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Death may occur when promethazine is combined with other depressants, such as opioids, benzodiazepines, barbiturates, thienodiazepines or other GABAergic substances like alcohol.[1]

Additionally, promethazine is an anticholinergic, and at high doses it may cause delirium and extremely unpleasant if not dangerous experiences. Please be extremely careful when trying this pharmaceutical and use responsible use practices such as always having a tripsitter when using promethazine, especially at high doses.

Summary sheet: Promethazine
Chemical Nomenclature
Common names Phenergan, Lergigan
Substitutive name Promethazine
Systematic name N,N,α-trimethyl-10H-phenothiazine-10-ethanamine
Class Membership
Psychoactive class Depressant / Deliriant
Chemical class Phenothiazine
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 5 - 12.5 mg
Light 12.5 - 25 mg
Common 25 - 50 mg
Strong 50 - 100 mg
Heavy 100 mg +
Total x - x hours
Onset 1 - 2 hours
Come up x - x minutes
Peak x - x hours
Offset x - x hours
After effects x 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.

Promethazine (commonly sold as Phenergan or Lergigan, and popularly known as one of the two active ingredients in "lean") is a first-generation antihistamine of the phenothiazine chemical class that produces muscle relaxing, nausea relieving and strong sedative effects when administered. It also reduces motion sickness and has anticholinergic properties.

Promethazine was developed in the mid-1940s when a team of scientists from Rhône-Poulenc laboratories was able to synthesize it from phenothiazine and a diamine side chain of diphenhydramine.[2] It was previously used as an antipsychotic,[3] although it is generally not administered for this purpose now. It has approximately 1/10 of the antipsychotic strength of chlorpromazine.

Today, promethazine is available in many countries under many brand names. Promethazine has been shown to have quality hypnotic effects and is sometimes used for this purpose.[4]

History and culture

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Promethazine became popular among the Houston rap and hip-hop scene in around 1990[5], and the trend resurfaced in around 2015 to 2016. Often, it was combined with the opiate drug codeine in a preparation called "lean." Lean usually consists of ice, Sprite or a citrus soda, the promethazine/codeine cough syrup, and occasionally jolly ranchers for enhanced flavor.



This chemistry section is incomplete.

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Promethazine is a phenothiazine-based compound.


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This pharmacology section is incomplete.

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Promethazine is a direct antagonist of histamine H1 receptors, whereas diphenhydramine is an inverse agonist. It is also an antagonist of muscarinic acetylcholine receptors, which is likely the cause of sedation and delirium that occurs with higher doses. It blocks dopaminergic D2 receptors, but weakly. [citation needed]

Subjective effects

Disclaimer: The effects listed below cite the Subjective Effect Index (SEI), a literature based on anecdotal reports and the personal experiences of PsychonautWiki contributors. As a result, they should be treated with a healthy amount of skepticism. It is worth noting that these effects will not necessarily occur in a consistent or reliable manner, although higher doses are more likely to induce the full spectrum of effects. Likewise, adverse effects become much more likely with higher doses and may include serious injury or death.

Physical effects

Cognitive effects

Visual effects

After effects
Aftereffects (3).svg

Experience reports

There are currently no anecdotal reports which describe the effects of this compound within our experience index. Additional experience reports can be found here:

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 strongly recommended that one use harm reduction practices when using this substance.

Lethal dosage

The lowest published toxic dose of promethazine in humans (oral) is 3.5 mg/kg. This means that a person weighing 70 kg can show signs of toxicity at 245 mg. The LD50 of promethazine in mice (oral) is 255 mg/kg. If applied to humans, this suggests that 50% of people weighing 70 kg would die after consuming 17.85 grams of promethazine. [8]

Tolerance and addiction potential

Promethazine is not addictive.

Dangerous interactions


This dangerous interactions section is a stub.

As such, it may contain incomplete or invalid information. You can help by expanding upon or correcting it.

Although many psychoactive substances are reasonably safe to use on their own, they can quickly become dangerous or even life-threatening when combined with other substances. The list below includes some known dangerous combinations (although it cannot be guaranteed to include all of them). Independent research (e.g. Google, DuckDuckGo) should always be conducted to ensure that a combination of two or more substances is safe to consume. Some interactions listed have been sourced from TripSit. Promethazine, because of its extensive pharmacology, has many interactions. According to the interactions checker on, promethazine is known to interact with over 1000 other prescription and OTC drugs.

  • Depressants (1,4-Butanediol, 2-methyl-2-butanol, alcohol, barbiturates, GHB/GBL, methaqualone, opioids) - This combination can result in dangerous or even fatal levels of respiratory depression. These substances potentiate the muscle relaxation, sedation and amnesia caused by one another and can lead to unexpected loss of consciousness at high doses. There is also an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should try to fall asleep in the recovery position or have a friend move them into it.
  • Anti-dopaminergics - Because promethazine also blocks dopamine receptors, other drugs and substances that do this will increase the chances of developing acute or tardive dyskinesia, neuroleptic malignant syndrome, or parkinsonism. [citation needed]
  • Anticholinergics - Promethazine with anticholinergics (or antimuscarinics) can cause increased blocking of acetylcholine, being potentially dangerous with cardiovascular effects as well as delirium. [citation needed]
  • Stimulants - Due to promethazine'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.

Legal status


This legality section is a stub.

As such, it may contain incomplete or wrong information. You can help by expanding it.

See also

External links



  1. Risks of Combining Depressants (Tripsit) |
  2. Li, Jie Jack (2006). Laughing Gas, Viagra, and Lipitor: The Human Stories behind the Drugs We Use. United Kingdom: Oxford University Press. p. 146. ISBN 9780199885282. Retrieved July 9, 2016.
  3. Archived from the original (PDF) on July 18, 2011. Retrieved October 30, 2008
  4. Adam K & Oswald, I. (1986). The hypnotic effects of an antihistamine: promethazine. British journal of clinical pharmacology, 22(6), 715-717.
  5. (2005) Tamara Palmer. Country Fried Soul: Adventures in Dirty South Hip-Hop
  6. Tsay, M. E., Procopio, G., Anderson, B. D., & Klein-Schwartz, W. (2015). Abuse and intentional misuse of promethazine reported to US poison centers: 2002 to 2012. Journal of addiction medicine, 9(3), 233-237. | PubMed Link:
  7. Tsay, M. E., Procopio, G., Anderson, B. D., & Klein-Schwartz, W. (2015). Abuse and intentional misuse of promethazine reported to US poison centers: 2002 to 2012. Journal of addiction medicine, 9(3), 233-237. | PubMed Link: