Ondansetron

Athanor · official

C₁₈H₁₉N₃O · 293.4 g/mol

IUPAC name: 9-methyl-3-[(2-methylimidazol-1-yl)methyl]-2,3-dihydro-1H-carbazol-4-one

Also called Zofran, 5-HT3 antagonist, antiemetic

Drugs Rings

Open in Athanor

Drawn from its SMILES with RDKit

DangerToxic if swallowed · Causes skin irritation · Causes serious eye damage · Causes serious eye irritation · May cause respiratory irritation · May cause harm to breast-fed children · Very toxic to aquatic life · Very toxic to aquatic life with long lasting effects

Names and identifiers

IUPAC name: 9-methyl-3-[(2-methylimidazol-1-yl)methyl]-2,3-dihydro-1H-carbazol-4-one
Synonyms: Zofran, 5-HT3 antagonist, antiemetic
+ 37 more
Zudan, Zofran ODT, Zuplenz, 9-methyl-3-[(2-methylimidazol-1-yl)methyl]-2,3-dihydro-1H-carbazol-4-one, DTXSID8023393, 4AF302ESOS, A04AA01, EUR-1025, NSC-757870, 1,2,3,9-Tetrahydro-9-methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-4H-carbazol-4-one, 9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-2,3,4,9-tetrahydro-1H-carbazol-4-one, DTXCID803393, 1,2,3,9-tetrahydro-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-4H-carbazol-4-one, 4H-Carbazol-4-one, 1,2,3,9-tetrahydro-9-methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-, Odansetron (common misspelling of ondansetron), Odansetron [common misspelling of ondansetron], Monohydrochloride, Ondansetron, Monohydrochloride Dihydrate, Ondansetron, ondansetronum, ondasetron, Ondansetron ODT, 9-methyl-3-((2-methylimidazol-1-yl)methyl)-2,3-dihydro-1H-carbazol-4-one, 9-methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-2,3,4,9-tetrahydro-1H-carbazol-4-one, ODT, Zofran, Ondansetron Monohydrochloride Dihydrate, RefChem:6085, Hydrochloride, Ondansetron, Ondansetron, (+,-)-, SN307, Dihydrate, Ondansetron Monohydrochloride, 9-Methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-2,3-dihydro-1H-carbazol-4(9H)-one, MFCD00833882, BRN 3622981, GR-38032, HSDB 8304, Ondansetron (Hydrochloride), 9-methyl-3-((2-methyl-1H-imidazol-1-yl)methyl)-1,2,3,9-tetrahydro-4H-carbazol-4-one
Molecular formula: C₁₈H₁₉N₃O
Empirical formula: C₁₈H₁₉N₃O
Molecular weight: 293.4 g/mol
Exact mass: 293.15281
CAS number: 99614-02-5
PubChem CID: 4595
Canonical SMILES: CC1=NC=CN1CC2CCC3=C(C2=O)C4=CC=CC=C4N3C
Isomeric SMILES: CC1=NC=CN1CC2CCC3=C(C2=O)C4=CC=CC=C4N3C
InChI: InChI=1S/C18H19N3O/c1-12-19-9-10-21(12)11-13-7-8-16-17(18(13)22)14-5-3-4-6-15(14)20(16)2/h3-6,9-10,13H,7-8,11H2,1-2H3
InChIKey: FELGMEQIXOGIFQ-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Calculated

Heavy atoms: 22
Rings: 4
Aromatic rings: 3
Fraction sp³ carbons (Fsp3): 0.33
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 2
TPSA (Å²): 39.8
Formal charge: 0
XLogP3: 2.3 PubChem
Complexity: 440 PubChem
Stereocenters: 0 defined, 1 undefinedCIP: C8: undefined
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C73.69%
H6.53%
N14.32%
O5.45%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 3.13 Crippen (Wildman and Crippen 1999)
log S (water solubility): -3.97 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 3.06 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 293.37
log P ≤ 5 (Crippen): 3.13
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 2

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Most widely reported: 17 company reports to ECHA. Source [2].

Corrosive
Acute toxicity
Harmful or irritant
Environmental hazard

H301Toxic if swallowed (88.2% of reports)
H315Causes skin irritation (64.7% of reports)
H318Causes serious eye damage (11.8% of reports)
H319Causes serious eye irritation (70.6% of reports)
H335May cause respiratory irritation (64.7% of reports)
H362May cause harm to breast-fed children (58.8% of reports)
H400Very toxic to aquatic life (82.4% of reports)
H410Very toxic to aquatic life with long lasting effects (82.4% of reports)

Precautionary statements: P203, P260, P261, P263, P264, P264+P265, P270, P271, P273, P280, P301+P316, P302+P352, P304+P340, P305+P351+P338, P305+P354+P338, P317, P318, P319, P321, P330, P332+P317, P337+P317, P362+P364, P391, P403+P233, P405, P501

View all classifications (2)

[2] European Chemicals Agency (ECHA) · 17 reports · DangerH301, H315, H318, H319, H335, H362, H400, H410
[1] Hazardous Substances Data Bank (HSDB) · DangerH301, H318, H400, H411

Storage

Store upright between 15 deg and 30 °C (59 deg and 86 °F). Protect from light. Store bottles upright in cartons.[1]
Keep container tightly closed in a dry and well-ventilated place. Recommended storage temperature: -20 °C. (ondansetron hydrochloride dihydrate)[1]

Incompatibilities

Incompatible materials: Strong oxidizing agents (ondansetron hydrochloride dihydrate)[1]

Safety data sheets on the supplier’s page: AppChem, AstaTech, Inc., MuseChem.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[3]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[4]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[5]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[6]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.