Pethidine

Fatal overdose may occur when opiates are combined with other depressants such as benzodiazepines, barbiturates, gabapentinoids, thienodiazepines, alcohol or other GABAergic substances.

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

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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. ⇣ Oral Dosage Bioavailability 50-60% Threshold 25 - 50 mg Light 50 - 100 mg Common 100 - 200 mg Strong 200 - 400 mg Heavy 400 mg + Duration 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.
Interactions
Stimulants
MAOIs
Nitrous
PCP
Alcohol
Benzodiazepines
DXM
GHB
GBL
Ketamine
MXE
Tramadol
Grapefruit
MAOIs
Serotonin releasers
SSRIs
5-HTP

Summary sheet: Pethidine

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 norpthidine can be extremely toxic.

Chemistry

This chemistry section is incomplete. You can help by adding to it.

Pethidine is an opioid in the phenylpiperidine class.

Pharmacology

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.

Subjective effects

The effects listed below are based upon the subjective effects index and personal experiences of PsychonautWiki contributors. The listed effects will rarely (if ever) occur all at once, but heavier dosages will increase the chances and are more likely to induce a full range of effects. Many users note that they find pethidine just as, or more euphoric than oxycodone.

Physical effects

The general sensation of pethidine can be described as one of euphoria, relaxation, anxiety suppression and pain relief.

• Pain relief
• Physical euphoria - This particular substance can be considered as very intense in its physical euphoria. The sensation itself can be described as extreme feelings of intense physical comfort, warmth, love and bliss.
• Itchiness
• Respiratory depression - At low to moderate doses, this effect results in the sensation that the breath is slowed down mildly to moderately, but does not cause noticeable impairment. At high doses and overdoses, opioid-induced respiratory depression can result in a shortness of breath, abnormal breathing patterns, semi-consciousness, or unconsciousness. Severe overdoses can result in a coma or death without immediate medical attention.
• Constipation
• Cough suppression
• Difficulty urinating
• Nausea
• Sedation or Stimulation - Some users find pethidine sedating, while others find it stimulating.
• Pupil constriction
• Decreased libido
• Appetite suppression
• Orgasm suppression
• Seizures - High doses of pethidine may cause seizures. This is because of its metabolite norpethidine.

Cognitive effects

• Cognitive euphoria - This particular substance can be considered as very intense in its cognitive euphoria. The sensation itself can be described as powerful and overwhelming feeling of emotional bliss, contentment, and happiness.
• Anxiety suppression
• Compulsive redosing
• Dream potentiation

Visual effects

• Acuity suppression - Pethidine is a muscarinic acetylcholine receptor antagonist which may cause blurred vision at high doses.

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 [[Toxicity::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 know 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.

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 [[Cross-tolerance::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. 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.

Dangerous interactions

Although many drugs are safe on their own, they can become dangerous and even life-threatening when combined with other substances. The list below contains some common potentially dangerous combinations, but may not include all of them. Certain combinations may be safe in low doses of each but still increase the potential risk of death. Independent research should always be done to ensure that a combination of two or more substances is safe before consumption.

• Depressants (1,4-Butanediol, 2m2b, alcohol, barbiturates, benzodiazepines, GHB/GBL, methaqualone) - 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 attempt to fall asleep in the recovery position or have a friend move them into it.
• Dissociatives - This combination can result in an increased risk of vomiting during unconsciousness and death from the resulting suffocation. If this occurs, users should attempt to fall asleep in the recovery position or have a friend move them into it.
• Stimulants - It is dangerous to combine pethidine, a depressant, with stimulants due to the risk of excessive intoxication. Stimulants decrease the sedative effect of pethidine, which is the main factor most people consider when determining their level of intoxication. Once the stimulant wears off, the effects of pethidine will be significantly increased, leading to intensified disinhibition as well as other effects. If combined, one should strictly limit themselves to only taking a certain amount of pethidine.
• Psychedelics - Pethidine is well known to lower seizure threshold and psychedelics also cause occasional seizures.

Serotonin syndrome risk

Pethidine is known to cause serotonin syndrome at a significantly higher rate than other serotonergic opioids such as tramadol. Combinations with the following substances can cause dangerously high serotonin levels. Serotonin syndrome requires immediate medical attention and can be fatal if left untreated.

• MAOIs - Such as banisteriopsis caapi, syrian rue, phenelzine, selegiline, and moclobemide.
• Serotonin releasers - Such as MDMA, 4-FA, methamphetamine, methylone and αMT.
• SSRIs - Such as citalopram and sertraline
• [[Wikipedia:SNRIs|DangerousInteraction::SNRIs]] - Such as tramadol and venlafaxine
• 5-HTP

Legal issues

This legality section is a stub. As such, it may contain incomplete or wrong information. You can help by expanding it.

• United States: Pethidine is a Schedule II Controlled Substance.
• United Kingdom: Pethidine is a Class A, Schedule 2 drug in the United Kingdom.

See also

• Responsible use
• Opioid
• Tramadol
• Fentanyl
• Dextropropoxyphene
• Haloperidol

External links

• Pethidine (Wikipedia)
• Pethidine (Tripsit)