Radical mechanisms in the radiosterilization of metoprolol tartrate solutions.
OBJECTIVE
Study of the radical mechanisms in the radiosterilization of metoprolol tartrate aqueous solutions in order to determine the parameters governing its radiostability.


METHODS
Pulse radiolysis with pseudo-first-order kinetics to measure Ihe reaction rate constants of hydrated electrons and hydroxyl radicals with metoprolol tartrate. Chemsimul was used to solve the decay kinetics of transients and to simulate the radiolysis of metoprolol tartrate solutions.


RESULTS
Hydrated electrons react with metoprolol and the tartrate ion with rate constants of 6.8 x 10(7) M(-1) s(-1) and 1.7 x 10(7) M(-1) s(-1), respectively. Hydroxyl radicals react with metoprolol and the tartrate ion with rate constants of 5.2 x 10(9) M(-1) s(-1) and 5.5 x 10(8) M(-1) s(-1), respectively. The hydroxyl-metoprolol transients are found to scavenge the superoxide anion (5.5 x 10(10) M(-1) s(-1)), react with oxygen (1.0 x 10(8) M(-1) s(-1)), and follow a biradical decay (2.0 x 10(8) M(-1) s(-1). A simplified radical mechanism is used to simulate the loss of potency of metoprolol tartrate aqueous solutions during radiosterilization.


CONCLUSIONS
To decrease the loss of potency of metoprolol tartrate. the sterilization dose must be lowered and very high dose rates used.
Slegers
Catherine
C
Unité d'Analyse Chimique et Physico-chimique des Médicaments, Université Catholique de Louvain, Brussels, Belgium. catherine.slegers@cham.ucl.ac.be
Baldacchino
Gérard
G
Le Parc
Dominique
D
Hickel
Bernard
B
Tilquin
Bernard
B
D000319:Adrenergic beta-Antagonists / Q000737:chemistry* / Q000528:radiation effects*; D000465:Algorithms; D003198:Computer Simulation; D004583:Electrons; D017665:Hydroxyl Radical; D007700:Kinetics; D008790:Metoprolol / Q000737:chemistry* / Q000528:radiation effects*; D010100:Oxygen / Q000737:chemistry; D011675:Pulse Radiolysis; D013056:Spectrophotometry, Ultraviolet; D013242:Sterilization; D013481:Superoxides / Q000737:chemistry
D000319:Adrenergic beta-Antagonists; D013481:Superoxides; D017665:Hydroxyl Radical; D008790:Metoprolol; D010100:Oxygen