Nurses Compass
Drug Guide
Thioridazine
Classification
Therapeutic: Antipsychotic
Pharmacological: Phenothiazine derivative (typical antipsychotic)
FDA Approved Indications
- Schizophrenia
- Severe behavioral disorders in psychiatric patients
Mechanism of Action
Thioridazine blocks dopamine D2 receptors in the central nervous system, reducing psychotic symptoms; it also has anticholinergic, antihistaminic, and alpha-adrenergic blocking properties.
Dosage and Administration
Adult: Initial: 50-100 mg twice daily. Dose may be increased gradually based on response and tolerability; usual range: 150-800 mg/day divided into multiple doses.
Pediatric: Not typically recommended due to safety concerns.
Geriatric: Lower initial doses are recommended due to increased sensitivity and risk of side effects.
Renal Impairment: Use caution; no specific adjustment data available, monitor closely.
Hepatic Impairment: Use caution; dose adjustments may be necessary, monitor liver function.
Pharmacokinetics
Absorption: Well absorbed orally.
Distribution: Widely distributed, crosses the blood-brain barrier; about 60-80% protein-bound.
Metabolism: Metabolized mainly in the liver via CYP2D6 and CYP3A4 enzymes.
Excretion: Metabolites excreted in urine and feces.
Half Life: Approximately 20-24 hours, allowing for once or twice daily dosing.
Contraindications
- Concurrent use of MAO inhibitors
- Known hypersensitivity to phenothiazines
- Comgrave cardiac conduction abnormalities (e.g., QT prolongation)
Precautions
- History of cardiac arrhythmias
- History of seizure disorders
- Peripheral circulatory problems
- Pregnancy category B (use only if clearly needed), lactation: may pass into breast milk
- Elderly patients with dementia-related psychosis treated with antipsychotics may have increased mortality
Adverse Reactions - Common
- Sedation (Common)
- Dizziness (Common)
- Dry mouth (Common)
- Blurred vision (Common)
- Weight gain (Common)
Adverse Reactions - Serious
- QT prolongation / Torsades de Pointes (Rare)
- Neuroleptic Malignant Syndrome (Rare)
- Retinal pigmentation and visual disturbances (Rare)
- Seizures (Rare)
- Blood dyscrasias (Rare)
Drug-Drug Interactions
- Other medications prolonging QT interval (e.g., amiodarone, quinidine)
- CNS depressants (additive sedation)
- CYP450 inhibitors or inducers (altering thioridazine levels)
Drug-Food Interactions
- Alcohol (enhanced sedation and risk of hypotension)
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor cardiac status (ECG) before and during therapy, assess mental status, check for EPS (extrapyramidal symptoms).
Diagnoses:
- Risk for cardiac arrhythmias
- Altered mental status
- Risk for falls
Implementation: Administer with meals to decrease nausea, monitor for side effects, educate patient on avoiding alcohol and driving if sedated.
Evaluation: Assess for reduction in psychotic symptoms, monitor for adverse effects, especially cardiac.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report any signs of dizziness, fainting, or irregular heartbeat.
- Avoid alcohol and other sedatives.
- Inform healthcare provider about all other medications.
- Regular ECG monitoring may be required.
Special Considerations
Black Box Warnings:
- Increased mortality in elderly patients with dementia-related psychosis.
Genetic Factors: CYP2D6 poor metabolizers may have increased plasma levels, consider dose adjustment.
Lab Test Interference: May cause false-positive results for catecholamine levels.
Overdose Management
Signs/Symptoms: Sedation, hypotension, tachycardia, dry mouth, diffuse ECG changes including QT prolongation, seizures.
Treatment: Supportive care, activated charcoal if early, cardiac monitoring, magnesium sulfate for torsades, advanced cardiac life support as needed.
Storage and Handling
Storage: Store at room temperature, protected from light and moisture.
Stability: Stable for the duration of the labeled expiry date.