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Pethidine, known as meperidine in the United States (sold under the brand name Demerol), is a synthetic opioidanalgesic 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.
WARNING: Always start with lower doses due to differences between individual body weight, tolerance, metabolism, and personal sensitivity. See responsible use section.
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.
Pethidine is a synthetic opioid of the phenylpiperidine class. Pethidine is the prototype of a large family of analgesics including the pethidine 4-phenylpiperidines (piminodine, anileridine and others), the prodines (alphaprodine, MPPP, etc.), bemidones (ketobemidone, etc.) and others more distant, including diphenoxylate and analogues.[2] The most coomon hydrochloride form is a white crystalline substance with a melting point of 186 C to 189 C. It is readily soluble in water and has a neutral reaction and a slightly bitter taste.[3]
Pethidine can be produced in a two-step synthesis. The first step is reaction of benzyl cyanide and chlormethine in the presence of sodium amide to form a piperidine ring. The nitrile is then converted to an ester.[4]
Pharmacology
Opioids exert their effects by binding to and activating the μ-opioidreceptor. 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 acetylcholinereceptorantagonist. Pethidine is also a dopaminereuptake inhibitor and norepinephrine reuptake inhibitor. Pethidine is a κ-opioid agonist and its metabolite norpethidine is also an extremely powerful serotonin reuptake inhibitor.[5]
Subjective effects
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 PsychonautWikicontributors. 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 ☠. Many users note that they find pethidine just as, or more euphoric than oxycodone.[6]
Physical effects
The general sensation of pethidine can be described as one of euphoria, relaxation, anxiety suppression and 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.
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.
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.
Acuity suppression - Pethidine is a muscarinic acetylcholine receptor antagonist which may cause blurred vision at high doses.
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:
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 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.[7]
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.[8] 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.[9]
Dangerous interactions
Warning:Many psychoactive substances that are reasonably safe to use on their own can suddenly become dangerous and even life-threatening when combined with certain other substances. The following list provides some known dangerous interactions (although it is not guaranteed to include all of them).
Always conduct independent research (e.g. Google, DuckDuckGo, PubMed) to ensure that a combination of two or more substances is safe to consume. Some of the listed interactions have been sourced from TripSit.
Alcohol - Both substances potentiate the ataxia and sedation caused by the other and can lead to unexpected loss of consciousness at high doses. Place affected patients in the recovery position to prevent vomit aspiration from excess. Memory blackouts are likely
Stimulants - Stimulants increase respiration rate which allows for a higher dose of opiates than would otherwise be used. If the stimulant wears off first then the opiate may overcome the user and cause respiratory arrest.
Benzodiazepines - Central nervous system and/or respiratory-depressant effects may be additively or synergistically present. The two substances potentiate each other strongly and unpredictably, very rapidly leading to unconsciousness. While unconscious, vomit aspiration is a risk if not placed in the recovery position blackouts/memory loss likely.
DXM - Generally considered to be toxic. CNS depression, difficulty breathing, heart issues, and liver toxicity have been observed. Additionally if one takes DXM, their tolerance of opiates goes down slightly, thus causing additional synergistic effects.
GHB/GBL - The two substances potentiate each other strongly and unpredictably, very rapidly leading to unconsciousness. While unconscious, vomit aspiration is a risk if not placed in the recovery position
Ketamine - Both substances bring a risk of vomiting and unconsciousness. If the user falls unconscious while under the influence there is a severe risk of vomit aspiration if they are not placed in the recovery position.
MAOIs - Coadministration of monoamine oxidase inhibitors (MAOIs) with certain opioids has been associated with rare reports of severe adverse reactions. There appear to be two types of interaction, an excitatory and a depressive one. Symptoms of the excitatory reaction may include agitation, headache, diaphoresis, hyperpyrexia, flushing, shivering, myoclonus, rigidity, tremor, diarrhea, hypertension, tachycardia, seizures, and coma. Death has occurred in some cases.
MXE - MXE can potentiate the effects of opioids but also increases the risk of respiratory depression and organ toxicity.
Nitrous - Both substances potentiate the ataxia and sedation caused by the other and can lead to unexpected loss of consciousness at high doses. While unconscious, vomit aspiration is a risk if not placed in the recovery position. Memory blackouts are common.
PCP - PCP may reduce opioid tolerance, increasing the risk of overdose.
Tramadol - Increased risk of seizures. Tramadol itself is known to induce seizures and it may have additive effects on seizure threshold with other opioids. Central nervous system- and/or respiratory-depressant effects may be additively or synergistically present.
Grapefruit - While grapefruit is not psychoactive, it may affect the metabolism of certain opioids. Certain opioids such as oxycodone and fentanyl primarily metabolized by the enzyme CYP3A4, which is potently inhibited by grapefruit juice[10]. This may cause the drug to take longer to clear from the body. it may increase toxicity with repeated doses. Methadone may also be affected[10]. Codeine, hydrocodone, and Tramadol are metabolized by CYP2D6. People who are on medicines that inhibit CYP2D6, or that lack the enzyme due to a genetic mutation will not respond to codeine as it can not be metabolized into its active product: morphine.
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.
. eISSN 1471-6771. ISSN 0007-0912. OCLC 01537271. PMID 16051647.