Comparison of the short-term effects of the loop diuretic piretanide and furosemide in patients with renal insufficiency

Summary The natriuretic effect of the new loop diuretic piretanide was investigated in patients with severe renal insufficiency and was compared with that of furosemide. In the first study 4 hospitalized patients (serum creatinine 407 to 1220 µmol/l) were examined after administration of piretanide (12, 24, 48 and 96 mg to two patients, and 24, 48, 96 and 192 mg to 2 other subjects, given every third day). In the second study 6 hospitalized patients (serum creatinine 194 to 698 µmol/l) were studied after receiving orally 2 different doses of piretanide and 2 different doses of furosemide orally, given every fourth day. The mean natriuretic effect of 48 mg and 96 mg piretanide was 250 and 340% of the control value for the entire group, and 311 to 480% in the subgroup of patients with serum creatinine below 530 µmol/l. For a given dose the natriuresis was inversely correlated with renal function, and at a given serum creatinine level the natriuretic response was dose-dependent. The drug had less effect on water and potassium diuresis than on natriuresis. No significant difference in natriuretic effect was found on comparison with furosemide given in the ratio furosemide: piretanide 3.33:1. The pharmacokinetic data showed a direct correlation between the dose and the mean plasma concentration and also between urinary recovery of the drug and the measured natriuretic response.     

Pharmacokinetics of the loop diuretic piretanide in renal failure

Summary Piretanide 60 mg was administered intravenously over 30 min to 15 men with different degrees of renal failure. The mean piretanide serum concentration at the end of the infusion period was 5.72±1.51 µg/ml. Serum piretanide concentration-time curves declined biexponentially and 24 hours after medication the serum level had fallen to less than twice the detection limit. The terminal half-life ranged from 1.63 to 3.44 h. A relationship to creatinine clearance was not demonstrable. The mean metabolic clearance of piretanide was 107.7±47.6 ml/min/1.73 m² body surface area and was the same as that reported for healthy subjects. The renal clearance of piretanide ranged from 3.33 to 43.9 ml/min/1.73 m² body surface area and very closely correlated with the creatinine clearance (p<0.01). Its renal clearance dependend principally on active secretion of the drug into the tubule, and glomerular filtration appeared unimportant. There was a close relationship between the amount of piretanide excreted in the urine and the creatinine clearance. Because the diuretic effect of piretanide depends on the concentration of the drug in the tubule, the observed correlation might be of use in evaluating the appropriate dosage of piretanide in patients with renal failure. The present data suggest that single daily doses of piretanide will not result in accumulation, even when high doses are administered to patients with advanced renal failure.     

Kinetics of a high dose of piretanide in renal failure

Summary 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 · 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.     

Effects of a new diuretic (piretanide) compared with furosemide on renal diluting and concentrating mechanisms in patients with the nephrotic syndrome

Summary The mode and site of action of the new diuretic agent piretanide were investigated in man. The effect of a single oral dose of 12 mg was compared with that of furosemide 80 mg p.o. in 6 patients with the nephrotic syndrome. Piretanide showed a greater diuretic and natriuretic response than furosemide during maximal water diuresis, but the effect was similar in the hydropenic state. Like furosemide, piretanide decreased free water clearance relative to delivery during water diuresis and the reabsorption of solute-free water during hydropenia. This inhibitory action on both the concentrating and diluting urinary mechanisms demonstrates an effect of piretanide localized in the ascending limb of Henle's loop. Consistent alterations in glomerular filtration rate, renal blood flow or filtration fraction were not observed.     

The influence of ascites on the pharmacokinetics of piretanide in cirrhotic patients

Summary The pharmacokinetics of piretanide, a new loop diuretic, were studied in seven patients with severe liver disease before and after resolution of ascites. The time to maximum concentration was significantly prolonged by the presence of ascites. T_max after relief of ascites was similar to that seen for normal volunteers. Area under the curves, bioavailability, volumes of distribution and elimination half-lives did not change after resolution of the ascites: two patients in whom diuretic resistant ascites occurred showed similar pharmacokinetics to that of the diuretic responders. Reduced responsiveness to piretanide therapy in patients with gross ascites does not appear to be the result of decreased bioavailability.     

Pharmacokinetics of tocainide in patients with severe renal failure

Summary The plasma levels of tocainide have been followed after oral administration of 600 mg p.o. to 20 patients with renal failure due to various causes, and to 8 healthy controls. The peak plasma concentrations in the patients with pyelonephritis (3.80 µg/ml) and interstitial nephritis (3.74 µg/ml) but not in those with glomerulonephritis (3.17 µg/ml) differed from that in healthy volunteers (3.24 µg/ml). The renal clearance of tocainide was well correlated with the endogenous creatinine clearance and was dependent on urine pH. No difference in renal clearance was observed between the patients groups. It is suggested that the changes in plasma levels are a consequence of decreased renal clearance. Creatinine clearance was shown to be a poor estimator of tocainide clearance, which suggests that extrarenal clearance plays an important role in the handling of the drug in the body. The findings are used to suggest a safe dosage regimen.     

Pharmacokinetics of pefloxacin in renal insufficiency

Summary The kinetics of pefloxacin has been studied after a single intravenous infusion of 8 mg·kg^–1 in 15 male patients with various degrees of renal failure. No difference in distribution or elimination of the drug was observed between patients with mild or severe renal impairment. The mean volume of distribution (Vd area) and the mean plasma clearance were 2.03l·kg^–1 and 121.3 ml·min^–1, respectively. The mean apparent elimination half-life was 13.5 h. These values are close to those observed in healthy subjects. No accumulation of the active N-desmethylmetabolite was observed in cases of severe failure as compared to mild impairment; its apparent elimination half-life was about twice that of the parent drug. The efficacy of a 4 h haemodialysis in 6 additional anuric subjects done to remove pefloxacin from the body was poor.     

Pharmacokinetics of nitrendipine in terminal renal failure

Summary The pharmacokinetics and plasma protein binding of nitrendipine in patients with terminal renal failure have been compared with those in subjects with normal renal function.Kinetic parameters were calculated after a single 40 mg oral dose, an i.v. injection of 3 mg and after a 15 mg i.v. infusion of nitrendipine. Steady-state plasma levels were determined after 5 days of oral treatment with 20 mg b.d.Pharmacokinetic parameters and steady-state plasma levels in patients with renal failure did not differ from those in subjects with normal renal function.Nitrendipine was as highly bound to plasma proteins in patients with renal failure, as in subjects with normal renal function. The plasma protein did not differ between the two.The dosage of nitrendipine need not be modified for kinetic reasons in patients with renal failure.     

Pharmacokinetics of ramipril in hypertensive patients with renal insufficiency

In an open trial, the pharmacokinetics of ramipril and its active metabolite ramiprilat were studied in 25 hypertensive patients with various degrees of renal insufficiency given 5 mg ramipril p.o. for 14 days. Ramipril was rapidly absorbed and reached a peak concentration after 1-2 h. Cmax was greater in patients with severe renal insufficiency, which might indicate a reduced renal elimination rate, although, the rapid decline of the concentration-time curve for ramipril was almost independent of renal function. The mean initial apparent half-lives on Days 1 and 12, respectively, were 2.8 and 3.4 h (Group I: creatinine clearance 5-15 ml/min), 1.8 and 2.3 h (Group II: creatinine clearance 15-40 ml/min), and 1.9 and 1.9 h (Group III: creatinine clearance 40-80 ml/min). No accumulation was observed after multiple dosing. In contrast, the kinetics of its active acid metabolite ramiprilat was significantly influenced by renal function. The mean times to the peak plasma concentration were 5.7 h in Group I, 4.4 h in Group II and 3.8 h in Group III. The initial decline in plasma ramiprilat was dependent upon renal function; the mean initial apparent half-lives (Days 1 and 12, respectively) were 16.0 and 14.8 h (Group I), 10.1 and 9.5 h (Group II) and 10.6 and 8.0 h (Group III). Mean trough concentrations and absolute accumulation also increased with worsening renal function, and the renal clearance of ramiprilat was significantly correlated with the creatinine clearance. The subsequent long terminal phase at low plasma ramiprilat concentrations represented slow dissociation of the ACE-inhibitor complex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of flecainide in patients with mild and moderate renal failure compared with patients with normal renal function

Summary We have studied the pharmacokinetics of flecainide after the oral administration of 100 mg to 8 patients without renal impairment and 8 patients with mild to moderate renal failure. Both groups gave comparable results with respect to the peak plasma concentrations and the time to peak. There was a significant correlation between renal flecainide clearance and endogenous creatinine clearance. The elimination half-time in the patients with impaired renal function was significantly longer (19.9, SD 9.9 h) than that in the patients with normal renal function (11.5, SD 4.2 h), but the variability in the elimination half-time in renal failure could not be explained on the basis of the available results.dedicated to Professor Dr. U. Geßler on the occasion of his 65th birthday     

Pharmacokinetics of isosorbide-5-nitrate in renal failure

Summary The pharmacokinetics of the antianginal drug isosorbide-5-nitrate (IS-5-N) was studied in 20 patients with varying degrees of chronic renal failure after repeated oral doses of standard 20 mg tablets t.d.s. Blood samples were taken in the steady state on the 2nd and 28th days, and the plasma level was assayed by HPLC. There was no statistically significant difference in C _max ^ss , t_1/2 and AUC _0–8 ^ss between the 2nd and 28th days, nor was a difference found between patients with mild and severe renal failure.     

Pharmacokinetics of intravenous salbutamol in renal insufficiency and its biological effects

Summary Salbutamol was administered intravenously to 5 patients with renal function impairment for estimation its pharmacokinetic parameters. The mean terminal half-life was 256 min, similar to previously reported values in healthy adults. The mean clearance (167 ml/min) and the mean volume of distribution (55 l) were decreased. These parameters were not correlated with the creatinine clearance. A slight but significant decrease was observed in the plasma potassium level up to 125 min after the salbutamol infusion. The heart rate was significantly increased, and the increase in 3 patients was correlated with the salbutamol concentration. The biological effects of the drug were less marked than expected.     

Pharmacokinetics of practolol in renal failure

Summary The effect of renal failure on the excretion of oral doses of practolol has been studied. The plasma half-life increased up to 6.6 times normal and the cumulative urinary excretion of the drug was reduced. There was a linear correlation between the overall elimination rate constant of practolol and inulin and creatinine clearances. A linear correlation was also found between the renal clearances of practolol and inulin. The dose of practolol required for maintenance therapy should be reduced in patients with impaired renal function.The results have been presented in part as a thesis for the M.D. degree of the University of Giessen.     

Pharmacokinetics of quinine in patients with chronic renal failure

Methods: We investigated the pharmacokinetics of quinine (Qn) following administration of a single oral dose of 600 mg Qn sulphate in six male Thai patients with a moderate degree of chronic renal failure (CRF), and six male Thai subjects with normal renal function. Results: The drug was well tolerated in both groups of subjects; no major adverse reactions were observed. A marked alteration in the pharmacokinetics of Qn was found in patients with CRF compared to healthy subjects; there were six signifiicant changes in the pharmacokinetic parameters. Absorption was delayed, but increased in CRF (t_max 4.5 vs 1.6 h, C_max 6.17 vs 3.45 g·ml^–1). Total clearance was significantly reduced 0.94 vs 2.84 ml·min^–1·kg^–1, whereas V_z/f remained unchanged (1.82 vs 2.78 1·kg^–1). This resulted in the increased values of AUC and prolongation of the t_1/2z and MRT in the patients (AUC 181.5 vs 61.8 g·min^–1·ml^–1, t_1/2z 26 vs 9.7 h, MRT 36.4 vs 11.3 h). Median concentrations of plasma unbound fraction of Qn collected at 4 h after drug administration in patients and healthy subjects were 7.3 vs 9.8%, respectively.     

Pharmacokinetics of bendazac-lysine and 5-hydroxybendazac in patients with renal insufficiency

Summary The pharmacokinetics of bendazac and its major metabolite, 5-hydroxybendazac, have been investigated in 15 patients with moderate to severe renal insufficiency and renal failure following a single oral dose of 500 mg bendazac-lysine. The pharmacokinetic parameters were compared to those obtained in 10 healthy adult volunteers.The rate and the extent of absorption of bendazac was not modified in the patients with moderate and severe renal insufficiency, nor was there any change in plasma t_max, C_max, apparent elimination t_1/2 and AUC.There was a significant increase in the unbound fraction of bendazac in renal failure patients undergoing haemodialysis, with a consequent increase in the apparent volume of distribution (V/F) and apparent plasma clearance (CL/F), and a decrease in plasma C_max and AUC. Simultaneous changes of V/F and CL/F lead to an unchanged plasma t_1/2 in these patients. Renal clearance (CL_R) was decreased, but CL/F was not affected, since renal excretion is a minor route of elimination of bendazac.Bendazac is mostly eliminated by metabolism to 5-hydroxybendazac, in healthy subjects >60% of a dose being excreted in urine as 5-hydroxybendazac and its glucuronide. In patients with renal insufficiency urinary excretion of 5-hydroxybendazac was decreased and the systemic availability of the metabolite (AUC), was increased about three-fold, irrespective of the degree of renal failure. Plasma 5-hydroxybendazac glucuronide accumulated according to the degree of renal insufficiency.Overall it can be assumed that the pharmacological effect of the drug will not be enhanced in renal failure and that the dosage regimen of bendazac-lysine in such patients need not be modified.     

Influence of renal failure on the kinetics of zimeldine and norzimelidine

Summary The kinetics of zimeldine (Z) and its demethylated metabolite, norzimelidine (NZ), were determined after administration of a single 200 mg oral dose of Z to 6 healthy volunteers (Group I), and to patients with mild (Group II) and severe renal failure (Group III). Z and NZ concentrations were assayed by HPLC in serial plasma and urine samples over 6 days following the dose. In Group I Z was rapidly absorbed and metabolized into NZ, and then the plasma concentrations declined with apparent elimination half-lives of 8.4 h and 24.9 h for Z and NZ respectively, whilst the renal clearance of both compounds was low, Z 15.7 ml/min and NZ 33.0 ml/min. The plasma level of Z differed little between Groups I and III, but the area under the curve was significantly higher in Group III than in Group I subjects (AUC_0–144=17.3 and 6.8 µmol·l^–1·h, respectively). Severe renal failure did not affect the peak plasma concentration of NZ but it did significantly increase peak time, apparent elimination half-life, and the area under the plasma concentration curve. A significant inverse relationship was found between renal clearance of NZ and plasma creatinine. Since NZ is as pharmacologically potent as Z, the results suggest that the dose of Z should be reduced in patients with severe renal insufficiency.     

The pharmacokinetics of single doses of metoclopramide in renal failure

Summary The pharmacokinetics of metoclopramide have been studied after intravenous and oral dosing (10 mg) to 6 patients with chronic renal failure. The mean terminal half-life was 13.9 h after intravenous and 14.8 h after oral administration. Total body clearance after i. v. dosing was 16.7 l/h. Oral bioavailability was 71.8%. In comparison to previous studies on normal subjects these results indicate that clearance of metoclopramide in renal failure is approximately 30% of normals. This difference is not accounted for by the change in renal clearance and suggests impaired metabolism or an alteration in enterohepatic circulation of metoclopramide in renal failure.     

Pharmacokinetics/pharmacodynamics of furosemide in man: A review

The pharmacokinetics of furosemide and the attempt to correlate biological fluid measurements with diuretic response have been the subject of a large number of studies since the original reports of HajdÚ, Rupp, and coworkers in the mid-1960s. This article attempts to critically review these studies under seven different sections: furosemide pharmacokinetics in normal volunteers, furosemide pharmacokinetics in patients with decreased renal function, furosemide pharmacokinetics in patients with congestive heart failure, furosemide metabolism and assay methods, furosemide bioavailability, dose-response relationships, and the role of inhibitors and mediators on furosemide effects. The literature is reviewed through August 1978.     

Pharmacokinetics of furosemide in patients with hepatic cirrhosis

Summary The pharmacokinetics of furosemide was studied in 7 patients with diagnosed liver cirrhosis and in 7 healthy subjects. Furosemide in plasma and ascitic fluid was analyzed spectrofluorometrically. After a single intravenous dose, the cirrhotic patients showed lower initial plasma concentrations of furosemide because of the larger volume of distribution. The mean half-life in cirrhotic patients was significantly greater than in healthy volunteers. The longer half-life was associated with a reduction in the serum clearance of furosemide. Ascitic fluid volume in the patients ranged from 4.6 to 7.71. There was no significant amount of furosemide in the fluid. The diuretic interchange between this fluid and plasma was slow, as peak concentrations ranged from 0.3 to 0.5 µg/ml within 3 to 5 h after bolus administration of furosemide. Diuresis and urinary sodium excretion, 5 h after furosemide injection, were similar in both groups; larger potassium excretion was found in the cirrhotic patients.