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The combination of DXM and DPH is reported to produce potentially dangerous experiences both physiologically and mentally, especially at higher doses.

The deliriant and dissociative effects associated with recreational doses of this combination are highly unpredictable and may result in erratic behaviors, self-injury, physical side effects such as dangerously elevated heart rate or blood pressure, hospitalization, or (in extreme cases) death. Please use harm reduction practices if using this combination (e.g. starting with low dosages and always having a trip sitter). Refer to this section for more details.

The molecular structure of Dextromethorphan.
The molecular structure of Diphenhydramine.
Class Membership
Psychoactive class Dissociative and Deliriant
Chemical class Morphinan and Antihistamine
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 50 / 50"/50" can not be assigned to a declared number type with value 50. mg
Light 100 / 100 mg
Common 200 / 200 mg
Strong 300 / 300 mg
Heavy 350 / 350 mg Heavy doses can produce dangerous side effects and are highly advised against.
Total 8 - 22 hours
Onset 20 - 60 minutes
Peak 3 - 12 hours
Offset 4 - 10 hours
After effects 6 - 48 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.


The Dextromethorphan (DXM) and Diphenhydramine (DPH) combination experience (also known as counterflipping, in reference to both DXM and DPH being over the counter (OTC) in the US) is a combination that when taken produces uniquely hallucinogenic, dissociative and powerful deliriant effects when administered.

This article is something that PsychonautWiki is documenting because although there are seemingly infinite amount of possible drug combinations, almost all of them simply induce the effects of the two separate drugs on top of each other in a very predictable manner. However, these two substances do just the opposite of that, producing a very unique synergy when taken together, potentiating the positive aspects of the other substance whilst simultaneously suppressing its perceived negative or uncomfortable side effects; with distinct visual and hallucinatory effects that are sometimes not found on neither of these substances when taken on their own. However, despite its unique and positive effects, this combination can readily produce significantly dangerous physical and psychological effects, already at common dosages.

Typically, dosages for both DXM and DPH are both taken in equal amounts, for example 300 milligrams of DXM with 300 milligrams of DPH, although some users prefer higher or lower amounts of either substance. This makes the spectrum of the combination very broad and the effects and dangers can vary significantly. Generally, it is strongly advised that users without extensive experience do not go over a light to common dose of both DXM and DPH alone when combining the two in recreational doses.

Both substances strongly amplify each others effects; while DPH inhibits the metabolism of DXM and increasing its concentration,[citation needed] DXM in turn suppresses the dysphoric and anxiolytic effects of DPH whilst powerfully amplifying its hallucinations and deliriant properties.[citation needed] Even at common doses, few may be subject to extreme states of dissociation and delirium, possibly not being able to communicate with the outside anymore. This is very heavily dependant on body chemistry, which is already a unique effect seen with DXM and one might respond completely differently from anoth person even with the same dosages.

This combination is especially extremely physically taxing, especially since the dangerous effects are suppressed and can become unnoticed. It is highly advised to go against the common or strong dosage range due to the risk of effects such as toxicity, increased heart rate, increased blood pressure, rhabdomyolysis and agitated mental states such as delirium or panic attacks. People with preexisting cardiovascular problems should avoid this combination and further substances should not be added to this mix. It is strongly advised to use harm reduction practices if using this combination and independent research should always be done prior.

History and culture




When taken in combination, Diphenhydramine acts as a pharmologically significant CYP2D/CYP2D6 inhibitor[1] and thus inhibits the breakdown of DXM into DXO.[2]

Subjective effects

When taken in combination, DXM and DPH both lessen the percieved uncomfortable side effects of the other substance. For example, due to DPH’s nausea suppressing abilities, the nausea associated with DXM is almost entirely abscent. In return, DXM’s dissociating and anesthetic-like qualities have an extremely positive effect on the unbearably strong physical dysphoria found within DPH. This completely eliminates the muscle cramps, nausea, dizziness, drowsiness, restless leg syndrome, and extreme dehydration experienced when DPH is tried by itself. This allows the unique delirium, hallucinations and visual effects of the DPH experience to become much more accessible to your average person.

Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), an open research literature based on anecdotal user reports and the personal analyses of PsychonautWiki contributors. As a result, they should be viewed with a healthy degree of skepticism.

It is also worth noting that these effects will not necessarily occur in a predictable or reliable manner, although higher doses are more liable to induce the full spectrum of effects. Likewise, adverse effects become increasingly likely with higher doses and may include addiction, severe injury, or death ☠.

Physical effects

Visual effects

Cognitive effects

Auditory effects


Toxicity and harm potential

When taken in combination, it should be noted that enormous amounts of strain can be put on the circulatory system, as both substances increase one's heart rate and blood pressure. This can become dangerous in high dosages. The toxicity of both substances is also present. States of agitated delirium can pose a significant risk to the person as they are subject to injuring themselves by falling or walking in dangerous areas such as roads.

Legal issues

See also

External links


  1. https://www.erowid.org/chemicals/dxm/faq/dxm_refs.shtml#r151
  2. Cytochrome P450-dependent metabolism of dextromethorphan: fetal and adult studies. (PubMed.gov / NCBI) | http://www.ncbi.nlm.nih.gov/pubmed/1306804
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Reissig, C. J., Carter, L. P., Johnson, M. W., Mintzer, M. Z., Klinedinst, M. A., & Griffiths, R. R. (2012). High doses of dextromethorphan, an NMDA antagonist, produce effects similar to classic hallucinogens. Psychopharmacology, 223(1), 1-15. https://doi.org/10.1007/s00213-012-2680-6
  4. QT interval prolongation in diphenhydramine toxicity | https://www.sciencedirect.com/science/article/abs/pii/S0167527304000786
  5. Block of sodium currents in rat dorsal root ganglion neurons by diphenhydramine | http://www.sciencedirect.com/science/article/pii/S0006899300028602?via%3Dihub