From PsychonautWiki
Jump to: navigation, search

Skull and crossbones darktextred2.png

Death may result when opiates are combined with other depressants such as benzodiazepines, barbiturates, gabapentinoids, thienodiazepines, alcohol or other GABAergic substances.[1]

It is strongly discouraged to combine these substances, particularly in common to heavy doses.

Summary sheet: Pethidine
Chemical Nomenclature
Common names Pethidine, Meperidine, Demerol, Dolantin, Dolcontral
Systematic name Ethyl 1-methyl-4-phenylpiperidine-4-carboxylate
Class Membership
Psychoactive class Opioid
Chemical class Phenylpiperidine
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.

Bioavailability 50-60%
Threshold 25 - 50 mg
Light 50 - 100 mg
Common 100 - 200 mg
Strong 200 - 400 mg
Heavy 400 mg +
Onset 30 - 60 minutes
Peak 4 - 6 hours
After effects 2 - 10 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.

Serotonin releasers
Selective serotonin re-uptake inhibitors
Serotonin-norepinephrine reuptake inhibitors

Pethidine, known as meperidine in the United States (sold under the brand name Demerol), is a synthetic opioid analgesic used for the treatment of moderate to severe pain. Compared to traditional opioids such as morphine, pethidine was originially thought to be much safer and have less potential for abuse. It was later discovered that pethidine is significantly less safe than morphine and its metabolite norpethidine can be extremely toxic.



This chemistry section is incomplete.

You can help by adding to it.

Pethidine is an opioid in the phenylpiperidine class.


Opioids exert their effects by binding to and activating the μ-opioid receptor. This occurs because opioids structurally mimic endogenous endorphins which are naturally found within the body and also work upon the μ-opioid receptor set. The way in which opioids structurally mimic these natural endorphins results in their euphoria, pain relief and anxiolytic effects. This is because endorphins are responsible for reducing pain, causing sleepiness, and feelings of pleasure. They can be released in response to pain, strenuous exercise, orgasm, or general excitement. The bioavailability of orally administered pethidine can vary from 50% to around 60%.

Compared to traditional opioids, pethidine has a very unique pharmacological profile. In addition to being an opioid, pethidine is also a muscarinic acetylcholine receptor antagonist. Pethidine is also a dopamine reuptake inhibitor and norepinephrine reuptake inhibitor. Pethidine is a κ-opioid agonist and its metabolite norpethidine is also an extremely powerful serotonin reuptake inhibitor.[2]

Subjective effects

The effects listed below are based upon the subjective effects index and personal experiences of PsychonautWiki contributors. These 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 of inducing a full range of effects. Likewise, adverse effects become much more likely on higher doses and may include serious injury or death. Many users note that they find pethidine just as, or more euphoric than oxycodone.[3]

Physical effects

Cognitive effects

Visual effects

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

Pethidine has a high toxicity relative to dose. As with all opioids, long-term effects can vary but can include diminished libido, apathy and memory loss. It is also potentially lethal when mixed with depressants like alcohol or benzodiazepines and generally has a wider range of substances which it is dangerous to combine with in comparison to other opioids.

One of pethdine's metabolites, norpethidine has little to no opioid action, but is known to cause seizures. Pethidine should not be taken during benzodiazepine withdrawals as this can potentially cause seizures. In 1984, Libby Zion, a teenager was brought to the emergency room due to a "flu-like" ailment. She was previously prescribed and taking phenelzine, a monoamine oxidase inhibitor, which in combination caused fatal serotonin syndrome.[4]

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

Tolerance and addiction potential

As with other opioids, the chronic use of pethidine can be considered extremely addictive with a high potential for abuse and is capable of causing psychological dependence among certain users. When addiction has developed, cravings and withdrawal symptoms may occur if a person suddenly stops their usage.

Tolerance to many of the effects of pethidine develops with prolonged and repeated use. The rate at which this occurs develops at different rates for different effects, with tolerance to the constipation-inducing effects developing particularly slowly for instance. 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). Pethidine presents cross-tolerance with all other opioids, meaning that after the consumption of pethidine all opioids will have a reduced effect.

The risk of fatal opioid overdoses rise sharply after a period of cessation and relapse, largely because of reduced tolerance.[5] To account for this lack of tolerance, it is safer to only dose a fraction of one's usual dosage if relapsing. It has also been found that the environment one is in can play a role in opioid tolerance. In one scientific study, rats with the same history of heroin administration were significantly more likely to die after receiving their dose in an environment not associated with the drug in contrast to a familiar environment.[6]

Dangerous interactions

Although many psychoactive substances are reasonably safe to use on their own, they can quickly become dangerous or even life-threatening when taken with other substances. The following lists some known dangerous combinations, but cannot be guaranteed to include all of them. Independent research 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.

  • Stimulants - It can be dangerous to combine depressants with stimulants due to the risk of accidental excessive intoxication. Stimulants mask the sedative effect of depressants, which is the main factor most people use to gauge their level of intoxication. Once the stimulant effects wear off, the effects of the depressant will significantly increase, leading to intensified disinhibition, motor control loss, and dangerous black-out states. This combination can also potentially result in severe dehydration if one's fluid intake is not closely monitored. If choosing to combine these substances, one should strictly limit themselves to a pre-set schedule of dosing only a certain amount per hour until a maximum threshold has been reached.

Serotonin syndrome risk

Pethidine is known to have a significantly increased chance of causing serotonin syndrome than other serotonergic opioids such as tramadol.[citation needed] Combinations with the following substances can cause dangerously high serotonin levels. Serotonin syndrome requires immediate medical attention and can be fatal if left untreated.

Legal issues


This legality section is a stub.

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

  • Germany: Pethidine is a controlled substance under Anlage III of the BtMG. It can only be prescribed on a narcotic prescription form.[8]
  • United States: Pethidine is a Schedule II Controlled Substance.[9]
  • United Kingdom: Pethidine is a Class A, Schedule 2 drug in the United Kingdom.[10]

See also

External links


  1. Risks of Combining Depressants (Tripsit) |
  2. Meperidine: A Critical Review |
  3. Subjective, Psychomotor, and Physiological Effects of Cumulative Doses of Opioid μ Agonists in Healthy Volunteers |
  4. Serotonin Syndrome and the Libby Zion Affair |
  5. Why Heroin Relapse Often Ends In Death - Lauren F Friedman (Business Insider) |
  6. Siegel, S., Hinson, R., Krank, M., & McCully, J. (1982). Heroin “overdose” death: contribution of drug-associated environmental cues. Science, 216(4544), 436–437.
  7. Gillman, P. K. (2005). Monoamine oxidase inhibitors, opioid analgesics and serotonin toxicity. British Journal of Anaesthesia, 95(4), 434-441.
  9. DEA Controlled Substances |
  10. UK Controlled Drugs |