Chemical instability of 5-aminolevulinic acid (ALA) in aqueous solution

Mercedes Novo Rodriguez; Gereon Huettmann; Heyke Cacile Diddens

doi:10.1117/12.203450

1 March 1995 Chemical instability of 5-aminolevulinic acid (ALA) in aqueous solution

Mercedes Novo Rodriguez, Gereon Huettmann, Heyke Cacile Diddens

Proceedings Volume 2371, 5th International Photodynamic Association Biennial Meeting; (1995) https://doi.org/10.1117/12.203450
Event: Fifth International Photodynamic Association Biennial Meeting, 1994, Amelia Island, FL, United States

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.

Citation Download Citation

Mercedes Novo Rodriguez, Gereon Huettmann, and Heyke Cacile Diddens "Chemical instability of 5-aminolevulinic acid (ALA) in aqueous solution", Proc. SPIE 2371, 5th International Photodynamic Association Biennial Meeting, (1 March 1995); https://doi.org/10.1117/12.203450

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