Inclusion Criteria:  informed consent Age 18-75 years American society of anesthesiologist classification 2-4 planned elective surgery with standard premedication with paracetamol 1g po. at least one regular medication ongoing perioperatively eligibility for elective surgery negative pregnancy test in fertile women  Exclusion Criteria:  American society of anesthesiologists classification 1 contraindication for use of paracetamol as standard premedication pregnancy or lactation less than 3 months from previous drug research less than 3 months from previous blood donation anticipated difficult puncture of veins Body Mass Index lower than 18.5 or higher than 35