The study is separated into two parts. In the first part the patients are undergoing cosmetic breast surgery, and in the second part the patient undergo inguinal og umbilical surgery.~The first part is a cohort at 12 patients undergoing breast surgery. All patients in this group will be treated with melatonin, and the investigators intend to investigate the pharmacokinetic parameters of melatonin. Melatonin will be administrated 60 min. before surgery and the evening after surgery at 9 pm.~All patients will receive an intravenous catheter. The intravenous catheter will be used for blood sampling. A baseline blood sample will be taken 65 min before surgery (baseline) and thereafter blood samples will be obtained 0 min., 15 min., 30 min., 45 min., 60 min., 90 min., 120 min., 180 min., 240 min., 300 min., 360 min. and 420 min. after administration of melatonin. Blood samples will be obtained again after administration of melatonin at 9 pm. in the evening in the same manner as described above. Plasma samples will be stored at minus 80 C and analyzed at the research laboratory of the Department of surgery, Herlev Hospital. The analysis will be preformed with the RIA-technique.~The second part is a randomized, double-blind, placebo-controlled study with a total of 32 participants divided into a intervention group (16) and a placebo group (16). In this part the investigators intend to investigate the anxiolytic and sleep-promoting effects of melatonin. Melatonin and placebo will be administrated at 9 pm. the evening before surgery, 120 min. before surgery, immediately after surgery in the PACU and at 9 pm the evening after surgery.~Anxiety will be measured by the State-Trait Anxiety Inventory (STAI) and a VAS-scale (0 mm = no anxiety and 100 mm = worst anxiety). Quality of sleep will be measured at the VAS-scale as well (0 mm = best sleep and 100 = worst sleep).~Randomization will be performed by a computer at randomization.com. The first generator function is used. The randomization will be preformed in blocks of 4 patients in each.~Manufacturing of medications and randomization will be made by an independent pharmacist.~The primary outcome is preoperative anxiety as measured on the STAI. A previous study investigated preoperative anxiety before hernia surgery and found a mean of 35.4 (SD 10.0) on the STAI scale. There does not exist any generally accepted measure of how large a change on the STAI scale constitutes a clinically important difference. However, a change equal to one standard deviation has been suggested. In the present study, this corresponds to a minimal relevant difference (MIREDIF) of 10 points on the STAI scale or 28%. A power of 80% was defined, a significance level of 5% and a minimal relevant difference (MIREDIF) of 28%. From these assumptions, 16 patients in each treatment group is needed~Statistics Anxiety and sleep quality will be compared at individual timepoints between groups Comparison will be performed either by Mann-whitheys-test or unpaired t-test, depending on the distribution of data. Values are considered significant at a p-value at 5% or less. Data will be reported as mean (SD) or median (IQR) depending on the distribution of data.~Data for the blood samples will be presented as AUC plasma concentrations, half-life, maximum concentration and time to maximum concentration.
The study's main objective is to investigate melatonin's anxiolytic and sleep-regulating effects in patients undergoing surgery. Moreover, the investigators intend to investigate the pharmacokinetic parameters of melatonin in this patient population.