Thiothixene API is a synthetic thioxanthene antipsychotic used primarily in the management of schizophrenia and other psychotic disorders. It is a dopamine-receptor antagonist and belongs to the conventional or first-generation antipsychotic class. The FDA-approved capsule labeling identifies thiothixene as the cis (Z) isomer of N,N-dimethyl-9-[3-(4-methyl-1-piperazinyl)propylidene]thioxanthene-2-sulfonamide.
Thiothixene has the molecular formula C₂₃H₂₉N₃O₂S₂ and molecular weight 443.63 g/mol. FDA GSRS identifies the substance as achiral with one E/Z center, while the pharmaceutical substance is specifically the Z/cis isomer.
The substance has a USP-NF monograph, which provides authoritative controls for assay, identification, melting range, loss on drying and residue on ignition. The current USP material also specifically controls (E)-thiothixene, reflecting the importance of geometric isomeric purity.
Thiothixene is also known as tiotixene and is marketed historically under the brand name Navane. PubChem lists CAS identifiers 3313-26-6 and 5591-45-7 for thiothixene records, with FDA GSRS identifying UNII 7318FJ13YJ for thiothixene.
The API should be distinguished from Thiothixene Hydrochloride, which is a separate salt form. USP identifies Thiothixene Hydrochloride as the dihydrochloride dihydrate or anhydrous form, with molecular weight 552.58 for the dihydrate and 516.56 for the anhydrous material.
FDA and USP identify the pharmaceutical substance as the Z/cis form.
Thiothixene exerts its antipsychotic activity principally through dopamine receptor antagonism, particularly involving central dopaminergic pathways. Its pharmacological profile is characteristic of conventional thioxanthene antipsychotics.
The FDA labeling identifies thiothixene as a thioxanthene derivative and describes its pharmacological action in the context of conventional antipsychotic therapy.
Thiothixene is indicated for the management of schizophrenia. The FDA-approved labeling states that thiothixene is effective in the treatment of patients with schizophrenia and provides oral capsule strengths of 1 mg, 2 mg, 5 mg and 10 mg.
The API is therefore primarily relevant to pharmaceutical formulations intended for conventional antipsychotic treatment.
Thiothixene is particularly suitable for pharmacopoeial quality control because the USP-NF monograph establishes defined acceptance criteria.
The current USP information specifies:
USP has subsequently proposed changes replacing the separate assay and (E)-thiothixene procedures with an LC procedure covering assay and organic impurities, and removing the selenium test because elemental impurities are to be controlled using the risk-based approach of USP <232>.
Therefore, for a CMS page intended to represent USP 2025/current specifications, it is important to distinguish the published USP acceptance criteria from the proposed/current revision status rather than combining values from different monograph versions.
Thiothixene is a synthetic small-molecule API produced through controlled chemical synthesis, purification and crystallization. Because the marketed pharmaceutical substance is the Z/cis isomer, control of the corresponding E/trans isomer is an important quality attribute.
A qualified Thiothixene API Manufacturer in India should maintain appropriate controls for chemical identity, assay, geometric isomeric purity, drying loss, inorganic residue and process-related impurities.
Thiothixene is a crystalline solid. Published reference data report a melting range of approximately 147–152°C for cis/Z-thiothixene, consistent with the USP melting range of 147–153.5°C.
The free-base API is practically insoluble in water and has been reported as very soluble in chloroform and slightly soluble in methanol and acetone.
The hydrochloride salt has substantially different aqueous-solubility characteristics and should not be confused with the free-base API.
USP specifies that Thiothixene should be preserved in tight, light-resistant containers.
Bulk API packaging should therefore protect the material from light, moisture and contamination, with storage conditions established through the applicable stability program.
A professional Thiothixene API supply package may include:
A reliable Thiothixene API Manufacturer in India should provide consistent pharmaceutical-grade material supported by validated analytical methods and appropriate geometric-isomer controls. The USP monograph's specific control of (E)-thiothixene makes isomeric purity an especially important consideration for API quality.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 96.0–101.5% |
| Loss on Drying | NMT 2.0% |
| Residue on Ignition | NMT 0.2% |
| Water Content | NMT 2.0% |
| Melting Point | 147–153.5°C |