The stability of noradrenaline in physiological saline solutions

Abstract

Although noradrenaline is known to be stable for at least 4 h at room temperature in sterile solutions for intravenous infusion (Haggendal & Johnsson, 1967), it is well appreciated that noradrenaline is highly susceptible to chemical degradation by oxidation especially under the conditions found in isolated tissue baths (physiological saline, pH 7.4,37", oxygenation). For this reason many workers include stabilizing agents (typically ethylenediaminetetraacetic acid (EDTA) or ascorbic acid) in the physiological saline during incubation of tissues with radiolabelled noradrenaline or when perfusing tissues with solution containing noradrenaline. A variety of concentrations of EDTA or ascorbic acid have been used by different workers but there appears to be little information in the literature concerning the effectiveness of these concentrations or about the actions of these materials on relevant biological processes, noradrenaline uptake for example.To clarify these points (-)-noradrenaline bitartrate (Sigma) (312 nM) was incubated in a stirred isolated tissue bath (100 ml) with physiological saline (NaCI 118, KCI 4.7, CaCI, 2.5, MgSOo 1.2, NaHCO, 25, KH,PO, 1.2, glucose 1l.lmM; aerated with 5 % carbon dioxide in oxygen (30 ml min-'); pH 7.4) at various temperatures. At appropriate times a portion of the bath fluid was removed and sufficient 2 . 0~ acetic acid was added to give 0.1 ml 2.0M acetic acid per 0.9 ml bath fluid. The solution was then assayed for noradrenaline by the following fluorimetric method using internal standards. To a 1.0 ml samplewasadded 0.2 ml 1 . 0~ K,HPO, and 0.1 ml 6.07 mM K,Fe(CN), and the solution was mixed well. After 5 min 0.5 ml of a freshly prepared mixture consisting of 6.25 ml ON NaOH + 3.25 ml 1 . 5 9~ Na,SO, + 0.5 ml 9 0 . 9 m~ ascorbic acid was added.After a further 5 min 0.5 ml of glacial acetic acid was added and the solution left to stand for 5 min. Fluorescence of the sample was measured in a Perkin Elmer MPF 3 fluorescence sepectrometer using an excitation wavelength of 395nm, an emission wavelength of 480 nm and a band pass of 10 nm. When noradrenaline assays were carried out with bath solutions containing EDTA or 2 8 4 . 1~~ ascorbic acid it was found necessary to increase the K,Fe(CN), to 0.2 ml and 0.3 ml respectively.This procedure provided a measure of the amount of noradrenaline in the bath fluid together with any preformed oxidation products expressed in terms of noradrenaline. Two types of blanks were used in conjunction. Firstly, 'faded blanks' (which assess the contribution of the reagents to the total fluorescence) were prepared by adding the NaOH component of the mixture at the normal time but delaying addition of the * Correspondence. Na,SO, and ascorbic acid until immediately before the addition of the acetic acid. Secondly, a 'reversed oxidant blank' was prepared by adding the K,Fe(CN), after the alkaline mixture and immediately before the acetic acid. This modification fails to oxidize the noradrenaline present which therefore does not form the fluorophore w...

Stability of Norepinephrine Solutions in Normal Saline and 5% Dextrose in Water

“…These results are in general agreement with all previously published studies, [5][6][7][8][9][10][11][12][13][14] which have all demonstrated the stability of norepinephrine. Of the papers published in English and reporting results obtained with stability-indicating analytical methods, 7,10-14 the study duration was relatively short, at only 24 h, 10,12,13 36 h, 7 or 7 days.…”

“…Several investigators have evaluated the stability of norepinephrine in solutions intended for IV administration. [5][6][7][8][9][10][11][12][13][14] The concentrations evaluated were generally 16 mg/L or lower, although Allwood 11 and Peddicord and others 13 evaluated concentrations of 40 mg/L and 64 mg/L, respectively. Most of these studies reported the percentage remaining after only 24 h, and none evaluated the effect of light.…”

Cold-induced cutaneous vasoconstriction is mediated by Rho kinase in vivo in human skin

“…Following baseline, 1 M norepinephrine ϩ 1 mg/ml L-ascorbate (preservative) (20) were added to the perfusate through all fibers for 4 min to test vascular responsiveness and the integrity of Y ϩ P adrenoceptor antagonism. After a washout period (ϳ30 min) to allow CVC to recover to pre-norepinephrine baseline values, all sites were cooled at a rate of 3°/min, and Tloc was clamped at 24°C for 40 min, after which sites were rewarmed back to 34°C.…”

Stability of norepinephrine infusions prepared in dextrose and normal saline solutions

“…Many studies, on which these recommendations are based, were conducted before the emergence of modern, precise, assay techniques such as high-performance liquid chromatography (HPLC). [2][3][4] The few studies performed, using modern measurement technology, reported the stability of NE in dextrose (5%) in water (D5W) at room temperature for a period up to 48 hr. [5][6][7][8] Stability of NE solutions for longer periods has not been studied.…”