Saturday, April 29, 2017
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DiphenhydramineDiphenhydramine is legal and available Over-the-Counter in the United States.

Addictive Potential: Low

Emergency Room Visits Yearly: Millions

Mandatory Minimum Sentence: None

Mechanism of Action: SERT inhibitor, mAChR receptor antagonist, H1 receptor antagonist and inverse agonist


Diphenhydramine (DPH) is an antihistamine possessing anticholinergic, antitussive, antiemetic, and sedative properties that is mainly used to treat allergies. It is also used in the management of Parkinson’s symptoms. The drug has a strong hypnotic effect and is FDA-approved as a non-prescription sleep aid, especially in the form of diphenhydramine citrate. It is produced and marketed under the trade name Benadryl by McNeil-PPC (a division of Johnson & Johnson) in the U.S., Canada and South Africa (trade names in other countries include Dimedrol, Daedalon and Nytol). It is also available as a generic or store brand medication.

From 1995 to 2009, diphenhydramine was one of the drugs most frequently involved in emergency room visits throughout the United States (ADIS, 2013).

Recreational Use:

Diphenhydramine is sometimes used as a recreational drug because of its sedative properties and (at higher doses) delirium-induced hallucinations. Users have also reported that diphenhydramine can induce a state of weak to moderate euphoria; this may be due to a rise in the dopamine/acetylcholine ratio in the CNS. Erowid (2005) noted that the positive effects include: increased awareness and appreciation of music, dream-like experiences, and muscle relaxation.

When used recreationally, Erowid (2011) reported that the dosage of diphenhydramine typically ranges from 10mg – 400mg and the effects last for 4 to 8 hours. Still, Erowid cautioned that “diphenhydramine products containing acetaminophen/paracetamol should not be used recreationally. High doses of acetaminophen can be fatal. Diphenhydramine products containing other medicines can be harmful if taken in doses above the recommended limits. Dangerous interactions can occur”.


Some users have experienced addiction as a consequence of the longterm use of diphenhydramine.

Substance Identification:

     Mecke Reagent          Marquis Reagent       
Diphenhydramine  Yellow  Yellow

(Info provided by Ring et al., 2006)

Diphenhydramine Side Effects and Adverse Reactions:

  • dry mouth, nose, and throat
  • drowsiness
  • dizziness
  • nausea and/or vomiting
  • loss of appetite
  • constipation
  • increased chest congestion
  • headache
  • muscle weakness
  • nervousness
  • vision problems
  • difficulty urinating or painful urination

Deaths and Overdoses:


Other Resources:

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