title: A specific and sensitive HPLC-MS/MS micromethod for milrinone plasma levels determination after inhalation in cardiac patients.
abstract: BACKGROUND
  Milrinone administered through inhalation is an emerging method aimed at specifically reducing pulmonary hypertension without affecting systemic pressures. Its administration has been shown to be useful both in patients undergoing cardiac surgery and for persistent pulmonary hypertension of the newborn. These populations are prone to receive many concomitant medications and/or blood sampling may require a low volume quantification method. To address these issues in view of pharmacokinetic studies, this article aims to develop and validate a specific and sensitive analytical assay using high performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS) detection for the quantification of milrinone plasma concentrations after inhalation in patients undergoing cardiac surgery.
  
  
  METHODS
  Plasma samples (50 μL) were extracted using ethyl acetate. Milrinone was separated on a C18 analytical column at 50°C. The mobile phase consisted of methanol and 10 mM ammonium acetate (45:55 vol/vol). The electrospray was operated in the negative ionization mode and monitored the following mass transitions: m/z 212.1 → 140.0 at 36 eV for milrinone and m/z 252.1 → 156.1 at 32 eV for olprinone.
  
  
  RESULTS
  Calibration curves followed a quadratic regression in the concentration range of 0.3125-640 ng/mL. The lower limit of quantification is 0.3125 ng/mL and is based on a low plasma volume of 50 μL. Mean drug recovery and accuracy were ≥72.3% and 96.0%, respectively. Intraday and interday precision coefficient of variation (%) was ≤7.4% and ≤11.5%, respectively. The specificity allowed milrinone quantification in the multidrug administration conditions of cardiopulmonary bypass.
  
  
  CONCLUSIONS
  This validated micromethod proved to be highly sensitive and specific while using a low volume of plasma. Its low volume and its lower limit of quantification indicate that this approach is suitable for further characterization of milrinone pharmacokinetics in both adults (inhalation) and neonates.
authors.affiliation: *Faculté de pharmacie, Université de Montréal; †Unité de Pharmacologie Clinique, CHU Ste-Justine; and ‡Department of Anesthesiology, Montreal Heart Institute, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Gavra
authors.forename: Anne Q-N
authors.initials: AQ
authors.lastname: Nguyen
authors.forename: Yves
authors.initials: Y
authors.lastname: Theoret
authors.forename: Catherine
authors.initials: C
authors.lastname: Litalien
authors.forename: André Y
authors.initials: AY
authors.lastname: Denault
authors.forename: France
authors.initials: F
authors.lastname: Varin
mesh_terms: D000280:Administration, Inhalation; D002315:Cardiopulmonary Bypass; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006331:Heart Diseases / Q000188:drug therapy*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000188:drug therapy; D007093:Imidazoles / Q000097:blood; D020105:Milrinone / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use; D011728:Pyridones / Q000097:blood; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use
chemical_list: D007093:Imidazoles; D011728:Pyridones; D014665:Vasodilator Agents; C059498:olprinone; D020105:Milrinone