Gaboxadol

Lore & Background

Gaboxadol was first described by Povl Krogsgaard-Larsen and colleagues in 1977. It is a conformationally constrained synthetic analogue of GABA and of muscimol, an alkaloid and hallucinogen found in Amanita muscaria mushrooms. The drug was assessed in clinical studies for various uses in the 1980s but was not found to be useful. In the 1990s and 2000s, it was repurposed for treatment of insomnia and completed phase 3 clinical trials, but development was discontinued for safety and effectiveness reasons in 2007. Subsequently, it was repurposed for Angelman syndrome and fragile X syndrome but was later abandoned completely.

Reader's Guide

Gaboxadol is significant as a unique GABAA receptor agonist that differs from benzodiazepines and Z drugs by acting at the orthosteric site rather than as a positive allosteric modulator. It produces sedative and hypnotic effects at lower doses and hallucinogenic effects at higher doses. In clinical studies for insomnia, it decreased sleep onset latency, increased sleep duration, and enhanced slow wave sleep, but showed reduced effectiveness after one month and mixed results in large trials. Its effects were much stronger in women than in men, likely due to sex differences in GABAA receptor function. The drug was found to have less robust effects on traditional hypnotic measures compared to zolpidem but caused no rebound insomnia or next-day residual symptoms. At supratherapeutic doses, it produced euphoria, dissociation, and hallucinations, with rates of psychiatric adverse effects increasing with dose. Gaboxadol was never marketed, and its development was ultimately abandoned.

Did You Know?

• Gaboxadol is a synthetic analogue of muscimol, the hallucinogenic alkaloid found in Amanita muscaria mushrooms.
• At a dose of 10 mg, its effects were anecdotally described as similar to having drunk two or three beers.
• The drug's hypnotic effects were found to be much stronger in women than in men.
• The median lethal dose (LD50) of gaboxadol in mice is greater than 320 mg/kg orally, considerably lower in lethal potency than muscimol.