Tandospirone

Tandospirone (Sediel), also known as metanopirone, is an anxiolytic and antidepressant used in China and Japan, where it is marketed by Dainippon Sumitomo Pharma. It is a member of the azapirone and piperazine chemical classes and is closely related to other agents like buspirone and gepirone.

Pharmacology
Tandospirone acts as a potent and selective 5-HT1A receptor partial agonist, with a Ki affinity value of 27 ± 5 nM and approximately 55-85% intrinsic activity. It has weak and clinically negligible affinity for the 5-HT2A (1,300 ± 200), 5-HT2C (2,600 ± 60), α1-adrenergic (1,600 ± 80), α2-adrenergic (1,900 ± 400), D1 (41,000 ± 10,000), and D2 (1,700 ± 300) receptors, and is essentially inactive at the 5-HT1B, 5-HT1D, β-adrenergic, and muscarinic acetylcholine receptors, serotonin transporter (SERT), and benzodiazepine (BDZ) allosteric site of the GABAA receptor (all of which are > 100,000). There is evidence of tandospirone having low but significant antagonistic activity at the α2-adrenergic receptor through its active metabolite 1-(2-pyrimidinyl)piperazine (1-PP), however.

Dosage
Tandospirone is typically used at a dose of 30 mg/daily taken in divided doses of 10 mg three times per day due to its short half-life. Though originally considered a relatively weak anxiolytic agent, a clinical study found that doubling the dose to 60 mg/daily resulted in a "remarkable anxiolytic effect with an early onset of action, and without significant adverse effects", as well as "excellent anxiolytic efficacy that is comparable to that of the benzodiazepines".

Side effects
Side effects of tandospirone and other 5-HT1A partial agonists are relatively mild and may include nausea, diarrhea, headache, dizziness, and restlessness.