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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Retrospectively registered

Titles & IDs
Public title
Comparison of two different doses of paracetamol for post-operative pain relief
Scientific title
Comparison of two different doses of paracetamol for post-operative pain relief
Secondary ID [1] 144 0
Comparison of two different doses of paracetamol for post-operative pain relief
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Fit ASA 1-2 adult patients 435 0
Condition category
Condition code
Alternative and Complementary Medicine 507 507 0 0
Spiritual care

Study type
Description of intervention(s) / exposure
Cross over trail with 60 mg/kg or 90 mg/kg of paracetamol.
Intervention code [1] 370 0
Treatment: Drugs
Comparator / control treatment
Control group
Dose comparison

Primary outcome [1] 578 0
Pain relief
Timepoint [1] 578 0
Secondary outcome [1] 1233 0
Blood levels (pharmacokinetics)
Timepoint [1] 1233 0
Secondary outcome [2] 1234 0
Metabolism of paracetamol
Timepoint [2] 1234 0

Key inclusion criteria
(ASA 1-2) with bilaterally impacted 3rd molar teeth are included.
Minimum age
18 Years
Maximum age
Not stated
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Pregnant patients, patients with liver disease, children.

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Drugs were available in sealed brown paper bags (with patient's number, name and weight written on it), which were opened immediately prior to operation on the first side. Each bag contained 2 bottles labelled with the name of patient, weight of the patients and operation sequence (first operation side or second operation side). Each bottle contained same number of indistinguishable capsules. Randomisation, allocation concealment and blinding were done by the pharmacy which made up the sealed brown paper bags with name of patient written on its outside, to be collected by one of the researchers the day before the trial on a patient. Investigators and patients were blinded to the treatment allocation.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Randomised in blocks using random number generator in Excel.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Placebo capsules along with active capsules (indistingushable)
Phase 4
Type of endpoint(s)
Pharmacokinetics / pharmacodynamics
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 170 0
New Zealand
State/province [1] 170 0

Funding & Sponsors
Funding source category [1] 569 0
Other Collaborative groups
Name [1] 569 0
Australina & New Zealand College of Anaesthetists
Address [1] 569 0
Country [1] 569 0
Primary sponsor type
Other Collaborative groups
Secondary sponsor category [1] 461 0
Name [1] 461 0
Dept of Anaesthesia, Dunedin Hospital
Address [1] 461 0
Country [1] 461 0
New Zealand

Ethics approval
Ethics application status
Ethics committee name [1] 1592 0
Otago Ethics Committee (Lower South Island Ethics Committee)
Ethics committee address [1] 1592 0
Ethics committee country [1] 1592 0
New Zealand
Date submitted for ethics approval [1] 1592 0
Approval date [1] 1592 0
Ethics approval number [1] 1592 0

Brief summary
Paracetamol is commonly used to reduce pain after operations. Recently anaesthetists have been using bigger doses of paracetamol because it has been suggested that bigger doses will work better. However these bigger doses have never been assessed scientifically in adult patients to see if they work better, and it has not been determined at which dose the maximum effect in reducing pain occurs. We will investigate whether a 90 mg per kg body weight dose works better than a 60 mg per kilogram dose, in reducing pain after wisdom tooth extraction. We will also examine the pharmacokinetics (the way the body removes the drug) of paracetamol, and whether paracetamol changes the way blood clots at these doses. We will also examine whether these doses are safe, by monitoring liver enzymes, and making sure the blood level of paracetamol is not greater than that previously recognised to cause liver disease. The patients will be healthy volunteers scheduled to have wisdom tooth extraction. They will have blood taken at intervals for four hours after having the paracetamol. They will fill in pain scores at the same times they have blood taken.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 36377 0
Address 36377 0
Country 36377 0
Phone 36377 0
Fax 36377 0
Email 36377 0
Contact person for public queries
Name 9559 0
Dr Mathew Zacharias
Address 9559 0
Department of Anaesthesia and Intensive Care
Dunedin Hosptial
Dunedin Otago 913
Country 9559 0
New Zealand
Phone 9559 0
+64 3 4740999
Fax 9559 0
+64 3 4747650
Email 9559 0
Contact person for scientific queries
Name 487 0
Dr Mathew Zacharias
Address 487 0
Department of Anaesthesia and Intensive Care
Dunedin Hosptial
Dunedin Otago 913
Country 487 0
New Zealand
Phone 487 0
+64 3 4740999
Fax 487 0
+64 3 4747650
Email 487 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary