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Proceedings Paper

Chemical instability of 5-aminolevulinic acid (ALA) in aqueous solution
Author(s): Mercedes Novo Rodriguez; Gereon Huettmann; Heyke Cacile Diddens
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Paper Abstract

Five-aminolevulinic acid (ALA) is being used to induce formation and accumulation of endogenous protoporphyrin IX both in preclinical and clinical studies on photodynamic therapy and diagnosis. At the high concentrations needed for clinical application, ALA is not stable in aqueous solutions in the neutral to basic pH range. This could be of critical importance for the clinical use of ALA. The chemical instability of ALA was studied by using UV-Vis absorption spectroscopy. Our results show that ALA undergoes a chemical reaction, which is a nonreversible condensation process yielding two different products -- a hydropyrazine and a pyrazine, the latter formed by oxidation of the hydropyrazine. Preliminary kinetic studies of this reaction showed a complex pH-, concentration and temperature-dependency of the reaction rate. On the basis of these studies we optimized conditions for the preparation of ALA solutions to be used in clinical trials, leading to the expected accumulation of protoporphyrin IX in tumor cells.

Paper Details

Date Published: 1 March 1995
PDF: 6 pages
Proc. SPIE 2371, 5th International Photodynamic Association Biennial Meeting, (1 March 1995); doi: 10.1117/12.203450
Show Author Affiliations
Mercedes Novo Rodriguez, Medizinisches Laserzentrum Luebeck (Germany)
Gereon Huettmann, Medizinisches Laserzentrum Luebeck (Germany)
Heyke Cacile Diddens, Medizinisches Laserzentrum Luebeck (Germany)

Published in SPIE Proceedings Vol. 2371:
5th International Photodynamic Association Biennial Meeting
Denis A. Cortese, Editor(s)

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