You should know how long Benadryl stays in your system and its interaction with other chemicals so that you can be safe from the side effects from the potent interaction.

All most all living individual on this planet has heard the name of Benadryl. We are not over exaggerating it, but this is a fact. However, there are certain myths regarding the use of Benadryl as a medicine as well as a drug.

Let’s now take a look at the various issues related to Benadryl – which is famously known as the most widely used cough syrup.

History of Benadryl

Benadryl is considered as a brand name for a variety of medications clinically belonging to the over-the-counter (OTC) class. Various chemical ingredients like diphenhydramine and others are the major constituents of the OTC class.

They are a type of antihistamines. Evidence says that Johnson & Johnson acquired the “Benadryl” brand from its previous holder (Pfizer) and is still the proprietary of Johnson & Johnson.

Considering the past and the present scenarios Benadryl is the only and the single most popular antihistamine to have come so far.

Benadryl cough syrup is manufactured in a variety of formulations by its makers. Its core functionalities include the treatment of a large variety of diseases.

It is targeted to treat a broad spectrum of clinical conditions. These conditions mainly include clinical symptoms like a cough, allergies, insomnia, motion sickness, nausea, and itchiness.

It is believed that the content of diphenhydramine which is present in Benadryl has certain therapeutic effects with the H1 histamine antagonism receptors. It is also known to produce an inhibition effect of the sodium channels within the cells(intracellular).

Around eight people out of ten are being reported to have consumed Benadryl at least once in their lifetime. Benadryl is stated as the most commonly used medication for all allergic conditions. It is also considered to be a safe medication when consumed in appropriate quantities.

However, there are chances that the drug might lead to some serious side effects. Therefore, it is a wise choice to seek some advice before consuming Benadryl!

Let’s now see the various effects, side effects and the effects on various age groups that Benadryl might lead to.

What Is Benadryl?

It is a good idea first to have some basic details of this medicine. As stated above this medicine is commonly known as Benadryl. However, it is clinically a variant of diphenhydramine. Although this utility of Benadryl is rarely taken into consideration, Benadryl is known to have positive effects in the treatment of Parkinson’s disease.

To have exact knowledge of how long Benadryl will stay in your body, it is highly necessary to have some insights about the medicines life cycle.

The life cycle and structure of Benadryl varies and depends on some factors. These mainly include age, inner metabolism, clinical history, psychological state, etc.

Let us see the amount of time the drug stays inside the human body by the age of the person.

  • Children – approximately 7 hours
  • Adults –approximately 12 hours
  • Elderly people –around 17 hours

It should be noted that the life cycle of Benadryl plays a vital role in determining how long the drug takes to leave your body. Considering the general statistic’s the time for elimination of Benadryl of the human body by each belonging to the following categories is as follows:

  • Children – 14 hours
  • Adults – 24 hours
  • Elderly – 34 hours

Considering the above value’s it will take approximately a day for Benadryl to leave your body entirely.

Variables That Influence How long Benadryl Stays In Your System

Variables That Influence How long Benadryl Stays In Your System
Variables That Influence How long Benadryl Stays In Your System

We have now understood that there is a significant amount of interindividual variation in the elimination time of this drug.

These interindividual differences in the elimination of this medicine are known to be a result of various factors.

These mainly consist of a frequency of ingestion, person’s age, dosage, hepatic function and co-administration of other drugs. It is these factors that are needed to be considered when contemplating the amount of time Benadryl stays in your body after you stop consuming it.

1. Age (Old vs. Young)

Research points out that old people (above the age of 65) are likely to retain Benadryl in their body for a longer duration as compared to the children and young adults. Based on this information, it can be concluded that it around 3.1 days for the complete elimination of diphenhydramine from the body systems of the elderly individuals.

The statistic’s say that around 2.11 days are required by the young adults for the complete elimination of Benadryl and only 1.24 days by kids.

2. Hepatic Function

The clinical study says that the content of diphenhydramine present in Benadryl is metabolized by certain enzymes present in our liver.

Thus, the elimination of Benadryl contents is affected because of the hepatic impairment. If the liver is damaged in any way, then the lifespan of Benadryl in the human body is highly affected.

It can take around 4 to 6 for the complete elimination of the entire content of Benadryl from the human body if you are suffering from or having the severe hepatic impairment.

Research proves that the increased time of complete elimination is longer among cirrhotic patients. This is mainly because of increase in the bilirubin content.

In case of adults having a normal hepatic functioning, complete elimination of Benadryl occurs in just 2 days or so.

3. Dosage (Low vs. High)

This is one of the major factors to be considered while checking out how long Benadryl will stay in your body. The dosage of Benadryl is given as per the individual’s age. It is as follows:

  • Children – 0 mg to 25 mg
  • Adults and old people – 25 mg to 50 mg

Thus, it can be easily noted that higher the amount of dose; greater is the time duration for which the medication will reside inside your body. However, there are other factors as well which influence the time span.

Frequency (Single vs. Multi-Dose)

How often do you consume Benadryl?

The answer to this question is surely going to affect the time duration for which the drug resides inside the human body. It is logical to say that a person who takes a single dose of the medication per day is bound to eliminate the drug at a faster rate.

On the contrary, the person taking it multiple times a day will take more time to eliminate it. This is primarily due to the logic that a user taking a single dose user is likely to have less amount of accumulated Benadryl in his body.

5. Co-administration of drugs (CYP2D6)

If you’re consuming other drugs along with Benadryl, then it is possible that there might be an increase or decrease in the time required for its complete elimination.

Clinically, it is proven that the enzyme Cytochrome P450(CYP2D6) affects the diphenhydramine which is the active ingredient in Benadryl.

Thus, taking into consideration the other medications the person is ingesting becomes important too.

Miscellaneous individual factors

  • Body mass: Usually, it is a fact that more massive the person is, faster the drug will be eliminated out of his body.
  • Genetics: This is a major factor affecting the amount for which Benadryl stays in an individual’s body. There is no concrete explanation available for the same.
  • Hydration: It refers to a number of fluids present in the body. The more the fluid content, faster is the urine produced. Benadryl is eliminated out of the body in the form of urine.
  • Metabolic rate: A person’s Basal Metabolic Rate is having a large influence on the time required for elimination of all the drugs, including Benadryl. It is a general scenario that an individual with a large count of BMR tends to burn more energy as well as fat. This greatly affects the rate at which the drugs are eliminated from the human body
  • Renal function: Medically it is proven that people suffering from issues with the liver are having a low dissemination rate of drugs.
  • Urinary pH: People had a high urinary pH are likely to require more time for complete elimination of Benadryl. High pH leads to increased acidity, which in turn affects the body metabolism.

Side Effects Of Benadryl

As with every drug, there are some side effects of Benadryl as well. These side effects range from mild, moderate to severe and also vary from person to person.

  • Vertigo (dizziness)
  • Headache
  • Dry oral and nasal cavities
  • Sensation of needing to urinate frequently
  • Drowsiness
  • Fatigue
  • Dysuria (difficulty urinating)
  • Some users may experience paranoia and anxiety when taking Benadryl over long periods of time.
  • Drug Interactions
  • Itching
  • Nausea
  • Lack of sleep
  • Swelling of internal body parts
  • Hot pulses

It is crucial and very important to know that consuming Benadryl along with Xanax is highly dangerous. Xanax contains an ingredient which is never to be consumed together with Benadryl. It increases the risk of antihistamine overdose. Thus, it is very important to consult a physician before taking Benadryl

How To Clear Benadryl From Your System

a. Urinary pH: It is possible to change the urinary pH using some additives. This helps in quick elimination of Benadryl from the body.

b. Activated charcoal: This is a very good option if you have consumed a lot of Benadryl and wished to get it out of your body. Activated charcoal is having an opposite charge and tends to attract Benadryl molecules and eliminated out of the body.

c. Calcium-D-Glucarate: This supplement is very helpful to facilitate the removal of various toxins like Benadryl through our kidneys.

d. Hydration/Exercise: Drinking a lot of water, makes a person urinate frequently. This facilitates the elimination of Benadryl from the body.


Thus, we can conclude with the following points:-

  • It is wrong to state that Benadryl is not excellent or conducive to the human health.
  • It is really necessary and a wise choice to consult a physician before deciding the dosage of Benadryl to be consumed.
  • Taking Benadryl in large amounts is surely going to have some negative effects in one form or the other.

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