How long does Benadryl (diphenhydramine) allergy med stay in your system?

7-18 hr, effectively. That's with a normal dose. The half-life (time it takes 1/2 the med to leave your body) is 3.4 to 9.2 hrs. Double that time and 75% of it has left your system at which point it's generally not helping anymore. Triple it and 87.5% is gone, etc. If you take twice the normal dose you could still have a significant amount after more than 24 hours.

Related Questions

How long does Benadryl (diphenhydramine) allergy stay in the body?

A long time. The half life is 8 hours. Assuming that after 4 half lives it is eassentially gone it would take upwards of 32 hours to be eliminated. Read more...

How many Benadryl (diphenhydramine) allergy pills do I take?

Perhaps, one. See prior answer for details about benadryl (diphenhydramine). An over the counter dose is 25 mg (the same dose they put in many 'sleep aides' like tylenol-pm, where the side effect of Benadryl (diphenhydramine) of drowsiness is the main ingredient). If taking it for typical allergies (runny nose, watery eyes, sneezing), could try one tablet. But there are better ones today with less side effects (zyrtec, allegra, claritin, etc). Read more...

What would happen if I took extra Benadryl (diphenhydramine) allergy pills?

Perhaps, one. See prior answer for details about benadryl (diphenhydramine). An over the counter dose is 25 mg (the same dose they put in many 'sleep aides' like tylenol-pm, where the side effect of Benadryl (diphenhydramine) of drowsiness is the main ingredient). If taking it for typical allergies (runny nose, watery eyes, sneezing), could try one tablet. But there are better ones today with less side effects (zyrtec, allegra, claritin, etc). Read more...

Could Benadryl (diphenhydramine) allergy and cold affect my awareness at all?

Yes. Benedryl is an antihistamine that can cross into the brain and interfere with the message bearing chemicals between the nerves. This often causes sleepiness. It is the main ingredient in most over the counter sleep aids. All such medications bear a warning in small print if you read the package insert. Read more...

What is the definition or description of: Benadryl (diphenhydramine) allergy?

Antihistamine med. This refers to the variety of Benadryl products available that contain diphenhydramine, an older antihistamine. They include dye-free liqui-gels, ultratab tablets, fast melt tablets, pre-filled spoons, allergy liquid and dye-free allergy liquid. The ultratab and allergy liquid are the only products currently available (per website today). Read more...

I took one 25mg Benadryl (diphenhydramine) allergy on monday it's now friday and I still feel out of it is this normal or did I overdose? I'm 19, 98 pounds 5'4

You did not. Overdose. I doubt it's from the med you took on Monday. I feel it is more due to the allergies that you took the Benadryl (diphenhydramine) to treat. Talk to your doctor about other options to treat allergies. Most are less sedating. . Read more...