Lynne asked
How many hours does one dose of benedryl last in your blood stream?
Answer
We will answer this in two parts:
- What Is The Duration Of Action of Benadryl (diphenhydramine)?
- How Long Does Benadryl Last In The Blood?
What Is The Duration Of Action of Benadryl (Diphenhydramine)?
The duration of action of Benadryl (diphenhydramine) ranges from about 4 to 6 hours, depending on the person. The drug reaches its highest concentration in the blood in about 1—3 hours. If you are taking Benadryl (diphenhydramine) as a sleep aid, plan on it being most effective during that time period.
How Long Does Benadryl Last In The Blood?
Diphenhydramine is widely distributed in the body and is metabolized in the liver which creates multiple metabolites that are found in the blood. The half life (time it takes for 50% of the drug to be metabolized) is between 2 and 8 hours. Typically we expect most drugs to be completely metabolized after about 5 half lives. Studies show that the unchanged drug (diphenhydramine) and the metabolites, are excreted with 24 to 48 hours. So while the effects of Benadryl (diphenhydramine) only last 4 to 6 hours, the actual drug is in your body for 1 to 2 days.
