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Stability of apomorphine in solutions containing selected antioxidant agents

Authors Ang ZY, Boddy M, Liu Y, Sunderland B

Received 9 July 2016

Accepted for publication 9 August 2016

Published 3 October 2016 Volume 2016:10 Pages 3253—3265


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Prof. Dr. Frank M. Boeckler

Video abstract presented by Zen Yang Ang.

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Zen Yang Ang, Michael Boddy, Yandi Liu, Bruce Sunderland

School of Pharmacy, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia

Abstract: Apomorphine in solution undergoes rapid autoxidation, producing greenish colored solutions, making it difficult to formulate as a stable pharmaceutical solution. To identify the optimum antioxidant agent/combination for apomorphine solution, a high performance liquid chromatography assay was used to study the stability of 50 µg/mL apomorphine HCl in 0.1% L-ascorbic acid (AA), 0.1% sodium metabisulfite (SMB), 0.1% EDTA, and in selected combinations at 25°C, 32°C, and 37°C over a period of 14 days. The stability of apomorphine HCl (10 mg/mL) in 0.1% AA solution and in 0.1% EDTA solution at 25°C and 37°C was also evaluated. Apomorphine HCl solution (50 µg/mL) in 0.1% AA plus 0.1% SMB solution retained 99.7% (at 25°C) and 95.9% (at 37°C) of the initial concentration, as 0.1% AA plus SMB solution minimized the reactive oxygen content in solution which, in turn, reduced the oxidation rate of apomorphine HCl, and there was no green coloration perceptible. Conversely, apomorphine HCl solution (50 µg/mL) in 0.1% SMB solution was unstable as only 0.53% (at 25°C) and 0.06% (at 37°C) of the initial concentration was retained after 14 days. All 10 mg/mL apomorphine HCl samples were stable in both studies. The initial concentration of apomorphine HCl solution markedly affected its rate of oxidation and discoloration. The addition of 0.1% AA to a current formulation of apomorphine HCl injection (Apomine®), which contains SMB as an antioxidant, was recommended as providing the most stable solution.

Keywords: apomorphine HCl, oxidation, ascorbic acid, EDTA, sodium metabisulfite, HPLC

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