The analgesic concentration of oxycodone with co-administration of paracetamol -- a dose-finding study in adult patients undergoing laparoscopic cholecystectomy.

We have previously shown that paracetamol has an opioid-sparing effect in tonsillectomy, and now, we evaluated the analgesic efficacy of paracetamol i.v. in early post-operative pain after laparoscopic cholecystectomy (LCC). Twenty-four patients with LCC were randomized to receive paracetamol i.v. 1 g (group 1) or 2 g (group 2) at the end of surgery. All patients were provided 0.1 mg/kg of oxycodone i.v. 15 min. before the end of surgery. At the recovery room when the wound pain at rest was ≥ 3/10 and/or ≥ 5/10 during the wound compression, plasma sample was taken for the determination of oxycodone (minimum effective concentration, MEC), its metabolites and paracetamol. After that the patients were titrated with further doses of oxycodone i.v. to wound pain < 3/10 at rest and < 5/10 during wound compression, plasma sample was taken for the determination of minimum effective analgesic concentration (MEAC) of oxycodone. The total oxycodone dose needed for pain relief was similar, about 0.3 mg/kg (range 0.2-0.5), in both groups (p = 0.80). At the onset of pain, P-oxycodone (MEC) was similar in both groups, 25 ng/ml (19-32) in group 1 and 24 ng/ml (16-34) in group 2. The pain relief (MEAC) was achieved in group 1 with P-oxycodone 70 ng/ml (30-131) and in group 2 with 62 ng/ml (36-100) (p = 0.48). In conclusion, in the early-phase after LCC, there was no significant difference between the effect of paracetamol doses of 1 g and 2 g i.v. on the need of i.v. oxycodone.