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The Median Effective Dose (ED50) of Paracetamol and Morphine : A Study of Interaction Study

Information source: Procare Riaya Hospital
ClinicalTrials.gov processed this data on August 23, 2015
Link to the current ClinicalTrials.gov record.

Condition(s) targeted: Postoperative Pain

Intervention: Paracetamol (Drug); Morphine (Drug); Paracetamol- Morphine (Drug)

Phase: N/A

Status: Completed

Sponsored by: Procare Riaya Hospital

Official(s) and/or principal investigator(s):
AHED ZEIDAN, MD, Study Chair, Affiliation: Procare Riaya Hospital


The aim of our study is to define the median effective analgesic doses (ED50) of paracetamol, morphine, and their combination and determination the nature of their interaction administered IV for postoperative pain after moderate painful surgery using up-and-down and isobolographic methods.

Clinical Details

Official title: The Median Effective Dose (ED50) of Paracetamol and Morphine for Postoperative Patients: A Study of Interaction.

Study design: Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Investigator, Outcomes Assessor), Primary Purpose: Treatment

Primary outcome: ED50s of Paracetamol, morphine and their combination

Secondary outcome: Paracetamol-Morphine interaction nature

Detailed description: Ninety patients scheduled to undergo moderately painful surgery were included in one of three groups. Determination of median effective (ED50) doses was performed by the Dixon and Mood up-and-down method. Initial doses were 1. 5g and 5mg, with dose adjustment intervals of 0. 5g and 1 mg, in the paracetamol and morphine groups, respectively. The initial doses of paracetamol and morphine were 1. 5g and 3mg, respectively in the paracetamol-morphine combination group with dose adjustment intervals of 0. 25g for paracetamol and 0. 5mg for morphine. Analgesic efficacy was defined as a decrease to less than 3 on a 0-10 numeric pain scale, 45 min after the beginning of drug administration. Isobolographic analysis was used to define the nature of their interaction.


Minimum age: 18 Years. Maximum age: N/A. Gender(s): Both.


Inclusion Criteria: 1. ASA physical status І or ІІ 2. Moderately painful surgery patients

3. postoperative pain more than 3 on a numerical pain score (NPS) -

Exclusion Criteria: 1. contraindication to the use of paracetamol and morphine 2. Pregnancy 3. age younger than 18 yr 4. patient weight less 65kg 5. intra-operative regional anesthesia, 6. intra-operative administration of analgesics other than fentanyl, 7. postoperative pain less than 3 on a numerical pain score (NPS)

Locations and Contacts

Procare Riaya Hospital, Al Khobar, Estern 31952, Saudi Arabia
Additional Information

Starting date: September 2007
Last updated: December 7, 2012

Page last updated: August 23, 2015

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