Iso-THIP, or isoTHIP, is a selective and potent GABA<sub>A</sub>-ÃÂ receptor (GABA<sub>C</sub> receptor) antagonist related to gaboxadol (THIP). It is 4-fold more potent than gaboxadol as a GABA<sub>A</sub>-ÃÂ receptor antagonist. In addition to its GABA<sub>A</sub>-ÃÂ receptor antagonism, iso-THIP shows much lower but still detectable affinity for the GABA<sub>A</sub> receptor, where it appears to be an antagonist similarly. The drug was first described in the scientific literature by Povl Krogsgaard-Larsen and colleagues by 1979.