Tobacco SmokingNCT06191419
Human Perception of Odors and Odor Blockers
A study testing Odorants in people with Tobacco Smoking and Smoking Behaviors, run by Tim McClintock at 1 site in United States.
Trial summary
The goal of this clinical trial is to determine whether blockers of perception of key odorants in cigarette smoke have any utility in smoking cessation. The main question it aims to answer is: Can odor blockers be used to suppress perception of the intensity of cigarette smoke in ways that reduce the ability of the… Read more about this study
- Who is it for?
- Ages 18 to 60 yearsHealthy volunteers can take part
- Conditions the study is for
- Tobacco Smoking, Smoking Behaviors
- What is being tested?
- Odorants
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 27 participants
- Where
- 1 siteUnited States
- Study dates
- 5 Apr 2024to 15 May 2025
- Phase
- Interventional
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 60 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Smoker
Who cannot join
- Non Smoker
- Self reported inability to smell or taste
Trial locations and contacts
1 site in 1 country.
About this study
The goal of this clinical trial is to determine whether blockers of perception of key odorants in cigarette smoke have any utility in smoking cessation. The main question it aims to answer is:
- Can odor blockers be used to suppress perception of the intensity of cigarette smoke in ways that reduce the ability of the odor of cigarette smoke to increase the urge to smoke.
Participants will be asked to smell up to 20 odor samples per session and report on odor pleasantness and desire to smoke.
Read the detailed description
The experimental treatments include controls (clean air, irrelevant odor), blocking odors, cigarette smoke odor, and cigarette smoke odor mixed with blocking odors or irrelevant odor. To obtain cigarette smoke odor a 1 inch length of a 1R6F research cigarette is burned to completion in a sealed 5 gallon chamber fitted with septa. Using a syringe fit with a needle and filter, 60 mL aliquots of smoke odor are obtained. These smoke odor aliquots, along with blocking odors, are injected into odor sample bags fit with a septum and a valve that can be attached to the CPAP nose mask worn by each participating smoker. Participants open the valve, inhale once through the nose, close the valve, and then remove the bag from the mask before reporting odor pleasantness and the desire to smoke. A 4 min wait period is enforced between each odor presentation to prevent odor adaptation and to allow acute motivational effects to subside. During these intervals, a nature documentary was available for viewing. Two measures of the desire to smoke are made. An objective method uses a validated relative reinforcing measure, requiring participants to record how many cigarettes they would purchase at each step along a logarithmically increasing price scale that ranges from $0 to $1,120 per cigarette. The breakpoint on this scale at which a participant is no longer willing to pay is the measure of the urge to smoke. As a subjective measure, participants report their urge to smoke as a value between 0 and 100. Participants also provide a forced choice measure of odor pleasantness, indicating either pleasant or unpleasant for each odor.
In a testing session a participant sniffs a mixture of blocking odors mixed with cigarette smoke, along with control odor samples. Presentation order is randomized. Each participant is assigned their own CPAP nose mask, and masks are disinfected after use. Participants also provide demographic (age, sex, ethnic and racial background) and smoking history information (cigarettes per day, preferred brand, age at onset, and time since last cigarette).
- Conditions
- Tobacco Smoking, Smoking Behaviors
- Being tested
- Odorants
- Keywords
- Odors, Sensory perception, Nicotine addiction, Motivation
- Medical subject headings
- Tobacco Smoking, Smoking, Tobacco Use Disorder
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
OdorantsOther
Each smoker is assigned a CPAP nose mask. Odor sample bags are attached to the mask. Smokers open the valve, inhale once through the nose, close the valve, remove the bag from the mask and report on the odor.
| Study group | Role | What they receive |
|---|---|---|
| Participants that Smoke | Experimental | Each smoker is asked to smell up to 20 samples per session. Samples include controls (clean air, irrelevant odor), blocking odors, cigarette smoke, and cigarette smoke mixed with blocking odors or irrelevant odors. Receives: Other: Odorants |
What is being measured
The primary outcome is the main question the study is designed to answer.
Cigarette Purchase Task
The Cigarette Purchase Task (Strickland et al., 2016) requires selecting how much the smoker is willing to spend for a single cigarette (their preferred brand) from a list of 19 amounts ranging from $0.00 (free) to $1,120. The measure from the selections is the breakpoint where the participants are no longer willing to purchase. These data are skewed and are log transformed (after adding 0.01) for statistical analysis.
Measured: 3 hours (total for all outcome measures)
Desire to Smoke
A rating of participant's desire to smoke on a scale of 0 - 100, where a higher score indicates increased desire.
Measured: 3 hours (total for all outcome measures)
Secondary outcomes (1)
Odor Pleasantness Score
Participants complete a forced-choice test by rating whether the odor is pleasant or unpleasant. Responses were recorded as a binary measure where 0=unpleasant and 1=pleasant. Scores range from 0 to 1, with higher score indicate greater odor pleasantness.
Measured: 3 hours (total for all outcome measures)
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Jan 2024
- Study start5 Apr 2024
- Primary completion15 May 2025
- Study completion15 May 2025
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Tobacco SmokingStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Model description
- Each subject experiences and reports on all of the odor blocker and control treatments.
- Masking
- None (open label)
- Enrolment
- 27 participants (actual)
Sponsor and investigators
- Lead sponsor
- Tim McClintock
- Sponsor type
- University, hospital or other
- Collaborators
- National Institute on Deafness and Other Communication Disorders (NIDCD)
- Responsible party
- Sponsor-investigator, Tim McClintock, University of Kentucky
- Investigators
- Timothy McClintock, PhD, Principal investigator, University of Kentucky
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06191419
- Sponsor's protocol ID
- 43123
- Other IDs
- 1K18DC020155
- Status last verified
- Jun 2026
- First submitted
- 20 Dec 2023
- Last updated
- 23 Jul 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 23 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Human Perception of Odors and Odor Blockers
- ClinicalTrials.gov ID
- NCT06191419
- Acronym / sponsor ID
- 43123
- Conditions
- Tobacco Smoking, Smoking Behaviors
- Keywords
- Odors, Sensory perception, Nicotine addiction, Motivation
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 27 participants (actual)
- Lead sponsor
- Tim McClintockUniversity, hospital or other
- Collaborators
- National Institute on Deafness and Other Communication Disorders (NIDCD)
- Study start
- 5 Apr 2024 (actual)
- Primary completion
- 15 May 2025 (actual)
- Study completion
- 15 May 2025 (actual)
- First posted
- 5 Jan 2024 (actual)
- Results
- Posted 8 Jul 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to determine whether blockers of perception of key odorants in cigarette smoke have any utility in smoking cessation. The main question it aims to answer is:
- Can odor blockers be used to suppress perception of the intensity of cigarette smoke in ways that reduce the ability of the odor of cigarette smoke to increase the urge to smoke.
Participants will be asked to smell up to 20 odor samples per session and report on odor pleasantness and desire to smoke.
Detailed description
The experimental treatments include controls (clean air, irrelevant odor), blocking odors, cigarette smoke odor, and cigarette smoke odor mixed with blocking odors or irrelevant odor. To obtain cigarette smoke odor a 1 inch length of a 1R6F research cigarette is burned to completion in a sealed 5 gallon chamber fitted with septa. Using a syringe fit with a needle and filter, 60 mL aliquots of smoke odor are obtained. These smoke odor aliquots, along with blocking odors, are injected into odor sample bags fit with a septum and a valve that can be attached to the CPAP nose mask worn by each participating smoker. Participants open the valve, inhale once through the nose, close the valve, and then remove the bag from the mask before reporting odor pleasantness and the desire to smoke. A 4 min wait period is enforced between each odor presentation to prevent odor adaptation and to allow acute motivational effects to subside. During these intervals, a nature documentary was available for viewing. Two measures of the desire to smoke are made. An objective method uses a validated relative reinforcing measure, requiring participants to record how many cigarettes they would purchase at each step along a logarithmically increasing price scale that ranges from $0 to $1,120 per cigarette. The breakpoint on this scale at which a participant is no longer willing to pay is the measure of the urge to smoke. As a subjective measure, participants report their urge to smoke as a value between 0 and 100. Participants also provide a forced choice measure of odor pleasantness, indicating either pleasant or unpleasant for each odor.
In a testing session a participant sniffs a mixture of blocking odors mixed with cigarette smoke, along with control odor samples. Presentation order is randomized. Each participant is assigned their own CPAP nose mask, and masks are disinfected after use. Participants also provide demographic (age, sex, ethnic and racial background) and smoking history information (cigarettes per day, preferred brand, age at onset, and time since last cigarette).
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
- Model description
- Each subject experiences and reports on all of the odor blocker and control treatments.
| Arm | Type | Receives |
|---|---|---|
| Participants that Smoke | Experimental | Other: OdorantsEach smoker is asked to smell up to 20 samples per session. Samples include controls (clean air, irrelevant odor), blocking odors, cigarette smoke, and cigarette smoke mixed with blocking odors or irrelevant odors. |
Who may qualify
- Ages
- 18 to 60 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (1 listed)
- Smoker
Key exclusion criteria (2 listed)
- Non Smoker
- Self reported inability to smell or taste
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| OdorantsEach smoker is assigned a CPAP nose mask. Odor sample bags are attached to the mask. Smokers open the valve, inhale once through the nose, close the valve, remove the bag from the mask and report on the odor. | Other | Participants that Smoke |
Primary outcome
Cigarette Purchase Task
Time frame: 3 hours (total for all outcome measures)
The Cigarette Purchase Task (Strickland et al., 2016) requires selecting how much the smoker is willing to spend for a single cigarette (their preferred brand) from a list of 19 amounts ranging from $0.00 (free) to $1,120. The measure from the selections is the breakpoint where the participants are no longer willing to purchase. These data are skewed and are log transformed (after adding 0.01) for statistical analysis.
Desire to Smoke
Time frame: 3 hours (total for all outcome measures)
A rating of participant's desire to smoke on a scale of 0 - 100, where a higher score indicates increased desire.
1 secondary outcome
Odor Pleasantness Score
Time frame: 3 hours (total for all outcome measures)
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 23 Jul 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Timothy McClintock, PhD principal investigator
University of Kentucky
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Odorants in people with Tobacco Smoking and Smoking Behaviors, run by Tim McClintock at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 1 inclusion and 2 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 23 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
Yes. Results are posted in the registry (first posted 8 Jul 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Cigarette Purchase Task (time frame: 3 hours (total for all outcome measures)). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 23 Jul 2026.