Benodrill medicine???!

The ingredient in Benadryl (diphenhydramine) is the same ingredient found in medicines such as Tylenol PM, which is meant for pain relief/sleep. Two capsules of Benadryl is the normal adult dose, meaning children 12 and older. I take it for sleep sometimes, but have for years. It actually takes me two or three hours to get sleepy because I imagine I've built up a tolerance to it? However, if you don't usually take Benadryl I would bet less than an hour. It will really knock you out. If you take it for sleep, also know that you need plenty of time to sleep it off, otherwise you'll be groggy in the morning. :)
Edit: Sorry, two capsules should be 50 miligrams. That is the usual dosage.

From my own experience. If I take about 5 pills it will usually take about an hour - an hour & a half for it to start kicking in.

You might feel not too tired 1 minute but then the next you start to feel all drowsy & your eyes will feel heavy & you'll either crawl to bed or just fall asleep were you are.

That is Benadryl and is often prescribed as a sleep aid. Any oral medication that you take regardless of age or weight takes about an hour to be absorbed and utalized by the body.

You mean benadryl?
It depends on how fast you usually fall asleep I would assume.
Probably about an hour.

Dont take it to fall asleep, youll hurt yourself