title: Magnocaine: Physical Compatibility and Chemical Stability of Magnesium Sulphate and Lidocaine Hydrochloride in Prefilled Syringes.
abstract: To evaluate the physical compatibility and chemical stability of mixtures of magnesium sulphate and lidocaine in order to determine the feasibility of manufacturing a prefilled syringe combining these two drugs for use as an intramuscular (IM) loading dose for eclampsia prevention and/or treatment. This ready-to-use mixture will provide a more tolerable and accessible route of administration appropriate for widespread use.
  
  
  
  Physical compatibility (pH, colour, and formation of precipitate) and chemical stability (maintaining > 90% of initial concentrations) of mixtures of MgSO4, using both commercially available MgSO4(50%) and MgSO4reconstituted from salt (61%), with lidocaine hydrochloride (2%) were evaluated every 14 days over six months. The concentration of lidocaine was determined by a stability indicating high performance liquid chromatographic method, while the concentration of magnesium was determined by an automated chemistry analyzer.
  
  
  
  No changes in pH, color or precipitates were observed for up to 6 months. The 95% confidence interval of the slope of the curve relating concentration to time, determined by linear regression, indicated that only the admixtures of commercially-available magnesium sulfate and lidocaine as well as the 61% magnesium sulfate solution (reconstituted from salt) maintained at least 90% of the initial concentration of both drugs at 25°C and 40°C at 6 months.
  
  
  
  Commercially available MgSO4 and lidocaine hydrochloride, when combined, are stable in a pre-filled syringe for at least six months in high heat and humidity conditions. This finding represents the first step in improving the administration of magnesium sulphate in the treatment and prevention of eclampsia in under-resourced settings.
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver BC.
authors.forename: Sara
authors.initials: S
authors.lastname: Houlihan
authors.affiliation: Department of Pharmacy, Children's and Women's Health Centre of BC, Vancouver BC.
authors.forename: Diane
authors.initials: D
authors.lastname: Decarie
authors.affiliation: Department of Laboratory Medicine, Surrey Memorial Hospital, Surrey BC.
authors.forename: Cindy
authors.initials: C
authors.lastname: Benes
authors.affiliation: Department of Laboratory Medicine, Surrey Memorial Hospital, Surrey BC.
authors.forename: Richard
authors.initials: R
authors.lastname: Cleve
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia, Vancouver BC.
authors.forename: Marianne
authors.initials: M
authors.lastname: Vidler
authors.affiliation: Institute of Cardiovascular and Cell Sciences, St George's University Hospitals, University of London, London, UK; Department of Obstetrics and Gynaecology, St George's University Hospitals, NHS Foundation Trust, London, UK.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Magee
authors.affiliation: Department of Pharmacy, Children's and Women's Health Centre of BC, Vancouver BC; Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver BC.
authors.forename: Mary H H
authors.initials: MHH
authors.lastname: Ensom
authors.affiliation: Institute of Cardiovascular and Cell Sciences, St George's University Hospitals, University of London, London, UK; Department of Obstetrics and Gynaecology, St George's University Hospitals, NHS Foundation Trust, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: von Dadelszen
mesh_terms: D004355:Drug Stability; D006358:Hot Temperature; D008012:Lidocaine / Q000032:analysis* / Q000737:chemistry*; D008278:Magnesium Sulfate / Q000032:analysis* / Q000737:chemistry*; D013594:Syringes
chemical_list: D008278:Magnesium Sulfate; D008012:Lidocaine
keywords: Preeclampsia; chemical stability; eclampsia; magnesium sulphate