Diphenhydramine (DPH): How Dangerous Is It to Abuse This Drug?

Diphenhydramine is often referred to as Benadryl, a medication you’ve likely heard of or consumed at some point in your life. When the drug is used as prescribed, the chances of becoming addicted to its active ingredients are very slim. But taking it for its euphoric effects increases the risk of abusing the drug exponentially. In 1943, a professor at the University of Cincinnati named George Rieveschl discovered diphenhydramine, and shortly after, in 1946, Pfizer purchased it, and the U.S. Food and Drug Administration approved it as the first prescription antihistamine.

A couple of decades later in the 1960s, diphenhydramine was found to inhibit the reuptake of the neurotransmitter serotonin. The discovery of these results led to a search for viable antidepressants that shared similar structures with fewer side effects.

Diphenhydramine was a significant contributor when it came to inventing the popular antidepressant medication fluoxetine (Prozac), which is a selective reuptake inhibitor SSRI.

The drug has also been known to be used as a potentiator of opiates, meaning it can enhance the effects of these drugs. Diphenhydramine has been deemed to have limited abuse potential in the United States and is not a controlled substance.

While the drug is widely used among the general population and considered to be safe for use, there are documented cases in which the drugs have been abused, and people have developed an addiction to it.

It is a cheap over-the-counter drug in most countries, and those without access to stronger illicit drugs are at risk. People who have underlying medical conditions such as schizophrenia are also at higher risk of abusing the drug.

Unfortunately, because it is seen as an over-the-counter medication that offers medicinal value in low doses, the stigma of it being dangerous is often overlooked.

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Over-the-counter medications are those that can be sold directly to consumers without a prescription. OTC medicines treat various illnesses that include cough, pain, diarrhea, constipation, and allergies. Some medications such as diphenhydramine have the potential for misuse at higher-than-recommended dosages. Misuse of an OTC medicine means to take the drug in a way or dose other than directed on the package, taking the medicine for its effects, or mixing the medications to create new products.

What Is Diphenhydramine Abuse?

Diphenhydramine is the generic name for the popular over-the-counter antihistamine drug Benadryl. The sole objective of antihistamines is to combat the actions of histamine,  a substance produced by the body in response to the presence of allergens such as pollen, dust, or animal hair. Histamine produces reactions that cause sneezing, itchy eyes, scratchy feelings in the nose and throat, runny nose, and difficulty breathing. Cold sufferers frequently use DPH to reduce their symptoms.


Diphenhydramine can be possessed without a prescription, but that does not mean there is a shortage of powerful side effects. Benadryl can cause extreme drowsiness in those who use it, and it has become popular for that reason. Often, it occurs by accident because someone didn’t read the directions and took the medication for too long. In other instances, users will mix the drug with alcohol and other intoxicants. Unfortunately, many individuals will abuse the medication on purpose to achieve a high. No matter how it’s abused, it can lead to dangerous and severe side effects, including an overdose.

Diphenhydramine can cause powerful side effects even when taken as directed, so it is vital to read the directions and learn what the signs of an overdose are.

Common Side Effects of Benadryl Abuse

Diphenhydramine (Benadryl) is considered an H1 receptor antagonist, and it works by blocking the effect of histamine in the body. The chemical reactions that diphenhydramine trigger in the body can cause other potentially significant sedative side effects on the central nervous system (CNS). Diphenhydramine effects are dose-dependent, and the peak effects will be achieved two to three hours after the drug is consumed. The effects, on average, last anywhere from four to six hours.

Common diphenhydramine central nervous system (CNS) effects can include:

  • Confusion
  • Blurred vision
  • Convulsions
  • Pins and needles sensation
  • Impaired coordination
  • Dizziness
  • Feelings of euphoria
  • Increased feelings of fatigue
  • Inflammation of peripheral nerves
  • Feelings of excitement
  • Sedation
  • Sleepiness
  • Tremors
  • Vertigo

Diphenhydramine Overdose Symptoms

An overdose that stems from diphenhydramine is possible even when the drug is not being abused. When too much is consumed, it will lead to an overdose. Taking more than 25 mg (milligrams) of DPH can be extremely dangerous and is more likely to cause harm than produce euphoria.

Symptoms of a diphenhydramine overdose include:

  • Extremely dry eyes
  • Dilated pupils
  • Blurred vision
  • Loud ringing in ears
  • Dangerously low blood pressure
  • Rapid heart rate
  • Agitation
  • Mood swings
  • Severe confusion
  • Seizures
  • Delirium
  • Physical tremors
  • Paranoia
  • Inability to urinate
  • Nausea
  • Vomiting
  • Nodding out
  • Passing out

The medication can cause an overdose on its own, but when it is used with other drugs such as alcohol or benzodiazepines, it can increase these risks exponentially. Alcohol or benzodiazepines effects can be enhanced by diphenhydramine, and this can create life-threatening effects.

If you believe that someone has overdosed on diphenhydramine, it is imperative to seek emergency medical attention. You must call 911 immediately to get them the help they need. Risking someone’s life to see if they will be OK is not worth it, and if you see something say something.

How Dangerous Is Diphenhydramine Abuse?

Like alcohol, diphenhydramine poses a special kind of problem — it is widely available by purchase at stores that are open sometimes 24-hours per day. Its availability is a cause for concern, and those with pre-existing drug addictions are more vulnerable to abusing it than others. Diphenhydramine is not considered an effective intoxicant, and taking more than the recommended dose will likely lead to an overdose or uncomfortable side effects rather than euphoria.

Less than 300 mg of the medication, 12 times the recommended dose, can cause a sense of disassociation and emotional restlessness. If an individual were to consume more than 500 mg, which is 40 times more than the recommended dose, this would lead to a state of delirium, hallucinations, and other overdose symptoms.

Abusing diphenhydramine long-term can include effects of

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  • Heart palpitations
  • Inability to think properly due to brain changes
  • Skin rashes
  • Vision changes
  • Physical tremors
  • Vertigo (constant dizziness)
  • Physical dependence

If you think that you or someone you know may have a problem with diphenhydramine, you probably do. As we have highlighted above, abusing diphenhydramine can lead to adverse effects and cause long-term or permanent damage. Your only option is to get to help and abstain from the drug before you cause any more damage that cannot be repaired. Fortunately, Serenity at Summit offers extensive care that can help pull you away from your dependence on diphenhydramine.

There is no reason to live trapped inside of a diphenhydramine dependence another day when there is so much help available to you.

Get on the Road to Recovery Today

Diphenhydramine dependence is less common, but it does occur. If you or a loved one is struggling with a dependence on diphenhydramine, there is help available.

Speak to an addiction treatment specialist at Serenity at Summit to learn more about addiction and how it can be treated. Call (844) 326-4514 or contact us online to learn more about your addiction therapy options.