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DPH is frequently reported to cause extremely unpleasant, if not dangerous, experiences.

The effects of DPH are very unpredictable and may result in serious injury. Please use harm reduction practices (such as always having a trip sitter) when using this substance. See this section for more details.

Summary sheet: Diphenhydramine
Chemical Nomenclature
Common names DPH, Benadryl, Nytol, Sominex, Unisom, ZzzQuil
Substitutive name Diphenhydramine
Systematic name 2-(diphenylmethoxy)-N,N-dimethylethanamine
Class Membership
Psychoactive class Deliriant
Chemical class Ethanolamine
Routes of Administration

WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.

Threshold Common Heavy
25 - 100 - 200 - 400 - 700 mg
Light Strong
Bioavailability 40-60%
Threshold 25 - 100 mg
Light 100 - 200 mg
Common 200 - 400 mg
Strong 400 - 700 mg
Heavy 700 mg +
Total 2 - 6 hours
Onset 30 - 90 minutes
Come up 45 - 90 minutes
Peak 1 - 4 hours
Offset 2 - 6 hours
After effects up to 24 hours

DISCLAIMER: PW's dosage information is gathered from users and resources for educational purposes only. It is not a recommendation and should be verified with other sources for accuracy.

Diphenhydramine (also known as DPH, Benadryl, and many others) is a deliriant substance of the ethanolamine class. Diphenhydramine is a first-generation H1 antihistamine that is widely used as a generic, over-the-counter medication for allergies. At doses that far exceed the recommended, it becomes a notoriously powerful deliriant.

Diphenhydramine was first synthesized in 1943 by George Rieveschl and patented by Parke-Davis. In 1946, it became the first prescription antihistamine approved by the U.S. Food and Drug Administration. It was approved for over-the-counter use in the 1980s.[1]

Diphenhydramine is typically used to treat allergies, but may also be used for a number of conditions including itchiness, insomnia, motion sickness, nausea and the symptoms of Parkinson's disease.[2]

Due to its extremely uncomfortable effects and body load, diphenhydramine may be overly challenging for those who are not already extensively experienced with hallucinogens. Therefore, it is highly advised to approach this substance with the proper amount of precaution, preparation, and harm reduction practices if using it.


Diphenhydramine, or 2-(diphenylmethoxy)-N,N-dimethylethanamine, is a first generation antihistamine originally synthesized in 1943. The chemical structure of DPH contains an ethylamine chain with two methyl groups bonded to the terminal nitrogen group RN. Additionally, this ethylamine chain is substituted at R2 with a diphenylmethoxy group, forming an ether. The diphenylmethoxy group consists of two aromatic phenyl rings bonded the carbon member of a methoxy group CH3O-. DPH is produced as a hydrochloride salt.


Diphenhydramine is an inverse agonist of the peripheral histamine H1 receptor and a central histamine H1 receptor.[citation needed] The peripheral inverse agonism induces the allergy reducing effects.[citation needed] Like many first-generation antihistamines, it is also a competitive antagonist at mACH receptors.[citation needed]

This substance works mainly via its antagonistic action on acetylcholine receptors, but has also been shown to block sodium channels and inhibit the reuptake of serotonin.[3][4] It is not known how significant this property is. However, the boxes of diphenhydramine-containing products do not warn users of diphenhydramine and SSRI interaction. Diphenhydramine also blocks voltage-gated potassium channels (VGKCs), meaning it has the potential to cause or lead to torsades de points, a potentially dangerous cardiac condition that can lead to sudden cardiac death. [5]

The receptor binding affinities are listed as follows:[6][7]

Receptor Site Binding Affinity (Lower = Stronger)
H1 9.6-16nM
H2 missing data
H3 >10,000nM
H4 >10,000nM
M1 80-100nM
M2 120-490nM
M3 84-299nM
M4 53-112nM
M5 30-260nM
SERT ≥3,800nM

Although the precise mechanism is not understood, the inhibition of the action of acetylcholine is thought to be primarily responsible for the delirium, sedation and intensely realistic hallucinations alongside the extremely uncomfortable and dysphoric physical side effects that this substance can produce.

Subjective effects

DPH is described by users as having non-linear dose-response. Doses under 300mg tend to induce more of a restless feeling, body high, and relaxation. Dosages above 500mg are typically what make the user enter a state of delirium and begin to see and hear fully-formed, extremely convincing hallucinations. Anything in between these two extremes is often reported to be a disappointing and extremely uncomfortable experience characterized by an extreme body high and sometimes terrifying hallucinations, depending on the lighting conditions and other factors.

The effects listed below are based upon the subjective effects index and personal experiences of PsychonautWiki contributors. The listed effects should be taken with a grain of salt and will rarely (if ever) occur all at once, but heavier doses will increase the chances and are more likely to induce a full range of effects. Likewise, adverse effects become much more likely on higher doses and may include serious injury or death.

Physical effects

Visual effects

Cognitive effects

Auditory effects

Experience reports

Anecdotal reports which describe the effects of this compound within our experience index include:

Additional experience reports can be found here:

Available forms

DPH is available in several different forms over the counter and online.

  • Pills are available over the counter and online. Well-known brands include Benadryl, Benylin, Dramamine, Nytol, Sominex and ZzzQuil. Rarely, some of these products may contain other medicines, including dextromethorphan, guaifenesin, and acetaminophen. Care should be taken when using these products to ensure that there is not an overdose on other medicines in these DPH-containing products.
  • Liquid is available over the counter and online. DPH in liquid form can be taken orally or injected. Well-known brands include Benadryl and ZzzQuil. Rarely, some of these products may contain other medicines, including dextromethorphan, guaifenesin, and acetaminophen. Care should be taken when using these products to ensure that there is not an overdose on other medicines in DPH-containing products.
  • Powder is available online. DPH in powdered form can be taken orally as well as via injection. Any other routes of administration other than oral are not recommended because DPH burns and dehydrates skin tissue, which leads to extremely painful burns and bleeding.

Toxicity and harm potential


This toxicity and harm potential section is a stub.

As such, it may contain incomplete or even dangerously wrong information. You can help by expanding or correcting it.
We also recommend that you conduct independent research and use harm reduction practices when using this substance.

It is critical to note that a single dose of DPH can be extremely unpredictable and has the potential to result in severe consequences, hospitalization or death. The toxicity and long-term health effects of regular DPH usage do not seem to have been studied in any scientific context. This is because long-term DPH usage is very rare and the vast majority of people who try this compound do not wish to repeat the experience.

If taken on a regular basis, anecdotal reports suggest that DPH can have some serious effects on one's kidneys with the potential to result in bladder issues similar to that of ketamine cystitis.


DPH has been reported to cause psychosis and delirium at a significantly higher rate than other hallucinogens like LSD, DMT, or ketamine. There are a large number of experience reports online which describe states of psychotic delirium, amnesia, and other serious consequences after abusing the substance. In many cases, it has resulted in hospitalization and death.

It is strongly recommended that one avoids this compound altogether or at least uses extreme caution and harm reduction practices when using this substance, such as having a sober trip sitter.

Lethal dosage

Diphenhydramine can become fatal at amounts close to or exceeding 2 grams. This can result in death when combined with most stimulants, depressants and MAOIs. It is worth noting, however, that a dosage of 1 gram is considered extreme in its strength and could potentially result in a fatal overdose if a person happened to be particularly sensitive to this substance.

It is strongly recommended that one use harm reduction practices when using this drug.

Tolerance and addiction potential

The use of DPH can be considered mildly addictive with a high potential for adverse side effects such as psychosis. In comparison to other hallucinogens, DPH has been reported to be significantly less addictive than that of MXE, ketamine, 2C-B or LSD. This is simply because the vast majority of people who try this substance do not wish to repeat the experience.

Tolerance to many of the effects of DPH develops with repeated use. This results in users having to administer increasingly large doses to achieve the same effects. After that, it takes about 3 - 7 days for the tolerance to be reduced to half and 1 - 2 weeks to be back at baseline (in the absence of further consumption). DPH presents cross-tolerance with all deliriants, meaning that after the consumption of DPH, all deliriants will have a reduced effect.

Dangerous interactions

Although many psychoactive substances are safe to use on their own, they can become dangerous or even life-threatening when taken with other substances. The list below contains some potentially dangerous combinations, but may not include all of them. Certain combinations may be safe in low doses but still increase the possibility of injury of death. Independent research should always be conducted to ensure that a combination of two or more substances is safe before consumption.

  • Selective serotonin re-uptake inhibitors (SSRIs) - This combination can suppress the visual effects of diphenhydramine, however it may be dangerous to combine them due to diphenhydramine also being a weak SSRI, and may cause serotonin syndrome.[citation needed]
  • Benzodiazepines - This combination can suppress the visual effects of diphenhydramine, however it may be dangerous due to being a sedative.[citation needed]
  • Stimulants - Because of diphenhydramine's excitatory cardiac effect, combining it with stimulants poses a risk of an abnormal heart rhythm, severe tachycardia, or a heart attack as well as other cardiovascular events.
  • Other anticholinergics - Because of diphenhydramine's excitatory cardiac effect, combining it with other anticholinergics poses a risk of an abnormal heart rhythm, severe tachycardia, or a heart attack as well as other cardiovascular events. (Inhibition of acetylcholine causes increased heart rate.)

Legal status

DPH is available either over the counter or by prescription in most countries. However, some countries require the purchaser to be over 16, 18 or 21.

  • Zambia: Possession and sale is illegal; foreigners have been detained for posession.

See also

External links


  1. Emanuel, M. B. (1999). Histamine and the antiallergic antihistamines: a history of their discoveries. Clinical & Experimental Allergy, 29(S3), 1-11. https://doi.org/10.1046/j.1365-2222.1999.00004.x-i1
  2. http://www.drugs.com/monograph/diphenhydramine-hydrochloride.html
  3. Domino, E. F. (1999). History of modern psychopharmacology: a personal view with an emphasis on antidepressants. Psychosomatic medicine, 61(5), 591-598.
  4. Kim, Y. S., Shin, Y. K., Lee, C. S., & Song, J. H. (2000). Block of sodium currents in rat dorsal root ganglion neurons by diphenhydramine. Brain research, 881(2), 190-198.
  5. halifa, M., Drolet, B., Daleau, P., Lefez, C., Gilbert, M., Plante, S., ... & Turgeon, J. (1999). Block of potassium currents in guinea pig ventricular myocytes and lengthening of cardiac repolarization in man by the histamine H1 receptor antagonist diphenhydramine. Journal of Pharmacology and Experimental Therapeutics, 288(2), 858-865.
  6. https://www.ncbi.nlm.nih.gov/pubmed/11036158
  7. https://www.ncbi.nlm.nih.gov/pubmed/10511010
  8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1885114/ | Relationship between sedation and pupillary function: comparison of diazepam and diphenhydramine
  9. Block of sodium currents in rat dorsal root ganglion neurons by diphenhydramine | http://www.sciencedirect.com/science/article/pii/S0006899300028602?via%3Dihub