THPC

Clinical data
Other names	1-Methyl-1,2,5,6-tetrahydropyridine-3-(N,N-diethylcarboxamide); 1-Methyl-1,2,5,6-tetrahydropyridine-3-diethylcarboxamide
Drug class	Serotonin antagonist;Serotonin5-HT2A receptorantagonist;Hallucinogen antidote
ATC code	None
Identifiers
IUPAC name N,N-diethyl-1-methyl-3,6-dihydro-2H-pyridine-5-carboxamide
CAS Number	26070-52-0
PubChemCID	3084450
ChemSpider	2341509
CompTox Dashboard(EPA)	DTXSID90180709
Chemical and physical data
Formula	C11H20N2O
Molar mass	196.294 g·mol−1
3D model (JSmol)	Interactive image
SMILES CCN(CC)C(=O)C1=CCCN(C1)C
InChI InChI=1S/C11H20N2O/c1-4-13(5-2)11(14)10-7-6-8-12(3)9-10/h7H,4-6,8-9H2,1-3H3 Key:QELRLWHVJBVJOI-UHFFFAOYSA-N

THPC, also known as1-methyl-1,2,5,6-tetrahydropyridine-3-diethylcarboxamide, is a greatly simplifiedanalogue of thepsychedeliclysergamidelysergic acid diethylamide (LSD) in which only a modified version of the D ring (and itssubstitutions) remains.^{[1][2][3][4][5]}

THPC was assessed and produced no behavioral effects by itself in rodents.^[1][2][4] However, the drug was reported to markedly potentiate the behavioral effects ofmescaline and to inhibit the effects of LSD in rodents.^[1][2][3][4] It was suggested that THPC might be clinically useful as ahallucinogen antagonist against LSD, for instance in the context ofrecreational LSD use.^[5] In any case, findings of these studies were based on very small numbers of animals and have been limitedly or not replicated.^[1][6]

Subsequent studies of THPC in severalin vitro andin vivo systems have provided mixed results.^[7] It has been found to stronglycontractsmooth muscle, but themechanism of this action, such asα-adrenergic orhistamine receptor activation, has not been determined, except that it was not reversed byserotonin antagonists.^[2] In another study, THPC antagonized the contractions ofsheepumbilicalvasculature induced byserotonin, mescaline, and LSD, and it was concluded that THPC is a weak serotonin antagonist.^[1][7][8] Accordingly, THPC was found to completely block LSD binding toreceptors insynaptosomalmembranes from rat forebrain.^[7][9][10] However, THPC reportedly did not block serotonin binding in this preparation.^[10] In any case, this binding site is said to have been later identified as the serotonin5-HT_2A receptor in 1979.^[1] In other studies, THPC did not block various specific effects of mescaline and LSD.^[1][7][6]

THPC was first described in thescientific literature byJohn Raymond Smythies and colleagues in 1970.^{[1][2][3][4][5]} It was reviewed byDavid E. Nichols in histhesis in 1973^[2] and by Steven A. Barker in 2025.^[1] Along with other drugs likechlorpromazine,2-bromo-LSD, andcinanserin, THPC was one of the first claimed antagonists of the behavioral effects of LSD to be identified.^[1][9][11] Various analogues of THPC have also beensynthesized and studied, including as serotonin antagonists.^[1][5][6]

• Partial lysergamide
• Nikethamide
• Arecoline
• Azacyclonol

• THPC - Isomer Design

• Drugs not assigned an ATC code
• 5-HT2A antagonists
• Carboxamides
• Diethylamino compounds
• Hallucinogen antidotes
• Methyl compounds
• Partial ergolines
• Serotonin receptor antagonists
• Tetrahydropyridines

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