Study to assess the analgesic efficacy in the prevention of postoperative pain in children undergoing minor surgery (herniorraphy, tonsillectomy) and to assess the tolerability of Metamizol in this group of patients.

Inclusion Criteria:

• Children of either sex between 6 and 11 years of age
• Patients undergoing routine inguinal hernia repair or tonsillectomy
• Written informed consents by the guardian, according to the guidelines of Good Clinical Practice and current legislation
• The ability of the patient to understand and carry out the visual analogue scale assessments
• Patients with a physical status American Society of Anesthesiologist I or II class

Exclusion Criteria:

• The use of any drug with analgesic properties in the 24 hours prior to the administration of the study drug
• Surgery with a foreseen duration over 60 minutes
• Patients with a nutritional index of less than 90 or greater than 120
• Patients with a body mass index which was not between the 3rd centile and the 97th centile for age
• Patients with any illness or malformation (except hernia) which, in the doctor's opinion, contraindicated the use of metamizol (aplastic anemia, agranulocytosis of a toxicological etiology, severe renal disease, etc.)
• Patients who have received in the previous 7 days or need currently anticoagulant treatment
• Significant allergy or known hypersensitivity to metamizol, its excipients and/or to other nonsteroidal antiinflammatory drugs
• Patients in whom the anesthetic regimen required by the protocol cannot be used
• Patients who have participated in another clinical trial in the past four weeks or are currently participating in another clinical trial
• Patients with any psychological disturbance which, in the investigator's opinion makes the patient unsuitable for inclusion in the trial