A fixed-dose combination of a typical antipsychotic (phenothiazine derivative) and an anticholinergic agent. Trifluoperazine is a high-potency antipsychotic used to manage psychotic disorders, while Trihexyphenidyl is added to counteract extrapyramidal symptoms (EPS) induced by the antipsychotic. This combination is primarily used in the management of schizophrenia and other psychotic disorders where EPS is a significant concern.
Adult: Initially: 1 tablet (5mg+2mg) once or twice daily. Usual maintenance: 2-4 tablets daily in divided doses. Maximum antipsychotic dose should not exceed 40mg trifluoperazine per day. The anticholinergic dose is fixed; additional trihexyphenidyl may be needed in some cases.
Note: Administer orally with or after food to minimize gastric upset. Tablet can be taken with a full glass of water. Do not crush or chew unless advised. Avoid abrupt discontinuation.
Trifluoperazine exerts its antipsychotic effect primarily through potent antagonism of postsynaptic dopaminergic D2 receptors in the mesolimbic pathway of the brain. Trihexyphenidyl competitively blocks central muscarinic acetylcholine receptors (M1), correcting the dopamine-acetylcholine imbalance in the nigrostriatal pathway caused by D2 blockade, thereby reducing or preventing extrapyramidal symptoms.
Pregnancy: Category C (US FDA). Not recommended unless potential benefit outweighs risk. Phenothiazines cross placenta. Risk of extrapyramidal symptoms and withdrawal in neonate. Use only if clearly needed.
Driving: ADVISE NOT TO DRIVE. Causes drowsiness, dizziness, blurred vision, and can impair cognitive and motor functions, especially during initial treatment or dose changes.
| Other CNS Depressants (Alcohol, Opioids, Benzodiazepines) | Additive CNS depression, respiratory depression, sedation | Major |
| Anticholinergics (Atropine, Antihistamines, TCAs) | Additive anticholinergic toxicity (hyperthermia, delirium, ileus) | Major |
| Levodopa, Dopamine Agonists | Mutual antagonism; reduced efficacy of both | Major |
| QT-prolonging drugs (Class IA/III antiarrhythmics, Macrolides, Fluoroquinolones) | Increased risk of torsades de pointes | Major |
| Enzyme Inducers (Phenobarbital, Carbamazepine, Rifampicin) | Reduced plasma levels of both components | Moderate |
| Enzyme Inhibitors (Fluoxetine, Paroxetine, Fluvoxamine - CYP2D6/1A2 inhibitors) | Increased plasma levels of trifluoperazine, risk of toxicity | Moderate |
| Antihypertensives | Potentiated hypotension | Moderate |
| Metoclopramide, Prochlorperazine | Increased risk of EPS | Moderate |
Same composition (Trifluoperazine (5mg) + Trihexyphenidyl (2mg)), different brands: