Des-Arg9-bradykinin metabolism in patients who presented hypersensitivity reactions during hemodialysis: role of serum ACE and aminopeptidase P.

Bradykinin (BK) has been proposed as the principal mediator of hypersensitivity reactions (HSR) in patients dialyzed using negatively charged membranes and concomitantly treated with angiotensin-converting enzyme (ACE) inhibitors. We investigated the metabolism of exogenous BK added to the sera of 13 patients dialyzed on an AN69 membrane with a history of HSR (HSR+ patients) and 10 others who did not present such a reaction (HSR- patients) while dialyzed under the same conditions. No significant difference in the t1/2 of BK was found between the patient groups. However, the t1/2 of generated des-Arg9-BK was significantly increased (2.2-fold) in HSR+ patients compared to HSR-subjects. Preincubation of the sera with an ACE inhibitor (enalaprilat) significantly increased the t1/2 of both BK and des-Arg9-BK in both groups. There was no significant difference between the groups with respect to the t1/2 of BK, but there was a significantly greater increase (3.8-fold) in the t1/2 of des-Arg9-BK in HSR+ patients compared to HSR-subjects. The level of serum aminopeptidase P (APP) activity showed a significant decrease in the HSR+ sera when compared to HSR-samples. In HSR- and HSR+ patients, a significant inverse relation (r2 = 0.6271; P < 0.00005) could be calculated between APP activity and des-Arg9-BK t1/2. In conclusion, HSR in hemodialyzed patients who are concomitantly treated with a negatively charged membrane and an ACE inhibitor can be considered as a multifactorial disease in that a decreased APP activity resulting in reduced degradation of des-Arg9-BK may lead to the accumulation of this B1 agonist that could be responsible, at least in part, for the signs and symptoms of HSR.

Metabolic and antihypertensive effects of nebivolol and atenolol in normometabolic patients with mild-to-moderate hypertension.

This was a double-blind, randomized, two-center, active-controlled, prospective, parallel study designed to evaluate the effects of nebivolol at daily doses of 5 mg on lipid and carbohydrate metabolism and on blood pressure in comparison with atenolol at daily doses of 50 mg. Normometabolic subjects with mild-to-moderate essential hypertension were recruited for this study, which included a 4-week, single-blind placebo washout phase and a 12-week double-blind treatment phase. After 12 weeks of treatment, both drugs demonstrated a significant decrease from baseline in high-density lipoprotein (HDL) apolipoprotein A-I (HDL-apoA-I) (nebivolol, P <.02; atenolol, P <.05). A significant reduction in HDL cholesterol (HDL-C) from baseline was also observed with nebivolol (P <.05). There were no significant differences between the drugs for these parameters, and the ratio low-density lipoprotein cholesterol (LDL-C)-to-HDL-C did not change significantly after 12 weeks of active treatment with nebivolol or atenolol. There were no significant changes in total cholesterol, HDL (2) -C, HDL (3) -C, LDL-C, very-low-density lipoprotein cholesterol (VLDL-C), total triglycerides, HDL-triglycerides (TG), LDL-TG, VLDL-TG, total apoB, LDL-B, VLDL-B (including the ratio LDL-C-to-LDL-apoB), or Lp(a) during treatment with both drugs. No significant differences in plasma apoA-I and apoC-III as well as in apoA-I-, C-III-containing lipoprotein particles (including the apoC-III ratio) were observed between the drugs, neither before nor after each active treatment. There were no significant differences between the drugs or within each treatment group in plasma glucose, insulin, or C-peptide concentrations after a 2-hour oral glucose tolerance test. Mean clinic trough sitting systolic blood pressure (SBP)/diastolic blood pressure (DBP) significantly decreased from 150/98 mm Hg at baseline to 141/90 mm Hg at termination for nebivolol and from 160/99 mm Hg at baseline to 145/88 mm Hg at termination for atenolol. No significant between-treatment differences were observed for the mean clinic trough sitting SBP/DBP. Both drugs significantly increased the atrial natriuretic factor (ANF) N-terminal plasma levels, whereas no changes were observed in ANF C-terminal plasma concentrations. A significant decrease (P <. 05) in the plasma adrenocorticotropic hormone levels was observed after administration of both drugs. A significant decrease (P <.05) in plasma cortisol levels was observed only after atenolol treatment. The incidence of adverse events reported during nebivolol treatment was comparable to that observed during atenolol treatment. Heart rate was significantly reduced by both drugs. There were no significant changes in hematology, biochemistry, or urinalysis studies. Neither nebivolol nor atenolol adversely affected lipid or carbohydrate metabolism in normometabolic hypertensive patients. Both treatments demonstrated adequate and similar antihypertensive effects and were well tolerated.

Pharmacokinetics of intravenous diltiazem and five of its metabolites in patients with chronic renal failure and in healthy volunteers.

The pharmacokinetics of diltiazem were studied in seven patients with chronic renal failure (CRF) not requiring dialysis and in three healthy volunteers after a rapid i.v. infusion of 20 mg. Mean plasma concentrations at the end of infusion were 3.15 times higher in patients with CRF than in healthy volunteers. From 0.5 to 12 h post-infusion, the difference remained between 25 per cent and 73 per cent. Mean AUC0-infinity was statistically greater in patients than in volunteers while mean V area, CLtot, and CLren were statistically lower. The t1/2 alpha and t1/2 beta values were not significantly (p greater than 0.05) different between patients and volunteers. Renal excretion was statistically more important in volunteers (6.6 per cent of the dose) than in patients (1.2 per cent of the dose). We therefore conclude that CRF does not influence t1/2 beta of diltiazem but it interferes with the extent and possibly the rate of its extravascular distribution. That could result in transient high plasma concentrations after rapid i.v. infusion.

Pharmacokinetics of oral diltiazem and five of its metabolites in patients with chronic renal failure.

The pharmacokinetics of oral diltiazem were studied in 10 patients with chronic renal failure not requiring dialysis and in five healthy volunteers after a single dose of 120 mg. We found that patients with chronic renal failure had lower amounts of unchanged diltiazem and of its main metabolite (MA) in urine and a trend to have slightly higher values of plasma concentration. Since the terminal elimination phase is not affected by chronic renal failure we conclude that this trend is probably the result of alterations in the volume of distribution of diltiazem in these patients.

Comparison of zopiclone pharmacokinetics in patients with impaired renal function and normal subjects. Effect of hemodialysis.

Maximal blood concentration (Cmax), time to concentration peak (Tmax), area under the serum concentration-time curve (AUC infinity) and half-life (t1/2) after the oral administration of zopiclone 7.5 mg were compared in patients with severe renal failure (group I), with moderate renal insufficiency (group II), and in healthy volunteers (group III) over a 72-h period. Cmax did not differ from one group to the other but Tmax was significantly longer in group II. Half-lives were longer in renal patients than in healthy volunteers and AUC infinity s tended to increase with the degree of renal failure. Hemodialysis of the severely ill renal patients did not increase the plasma clearance of zopiclone. Finally, only small amounts of drug were found in urine in the three groups. Overall, results allow the conclusion that zopiclone may be safely used in patients with various degrees of renal impairment.

Modulation of plasma and platelet vasopressin by cardiac function in patients with heart failure.

Two groups of patients with congestive heart failure were studied, one with elevated (Group I) and another (Group II) with suppressed plasma concentrations of vasopressin. The mean plasma arginine vasopressin (AVP) concentration in the 17 patients in group I was 3.1 +/- 0.4 pg/mliter whereas the eight patients in group II had plasma concentration less than 0.5 pg/mliter. Platelet AVP concentrations were also higher in the Group I than Group II patients (7.8 +/- 1.5 vs. 2.2 +/- 0.7 pg/mliter, P less than 0.001). Plasma effective osmolality (262 vs. 268 mOsm/kg H2O, P less than 0.05) and plasma sodium concentration (134 vs. 137 mEq/liter, P less than 0.05) were lower in Group I. The Group I patients had a lower cardiac index (CI, 1.9 vs. 2.5 liter/min/m2, P less than 0.05) and higher pulmonary capillary wedge pressure (PCWP, 30 vs. 22 mm Hg, P less than 0.02), plasma renin activity (4.4 vs. 2.0 ng/mliter/hr, P less than 0.01), and plasma aldosterone (74 vs. 10 ng/dliter, P less than 0.001) than the Group II patients. The Group I patients also excreted a smaller percentage of a 15 mliter/kg waterload (31 vs. 57%, P less than 0.005). Group I patients then were treated with agents to decrease cardiac afterload, either captopril or prazosin. CI increased (1.9 to 2.1 liter/min/m2, P less than 0.001) and PCWP decreased (30 to 27 mm Hg, P less than 0.001). This improved cardiac performance was associated with enhanced water excretion (31 vs. 52%, P less than 0.001) and decreased minimal urinary osmolality (375 vs. 208 mOsm/kg H2O, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and metabolism of zopiclone.

Pharmacokinetics and metabolism of a new hypnotic, zopiclone (ZD), were studied under the following conditions: (1) rats and dogs were given oral doses of the molecule, 14C-labeled either on the side chain or on the pyrrolopyrazine nucleus; (2) rats, rabbits and dogs were given increasing oral doses of the cold compound; (3) human subjects in various physiopathological situations--young and elderly healthy volunteers, patients with liver or renal impairments, nursing mothers--were given single or repeated doses, p.o. or i.v. (range 3.5-15 mg). ZD is rapidly and efficiently absorbed: its oral bioavailability was greater than 75% in all species except rats, where a first-pass effect of about 65% was recorded. Plasma protein binding is about 45%. The radioactive material rapidly diffuses from the vascular compartment, with a marked affinity for the brain. Plasma kinetics of ZD are generally well described by a two-compartment open model; in man, terminal half-life is 4-5 h; total body clearance is large (300 ml/mn), renal clearance very low (10 ml/min). The relationship between doses and concentrations, doses and urinary excretion of unchanged compound and major metabolites was linear in all species, except rabbits. The major metabolic routes involve decarboxylation affecting more than 50% of dose (rats and dogs), N-demethylation and N-oxidation--more than 30% as N-desmethyl and N-oxide derivatives in urine (humans). Due to intensive metabolism, only 7-10% of the dose is recovered in urine and feces as unchanged compounds (all species). In nursing mothers, milk and plasma kinetics of ZD are similar with a milk/plasma ratio around 0.80. In human volunteers, plasma half-life of ZD increases with age, while patients with liver or renal impairments show little or no modification of pharmacokinetic parameters.

Renal intracortical blood flow and renin secretion after denervation by 6-hydroxydopamine.

A new method of unilateral renal denervation (DNX) was developed in dogs by rapidly injecting 6-hydroxydopamine (6-OHDA) into the renal artery with simultaneous collection of the venous effluent to avoid systemic effects. The procedure induced a 93.1 +/- 2.7% destruction of the adrenergic innervation as assessed by a histochemical fluorescence technique. A comparative study of both kidneys was carried out 3 days after DNX. Renal blood flow (RBF) and its cortical distribution were measured with radioactive microspheres at mean perfusion pressures of 117 mmHg (1 mmHg = 133.322 Pa) (normotension) and 70 mmHg (hypotension). The comparison of renal perfusion between kidney halves revealed a remarkable perfusion symmetry during normotension and hypotension in both the intact and the DNX kidney. Renal DNX by 6-OHDA did not alter RBF when the kidneys were perfused at normotension. During hypotension, RBF fell by 45% on the control side, while a nonsignificant decrease was noted in the DNX kidney. The redistribution of blood flow to inner cortical zones was less marked in the DNX side during hypotension. The DNX kidney did not release renin during normotension, but exhibited a normal renin response to hypotension. These data are partly in agreement with classical denervation models, and indicate that (1) denervation by 6-OHDA protects renal perfusion during hypotension; and (2) the redistribution of blood flow to inner cortical nephrons is independent of release of renin, but modulated by adrenergic innervation.

Pharmacokinetics and metabolism of zopiclone.

Pharmacokinetics and metabolism of a new hypnotic, zopiclone (ZD), were studied under the following conditions: (1) rats and dogs were given oral doses of the molecule, 14C-labeled either on the side chain or on the pyrrolopyrazine nucleus; (2) rats, rabbits and dogs were given increasing oral doses of the cold compound; (3) human subjects in various physiopathological situations - young and elderly healthy volunteers, patients with liver or renal impairments, nursing mothers - were given single or repeated doses, p.o. or i.v. (range 3.5-15 mg). ZD is rapidly and efficiently absorbed: its oral bioavailability was greater than 75% in all species except rats, where a first-pass effect of about 65% was recorded. Plasma protein binding is about 45%. The radioactive material rapidly diffuses from the vascular compartment, with a marked affinity for the brain. Plasma kinetics of ZD are generally well described by a two-compartment open model; in man, terminal half-life is 4-5 h; total body clearance is large (300 ml/mn), renal clearance very low (10 ml/min). The relationship between doses and concentrations, doses and urinary excretion of unchanged compound and major metabolites was linear in all species, except rabbits. The major metabolic routes involve decarboxylation affecting more than 50% of dose (rats and dogs), N-demethylation and N-oxidation - more than 30% as N-desmethyl and N-oxide derivatives in urine (humans). Due to intensive metabolism, only 7-10% of the dose is recovered in urine and feces as unchanged compounds (all species). In nursing mothers, milk and plasma kinetics of ZD are similar with a milk/plasma ratio around 0.80. In human volunteers, plasma half-life of ZD increases with age, while patients with liver or renal impairments show little or no modification of pharmacokinetic parameters.