TmG), plasma glucose threshold ( PGT ) and fractional maximal tubular reabsorption (TmG/GFR) were measured in fourteen kidney-grafted patients. Seven patients showed decreased PGT and normal or decreased TmG/GFR (type A or B renal glycosuria (RG) ), whereas seven other patients showed normal values. No difference was found between the two groups with respect to parameters of renal function and to clinical parameters characterizing kidney transplantation. The only difference observed between the two groups was the rate of decrease of plasma creatinine levels during the 1st week after transplantation: it was faster in the group without renal glycosuria. No difference was seen between the two groups of patients with respect to the number of rejection episodes occurred over the first 12 months.

Adult↗
PubMed1984

[Diagnosis of relative hypomagnesurea in calcium lithiasis: reference values for a new parameter].

In calcium stone formers, the ratio of urinary magnesium concentration to urinary calcium concentration (Mg/Ca) is used to express the already reported low Mg excretion relatively to Ca excretion. However the Mg/Ca value depends on the Ca excretion rate, decreases after oral Ca load and is not directly related to Mg excretion. Therefore when studying patients with different Ca excretion rates, or when performing an oral Ca load, Mg/Ca is not directly useful to express a relative hypomagnesuria. We established a new parameter from the normal relationship between urinary Mg and Ca excretion rates. Its value is above - .065 in 97.5% of 99 control urinary samples. It is stable for any studied Ca excretion rate, including post Ca load excretion rates, and is highly correlated with Mg excretion rate. This parameter allows for the accurate diagnosis of relative hypomagnesuria in stone formers.

Adult↗
PubMed1983

Pharmacokinetics of diltiazem in severe renal failure.

The acute effects of a single dose of diltiazem (Tildiem), a calcium antagonist, were studied in 9 patients with severely impaired renal function (GFR between 0.03 and 0.87 ml/s/1.73 m2). Control measurements were made of inulin and PAH clearance, creatinine, blood pressure, heart rate and ECG. Following administration of diltiazem 120 mg, 7 blood samples were collected in the first 12 h and after 24 h, 32 h, 48 h; urine was collected for the first 12 h, 12-24 h and 24-48 h, and blood pressure, heart rate and ECG were recorded after 6 h. Diltiazem and its main metabolite, desacetyldiltiazem, had a pharmacokinetic profile similar to that in patients with normal renal function (peak plasma concentration, half-life and urinary excretion). Diltiazem is normally eliminated in the urine to a small extent, because it is metabolized, and this also applies to desacetyldiltiazem, which is probably further metabolized.

Adult↗
PubMed1983

Ranitidine kinetics in chronic renal impairment.

The effects of moderate to severe renal impairment on kinetics of the H2-blocker ranitidine were investigated in 16 patients divided into two groups. Mean inulin clearance (ClIn) was 35 +/- 18.3 ml/min/1.73 m2 in group I and 7.4 +/- 3.5 ml/min/1.73 m2 in group II. Each patient received a single 150-mg oral dose of ranitidine. Values determined were maximum plasma concentration (MC) and time of occurrence, AUC, elimination t 1/2 (t 1/2 beta), total amount of unchanged ranitidine recovered in urine, and ranitidine renal clearance (ClR). MC values were higher and longer delayed than values reported in subjects with normal renal function. The t 1/2 beta was longer in group I and group II and correlated with the degree of renal impairment. The amount of ranitidine excreted within the first 24 hr decreased (18% of the dose in group I and 6% of the dose in group II), and ClR correlated strongly with ClIn, indicating that the observed changes in ranitidine kinetics are mainly related to changes in its renal excretion.

Adult↗
PubMed1983

[Comparative effects on renal function of 4 beta-blockers injected intravenously].

Four beta-blockers: atenolol 15 mg i.v., metoprolol 25 mg i.v., acebutolol 45 mg i.v. and labetalol 50 mg i.v. were administered to 106 patients suffering from hypertension and with normal or disturbed renal function. During an identical test protocol, measurements of clearance of inulin, of PAH, urine sodium and the fraction of sodium excreted were recorded one hour before and four or five hours after administration of the antihypertensive. Mean blood pressure and heart rate were also recorded. The three pure beta-blockers reduced inulin and PAH clearance and lowered urine sodium. These modifications were the same for all three drugs. Labetalol, which also possesses alpha-blocking properties, did not reduce renal function values or urine sodium. While a slight fall in blood pressure occurred with all the antihypertensives, heart rate was reduced only by the three pure beta-blockers. The action of the four drugs was very similar whatever the state of the subject's renal function. The study of the renal effects of the beta 1-selective atenolol and metoprolol, and acebutolol which has a higher intrinsic sympathomimetic activity does not demonstrate any significantly different renal action among these three drugs, but the effects of labetalol on renal function values and urine sodium are slighter. The renal action of the beta-blockers cannot be fully explained. Though the fall in the renal plasma flow and in the glomerular filtration rate can be related partly to the decrease in the cardiac output consequent to induced bradycardia, stimulation of renal alpha-receptors must be considered.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1983

[Comparative effects of an alpha 1 and beta 1-2 blocker (labetalol) and a beta-1 blocker (atenolol) in the hypertensive patient].

The effects of a single oral dose and of an 8 week treatment with labetalol--an alpha 1- and beta 1-2-adrenoceptor blocking agent--and with atenolol--a beta 1-adrenoceptor blocking agent--were compared in 52 hypertensives. A single oral dose of atenolol induced a marked bradycardia without decrease in blood pressure. On the contrary labetalol lowered blood pressure but not resting heart rate. After an 8 week treatment both drugs exhibited a similar antihypertensive effect. However labetalol did not decrease heart rate and plasma renin activity as markedly as atenolol did. It was concluded that the alpha 1 blocking properties of labetalol were of importance in the development of the antihypertensive properties that this drug exhibits after a single or multiple administrations.

Adult↗
PubMed1982

Kinetics of a high dose of piretanide in renal failure.

The kinetics of piretanide was studied in patients with renal failure. After oral administration of a high dose of piretanide (96 mg), the pharmacokinetic parameters were: elimination rate constant 0.346 +/- 0.072 h-1, half life 2.00 +/- 0.35 h, and total plasma clearance 119.55 +/- 35.90 ml x min-1. Compared to the values obtained in adults with normal renal function, these results show a decrease in total plasma clearance, but conservation of the metabolic clearance which amounts to 45% of the total clearance in the healthy adult.

Administration, Oral↗
PubMed1982

Ranitidine kinetics in normal subjects.

A 1-mg/kg IV bolus injection and a 150-mg (one tablet) oral dose of ranitidine were given to seven normal subjects. At least 1 wk separated the two doses. Ranitidine disappeared from plasma with a half-life of about 2.5 hr. Half of the oral dose was effectively absorbed and half of the absorbed amount was found unchanged in urine. Total body clearance was 10.1 ml/min/kg. Urinary clearance was the same after oral and intravenous doses (6.4 and 6.9 ml/min/kg, P greater than 0.10). Intravenous ranitidine kinetics included three phases, with a central distribution volume of 0.2 l/kg and a total distribution volume of 1.2 l/kg. Absorption kinetics were apparently order zero: of the 150-mg dose, 75 mg was absorbed during 5 hr at a constant rate of 15 mg/hr.

Administration, Oral↗
PubMed1982

Nalidixic acid kinetics in renal insufficiency.

1 A pharmacokinetic study of nalidixic acid (NA) and metabolites was carried out in 23 patients with differing renal function so as to determine the influence of renal insufficiency on the excretion and biotransformation rate of this antibacterial agent. Plasma and urine concentration of NA and of its 7-hydroxy (HNA) and 7-carboxy (CNA) derivatives were measured after a single oral administration. 2 Renal insufficiency did not markedly affect the renal clearance of NA while it significantly decreased the elimination rate of HNA, a compound which largely excreted into the urine. 3 Interestingly, CNA which could never be detected in the plasma of patients with normal renal function appeared in that of patients with renal insufficiency. Plasma concentrations of CNA and creatinine were positively related, and the amount of urinary CNA increased with the renal impairment. 4 These results suggest that HNA can still be biotransformed into CNA by the impaired kidney. Since CNA cannot be easily excreted in the urine of patients with renal insufficiency it is hypothesized that this compound back diffuses into the plasma. 5 Finally, the study of the urinary concentrations of NA and metabolites shows that a standard NA dosage can be used, at least in patients with mild renal insufficiency.

Adult↗
PubMed1981

Cystine crystalluria and urinary saturation in cystine and non-cystine stone formers.

It has been suggested recently that the first step in the formation of calcium oxalate stones appears to be crystallisation. This step is said to depend on the state of saturation of the urine. This hypothesis was checked in cystine stone formers. Cystine crystalluria was found in 83% of 24 urine samples from cystine stone formers (CSF) but in one of the 400 control samples and appears to be a good guide in the diagnosis of cystine lithiasis. Urinary cystine saturation was constantly higher in CSF than in non-cystine stone formers (NCSF) who exhibited undersaturated urine with respect to cystine. There was almost no overlap between these 2 groups. Crystals were never found in undersaturated urine and were always present when the saturation was above 1. There appears to be a good correlation between the level of urinary saturation and the presence of crystalluria and there is no need for any additional factor such as a defective inhibitor. The study underlines the limits of a therapeutic regimen of a high fluid intake and alkalinisation of the urine.

Crystallization↗
PubMed1981

Nalidixic acid kinetics after single and repeated oral doses.

The kinetics of nalidixic acid (NA) and its two metabolites, 7-hydroxynalidixic acid (HNA) and 7-carboxynalidixic acid (CNA) were studied after a single oral dose and after two doses a day for 7 days. Total unconjugated NA, HNA, and CNA concentrations in plasma and urine samples were assayed by a new high-pressure liquid chromatographic (HPLC) technique. NA was rapidly absorbed and hydroxylated to HNA. Both were rapidly excreted in urine with an apparent elimination half-life (t1/2) of 6 to 7 hr. CNA was never detected in the plasma, although it accounted for about 25% of total urinary NA and metabolites. No major sex-related differences in the kinetics and the metabolic pattern were observed. During the 7-day treatment there was no significant cumulation of NA and HNA. The study demonstrated that the concentration of the active compounds, unconjugated NA and HNA, was more than five times the minimum bacteria inhibiting concentration for 8 hr after drug and slightly above this concentration during the next 4 hr.

Adult↗
PubMed1981

Acute effect of high dose (48 mg) of piretanide in advanced renal insufficiency.

1 The acute effects of a high dose of piretanide, a new potent diuretic were studied in eight patients with severely impaired renal function (GFR between 0.09 and 0.17 ml s-1 1.73 m-2). 2 After hydration and following two control periods, a single dose of 48 mg piretanide was ingested. Thereafter, urine was collected every 30 min for 2 h and every hour for the next 4 h. Urinary fluid losses were replaced orally (100 ml of water ever hour) and intravenously (isotonic saline + glucose infusion). 3 The following measurements were made: urine flow rate, clearances of inulin, PAH, urea, creatinine, uric acid, osmolar and free water clearances, excretion rates of sodium, chloride, potassium, calcium, phosphate, bicarbonate, ammonium, titratable acidity and urine pH. 4 Piretanide (48 mg) appeared to be effective in advanced renal insufficiency, producing a significant increase in urine flow rate, in sodium, chloride, potassium and calcium excretion and in Cosm. 5 There was no significant change in GFR, as measured by inulin clearance, or in the other measured parameters.

Adult↗