THIOTHIXENE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for THIOTHIXENE (THIOTHIXENE).
Thiothixene is a typical antipsychotic that blocks postsynaptic dopamine D1 and D2 receptors in the brain. It also has alpha-adrenergic and histamine H1 blocking activity, with minimal anticholinergic effects.
| Metabolism | Extensively metabolized in the liver primarily via CYP2D6 and CYP3A4. Minor pathways include CYP1A2 and CYP2C19. |
| Excretion | Primarily renal: 65-70% as metabolites, <1% unchanged. Fecal: 15-20% via biliary elimination. |
| Half-life | Terminal half-life: 10-20 hours (mean ~14 h). Clinical context: Steady-state achieved in ~2-3 days; allows once-daily dosing for maintenance. |
| Protein binding | ~90% bound to plasma proteins (albumin and alpha-1-acid glycoprotein). |
| Volume of Distribution | 10-20 L/kg; indicates extensive tissue distribution, including brain penetration. |
| Bioavailability | Oral: ~88%; IM: 100%. |
| Onset of Action | Oral: 1-2 hours for initial sedation; antipsychotic effect days to weeks. Intramuscular: 30-60 minutes for acute behavioral control. |
| Duration of Action | Oral: 12-24 hours; antipsychotic effect persists with regular dosing. Intramuscular: 12-24 hours for sedative effects. |
| Molecular Weight | 331.4 |
Initial: 2 mg orally three times daily; maintenance: 5-30 mg/day orally in divided doses; maximum: 60 mg/day. IM: 4 mg 2-4 times daily; maximum 30 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | No specific guidelines; use caution with severe impairment (GFR <10 mL/min) and consider dose reduction. |
| Liver impairment | Contraindicated in severe hepatic disease; in mild-moderate impairment, reduce dose by 50% and titrate slowly. |
| Pediatric use | Not recommended for children under 12 years; for adolescents, initial 2 mg three times daily, increase gradually to 10-30 mg/day in divided doses. |
| Geriatric use | Initial dose 1-2 mg once or twice daily; increase slowly due to increased sensitivity to anticholinergic and extrapyramidal effects; maximum 15 mg/day. |
| 1st trimester | Limited human data; animal studies show risk. Use only if potential benefit justifies potential risk to fetus. May cause extrapyramidal symptoms or withdrawal in neonates. |
| 2nd trimester | Limited human data; animal studies show risk. Use only if potential benefit justifies potential risk to fetus. Monitor for maternal hypotension and sedative effects. |
| 3rd trimester | Avoid during third trimester due to risk of neonatal extrapyramidal symptoms, withdrawal, and respiratory depression. Use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for THIOTHIXENE (THIOTHIXENE).
| Placental transfer | Crosses placenta; detected in cord serum at concentrations 50-100% of maternal serum levels. |
| Breastfeeding | Excreted into breast milk in low amounts; manufacturer advises caution due to potential for adverse effects in infants. Monitor for sedation, feeding difficulties, and extrapyramidal symptoms. Consider risk-benefit. |
■ FDA Black Box Warning
Elderly patients with dementia-related psychosis treated with antipsychotic drugs are at an increased risk of death. Thiothixene is not approved for the treatment of dementia-related psychosis.
| Serious Effects |
Hypersensitivity to thiothixene or any componentComatose statesCNS depression (e.g., barbiturates, alcohol)Blood dyscrasias (e.g., leukopenia, agranulocytosis)Severe hepatic disease
| Precautions | Neuroleptic Malignant Syndrome (NMS): Potentially fatal, characterized by hyperthermia, muscle rigidity, autonomic instability, and altered mental status., Tardive Dyskinesia: A syndrome of potentially irreversible, involuntary dyskinetic movements., QT Prolongation: Risk of torsades de pointes, especially in patients with electrolyte imbalances or those on other QT-prolonging drugs., Seizures: May lower seizure threshold; use with caution in patients with a history of seizures., Leukopenia/Neutropenia: Risk of agranulocytosis; monitor CBCs if signs of infection occur. |
| Food/Dietary | Avoid excessive consumption of caffeine or tobacco, as they can alter thiothixene metabolism. No specific food interactions; maintain a balanced diet. Grapefruit juice has not been reported to interact, but caution with any CYP1A2 substrates. |
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| Lactation Rating | L3 - Limited Data |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Limited human data; animal studies show fetal toxicity (decreased fetal weight, skeletal variations) at high doses; risk of neural tube defects cannot be excluded. Second/third trimester: Exposure may cause extrapyramidal symptoms (EPS) or withdrawal in neonates; risk of gestational diabetes, hypertension, and preterm birth. No systematic studies in pregnant women. |
| Fetal Monitoring | Monitor maternal blood pressure, blood glucose, weight gain, and drug levels (if available). Fetal monitoring: serial ultrasound for growth and anomalies; neonatal monitoring for EPS, jaundice, and withdrawal symptoms (hypertonicity, tremors) after delivery. |
| Fertility Effects | May cause hyperprolactinemia, leading to menstrual irregularities, anovulation, and reduced libido in women; men may experience impotence or gynecomastia. Reversible upon dose reduction or discontinuation. No direct impairment of spermatogenesis or oogenesis. |
| Clinical Pearls | Thiothixene is a typical antipsychotic with high potency and a high risk of extrapyramidal symptoms (EPS), especially akathisia and dystonia. Use the lowest effective dose to minimize EPS. It is metabolized by CYP1A2, so smoking increases clearance; monitor dose adjustments. Avoid concurrent use with other drugs that prolong QTc interval. Monitor for neuroleptic malignant syndrome (NMS) and tardive dyskinesia. |
| Patient Advice | Take this medication exactly as prescribed, do not stop abruptly. · Report any involuntary muscle movements, restlessness, or stiffness to your doctor. · Avoid driving or operating heavy machinery until you know how this drug affects you. · Avoid alcohol and other central nervous system depressants. · Rise slowly from sitting or lying down to prevent dizziness. · Contact your doctor if you experience fever, confusion, or stiff muscles (signs of NMS). · Use sun protection, as this medication may increase sensitivity to sunlight. |