Abdominal pain is one of the most common presentations to an emergency department (ED). Among patients presenting with abdominal pain, a common diagnosis in the Middle East is renal colic (urolithiasis or Kidney stones). As the patients with renal colic writhe around in agonizing pain, the first priority in an ED from a patient's perspective is fast and safe analgesia and to be pain free as early as possible. There are variations in physician preference to choose initial analgesic drug for managing such pain. Commonly used drugs are:

• Opioids such as Morphine or Fentanyl
• Non steroidal drugs such as Diclofenac, Ketorolac or Brufen
• and Paracetamol intravenous injection.

A robust evidence in comparison of diclofenac versus morphine and paracetamol is lacking. This study is design to obtain data on efficacy of these three drugs within 30 minutes in a non inferiority trail.

This will be a double blind RCT, where participants will be enrolled consecutively after meeting eligibility criteria and obtaining a written informed consent. They will be assign to one of the three study arms by computer generated randomization process. The study packets will be prepared by a dedicated nurse or pharmacist who will not a part of investigating team. Each Patients will receive one analgesic drug (active drug) and two placebos. Drugs will be given as one intramuscular injection and two intravenous solutions.

Pain score will be recorded using NRS at 0, 30, 60, and 90 minutes. Data will be collected on standard Data collection form. Each participant will receive analgesia from study packet which contains, one active drug and two placebos to be administer as one intramuscular and two intravenous solutions. At any given time every patient will receive one analgesia from either Diclofenac, Paracetamol or Morphine. If patient pain does not respond to initial treatments, at 30 minutes a rescue analgesia in form of morphine will be administered till patient is pain free or NRS<=2 or adverse event to morphine.

Based on the results of previous studies (1-3), proportion of patients achieving more than 50% pain reduction, is between 65-75% for diclofenac, morphine and paracetamol when compared with other drugs. In each group, 437 patients are required to detect a difference of 10% in primary outcome, in a superiority trial with power (1-beta) of 90% and significance level (alpha) of 5% in this study. Considering 15% extra, total sample size required in this superiority trial will be 1507 patients in total.

Data will be collected on a standard data recording form and it will be converted to electronic excel sheet hiding patient identifiable details. Continuous variables will be presented as mean with standard deviation (SD). Categorical variables will be calculated as proportions and presented with 95% Confidence interval (CI). Statistical analyses will be undertaken using Stata 12.0 (College Station, Texas).

Inclusion Criteria:

• Age >=18 years and < 65 years
• Acute onset, one side flank or loin pain, with or without radiation to groin or genital areas.
• Pain intensity on NRS more than or equal to 4. (Moderate to Severe Pain)
• Diagnosis confirmed by non contrast CT KUB within the ED visit.

Exclusion Criteria:

• Traumatic flank pain
• Pregnancy
• Known renal failure or impairment
• Known allergy to morphine, diclofenac or paracetamol
• Bronchial asthma
• Previously enrolled in the study.
• Use of any analgesia in last 6 hour.