On day 5 of dosing subjects underwent an interdosing interval study where blood , withdrawal scores , heart rate and blood pressure ( BP ) were collected at 0 , 1 , 3 and 8 h. Plasma morphine concentrations were quantified by high-performance liquid chromatography , and plasma morphine-3-glucuronide ( M3G ) and morphine-6-glucuronide ( M6G ) concentrations by LCMS .
