Title: Gaboxadol
CAS Registry Number: 64603-91-4
CAS Name: 4,5,6,7-Tetrahydroisoxazolo[5,4-c]pyridin-3(2H)-one
Additional Names: 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol; THIP
Manufacturers' Codes: Lu-02-030; MK-0928
Molecular Formula: C6H8N2O2
Molecular Weight: 140.14
Percent Composition: C 51.42%, H 5.75%, N 19.99%, O 22.83%
Literature References: Selective extrasynaptic GABA agonist (SEGA); structural analog of muscimol, q.v. Prepn: P. Krogsgaard-Larsen, Acta Chem. Scand. B 31, 584 (1977); idem, EP 167; idem, US 4278676 (1979, 1981 both to H. Lundbeck & Co.). GABA agonist effects: idem et al., Nature 268, 53 (1977). 3H-THIP binding study: E. Falch, P. Krogsgaard-Larsen, J. Neurochem. 38, 1123 (1982). HPLC determn: S. M. Madsen, J. Chromatogr. 238, 509 (1982). Pharmacokinetics: idem et al., Acta Pharmacol. Toxicol. 53, 353 (1983). Pharmacodynamics and potential therapeutic uses: A. V. Christensen et al., Pharm. Weekbl. Sci. Ed. 4, 145 (1982). Clinical effects on nocturnal sleep and hormone secretion: M. Lancel et al., Am. J. Physiol. Endocrinol. Metab. 281, E130 (2001); on night sleep and cognitive performance: S. Mathias et al., Neuropsychopharmacology 30, 833 (2005). Review of clinical development: R. Huckle, Curr. Opin. Invest. Drugs 5, 766-773 (2004).
Properties: Colorless cryst, mp 242-244° (dec). uv max (methanol): 212 nm (log e 3.64). pKa (water, 25°): 4.44 ±0.03; 8.48 ±0.04.
Melting point: mp 242-244° (dec)
pKa: pKa (water, 25°): 4.44 ±0.03; 8.48 ±0.04
Absorption maximum: uv max (methanol): 212 nm (log e 3.64)
Derivative Type: Hydrobromide
CAS Registry Number: 65202-63-3
Molecular Formula: C6H8N2O2.HBr
Molecular Weight: 221.05
Percent Composition: C 32.60%, H 4.10%, N 12.67%, O 14.48%, Br 36.15%
Properties: Faintly reddish cryst from methanol-ether, mp 162-163° (dec). LD50 in mice (mg/kg): 80 i.v., 145 i.p.; >320 orally (U.S. patent).
Melting point: mp 162-163° (dec)
Toxicity data: LD50 in mice (mg/kg): 80 i.v., 145 i.p.; >320 orally (U.S. patent)
Derivative Type: Hydrochloride
CAS Registry Number: 85118-33-8
Molecular Formula: C6H8N2O2.HCl
Molecular Weight: 176.60
Percent Composition: C 40.81%, H 5.14%, N 15.86%, O 18.12%, Cl 20.08%
Use: As a molecular probe to study GABA receptors.
Therap-Cat: Sedative, hypnotic.
Keywords: Sedative/Hypnotic.
Gadobenate Dimeglumine Gadodiamide Gadofosveset Gadopentetic Acid Gadoteridol

Systematic (IUPAC) name
Clinical data
Legal status  ?
CAS number 64603-91-4 N
ATC code None
PubChem CID 3448
ChemSpider 3330 YesY
KEGG D04282 YesY
Chemical data
Formula C6H8N2O2 
Mol. mass 140.14 g/mol
 N (what is this?)  (verify)

Gaboxadol also known as 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP) is an experimental sleep aid drug developed by Lundbeck and Merck.[1] In March, 2007, Merck and H. Lundbeck cancelled work on the drug, citing safety concerns and the failure of an efficacy trial. It acts on the GABA system, but possibly in a different way from benzodiazepines, nonbenzodiazepines and barbiturates - (Valium, Sodium Pentothal, Ambien etc.). Lundbeck states that gaboxadol also increases deep sleep (stage 4). It is, however, not reinforcing like benzodiazepines are.[2]