A Phase 4 interventional study of 50 mg Diphenhydramine and 10 mg Loratadine in Heat Illness, Allergic Rhinitis and Heat Injury, sponsored by Lakehead University. Recruiting at 1 site in Canada. Open to participants aged 19 Years to 39 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2024-01-22.
Sponsored by Lakehead University · Phase 4, Interventional, and Other
Allergic rhinitis (AR) currently affects \~25% of Canadians, and due to factors of climate change, this number is expected to increase over the coming decade. AR symptoms can significantly impact individuals' quality of life by compromising sleep, productivity, and social interactions. To alleviate AR symptoms, North Americans tend to rely on H1 antihistamine medications available over-the-counter (OTC) at most pharmacies. However, public health authorities currently suggest restraining all antihistamines during heat waves due to beliefs that M3 muscarinic receptor and H1 receptor antagonism, independent pharmacological mechanisms of H1 antihistamines, might suppress thermoregulatory responses to heat stress and increase individuals' susceptibility to heat-related illness/injury. To date, studies using supramaximal doses of antihistamines have demonstrated reductions in sweating, however these doses and administration routes are not the typical use case. Additional studies utilizing fexofenadine, a second-generation H1 antihistamine, have linked H1 receptor antagonism to reductions in skin blood flow, potentially impacting thermoregulation by reducing peripheral blood redistribution. Empirical evidence supporting OTC H1 antihistamines impacting thermoregulatory control at recommended doses is scarce. Thus, this study aims to systematically assess whether three common OTC H1 antihistamines, taken as prescribed, alter thermoregulatory responses during thermal stress.
118 studies on the registry are indexed under Heat Stress Disorders; 45 are open to participants now.
This study's planned enrollment of 16 is below the median of 24 across 104 interventional studies indexed under Heat Stress Disorders.
Browse Heat Stress Disorders studies →Lakehead University is the lead sponsor of 24 studies on the registry; 6 are open to participants now.
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Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Drug: 50 mg Diphenhydramine
Drug: 10 mg Loratadine
Drug: 5 mg Desloratadine
Other: Placebo (Sugar Pill)
Participants ingest 50mg of diphenhydramine orally \~2 hours prior to a passive heating protocol. Participants then don a water-perfusion heat suited and lay supine on assessment table while 49℃ is circulated throughout the garment. Heating persists until participants reach a 1.5℃ increase in core temperature from baseline.
Also known as: Benadryl®
Participants ingest 10 mg of loratadine orally \~2 hours prior to a passive heating protocol. Participants then don a water-perfusion heat suited and lay supine on assessment table while 49℃ is circulated throughout the garment. Heating persists until participants reach a 1.5℃ increase in core temperature from baseline.
Also known as: Claritin®
Participants ingest 5 mg of desloratadine orally \~2 hours prior to a passive heating protocol. Participants then don a water-perfusion heat suited and lay supine on assessment table while 49℃ is circulated throughout the garment. Heating persists until participants reach a 1.5℃ increase in core temperature from baseline.
Also known as: Aerius®
Participants ingest placebo pill orally \~2 hours prior to a passive heating protocol. Participants then don a water-perfusion heat suited and lay supine on assessment table while 49℃ is circulated throughout the garment. Heating persists until participants reach a 1.5℃ increase in core temperature from baseline.
Whole-Body Sweat Losses
Difference in participants' pre/post body mass
Time frame: For each study arm (all completed within 4 months), measurements taken immediately before heating protocol & immediately following the heating protocol
Skin Blood Flow
Measured using laser-doppler skin blood blow sensor affixed to forearm
Time frame: For each study arm (all completed within 4 months), measured before heating, and at every 0.25C increase in core temperature (+0.25C, +0.50C, +0.75C, +1.0C, +1.25C, and +1.5C), or every ~15 minutes of (up to ~90 minutes) and immediately after heating
Heart Rate
Measured using electrocardiogram
Time frame: For each study arm (all completed within 4 months), measured before heating, and at every 0.25C increase in core temperature (+0.25C, +0.50C, +0.75C, +1.0C, +1.25C, and +1.5C), or every ~15 minutes of (up to ~90 minutes) and immediately after heating
Mean Arterial Pressure
Measured using brachial blood pressure cuff
Time frame: For each study arm (all completed within 4 months), measurements taken at baseline before heating, and every 10 minutes throughout heating protocol (up to ~ 90 minutes), and immediately after heating
Local Sweat Rate
Measured using ventilated sweat capsules affixed to forearm and chest
Time frame: For each study arm (all completed within 4 months), measured before heating, and at every 0.25C increase in core temperature (+0.25C, +0.50C, +0.75C, +1.0C, +1.25C, and +1.5C), or every ~15 minutes of (up to ~90 minutes) and immediately after heating
Thermal Sensation
Self-assessments of thermal sensation using a 7-point analog scale where -3 is "Cold" and +3 is "Hot".
Time frame: For each study arm (all completed within 4 months), measured before heating, and at every 0.25C increase in core temperature (+0.25C, +0.50C, +0.75C, +1.0C, +1.25C, and +1.5C), or every ~15 minutes of (up to ~90 minutes) and immediately after heating
Thermal Comfort
Self-assessments of thermal comfort using four-point analog scale where 1 is "Not uncomfortable" and 4 is "Very uncomfortable"
Time frame: For each study arm (all completed within 4 months), measured before heating, and at every 0.25C increase in core temperature (+0.25C, +0.50C, +0.75C, +1.0C, +1.25C, and +1.5C), or every ~15 minutes of (up to ~90 minutes) and immediately after heating
Mental Acuity
Indexed with digital Stroop test
Time frame: For each study arm (all completed within 4 months), measurements taken 2 hours before heating (pre-pill ingestion), 5-minutes before initiating heating, and within 5-minutes after the heating protocol
Sleepiness/Fatigue level
Measured using Stanford Sleepiness Scale (min: 1, max: 7 (more fatigued))
Time frame: For each study arm (all completed within 4 months), measurements taken 2 hours before heating (pre-pill ingestion), 5-minutes before initiating heating, and within 5-minutes after the heating protocol
Started Dec 2023 (actual). Primary completion is estimated for Jun 2024, 6 months after the start.
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Studies of the drugs tested here: Diphenhydramine · Loratadine · Desloratadine
Lakehead University