title: Radical mechanisms in the radiosterilization of metoprolol tartrate solutions.
abstract: 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.
authors.affiliation: Unité d'Analyse Chimique et Physico-chimique des Médicaments, Université Catholique de Louvain, Brussels, Belgium. catherine.slegers@cham.ucl.ac.be
authors.forename: Catherine
authors.initials: C
authors.lastname: Slegers
authors.forename: Gérard
authors.initials: G
authors.lastname: Baldacchino
authors.forename: Dominique
authors.initials: D
authors.lastname: Le Parc
authors.forename: Bernard
authors.initials: B
authors.lastname: Hickel
authors.forename: Bernard
authors.initials: B
authors.lastname: Tilquin
mesh_terms: 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
chemical_list: D000319:Adrenergic beta-Antagonists; D013481:Superoxides; D017665:Hydroxyl Radical; D008790:Metoprolol; D010100:Oxygen