Gaboxadol

Gaboxadol produces sedative and hypnotic effects at lower doses and hallucinogenic effects at higher doses. and sometimes euphoria. Gaboxadol's hypnotic effects have been found to be stronger in women than in men. The drug was also studied in experimental sleep restriction and was found to increase SWS and improve daytime functioning, for instance symptoms of sleepiness and fatigue, despite equal total sleep durations. There was no tolerance to the hypnotic effects of gaboxadol after 5days of repeated administration in animals. Similarly, it maintained effectiveness in short-term clinical studies in humans. In addition, unlike such agents, gaboxadol caused no rebound insomnia on discontinuation and produced no next-day residual symptoms. While dissimilar from GABAA receptor positive allosteric modulators, the effects of gaboxadol on sleep are similar to those of the related GABAA receptor agonist muscimol and of the GABA reuptake inhibitor tiagabine. In addition, it was more effective for improving sleep maintenance than for improving sleep onset. At these doses, gaboxadol produced euphoria and hallucinogenic effects such as dissociation, perceptual changes, and hallucinations. Morris has described hallucinogenic effects he experienced with gaboxadol as follows: : "The next night I increased the dose to 35mg sublingually, and it was then that gaboxadol's relationship to muscimol became manifest. In my darkened bedroom I could hear otherworldly music emanating from the motor of a box fan, the white-noise buzzing slowing, taking on the character of an electric viola, the room’s various shadows animated by strange movements, as if cast by a flickering candle — but none of this proved distracting. Once again I fell into an all-consuming slumber." He has also reported other qualitative accounts of the hallucinogenic effects of gaboxadol. Morris has stated that gaboxadol is every bit as powerful as a hallucinogen as serotonergic psychedelics like ayahuasca, but is qualitatively completely different. ==Side effects==

Side effects of gaboxadol include dizziness, sedation, somnolence, headache, nausea, vomiting, and tachycardia, among others. It has also been reported to produce giddiness, depersonalization, impaired concentration, and bradycardia. In clinical studies for insomnia, gaboxadol has been found to be generally well-tolerated for up to 12months. At high doses, it can produce hallucinogenic effects and delirium. == Interactions ==

Gaboxadol is metabolized exclusively via glucuronidation and is not appreciated metabolized by cytochrome P450 enzymes, and hence would not be expected to interact with cytochrome P450 inhibitors or inducers. In addition, gaboxadol did not show synergistic effects in combination with alcohol or benzodiazepines in vitro or in vivo in animals. ==Pharmacology==

Pharmacodynamics Gaboxadol acts as a potent and selective GABAA receptor partial agonist. Unlike muscimol, it is not also a GABA reuptake inhibitor to any extent, and it does not inhibit the enzyme GABA transaminase (GABA-T). Its values at GABAA receptors were approximately 71% at α1 subunit-containing receptors, 98% at α2 subunit-containing receptors, 54% at α3 subunit-containing receptors, 40% at α4 subunit-containing receptors, 99% at α5 subunit-containing receptors, and 96% at α6 subunit-containing receptors. Its affinity for extrasynaptic α4β3δ subunit-containing GABAA receptors is 10-fold greater than for other subtypes. Gaboxadol has a unique affinity for extrasynaptic α4β3δ subunit-containing GABAA receptors, which mediate tonic inhibition and are typically activated by ambient, low levels of GABA in the extrasynaptic space. The supra-maximal efficacy of gabaxadol at α4β3δ subunit-containing GABAA receptors has been attributed to an increase in the duration and frequency of channel openings relative to GABA. Because of its preferential agonism of extrasynaptic GABAA receptors, gaboxadol has been referred to as a "selective extrasynaptic GABAA agonist" or "SEGA". In contrast to gaboxadol, benzodiazepines and nonbenzodiazepines do not activate δ subunit-containing GABAA receptors. On the other hand, alcohol is known to selectively potentiate δ subunit-containing extrasynaptic GABAA receptors analogously to gaboxadol. In addition, neurosteroids and propofol act on extrasynaptic δ subunit-containing GABAA receptors. This is attributed mainly to gaboxadol's much greater ability to cross the blood–brain barrier than muscimol. In rodent drug discrimination studies, gaboxadol has been found to fully generalize with muscimol. However, gaboxadol, GABAA receptor positive allosteric modulators like benzodiazepines and Z drugs, and the GABA reuptake inhibitor tiagabine all do not generalize between each other, suggesting that their interoceptive effects are different. This is in contrast to benzodiazepines like diazepam. It is a zwitterionic compound and its absorption involves active transport via intestinal transporters such as the proton-coupled amino acid transporter 1 (PAT-1). Coadministration of PAT-1 inhibitors like tryptophan or 5-hydroxytryptophan (5-HTP) has been found to decrease the absorptive permeability of gaboxadol by 53 to 89%. However, they may simply delay the absorption of gaboxadol and decrease peak levels. Distribution The distribution of gaboxadol has been studied in rodents. The drug is distributed unevenly in the brain in rodents. It is said to be more resistant to metabolism than muscimol. Gaboxadol-O-glucuronide is the only metabolite of gaboxadol formed in significant amounts. Twohours following attainment of peak concentrations, levels of gaboxadol are reduced by about 50% in humans. In rodents, the half-life of gaboxadol was about twice as long as that of muscimol. In people with severe renal impairment, circulating levels of gaboxadol were increased by 5-fold, and the renal clearance of gaboxadol was decreased by 34% while that of gaboxadol-O-glucuronide was decreased by 50%. ==Chemistry==

Gaboxadol, also known by its chemical name 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP), is a conformationally constrained synthetic analogue of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA) and of the Amanita alkaloid muscimol. It was formulated pharmaceutically as the hydrochloride salt. Numerous attempts to develop pharmacologically interesting analogues of gaboxadol have failed over the decades. This can be attributed to the very strict structural requirements for GABAA receptor binding and activation. As such, gaboxadol has been described as a unique compound and GABAA receptor agonist. ==History==

Gaboxadol was first synthesized and described by the Danish chemist Povl Krogsgaard-Larsen in 1977. It was developed via structural modification of muscimol, a constituent of Amanita muscaria mushrooms. In 1997, Lancel and colleagues published the first clinical study of the effects of gaboxadol on sleep in humans and found similar sleep improvements as in rodents. Subsequently, gaboxadol underwent formal clinical development for treatment of insomnia by Lundbeck and Merck. It reached phase 3 trials for this indication by at least 2004. Moreover, there was anxiety in the pharmaceutical industry concerning hypnotics at the time owing to bizarre reports of zolpidem (Ambien)-induced delirium that had emerged in the media in 2006. It was known internally at Ovid Therapeutics under the developmental code name OV101. ==Society and culture==

Names Gaboxadol is the generic name of the drug and its and . It is also known by its former developmental code names Lu-2-030 or Lu-02-030 (Lundbeck), MK-0928 (Merck), and OV101 (Ovid Therapeutics). Media coverage Gaboxadol was covered, along with muscimol and Amanita muscaria, in an episode of Hamilton Morris's ''Hamilton's Pharmacopeia''. Notable individuals Povl Krogsgaard-Larsen and Hamilton Morris have both self-experimented with gaboxadol. While gaboxadol was never approved for medical use, informal microdosing of muscimol and Amanita mushrooms for improvement of sleep has become increasingly prevalent by the mid-2020s. However, muscimol is far less-researched compared to gaboxadol, Povl Krogsgaard-Larsen has warned about safety concerns with regard to medicinal use of Amanita mushrooms. Legal status Gaboxadol is not a controlled substance anywhere in the world as of October 10, 2025. ==Research==

Gaboxadol was studied in the 1980s by Lundbeck and others in the treatment of a variety of medical conditions, anxiety, schizophrenia and tardive dyskinesia, epilepsy, Huntington's disease, and Alzheimer's disease. It showed poor clinical effectiveness as an anticonvulsant, in accordance with prior animal studies. The drug was also studied for treatment of major depressive disorder in combination with escitalopram in a phase 2 trial, but was ineffective. Following discontinuation of its development for insomnia, gaboxadol was repurposed by Ovid Therapeutics for treatment of the Angelman syndrome and fragile X syndrome. It reached phase 3 and phase 2 clinical trials for these conditions, respectively. Subsequently, another company known as Healx appears to have begun developing gaboxadol under the developmental code name HLX-0206 for the treatment of fragile X syndrome. ==See also==