The aim of this randomized, double-blind study is to compare parenteral pre-emptive oxycodone, morphine and dexamethasone with placebo in the treatment of postoperative pain in paediatric patients 4 to 12 years of age. The investigators hope to find out whether there are any differences in postoperative pain and/or adverse effects among these groups.

After the induction of anaesthesia and before intubation the child receives one of the research drugs in a double-blind fashion: 0.1 mg/kg of oxycodone , 0.1 mg/kg of morphine, 0.5 mg/kg dexamethasone (max 24 mg), or placebo. All the research drugs are diluted into a dose of 10 ml with NaCl 0.9%, the placebo being solely the dilute.

The patients are followed minimum 4h postoperatively: first in the recovery room, and after the patient is stable enough the study is continued in the day-patient unit. Level of pain and adverse effects are registered all on same predetermined intervals being 15 min during the first postoperative hour, followed by interval of 30 min until the discharge.

The safety measurements noted include pulse, respiratory rate, non-invasive blood pressure and peripheral oxygen saturation are recorded on the same intervals The registering of pain, adverse effects and given medication continues at home for 48 hours post operatively with a questionnaire filled by the parents.

Inclusion Criteria:

• 4 to 12 years of age
• Scheduled to tonsillectomy
• ASA class I or II
• Written informed consent is obtained from the parents and the child (when appropriate).

Exclusion Criteria:

• Allergy to morphine, oxycodone or dexamethasone