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how long does it take for benadryl to take effect

A female asked:
Dr. Charles Cattano
38 years experience Gastroenterology
Some variables here: IV is faster than oral, but what dose and for what indication (sleep, rash, allergy, etc.) are you questioning please.

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A 49-year-old member asked:
Dr. Andrew Oswari
23 years experience Family Medicine
Half life is 8 hours: Its effectiveness only lasts 6-8 hours usually. It's half life is 8 hours, so it may take up to 72 hours to leave your system completely.
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A 45-year-old member asked:
Dr. Tammi Schlichtemeier
30 years experience Pediatrics
About 45 minutes: Benadryl (diphenhydramine) can make some people drowsy. The maximum effect occurs in about 45 minutes or so. However, it can result in hyperalertnes ... Read More
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A 53-year-old member asked:
Dr. Jeffrey Rumbyrt
31 years experience Allergy and Immunology
4-6 hours: Typically, the effect of Benadryl (diphenhydramine) is 4-6 hours. It may be longer in people with liver disease.
A 46-year-old member asked:
Dr. Yash Khanna
56 years experience Family Medicine
WILL MAKE YOU SICK: It is not a good idea to overdose on 250mgm of Benadryl (diphenhydramine) to get high it can make you sick.It will cause extreme sleepiness, confusio ... Read More
A 39-year-old member asked:
Dr. Jeffrey Rumbyrt
31 years experience Allergy and Immunology
4-6 hours: Typically, the effect of Benadryl (diphenhydramine) is 4-6 hours. It may be longer in people with liver disease.
A 39-year-old female asked:
Dr. Manuel Lopez diaz
27 years experience Emergency Medicine
25-45 min: It usually takes from 25 to 45 for a pill to start to make effect has to be dissolved and absorb into the blood stream to make effect.
A 37-year-old member asked:
Dr. Bennett Werner
43 years experience Cardiology
How much?: Depends on how much you took and how you metabolize it. The half life is 3-9 hours. That means that in general it will be out of your system in 15 hou ... Read More
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A 35-year-old female asked:
Dr. Gregory Cowan
12 years experience Pediatric Allergy and Asthma
Hours to days: Epi is short acting and leaves the body in a matter of minutes. Benadryl (diphenhydramine) in about three days and prednisone up to a week.
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A member asked:
Dr. John Chiu
Dr. John Chiu answered
56 years experience Allergy and Immunology
About an hour: It will take about an hour to take effect.

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