title: The photochemical stability of cis- and trans-isomers of tricyclic neuroleptic drugs.
abstract: The irradiation of the tranquillizers flupenthixol, clopenthixol and chlorprothixene has been found to induce rapid cis-trans isomerization. The composition of the photosatitionary mixture is not that of the batch drug and hence this process may affect the activity. Further decomposition to a thioxanthone derivative occurs rapidly in the presence of air. Exclusion of oxygen, however, does not prevent further degradation and a slower secondary isomerization is observed on prolonged irradiation. Doxepin and dothiepin also undergo analogous reactions but the isomerizations are much slower and the oxidative degradation yields many products.
mesh_terms: D000929:Antidepressive Agents, Tricyclic / Q000032:analysis / Q000528:radiation effects; D014150:Antipsychotic Agents / Q000032:analysis / Q000528:radiation effects*; D004355:Drug Stability; D010777:Photochemistry; D013237:Stereoisomerism
chemical_list: D000929:Antidepressive Agents, Tricyclic; D014150:Antipsychotic Agents