PruritusPhase 1/2NCT03997851
Topical Acetaminophen for Itch Relief: a Proof of Concept Study in Healthy Subjects
A Phase 1/2 study testing Acetaminophen and Carbomer 980 in people with Pruritus, run by University of Miami at 1 site in United States.
Trial summary
Currently, topical antihistamines and corticosteroids are mainly used for itching relief. However, the over the counter antihistamines are not effective on all itch conditions. Acetaminophen is a popular and widely used OTC drug for pain relief. Read more about this study
- Who is it for?
- Ages 18 to 50 yearsHealthy volunteers can take part
- Conditions the study is for
- Pruritus
- What is being tested?
- Acetaminophen and Carbomer 980
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 17 participants
- Where
- 1 siteUnited States
- Study dates
- 22 Jul 2019to 18 Mar 2020
- Phase
- Phase 1/2
- 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 50 years
- All sexes
- Healthy volunteers accepted
- Adult
Who may be able to join
- Healthy subjects must be between 18 and 50 years of age.
- Must be in general good health with no disease or physical conditions that would impair evaluation of itch and pain perception.
- No history of chronic itch or pain.
- Must abstain from the use of any systemic or topical anti-histamine, steroid, or pain relief medications from the week prior to the study till the completion of the study.
- Must abstain from the use of moisturizers on the arms 24 hours before study visits.
Who cannot join
- Individuals under 18 or over 50 years of age.
- Inability to complete the required measures.
- The presence of an itchy skin disease.
- Diagnosis of diseased that would affect itch or pain perception (e.g. neuropathies).
- Currently enrolled in any investigational study in which the subject is receiving any type of drug, biological, or non-drug therapy.
- Use of oral, topical analgesics, or other medications known to interfere with itch or pain perception in the week prior to the study and throughout the study (e.g. antihistamines, anesthetics, opioids, neuroleptics, etc.).
Show all 10Show fewer
- Use of emollients on the arms a week prior to the study and throughout the study.
- Known allergies to acetaminophen and cowhage.
- Pregnant women. (Women of child bearing potential will undergo an hCG pregnancy test).
- Currently incarcerated.
Trial locations and contacts
1 site in 1 country.
About this study
Currently, topical antihistamines and corticosteroids are mainly used for itching relief. However, the over the counter antihistamines are not effective on all itch conditions. Acetaminophen is a popular and widely used OTC drug for pain relief. Although its mode of action is still unknown, recent studies have shown that acetaminophen indirectly activates cannabinoid CB1 receptors. Recent studies have shown that topical cannabinoid agonists are effective for itch relief, the efficacy of topical acetaminophen will be tested for non-histaminergic itch relief.
Read the detailed description
This will be a single-blinded, vehicle-controlled randomized study in healthy controls to test the efficacy of the topical gel formulation with three differing concentrations of acetaminophen (APAP) for itch relief. To detect medium effects of the treatments with a given α of 0.5 and an error probability of 0.05, with a power of 0.95, the number of participants needed is 36 (10 within post hoc pairwise comparisons).
- Conditions
- Pruritus
- Being tested
- Acetaminophen, Carbomer 980
- Medical subject headings
- Pruritus
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
AcetaminophenDrug
Also called Topical acetaminophen gel
Topical acetaminophen gel
Carbomer 980Drug
Also called Topical vehicle gel
Topical vehicle gel
| Study group | Role | What they receive |
|---|---|---|
| Topical 5% acetaminophen gel | Experimental | Topical 5% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. Receives: Drug: Acetaminophen |
| Topical 2.5% acetaminophen gel | Experimental | Topical 2.5% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. Receives: Drug: Acetaminophen |
| Topical 1% acetaminophen gel | Experimental | Topical 1% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. Receives: Drug: Acetaminophen |
| Topical vehicle gel | Placebo comparator | Topical vehile gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. Receives: Drug: Carbomer 980 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Peak Itch Intensity Between the Vehicle and Active Treatments During Non-histaminergic Itch Induction
Peak itch intensity between the vehicle and 3 other active treatments (5%, 2.5%, and 1% acetaminophen gels) after non-histaminergic itch induction (cowhage). Itch intensity was measured on a 10cm scale visual analog scale for 10 minutes. 0 was weighted with "no itch" and 10 was weighted with "most itch imaginable".
Measured: 10 minutes
Peak Itch Intensity Between the Vehicle and Active Treatments During Histaminergic Itch Induction
Peak itch intensity between the vehicle and 3 other active treatments (5%, 2.5%, and 1% acetaminophen gels) after histaminergic itch induction. Itch intensity was measured on a 10cm scale visual analog scale for 10 minutes. 0 was weighted with "no itch" and 10 was weighted with "most itch imaginable".
Measured: 10 minutes
Secondary outcomes (1)
Thermal Threshold Detection (Heat Pain)
Standardized quantitative sensory testing is performed to measure heat pain threshold (assesses the threshold at which heat pain sensation is first detected). Measured in Celsius.
Measured: 3 minutes
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted25 Jun 2019
- Study start22 Jul 2019
- Primary completion18 Mar 2020
- Study completion18 Mar 2020
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 PruritusStudies of the same condition, open and under way.
- More trials run by University of MiamiThe sponsor's other registered studies.
- 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 1/2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- The antipruritic effect of 3 topical treatments of varying doses and 1 vehicle treatment will be explored in each subject. One study visit will consist of testing all topical formulations on histaminergic induced itch, and second study visit will test all topical formulations on non-histaminergic induced itch.
- Masking
- Double blind
- Who is masked
- Participant, Investigator
- Enrolment
- 17 participants (actual)
Sponsor and investigators
- Lead sponsor
- University of Miami
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Gil Yosipovitch, University of Miami
- Investigators
- Gil Yosipovitch, MD, Principal investigator, University of Miami
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03997851
- Sponsor's protocol ID
- 20190133
- Status last verified
- Dec 2025
- First submitted
- 24 Jun 2019
- Last updated
- 8 Dec 2025
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 8 Dec 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Topical Acetaminophen for Itch Relief: a Proof of Concept Study in Healthy Subjects
- ClinicalTrials.gov ID
- NCT03997851
- Acronym / sponsor ID
- 20190133
- Conditions
- Pruritus
- Phase
- Phase 1/2
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 17 participants (actual)
- Lead sponsor
- University of MiamiUniversity, hospital or other
- Study start
- 22 Jul 2019 (actual)
- Primary completion
- 18 Mar 2020 (actual)
- Study completion
- 18 Mar 2020 (actual)
- First posted
- 25 Jun 2019 (actual)
- Results
- Posted 19 Apr 2021
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Currently, topical antihistamines and corticosteroids are mainly used for itching relief. However, the over the counter antihistamines are not effective on all itch conditions. Acetaminophen is a popular and widely used OTC drug for pain relief. Although its mode of action is still unknown, recent studies have shown that acetaminophen indirectly activates cannabinoid CB1 receptors. Recent studies have shown that topical cannabinoid agonists are effective for itch relief, the efficacy of topical acetaminophen will be tested for non-histaminergic itch relief.
Detailed description
This will be a single-blinded, vehicle-controlled randomized study in healthy controls to test the efficacy of the topical gel formulation with three differing concentrations of acetaminophen (APAP) for itch relief. To detect medium effects of the treatments with a given α of 0.5 and an error probability of 0.05, with a power of 0.95, the number of participants needed is 36 (10 within post hoc pairwise comparisons).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Double blind (participant, investigator)
- Number of arms
- 4
- Model description
- The antipruritic effect of 3 topical treatments of varying doses and 1 vehicle treatment will be explored in each subject. One study visit will consist of testing all topical formulations on histaminergic induced itch, and second study visit will test all topical formulations on non-histaminergic induced itch.
| Arm | Type | Receives |
|---|---|---|
| Topical 5% acetaminophen gel | Experimental | Drug: AcetaminophenTopical 5% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. |
| Topical 2.5% acetaminophen gel | Experimental | Drug: AcetaminophenTopical 2.5% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. |
| Topical 1% acetaminophen gel | Experimental | Drug: AcetaminophenTopical 1% acetaminophen gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. |
| Topical vehicle gel | Placebo comparator | Drug: Carbomer 980Topical vehile gel will be applied to one 4x4 cm predefined skin area on the ventral forearm during 2 study visits. The gel will be applied to the test area and will be allowed 30 minutes to adsorb. Following this pre-treatment, residual gel will be removed and itch induction/sensory testing will commence, strictly within the pre-treated area. |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (5 listed)
- Healthy subjects must be between 18 and 50 years of age.
- Must be in general good health with no disease or physical conditions that would impair evaluation of itch and pain perception.
- No history of chronic itch or pain.
- Must abstain from the use of any systemic or topical anti-histamine, steroid, or pain relief medications from the week prior to the study till the completion of the study.
- Must abstain from the use of moisturizers on the arms 24 hours before study visits.
Key exclusion criteria (10 listed)
- Individuals under 18 or over 50 years of age.
- Inability to complete the required measures.
- The presence of an itchy skin disease.
- Diagnosis of diseased that would affect itch or pain perception (e.g. neuropathies).
- Currently enrolled in any investigational study in which the subject is receiving any type of drug, biological, or non-drug therapy.
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 |
|---|---|---|
| AcetaminophenAlso: Topical acetaminophen gelTopical acetaminophen gel | Drug | Topical 1% acetaminophen gel, Topical 2.5% acetaminophen gel, Topical 5% acetaminophen gel |
| Carbomer 980Also: Topical vehicle gelTopical vehicle gel | Drug | Topical vehicle gel |
Primary outcome
Peak Itch Intensity Between the Vehicle and Active Treatments During Non-histaminergic Itch Induction
Time frame: 10 minutes
Peak itch intensity between the vehicle and 3 other active treatments (5%, 2.5%, and 1% acetaminophen gels) after non-histaminergic itch induction (cowhage). Itch intensity was measured on a 10cm scale visual analog scale for 10 minutes. 0 was weighted with "no itch" and 10 was weighted with "most itch imaginable".
Peak Itch Intensity Between the Vehicle and Active Treatments During Histaminergic Itch Induction
Time frame: 10 minutes
Peak itch intensity between the vehicle and 3 other active treatments (5%, 2.5%, and 1% acetaminophen gels) after histaminergic itch induction. Itch intensity was measured on a 10cm scale visual analog scale for 10 minutes. 0 was weighted with "no itch" and 10 was weighted with "most itch imaginable".
1 secondary outcome
Thermal Threshold Detection (Heat Pain)
Time frame: 3 minutes
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 8 Dec 2025.
- 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.
Gil Yosipovitch, MD principal investigator
University of Miami
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1/2 study testing Acetaminophen and Carbomer 980 in people with Pruritus, run by University of Miami 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 5 inclusion and 10 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 8 Dec 2025. 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. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this combined phase mean?
Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 19 Apr 2021). 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?
Peak Itch Intensity Between the Vehicle and Active Treatments During Non-histaminergic Itch Induction (time frame: 10 minutes). 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 8 Dec 2025.