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Biomedical subjects

R N Gupta

Publications and source records attributed to R N Gupta.

At least 55 records · Page 3Linked to original sources
PubMed1982

A placebo-controlled study to determine the efficacy of oral disopyramide phosphate for the prophylaxis of ventricular dysrhythmias after acute myocardial infarction.

1 To evaluate oral disopyramide phosphate in the prophylaxis of dysrhythmias occurring in acute myocardial infarction (MI) patients (presenting within 12 h of symptoms, age 21-70 years), a placebo-controlled, randomized double-blind, in hospital trial was conducted. After prognostic stratification (anterior and non-anterior MI at each of 4 regional hospitals) patients were randomly assigned to receive oral disopyramide phosphate (loading dose 150, 200, or 300 mg followed 6 h later by 100, 150, or 200 mg every 6 h for patients assessed to weigh less than 55, 55-85, or greater than 85 kg, respectively or matching placebo. The primary exclusion criteria were overt heart failure, systolic BP less than 100 mmHg, significant heart block or history of urinary retention. Active drug or placebo was continued for 7 days or until (a) detection of "warning arrhythmias' requiring i.v. lignocaine intervention (greater than 5 for 7 days or until (a) detection of "warning arrhythmias' requiring i.v. lignocaine intervention (greater than 5 premature ventricular contractions (PVCs)/min, R on T PVCs, multifocal PVCs, bigeminal PVCs, ventricular tachycardia or ventricular fibrillation) or (b) onset of exclusion criteria. In addition, plasma drug concentrations were determined and 24 h electrocardiographic tapes were obtained on day 1, and on one of days 4-7 but these results are not presented here. 2 Out of 121 patients entering the trial, 101 had confirmatory ECG and enzyme changes. Of these, 9 of 47 patients receiving disopyramide phosphate required lignocaine compared to 20 of 54 receiving placebo (19% v 37%; P = 0.047). Corresponding numbers for patients discontinuing trial medication for other non-fatal complications of MI were 5 and 3, and for those dying, were 3 (2 infarct extensions and 1 massive infarction), and 0, respectively. Respective numbers discontinuing trial medication for possible drug side effects (viz. urinary retention requiring catheterization) were 6 and 1 (P = 0.031). 3 In circumstances where i.v. therapy is deemed impractical, use of oral disopyramide phosphate given prophylactically in patients with acute MI may reduce the incidence of "warning arrhythmias' by a clinically significant extent.

Adult↗
PubMed1982

Liquid-chromatographic determination of ethylene glycol in plasma.

In this novel procedure for determining ethylene glycol in plasma by liquid chromatography, benzoyl esters of ethylene glycol and of benzyl alcohol (used as the internal standard) are prepared directly in plasma. The benzoyl esters, highly ultraviolet-absorbing chromogens, are ideal compounds for analysis by reversed-phase liquid chromatography with methanol/water as the mobile phase. The benzoyl derivative of ethylene glycol is well separated from the derivative of the internal standard and from plasma constituents. The standard curve is linear to 400 mg of ethylene glycol per liter. As little as 10 mg of ethylene glycol per liter of plasma can be measured. Other commonly ingested alcohols do not interfere.

Chromatography, Gas↗
PubMed1982

Liquid-chromatographic determination of pentobarbital in plasma with use of a resin column and an alkaline mobile phase.

We describe a liquid-chromatographic method involving a new, nonsilica column (XAD-2, Hamilton Co.) for pentobarbital in plasma. Plasma is extracted with chloroform after addition of the internal standard, 5-ethyl-5-p-tolyl-barbituric acid. Acidic drugs are back-extracted into alkali, then chromatographed on the resin-base reversed-phase column. The use of alkaline mobile phase allows enhanced sensitivity and detection of barbiturates at 240 nm. The within-run CV for 10 samples was 1.9%, the between-run CV 1.8%. Ten commonly used barbiturates are separated isocratically in less than 15 min. Other commonly prescribed acidic drugs do not interfere with determination of pentobarbital.

Chromatography, Liquid↗
PubMed1981

Measurement of pulmonary tissue volume and blood flow in persons with normal and edematous lungs.

We measured pulmonary tissue volume (Vt) and pulmonary capillary blood flow (Qc) by a rebreathing method using two soluble gases, acetylene (C2H2) and dimethyl ether (DME), in 32 normal subjects and 14 patients who had had pulmonary edema. In 18 of the normal subjects, studies were performed at three or more different rebreathing volumes (VA). To normalize for differences in body size, results were expressed as the ratio of Vt or VA to predicted total lung capacity (TLC). We found that 1) changes in VA/TLC had a significant effect on Vt/TLC and Qc measured with both gases, 2) the range of normal values for Vt was best defined by expressing the relationship between Vt/TLC and VA/TLC, 3) using this approach, many patients with clinically mild or inapparent pulmonary edema had abnormal values of Vt, and 4) when comparing mean values of C2H2 and DME in 82 simultaneous measurements at constant VA/TLC, Vt was significantly higher in 87% (71/82) and Qc in 63% (52/82) of the paired tests.

Acetylene↗
PubMed1979

The biosynthetic route from ornithine to proline.

It is shown by tracer experiments with DL-[2-3H,5-14C]- and DL-[(RS)-5-3H,5-14C]rnithine, that the metabolic conversion of ornithine into proline, in three plant species (Nicotiana tabacum, Datura stramonium, and Lupinus angustifolius), takes place with maintenance of the delta-hydrogen atoms but with loss of the alpha-hydrogen atom. This indicates a route via alpha-keto-delta-aminovaleric acid (5-amino-2-oxopentanoic acid) and disproves the accepted route via glutamic gamma-semialdehyde (2-amino-5-oxopentanoic acid).

Carbon Radioisotopes↗
PubMed1979

Gas-chromatographic analysis for valproic acid as phenacyl esters.

We describe a novel isothermal gas-chromatographic procedure for measuring valproic acid. Plasma, with cyclohexanecarboxylic acid added as internal standard, is selectively extracted with pentane to minimize the extraction of other acidic drugs. To convert carboxylic acids to their phenacyl esters, alpha-bromoacetophenone is added to the organic extract before evaporating the solvent. These esters are relatively less volatile than the acids themselves and the extracting solvent can be removed without any loss of valproic acid or internal standard. The phenacyl esters, when chromatographed on 3% OV-17, produce sharp, well-shaped peaks and show high response for the flame ionization detector. Valproic acid is well separated from the internal standard, from reagents and plasma constituents, and from some commonly prescribed drugs that we examined. When alpha-bromo-p-nitroacetophenone is sued as the derivatizing agent, the resulting nitrophenacyl esters can be analyzed with use of a nitrogen-specific detector.

Acetophenones↗
PubMed1978

Withdrawal from long-term high-dose desipramine therapy. Clinical and biological changes.

Investigation was undertaken on a patient whose long-term intake of desipramine hydrochloride was amongst the highest reported. Desipramine treatment instituted at a daily dosage of 75 mg for depressive equivalents of head, chest, and abdominal pain was increased to 1,000 mg daily over a 12-year interval with minimal side effects. Plasma desipramine level dropped immediately on withdrawal, and urinary metabolite values dropped over the subsequent five days. The electrocardiographic abnormalities of first-degree atrioventricular block and incomplete left bundle branch block rapidly disappeared on cessation of medication. Electroencephalographic changes with symmetrical generalized irregular 5- to 7-cps theta activity and 18- to 28-cps beta activity also improved. Longitudinal polygraphic sleep studies showed prolonged rapid eye movement rebound and increased delta sleep coincident with withdrawal. It took ten days after cessation of desipramine for urinary 3-methoxy-4-hydroxyphenylglycol concentration to increase substantially. Although catecholamines are involved in growth hormone (GH) and cortisol regulation, no abnormalities were found in GH or cortisol levels.

Adult↗
PubMed1978

Estimation of theophylline in plasma by thin-layer chromatography.

1. A quantitative thin-layer chromatographic procedure for theophylline has been evaluated. An internal standard, 3-isobutyl-1-methylxanthine, a compound similar in properties to those of theophylline is added to the specimen prior to extraction to eliminate the need for accurate measurements of volume during extraction or analysis. 2. This method does not show interference from other xanthines and from a number of drugs commonly prescribed with thephylline. It has an acceptable correlation with a reference gas-liquid chromatographic procedure. 3. This procedure is capable of handling batches of six or more samples faster than the serial processing of either high performance liquid chromatography or gas-liquid chromatography.

Chromatography, Thin Layer↗
PubMed1977

Estimation of maprotiline in serum by gas-chromatography, with use of a nitrogen-specific detector.

We describe a gas-chromatographic procedure for estimating therapeutic concentrations of maprotiline, a new tetracyclic antidepressant, in serum by use of a nitrogen-specific detector. Desmethyldoxepin, a secondary amine similar in structure to maprotiline, is added as a mass internal standard to the specimen before extraction, to obviate the need for accurate measurements of volumes during extraction and analysis. Both maprotiline and the internal standard are converted to acetyl derivatives, to avoid the adsorption of secondary amines on the column. A highly selective liquid phase is used, which allows a very good separation of desmethyldoxepin, maprotiline, desmethylmaprotiline, and the interferences from serum and reagents.

Anthracenes↗