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Summary sheet: Phenmetrazine
Chemical Nomenclature
Common names Preludin
Substitutive name Phenmetrazine
Systematic name 3-methyl-2-phenylmorpholine
Class Membership
Psychoactive class Stimulant
Chemical class Amphetamine
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.

Common 20 - 80 mg
Total 4 - 8 hours
Onset 15 - 30 minutes
After effects 1 - 12 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.


Phenmetrazine (also known as Preludin among many others) is a phenylmorpholine stimulant substance of the substituted amphetamine chemical class. Although it produces classical stimulant effects which includes stimulation, focus & motivation enhancement, thought acceleration, wakefulness, and euphoria when administered, it has been uniquely distinguished as having been historically preferred by users over amphetamine and even methamphetamine, at least in Sweden.[1]

Phenmetrazine was first patented in Germany in 1952 by Boehringer-Ingelheim,[2][3] with some pharmacological data published in 1954.[4] It was the result of a search by Thomä and Wick for an anorectic drug without the side-effects of amphetamine.[5]

In clinical use, phenmetrazine produces less nervousness, hyperexcitability, euphoria and insomnia than drugs of the amphetamine family.[6] It tends not to increase heart rate as much as other stimulants. Due to the relative lack of side effects, one study found it well tolerated in children.[7]

Phenmetrazine was clinically used in Europe as an anorectic (weight-loss agent) in the 1950s. It was later withdrawn due to concerns over misuse and addiction stemming from widespread recreational use.[8] Prodrug Phendimetrazine was synthesized and is still in use today, use appears regulated internationally as under the Convention of Narcotic Substances, Phendimetrazine is a Schedule III controlled substance.[9] Today, phenmetrazine is no longer produced and although detection of use has been noted in some countries</ref>Choi H, Baeck S, Jang M, Lee S, Choi H, Chung H (February 2012). "Simultaneous analysis of psychotropic phenylalkylamines in oral fluid by GC-MS with automated SPE and its application to legal cases". Forensic Science International. 215 (1–3): 81–7. PMID 21377815, it appears to have been largely superseded by amphetamine in both its pharmaceutical and street forms as well as by its research chemical analog 3-fluorophenmetrazine (3-FPM).


Phenmetrazine is a synthetic molecule of the amphetamine family. Molecules of the amphetamine class contain a phenethylamine core featuring a phenyl ring bound to an amino (NH2) group through an ethyl chain with an additional methyl substitution at Rα. Amphetamines are alpha-methylated phenethylamines.

Phenmetrazine is comprised of an amphetamine skeleton that has been incorporated into a morpholine ring. At R2 of its chain, an oxygen group is bound -- this oxygen group is linked by an ethyl chain to the terminal amine of the amphetamine chain to form a morpholine group.

Phenmetrazine is the parent compound of the popular research chemical 3-fluorophenmetrazine.


Phenmetrazine acts as a releasing agent of norepinephrine and dopamine with EC50 values of 50.4 ± 5.4 nM and 131 ± 11 nM, respectively.[10] It has negligible efficacy as a releaser of serotonin, with an EC50 value of only 7,765 ± 610 nM.[10] This accumulation of neurotransmitters in the synaptic cleft results in its euphoric and stimulating effects.

After an oral dose, about 70% of the drug is excreted from the body within 24 hours. About 19% of that is excreted as the unmetabolized drug and the rest as various metabolites.[11]

In trials performed on rats, it has been found that after subcutaneous administration of phenmetrazine, both optical isomers are equally effective in reducing food intake, but in oral administration the levo isomer is more effective. In terms of central stimulation, however, the dextro isomer is about 4 times as effective in both methods of administration.[12]

Below is a table showing phenmetrazine's potency for inducing release (EC50) of dopamine (DA), serotonin (5-HT) and noradrenaline (NE):

DA Release 131 ± 11 nM
NE Release 50.4 ± 5.4 nM
5-HT Release 7,765 ± 610 nM

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 PsychonautWiki contributors. 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 ☠.

Physical effects

Cognitive 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 a result, it may contain incomplete or even dangerously wrong information! You can help by expanding upon or correcting it.
Note: Always conduct independent research and use harm reduction practices if using this substance.

The toxicity and long-term health effects of recreational phenmetrazine use do not seem to have been studied in any scientific context and the exact toxic dosage is unknown.[citation needed]

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

Tolerance and addiction potential

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

Tolerance to many of the effects of phenmetrazine develops with prolonged and repeated use. 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). Phenmetrazine presents cross-tolerance with all dopaminergic stimulants, meaning that after the consumption of phenmetrazine all stimulants will have a reduced effect.

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.

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. Brecher EM. "The Swedish Experience"
  2. Albert Boehringer; Ernst Boehringer. Improvements in or relating to the preparation of substituted morpholines. GB773780.
  3. US Patent 2835669 - Process for the Production of Substituted Morpholines
  4. Thomä, O & Wick, H (1954). "Über einige Tetrahydro-1,4-oxazine mit sympathicomimetischen Eigenschaften". Arch. Exp. Pathol. Pharmakol. 222: 540.
  6. "Phenmetrazine Hydrochloride". J. Am. Med. Assoc. 163 (5): 357. 1957.
  7. Martel, Antonio (1957). "Preludin (Phenmetrazine) in the Treatment of Obesity". Can. Med. Assoc. J. 76 (2): 117–20. PMC 1823494 Freely accessible. PMID 13383418.
  8. Kalant, Oriana Josseau (1966). The Amphetamines: Toxicity and Addiction. ISBN 0-398-02511-8.
  10. 10.0 10.1 10.2 Rothman RB, Baumann MH (2006). "Therapeutic potential of monoamine transporter substrates". Current Topics in Medicinal Chemistry. 6 (17): 1845–59. PMID 17017961.
  11. Anthony C Moffat, M David Osselton and Brian Widdop. Clarke's Analysis of Drugs and Poisons. ISBN 0-85369-473-7.
  12. Engelhardt, A (1961). "Studies of the Mechanism of the Anti-Appetite Action of Phenmetrazine". Biochem. Pharmacol. 8 (1): 100. doi:10.1016/0006-2952(61)90520-2.
  13. Talaie, H.; Panahandeh, R.; Fayaznouri, M. R.; Asadi, Z.; Abdollahi, M. (2009). "Dose-independent occurrence of seizure with tramadol". Journal of Medical Toxicology. 5 (2): 63–67. doi:10.1007/BF03161089. eISSN 1937-6995. ISSN 1556-9039. OCLC 163567183. 
  14. Gillman, P. K. (2005). "Monoamine oxidase inhibitors, opioid analgesics and serotonin toxicity". British Journal of Anaesthesia. 95 (4): 434–441. doi:10.1093/bja/aei210Freely accessible. eISSN 1471-6771. ISSN 0007-0912. OCLC 01537271. PMID 16051647.