Levonantradol.

Levonantradol is a synthetic cannabinoid of the nantradol series (an octahydro-phenanthridine skeleton), the active (−) enantiomer of nantradol: in mice it is active from 0.123 to 1.5 mg/kg whereas its (+) enantiomer is inactive, and the (−) enantiomers of the three pairs of cannabinoids studied are up to 770 times more potent than Δ9-6a,10a-trans-THC (Little et al., J Pharmacol Exp Ther 1988, PMID 2849657). In human plasma only its deacetylated metabolite is detected, at concentrations of less than 5 to 51 ng/mL for doses of 0.25 to 3.0 mg (Shepard et al., J Clin Pharmacol 1981, PMID 7298868). Clinically, a single intramuscular dose produced an analgesic effect superior to placebo in 56 patients with postoperative or trauma pain, with no dose-effect relation, and with side effects in 57% of treated patients against 2 of 16 on placebo, mostly drowsiness (Jain et al., J Clin Pharmacol 1981, PMID 7028791). In 23 patients on chemotherapy, eight were partly protected from acute digestive disturbance, 21 showed toxicity, six of them major affective effects, and the authors did not recommend its use as an antiemetic (Joss et al., Cancer Chemother Pharmacol 1982, PMID 7139853). Pfizer ended its cannabinoid analgesic programme after early clinical trials with levonantradol; there is no modern human data and no authorised medical use.

Source

A wholly synthetic molecule, absent from cannabis and from the human body. It comes from the programme to find non-opioid analgesics run at Pfizer, which also delivered CP 55,940. Levonantradol is the levorotatory, active enantiomer of the racemic nantradol (Little et al. 1988: the (+) enantiomer is inactive).

No biological pathway: levonantradol is produced neither by cannabis nor by the human body. It is a wholly synthetic molecule of the phenanthridine series (a nitrogen analogue of pyran-ring cannabinoids), whose active enantiomer was obtained by an asymmetric route in 2013 (Sheshenev et al.).

European Union

No European Union control measure was found in the sources consulted; the regime depends on the national law of each Member State. No marketing authorisation appears in the sources consulted.

France

Not classified: absent from the ANSM list of narcotics (consolidated version updated 16/02/2026), whose generic families in Annex IV (benzo[c]chromene, indoles, indazoles, cyclohexylphenols) do not cover the phenanthridine skeleton; nabilone is named there, but it is a different molecule. No marketing authorisation; a research reagent.

Sources: EUR-Lex, UNODC, CND, ANSM, IUPHAR/BPS, ChEBI, EUDA. Our method.

Family

Synthetic CB receptor agonist › Research ligand or medicine

Class

non-classical

Verification

Classification, sources and binding values checked on 20 October 2026; text read against its sources and Wikipedia.

Wikipedia (English)

Levonantradol (new tab)

Article paired by the molecule's structure (InChIKey), revision read on 19 October 2026. Read as a second opinion, never cited as a source.

1. 1Jain AK et al., J Clin Pharmacol 1981: intramuscular levonantradol and placebo in acute postoperative pain (new tab)PMID 7028791
2. 2Shepard RM et al., J Clin Pharmacol 1981: pharmacokinetics of levonantradol in animals and in humans (new tab)PMID 7298868
3. 3Joss RA et al., Cancer Chemother Pharmacol 1982: levonantradol, an antiemetic with a high rate of adverse effects (new tab)PMID 7139853
4. 4Howlett AC et al., Mol Pharmacol 1988: non-classical cannabinoid analgesics inhibit adenylate cyclase (new tab)PMID 3352594
5. 5Little PJ et al., J Pharmacol Exp Ther 1988: pharmacology and stereoselectivity of novel cannabinoids in mice (new tab)PMID 2849657
6. 6Sheshenev AE et al., Chem Commun 2013: asymmetric synthesis and structural analysis of levonantradol (new tab)PMID 23535893
7. 7Howlett AC, Thomas BF, Huffman JW, Molecules 2021: Pfizer stopped its cannabinoid analgesic programme after the early levonantradol trials (new tab)
8. 8Maccarrone M et al., Pharmacol Rev 2023: levonantradol, project stopped owing to sedative and euphoric or dysphoric properties (new tab)
9. 9PubChem, Levonantradol (CID 5361881): identifiers and synonyms (CP 50,556-1) (new tab)

SMILES

C[C@H]1[C@@H]2CC[C@H](C[C@H]2C3=C(N1)C=C(C=C3OC(=O)C)O[C@H](C)CCCC4=CC=CC=C4)O

Machine-readable entry (JSON)

LLM ingestion format: a structured superset of the entry (identifiers, binding, versioned legal status). Full corpus.