Promethazine
Also called Phenergan, Lergigan, Diphergan, Protazine, Dimapp
Dosage
Oral bands as drawn from PsychonautWiki's ranges below. The table is the source of truth.
When sources disagree, both rows are shown as published. Nothing is averaged or merged.
Oral
| Source | Threshold | Light | Common | Strong | Heavy |
|---|---|---|---|---|---|
| PsychonautWiki | 5–12.5 mg PW | 12.5–25 mg PW | 25–50 mg PW | 50–100 mg PW | 100 mg+ PW |
| TripSit | – | – | 25–75 mg TS | – | – |
NOTE: This is what is normally used in medicinal settings, and is usually what is prescribed to you, since it has anticholinergic properties; IE; Delirant. TS
TripSit dose text
TripSit's factsheet also states its doses as text.
Common: 25-75mg's. | NOTE: This is what is normally used in medicinal settings, and is usually what is prescribed to you, since it has anticholinergic properties; IE; Delirant. TS
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Duration
Oral, drawn at the midpoint of each PsychonautWiki range.
| Route · source | Onset | Come-up | Peak | Offset | Total | After-effects |
|---|---|---|---|---|---|---|
| Oral · PsychonautWiki | 30–60 minutes PW | 20–60 minutes PW | 1–2 hours PW | 3–5 hours PW | 4–6 hours PW | 12 hours PW |
TripSit factsheet
Mixing
For best safety practice, don't mix this drug with other depressants.
Why: respiratory depression. PsychonautWiki says:
- “Respiratory depression (also known as hypoventilation) can be described as a reduced urge to breathe that can be fatal depending on its intensity.” (PsychonautWiki, Respiratory depression, revision 150612)
- “... otherwise safe dosages of these compounds can become fatal when combined with even small amounts of other classes of depressant. For example, benzodiazepines combined with opioids are an extremely common cause of fatal respiratory depression. It is therefore strongly discouraged to combine these depressants at any dosage range.” (PsychonautWiki, Respiratory depression, revision 150612)
- “The most common cause of substance-related deaths is the combination of depressants (such as opiates, benzodiazepines, or alcohol) with other depressants.” (PsychonautWiki, Responsible drug use, revision 168206)
- “This combination potentiates the muscle relaxation, amnesia, sedation, and respiratory depression caused by one another. At higher doses, it can lead to a sudden, unexpected loss of consciousness along with a dangerous amount of depressed respiration.” (PsychonautWiki, dangerous interactions table, "Depressants" row, revision 156847)
Quotes from PsychonautWiki, CC BY-SA 4.0.
Acute combinations: what happens when these are taken close together. Entries backed by a medical journal or agency are listed first.
Backed by medical journals
Other documented combinations
- 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. PW⚠ PsychonautWiki lists this combination without a danger rating.
- 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. PW⚠ PsychonautWiki itself has flagged this text: citation needed.⚠ PsychonautWiki lists this combination without a danger rating.
- Anticholinergics - Promethazine with anticholinergics (or antimuscarinics) can cause increased blocking of acetylcholine, being potentially dangerous with cardiovascular effects as well as delirium. PW⚠ PsychonautWiki itself has flagged this text: citation needed.⚠ PsychonautWiki lists this combination without a danger rating.
- 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. PW⚠ PsychonautWiki lists this combination without a danger rating.
Risks and toxicity
It is strongly recommended that one use harm reduction practices when using this substance. PW
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.[1] PW
Tolerance and addiction potential
Promethazine is not addictive. PW
Dangerous interactions
Promethazine, because of its extensive pharmacology, has many interactions. According to the interactions checker on Drugs.com, promethazine is known to interact with over 1000 other prescription and OTC drugs. PW
Median lethal dose (LD50) in animals
Quoted from PubChem's Non-Human Toxicity Values, which come from the Hazardous Substances Data Bank (HSDB). PubChem describes them as: “Quantitative non-human toxicity values (e.g., lethal dose) for this compound. The data shown here are mostly for lab animals (e.g., rat, mouse, guinea pig, and rabbit).” and defines the “LD50 (median lethal dose, the estimated amount of a chemical expected to kill 50% of test animals in a single dose)”. PC
| LD50 (as the source gives it) | Reference |
|---|---|
| LD50 Rabbit iv 19 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1393 (via HSDB record 3173) |
| LD50 Rabbit oral 580 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1393 (via HSDB record 3173) |
| LD50 Mouse im 175 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1393 (via HSDB record 3173) |
| LD50 Mouse iv 40 mg/kg PC | Lewis, R.J. Sr. (ed) Sax's Dangerous Properties of Industrial Materials. 11th Edition. Wiley-Interscience, Wiley & Sons, Inc. Hoboken, NJ. 2004., p. 1393 (via HSDB record 3173) |
Testing
Effects
Overview
Promethazine (commonly sold as Phenergan or Lergigan) is a depressant substance of the phenothiazine class. Alongside codeine, it is popularly known as one of the active two ingredients in "lean". It acts as an antihistamine. PW
A first generation antihistamine, which also possesses anticholinergic, strong sedative and antipsychotic properties. Once commonly used as a treatment for psychosis, it is now more commonly seen as a component of codeine cough syrups as an anti-nausea agent. TS
History
Legal status
- Austria: Promethazine is no longer marketed or available by standard prescription. Personal import from Germany or another EEA country may be possible through an Austrian pharmacy.[2] PW
- Germany: Promethazine is available through a prescription.[3] PW
- Russia: Promethazine is available through a prescription. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- United States: Promethazine is available through a prescription.[4] PW
- Canada: Promethazine is available over the counter. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- Japan: Promethazine is available through a prescription. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- Australia: Promethazine is available over the counter. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- United Kingdom: Promethazine is available over the counter. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- Italy: Promethazine is available over the counter, both as a cream and as a syrup in combination with paracetamol and DXM. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
- The Netherlands: Promethazine is available through a prescription. PW⚠ PsychonautWiki itself has flagged this text: citation needed.
Pharmacology
Chemistry
User reports
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References
- Other https://www.caymanchem.com/msdss/16478m.pdf
- Other https://ris.bka.gv.at/NormDokument.wxe?Abfrage=Bundesnormen&Anlage=&Artikel=&FassungVom=2026-02-11&Gesetzesnummer=20006868&Paragraf=11
- Other BfArM. &. link 2
- Journal / agency FDA. Promethazine Monograph
Text and values on this page are quoted from PsychonautWiki (CC BY-SA 4.0), TripSit factsheets, PubChem (public domain). Each value links to the exact revision it came from.