Acute abdominal pain is a frequent symptom in children admitted to the emergency department . In the past the fear of masking a surgical condition has justified withholding analgesia in patients with acute abdominal pain. By the 2000s, some clinical trials established that opioid analgesia before surgical consultation does not affect diagnostic accuracy or outcome in children with acute abdominal pain. Despite this, acute abdominal pain is still undertreated in this setting. Published paediatric trials studied the effect of opioid analgesia administered by parenteral route or by mouth. To the best of our knowledge no study investigated the effectiveness of sublingual analgesia.

The purpose of this randomized controlled trial is to assess the effectiveness of three different drugs (ketorolac, tramadol, paracetamol), administered by the sublingual route, in children complaining of acute abdominal pain.

Inclusion Criteria:

• Age 4 to 18 years
• Emergency department admission for moderate to severe acute abdominal pain (VAS/NRS score >=6)
• Informed consent signed by parents or legal guardians

Exclusion Criteria:

• Known allergy or sensitivity to nonsteroidal anti-inflammatory drug, opioids or acetaminophen
• Use of analgesic drugs in the 8 hours before
• Clinical suspicion of abdominal pain due to fecal stasis
• Moderate or severe dehydration (weight loss of more than 5%)
• Known nephropathy, liver disease, metabolic or neurologic disease
• Thrombocytopenia or history of bleeding disease