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Biomedical subjects

R E Rangno

Publications and source records attributed to R E Rangno.

34 records · Page 2Linked to original sources
PubMed1977

Theophylline disposition in patients with hepatic cirrhosis.

To determine the role of liver dysfunction in theophylline toxicity, we administered single intravenous doses of the drug to nine patients with cirrhosis and observed its disposition over a period of 24 to 48 hours. As compared to 19 normal subjects, these patients had a prolonged plasma half-life (mean, 25.6 vs. 6.7 hours) and a decreased plasma clearance (mean, 0.042 vs. 0.062 liter[kg-1]hr-1). Volumes of distribution of theophylline in the cirrhotic patients (central-compartment volume of 0.330, and steady-state volume of distribution of 0.785 liter per kilogram) did not substantially differ from normal (0.246 and 0.508 respectively). Plasma theophylline binding in three patients with cirrhosis averaged 36.8 per cent as compared to 52.6 per cent in four normal subjects. There was no correlation between any laboratory test of liver function and the plasma theophylline half-life, except for serum albumin (r = 0.92, P less than 0.001). The variable capacity to eliminate theophylline precludes the use of usual maintenance dose schedules for bronchodilation in cirrhosis.

Adult↗
PubMed1977

Theophylline kinetics in acute pulmonary edema.

Nine patients with acute cardiogenic pulmonary edema were given theophylline intravenously, and its disposition was observed over the next 24 hr. Compared to that in 19 normal subjects, these patients had prolonged plasma half-lifes (mean, 22.9 from 6.7 hr) and decreased plasma clearances of theophylline (mean, 0.041 from 0.062 L [kg-1] hr-1). The intersubject variation in these parameters was 20-fold in patients with pulmonary edema and 4-fold in normal subjects. Since the peak plasma concentrations attained and the apparent volumes of distribution were not different in the two groups, a suitable initial dose can be calculated. A loading dose of 4.5 to 5 mg/kg theophylline (6 mg/kg aminophylline) given over 20 min appears safe. Because of the great variability in the plasma clearance of this drug in patients with heart failure, plasma concentrations and toxicity would be unpredictable after repeated doses or constant infusions.

Acute Disease↗
PubMed1976

Modified colorimetric method for procainamide in plasma.

We describe a modified colorimetric method for determining procainamide in plasma by use of a diazotization and coupling reaction with N-(1-naphthyl)-ethylenediamine dihydrochloride (Marshall's reagent). The sensitivity of the assay is increased twofold over the originally reported colorimetric method, and the lower limit of detection for the assay of a 1.0-ml plasma sample has been decreased to 0.5 mg/liter.

Colorimetry↗
PubMed1975

Plasma theophylline concentrations measured by high-pressure liquid chromatography.

We present a specific, sensitive high-pressure liquid-chromatographic assay for theophylline in plasma. Only 0.5 ml of plasma is required for each determination, and the lower limit of detection by this method is 0.1 mg/liter. Other xanthines and their metabolites do not interfere. This method is suitable for use in studying the pharmacokinetics of this drug in infants and children, from whom only small volumes of blood are available.

Aminophylline↗
PubMed1973

Effects of a false neurotransmitter, p-hydroxynorephedrine, on the function of adrenergic neurons in hypertensive patients.

Previous studies have shown that amphetamine and p-hydroxyamphetamine impair adrenergic transmission, and it has been suggested that this effect is mediated by an active metabolite, p-hydroxynorephedrine (PHN). Studies in experimental animals have shown that PHN can deplete and substitute for norepinephrine (NE) in the transmitter pool, thus meeting the criteria of a false neurotransmitter. The pharmacologic effects of PHN on adrenergic function and NE synthesis were studied in eight hypertensive patients and compared with placebo. Mean erect and supine blood pressure (BP) decreased 22/14 and 9/6 mm Hg, respectively, during PHN 600 mg daily. The post-Valsalva diastolic overshoot was abolished. The pressor sensitivity to tyramine decreased whereas the pressor response to NE was enhanced. A mild natriuresis occurred. The 24 h urinary excretion of catecholamines and catecholamine metabolites during the administration of PHN compared with placebo changed as follows: vanillylmandelic acid (VMA), 42% decrease; NE. 42% decrease; normetanephrine (NM), 400% increase: metanephrine, unchanged; dopamine, 40% decrease; while homovanillic acid was unchanged. The sum of VMA, NE, and NM decreased 23%. The posttreatment urinary excretion of PHN was biexponential with first and second phase half-lives of 13 and 55 h. respectively. The time of the second phase closely approximated the recovery of the changes in BP and excretion of VMA. No effects of PHN on the central nervous system were observed. These studies show that PHN acts peripherally to interfere with adrenergic function and NE synthesis in hypertensive patients with a resultant decrease in BP.

Adult↗