Diphenhydramine and Sweating

Study Overview
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Brief Summary
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In 2012, it was estimated that nearly 1 in 4 Canadians suffer from allergic rhinitis. To add, 78% of individuals working in predisposing environments are predicted to develop occupational rhinitis. Currently, the most popular treatment for rhinitis is antihistamine medication such as diphenhydramine, a first-generation antihistamine sold commercially as Benadryl®. Due it its anticholinergic effects, diphenhydramine has been suggested to impair the whole body sweating response during heat stress, potentially leaving consumers at an increased risk of heat-related illness. This randomized control trial approved by Health Canada will investigate whether ingesting extra strength diphenhydramine (50mg) will alter whole-body sweat losses during 60 minutes of exercise.

Official Title
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Does Diphenhydramine Alter Thermoregulatory Responses During Exercise?

Conditions
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Diphenhydramine Causing Adverse Effects in Therapeutic Use, Hyperthermia, Allergic Rhinitis, Sweating

Intervention / Treatment
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* Drug: Placebo
* Drug: Diphenhydramine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Able to safely perform  60 minutes of moderate intensity exercise No known hypersensitivity to diphenhydramine Not on any prescribed medication Body-mass index (BMI) less than 30 Exclusion Criteria: Outside 18 - 49 years of age Diagnosed with any cardiovascular, respiratory, neurological or metabolic disease History of any cardiovascular, respiratory, neurological or metabolic disease Unable to exercise for 60 minutes at moderate intensity, or have a musculoskeletal injury BMI > or = 30

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 49 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Intervention Order (Placebo - Diphenhydramine)<br>On separate days, participants will march on a treadmill for 60 minutes at a fixed rate of oxygen consumption ( 1.75 liters of oxygen consumption per minute) in  28°C and 30% relative humidity | Drug: Placebo<br>* A placebo pill (i.e., sugar) will be consumed 2 h before intervention.<br>Drug: Diphenhydramine<br>* Extra strength Benadryl (DIN 02470144) will be consumed 2 h before intervention<br>|
| Other: Intervention Order (Diphenhydramine -Placebo)<br>On separate days, participants will march on a treadmill for 60 minutes at a fixed rate of oxygen consumption ( 1.75 liters of oxygen consumption per minute) in  28°C and 30% relative humidity | Drug: Placebo<br>* A placebo pill (i.e., sugar) will be consumed 2 h before intervention.<br>Drug: Diphenhydramine<br>* Extra strength Benadryl (DIN 02470144) will be consumed 2 h before intervention<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Whole body sweat loss | Change in body mass from pre- to post-exercise corrected for respiratory and metabolic water losses using a digital platform scale accurate to +/- 2 grams. | Measured during both placebo and diphenhydramine intervention trials trials, separated by no more than 28 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in rectal temperature | Change in rectal temperature from pre- to post- exercise using a pediatric grade thermistor | Measured during both placebo and diphenhydramine intervention trials trials, separated by no more than 28 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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thermoregulation, diphenhydramine, anticholinergic, sweating