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Biomedical subjects

D T Lowenthal

Publications and source records attributed to D T Lowenthal.

At least 145 records · Page 8Linked to original sources
PubMed1976

Pentobarbital elimination in patients with poor renal function.

Drug oxidation is slowed in experimental uremia in animals but has been reported to be normal or accelerated in uremic patients. Eleven normal subjects and 9 uremic patients were each given 100 mg pantobarbital orally. Several blood samples were drawn over a 36-hr period starting on the morning after the dose. Plasma pentobarbital concentration was measured by GLC. The log concentration values were graphed against time elapsed after dose for each patient, and the plasma T/2 and extrapolated value of concentration at the time of drug administration (Co) were determined. The T/2 values in normals ranged from 18 to 48 hr; mean, 26.5 +/- 9.2 (SD). In uremic patients, T/2 values are 10 to 38 hr, mean, 21.3 +/- 8.7. Four of the uremic patients had T/2 values below 18 hr (which was the lowest in the normals). The apparent volumes of distribution of pentobarbital (aVD = dose divided by Co) were 62 +/- 25 L in the normal subjects and 58 +/- 24 L in the uremic patients. The four uremic patients with the short T/2 values tended to have small apparent volumes of distribution so that the metabolic clearnce rates (aVd X 0.693 divided by half-life) were normal in 3 of them. We conclude that pentobarbital elimination is normal in renal failure. Some uremic patients have short plasma T/2 values for pentobarbital, and these more likely result from low apparent volumes of distribution with normal metabolic clearance rates than from accelerated metabolism of pentobarbital.

Blood Proteins↗
PubMed1976

Pharmacokinetics of acetaminophen elimination by anephric patients.

The pharmacokinetics of acetaminophen elimination were determined in five surgically anephric and five physiologically anephric patients on an interdialysis day, and in three normal adult volunteers. There was no significant difference in the biologic half-life and no apparent difference in the volume of distribution of acetaminophen between the three groups of subjects but the anephrics, unlike the normal subjects, showed pronounced accumulation of acetaminophen glucuronide and sulfate in plasma. The apparent volume of distribution for conjugated acetaminophen is considerably smaller than that for the unmetabolized drug even though neither acetaminophen nor its glucuronide or sulfate is significantly bound to plasma proteins. The results of this study indicate that the kidneys do not contribute significantly to the elimination of acetaminophen in man. Sin ce acetaminophen is eliminated largely by conjugation with glucuronic acid and sulfate, it can be concluded that the kidneys do not contribute significantly to the formation of these metabolites.

Acetaminophen↗
PubMed1976

Long-term effects of minoxidil in the treatment of malignant hypertension in chronic renal failure.

Thirteen acutely symptomatic malignant hypertensive patients were treated with minoxidil in combination with a beta-adrenergic blocking agent and diuretics or dialysis. The degree of endorgan involvement varied, with the kidney being the most compromised in 11 of 13 patients. In 12 of 13 patients, MABP (mean arterial blood pressure) fell significantly within 72 hours, P less than 0.005. After 20 months of therapy, all have now had a favorable response, with a mean reduction in MABP of 48 mm Hg, and with no adverse cardiac disturbances. In addition, the patients with mild azotemia had an improvement in renal function as determined by a reduction in serum creatinine. PRA (peripheral renin activity) rose with the addition of minoxidil despite therapeutic concentration of serum propranolol and a reduction in MABP and heart rate. It was also noted that those patients who had been on guanethidine prior to minoxidil had a more pronounced lowering of MABP within 72 hours of minoxidil therapy. It is concluded that minoxidil is a safe, fast, and effective agent to achieve rapid and sustained control of MABP in malignant hypertensive states associated with chronic renal insufficiency.

Adolescent↗
PubMed1975

Elimination of procainamide in end stage renal failure.

To investigate the effect of end stage renal insufficiency and hemodialysis on the serum half-life of procainamide, 500 mg of procainamide was given orally to control subjects and dialysis patients on interdialysis days. Procainamide was assayed by spectrophotometry and spectrophotofluorometry. Mean half-life in normal subjects was 3.2 hr by spectrophotometry and 3.5 hr by spectrophotofluorometry. Mean half-life in patients was 11.3 hr by spectrophotometry and 16.0 hr by spectrophotofluorometry (p less than 0.001 compared to control subjects). Half-life of procainamide during dialysis in patients given 500 mg of procainamide 1 hr before dialysis was 4.3 hr and 9.6 hr on a nondialysis day (p less than 0.001). Both methods of assay gave higher levels of procainamide when the metabolite, N-acetylprocainamide, was present in serum and the extract allowed to stand in 1 N HCl, but spectrophotometry was less affected. Thus, end stage renal insufficiency greatly prolongs the half-life of procainamide, procainamide is readily dialyzable, and N-acetylprocainamide is hydrolyzed in 1 N HCl to procainamide during routine serum determinations.

Acetylation↗
PubMed1975

Propranolol in hypertensive dialysis patients: efficacy and compliance.

The effect of propranolol therapy on plasma renin activity and blood pressure control was evaluated in 35 uremic patients receiving intermittent center-based outpatient hemodialysis. Patients were determined to be either compliant or noncompliant with therapy based on the steady-state predialysis plasma propranolol concentration. Noncompliance occurred with remarkable frequency and was associated with persistent hyperreninemia and poorly controlled hypertension. Blood pressure control was significantly better in compliant patients, in whom plasma renin activity was generally, but not universally, suppressed. Propranolol can be effectively used in the management of hypertensive dialysis patients, but steady-state plasma propranolol levels should be measured to assess compliance in patients apparently refractory to treatment.

Adolescent↗
PubMed1975

Effect of hemodialysis on kinetics of acetaminophen elimination by anephric patients.

The pharmacokinetics of acetaminophen elimination were determined in 4 anephric patients during hemodialysis and on an interdialysis day. The biologic half-life of acetaminophen ranged from 119 to 147 min on an interdialysis day and was decreased by 42% to 53% during hemodialysis. Individual mean dialyzer extraction ratios, based on assay of plasma samples from blood flowing into and out of the dialysis unit, were 0.46 to 0.78 for acetaminophen, 0.53 to 0.57 for acetaminophen glucuronide, 0.13 to 0.60 for acetaminophen sulfate, and 0.70 to 0.87 for urea nitrogen. There was a strong correlation between the extraction ratios of acetaminophen and urea nitrogen. Hemodialysis was the major or sole routine of elimination of acetaminophen glucuronide and sulfate in the anephric patients.

Acetaminophen↗
PubMed1975

Nephrectomy in selected patients with severe refractory hypertension receiving dialysis.

The effect of bilateral nephrectomy was examined in ten patients with severe hypertension in whom dialysis and multiple drug therapy had not resulted in blood pressure control and was compared with that in 15 patients undergoing nephrectomy solely in preparation for transplantation. A highly significant, P less than 0.0005, and clinically impressive reduction in mean blood pressure occurred in the first group of patients, permitting discontinuation of all drugs. Although impossible to quantitate, these patients also demonstrated a reversal of a failure-to-thrive syndrome which had seriously compromides prenephrectomy management. Nephrectomy resulted in a reduction in mean hematocrit values of greater than 20 per cent and less than or equal to 20 percent showed a significant fall in the former but not in the latter. No increase in transfusion requirements developed in these patients. Until more potent and reliable medical therapy becomes generally availabe, nephrectomy will remain an important treatment modality in those patients requiring dialysis and having severe unremitting hypertension.

Antihypertensive Agents↗
PubMed1974

Kinetics of salicylate elimination by anephric patients.

The objectives of this research were to determine the kinetics of salicylate elimination in anephric patients and particularly to establish if these patients form the major metabolite of salicylic acid, salicyluric acid, at a normal rate. This investigation was initiated because of conflicting reports concerning the contribution of the kidneys to the formation of salicyluric acid in man. Six patients, 20-44 yr old, three of whom were anatomically anephric while the other three were physiologically anephric, received an intravenous injection of 500 mg salicylic acid (as sodium salicylate)/1.73 m(2) body surface area on an interdialysis day. Serial blood samples were obtained for 12 or 16 h after injection and the plasma was assayed for salicylic acid, salicyluric acid, total protein, albumin, and creatinine. Detailed pharmacokinetic analysis based on an open, two-compartment linear model revealed no significant differences in apparent volume of distribution and apparent first-order distribution and elimination rate constants between the anephric patients and normal adult subjects. An estimate of salicyluric acid formation rate by the anephric patients, based on the initial rate of increase of salicylurate concentrations in plasma, indicates that the metabolite is formed at a normal rate. These results suggest that the kidneys do not contribute significantly to the formation of salicyluric acid from salicylic acid in man.

Adult↗