title: Radiation effects on dopamine and norepinephrine.
abstract: OBJECTIVE
  Radiation sterilization is becoming increasingly popular for the sterilization of many pharmaceutical products. We have investigated the gamma radiation induced effects on dopamine and norepinephrine by ESR spectroscopy.
  
  
  CONCLUSIONS
  Equations to describe the evolution of the ESR curves versus doses and time of storage are presented. Linear regression is, for dopamine hydrochloride, applicable for doses ranging from 10 to 25 kGy. Since the radiation dose selected must always be based upon the bioburden of the products and the degree of sterility required, doses in the range 10-25 kGy could be investigated and linear regression would appear to be the least expensive route to follow and gives good results. The comportment of noradrenaline bitartrate is more complex and the use of linear regression would appear more hazardous especially for low doses. For doses higher than 25 kGy, a more general equation is required. Power function using only 2 parameters could give good results but must be validated. Decay kinetics for radicals versus storage were considered. Non-homogeneous kinetics with time dependent rate constant and bi-exponential function appeared valid to reproduce the decay of radicals for, respectively, dopamine and norepinephrine.
  
  
  CONCLUSIONS
  It is worth noting that, at present, ESR is the only technique which proved to be suitable for identification and quantification purposes in irradiated pharmaceuticals. Moreover, other features such as sensitivity, precision, ease and non-destructive readout make ESR superior to other proposed analytical techniques.
authors.affiliation: Laboratoire de Chimie Analytique et Bromatologie, UFR de Pharmacie, Université de Limoges, France. Basly@alpha1.unilim.fr
authors.forename: J P
authors.initials: JP
authors.lastname: Basly
authors.forename: I
authors.initials: I
authors.lastname: Longy
authors.forename: M
authors.initials: M
authors.lastname: Bernard
mesh_terms: D004298:Dopamine / Q000528:radiation effects*; D004578:Electron Spin Resonance Spectroscopy; D018377:Neurotransmitter Agents / Q000528:radiation effects*; D009638:Norepinephrine / Q000528:radiation effects*; D013242:Sterilization
chemical_list: D018377:Neurotransmitter Agents; D004298:Dopamine; D009638:Norepinephrine