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Trial registered on ANZCTR

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

Titles & IDs
Public title
Effects of inhaled methoxyflurane (Penthrox) on psychomotor function in humans: a randomized placebo trial
Scientific title
For healthy volunteers and subjects who undergo colonoscopy, will using Penthrox as a modality of analgesia have little or no effect on psychomotor function because of its minimal sedative effect.
Secondary ID [1] 282656 0
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Psychomotor function in humans who inhale methoxyflurane (Penthrox) as a mode of analgesia 289357 0
Condition category
Condition code
Neurological 289693 289693 0 0
Studies of the normal brain and nervous system
Anaesthesiology 289740 289740 0 0
Pain management

Study type
Description of intervention(s) / exposure
Name: Methoxyflurance Inhalation Analgesic
Dose: 1 x 3mL bottle of Penthrox (methoxyflurane) ,
vaporised in and then inhaled through a Penthrox Inhaler.
For colonoscopy patients, a nurse will teach and instruct patients to take several inhalations initially before the commencement of the procedure. Depending on the amount of pain experienced during the procedure, they are allowed to take further inhalations as required. Furthermore, if the colonoscopist is able to anticipate discomfort due to a difficult section of the bowel, they will ask the patient to take a few more inhalations to cover for potential discomfort or pain. All inhalations will be from one Penthrox bottle.
For Healthy patients, methroxyflurane is inhaled continuously through one Penthrox Bottle for a duration of 20 min before psychomotor testing
Intervention code [1] 287322 0
Treatment: Drugs
Comparator / control treatment
All colonoscopy patients will recieve Penthrox. The Healthy volunteers psychomotor function will be evaluated on 2 occasions, after inhalation of Penthrox or placebo, separate by at least 1-week duration. The order of the study will be randomized. On the occasion where placebo is to be given, 3ml of normal saline will be poured into the green portable inhaler and thus, only air will be inhaled.
Control group

Primary outcome [1] 289786 0
Differences in psychomotor functions between inhaled Penthrox and placebo in healthy as assessed by a battery of psychomotor tests.
These psychomotor tests have all been previously validates and include tests such as:
The Digit Symbol Substitution Test (DSST), which assesses a number of different functions, including visual scanning, mental flexibility, logic reasoning, sustained attention, psychomotor speed, and speed of information processing (Lezak, 1995; Wetherell, 1996; Van Hoof et al., 1998), was a 1-min paper-and-pencil test that required the subject to replace digits with corresponding symbols according to a digit-symbol code listed on the top of the paper (Wechsler, 1958). The dependent measures were total number of symbols drawn and number of symbols drawn correctly. This test is done at 30-min intervals.

The computerized logical reasoning test (LRT) consisting of true-false statements about the juxtaposition of the two letters A and B (e.g., A is preceded by B--true or false). The dependent measures were the total number of statements answered and number of statements answered correctly. The 1-min test assessed higher mental processes such as reasoning, logic, and verbal ability (Baddeley, 1968).
The locally developed recall memory test measures short- and long-term memory by presenting a sequential list of 15 words on the computer (Zacny et al. 2011). These 15 words were presented in approximately 30 s. The subject was then given 120 s to write down as many words as he or she could remember. Different word lists were used for all sessions.
Timepoint [1] 289786 0
Tests taken at baseline, as well as 30min, 60min, 120min and 180 min after Penthrox Inhalation.
Primary outcome [2] 289787 0
Differences in psychomotor function between pre and post-colonoscopy with inhaled Penthrox as assessed by a battery of psychomotor tests. The psychomotor tests used are the same as for the healthy control above.
Timepoint [2] 289787 0
Tests taken at baseline, and then 30min, 60min, 120min and 180 min after arriving to the recovery.
Secondary outcome [1] 303237 0
Timepoint [1] 303237 0

Key inclusion criteria
Able to give informed consent
Adequate understanding of use of the Penthrox inhaler
Minimum age
18 Years
Maximum age
79 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
History of significant alcohol (>40gms/d for males, 20gms/d for females) or narcotic use.
Previous history of significant cardiac or respiratory illnesses (ie. ischaemic heart disease, chronic obstructive pulmonary disease).
Significantly underweight (<45kg)
Significant smoking history of more than 20 packs / year.
Previous history of gastrointestinal surgery (likely to increase difficulty of colonoscopy)
Renal impairment
Diabetes Mellitus
Previous possible allergy to the medication by the patient or a relative
Hypersensitivity to fluorinated agents
Previous head injury
Difficulty in following instructions (including language barrier)
Patients taking any potential nephrotoxic drugs (e.g. aminoglycosides)
Malignant hyperthermia

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Patients on the list to undergo colonoscopies at the Royal Adelaide Hospital will be contacted and asked if they want to volunteer as a patient. Patients are not randomized. Healthy patients will be recruited via flyers placed around the Royal Adelaide Hospital and will be studied on two occasions. Healthy volunteers will be evaluated in a randomised, placebo-controlled, cross-over manner. Each subject will be studied on 2 occasions with either placebo or Penthrox, separated by at least 1-week duration and the order is randomized. Placebo will be consisted of a 3ml of normal saline, which is poured into the green portable Penthrox as if it is methoxyflurane by a person in pharmacy. As this specifically appointed person in the pharmacy deprtment will be dispensing the liquids into the penthrox inhalers for the researchers, they will assign either the label A or B to the placebo and Penthrox, and give them out as treatment A and B, so that neither the people administering the treatment, those assessing outcomes nor the patients will know if treament A or B is the Penthrox or placebo until after the study on the patients is complete and all outcomes have been assessed, whereupon the identity of the treatments A and B will be revealed by the person who assigned the treatments to their groups. Half of the Healthy volunteers will be assigned to group 1 to have treatment A in their first week, the other half will be assigned to group two to have treatment B in their first week. Allocation is randomized via a computer generated sequence but not concealed as both those assigning people to the groups, administering the treatment and assessing the outcomes are blind to which treatment the patients are getting.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
We will use the computer program Graphpad Prism to generate a random sequence of the numbers to assign the patients to group 1 to receive treatment A first, the rest will be assigned to group 2 to receive treatment B first, then there will be a crossover in the treatments that the groups recieve.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
Intervention assignment
Other design features
The healthy volunteers are evaluated in a randomised, placebo-controlled, cross-over manner. The patients are not randomized and all recieve the Penthrox treatment.
Phase 4
Type of endpoint(s)
Statistical methods / analysis
As there are no previous data on the effects of Penthrox on psychomotor functions in humans, power calculation for sample size determination is not possible. The sample size of 30 subjects in each group is based on previous studies that examined the effects of analgesics or sedation on psychomotor fuctions (Zacny et al. 2011, Galinkin et al. 1997, Janiszewsk et al. 1999).

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment in Australia
Recruitment state(s)
Recruitment hospital [1] 1121 0
The Royal Adelaide Hospital - Adelaide
Recruitment postcode(s) [1] 6958 0
5000 - Adelaide

Funding & Sponsors
Funding source category [1] 287441 0
Commercial sector/Industry
Name [1] 287441 0
Medical Developments International Ltd.
Address [1] 287441 0
Factory 6, 56 Smith Road
Springvale, VIC 3171 Australia
Country [1] 287441 0
Funding source category [2] 287442 0
Name [2] 287442 0
Department of Gastroenterology and Hepatology, Royal Adelaide Hospital
Address [2] 287442 0
Department of Gastroenterology and Hepatology
Royal Adelaide Hospital, North Wing
Q7, Level 7
North Terrace, Adelaide, SA, 5000
Country [2] 287442 0
Primary sponsor type
Department of Gastroenterology and Hepatology, Royal Adelaide Hospital
Department of Gastroenterology and Hepatology
Royal Adelaide Hospital, North Wing
Q7, Level 7
North Terrace, Adelaide, SA, 5000
Secondary sponsor category [1] 286185 0
Commercial sector/Industry
Name [1] 286185 0
Medical Developments International Ltd.
Address [1] 286185 0
Factory 6, 56 Smith Road
Springvale, VIC 3171 Australia
Country [1] 286185 0

Ethics approval
Ethics application status
Ethics committee name [1] 289416 0
Royal Adelaide Hospital Research Ethics Committee
Ethics committee address [1] 289416 0
The Royal Adelaide Hospital Research Ethics Committee

Level 3, Hanson Institute IMVS Building

North Terrace

Adelaide SA 5000

Ethics committee country [1] 289416 0
Date submitted for ethics approval [1] 289416 0
Approval date [1] 289416 0
Ethics approval number [1] 289416 0

Brief summary
An unanswered issue relates to the use of Penthrox in clinical setting is its impact on psychomotor function and the ability to driving or operating complex tasks, as the lack of adverse psychomotor effects from Penthrox may allow patients to drive, and even return to work on the same day of the colonoscopy. Given colonoscopy is increasingly performed for screening and surveillance purposes, the ability to return home or work place without carers would carry significant cost benefit and minimize work disruption. Currently, there are no data on the impact of inhaled Penthrox, or methoxyflurane in general, on the psychomotor function in humans. The aim of this study is, therefore, to evaluate the effects of inhaled Penthrox on psychomotor functions of healthy volunteers as well as subjects who undergo colonoscopy with Penthrox.
Inhaled methoxyflurane has minimal sedative effect and thus, has minimal or no effect of psychomotor function in humans.
Trial website
Trial related presentations / publications
Nam Quoc Nguyen, Jenna Elise Burgess, Leanne Toscano, Tamara Lisa Debreceni
UEGW Abstract October 2015
Public notes

Principal investigator
Name 40682 0
Dr Nam Q Nguyen
Address 40682 0
Department of Gastroenterology & Hepatology,
Q7 Level 7 North Wing
Royal Adelaide Hospital.
North Terrace, Adelaide, SA, 5000
Country 40682 0
Phone 40682 0
+61 422 113 598
Fax 40682 0
+61 8 8222 5885
Email 40682 0
Contact person for public queries
Name 40683 0
Dr Nam Q Nguyen
Address 40683 0
Department of Gastroenterology & Hepatology,
Q7 Level 7 North Wing
Royal Adelaide Hospital.
North Terrace, Adelaide, SA, 5000
Country 40683 0
Phone 40683 0
+61 422 113 598
Fax 40683 0
Email 40683 0
Contact person for scientific queries
Name 40684 0
Dr Nam Q Nguyen
Address 40684 0
Department of Gastroenterology & Hepatology,
Q7 Level 7 North Wing
Royal Adelaide Hospital.
North Terrace, Adelaide, SA, 5000
Country 40684 0
Phone 40684 0
+61 422 113 598
Fax 40684 0
Email 40684 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