Home Drug Guide Thioridazine Hydrochloride

Drug Guide

Generic Name

Thioridazine Hydrochloride

Brand Names Mellaril, Thioridazine Hydrochloride Intensol

Classification

Therapeutic: Antipsychotic, typical (first-generation)

Pharmacological: Phenothiazine antipsychotic

FDA Approved Indications

Schizophrenia

Mechanism of Action

Thioridazine blocks dopamine receptors (primarily D2) in the brain, thereby reducing psychotic symptoms. It also has anticholinergic, antihistaminic, and antiadrenergic properties.

Dosage and Administration

Adult: Initially 50-100 mg 2-3 times daily, titrated based on response and tolerability. Maintenance doses generally range from 100-300 mg daily, divided into 2-3 doses.

Pediatric: Use is not well established in pediatric patients; consult specific guidelines.

Geriatric: Start at lower doses, typically 25-50 mg daily, due to increased sensitivity and risk of adverse effects.

Renal Impairment: Use with caution; no specific adjustment, but monitor closely.

Hepatic Impairment: Use cautiously; monitor for increased effects or toxicity.

Pharmacokinetics

Absorption: Well absorbed from GI tract

Distribution: Widely distributed, crosses blood-brain barrier and placenta, enters breast milk

Metabolism: Primarily hepatic via CYP2D6 and other enzymes

Excretion: Metabolites excreted in urine and feces

Half Life: Approximately 12-20 hours, can be longer in elderly or hepatic impairment

Contraindications

Pigmentary retinopathy
Known hypersensitivity to phenothiazines

Precautions

Use cautiously in patients with cardiac disorders, history of seizures, or blood dyscrasias. Avoid in pregnancy unless clearly needed; utilize contraception during therapy. Monitor for neuroleptic malignant syndrome and significant changes in blood pressure.

Adverse Reactions - Common

Sedation (Common)
Dry mouth (Common)
Extrapyramidal symptoms (Common)
Orthostatic hypotension (Common)

Adverse Reactions - Serious

QT prolongation and risk of torsades de pointes (Serious; monitor EKG)
Neuroleptic malignant syndrome (Rare but serious)
Retinal pigmentary degeneration leading to vision loss (Rare; black box warning)

Drug-Drug Interactions

Other QT prolonging agents
CNS depressants
Anticholinergic drugs

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor for EPS, cardiac status, vision changes, and signs of NMS.

Diagnoses:

Risk for falls due to orthostatic hypotension
Risk for neuroleptic malignant syndrome
Impaired visual perception

Implementation: Administer with meals if GI upset occurs and monitor EKG during therapy.

Evaluation: Assess for therapeutic response and adverse effects regularly.

Patient/Family Teaching

Take medication exactly as prescribed and do not stop abruptly.
Report any vision changes, signs of movement disorders, or cardiac symptoms immediately.
Avoid alcohol and CNS depressants. Advise on sun protection due to photosensitivity.

Special Considerations

Black Box Warnings:

Retinal pigmentary degeneration leading to vision loss
QT prolongation which may lead to torsades de pointes

Genetic Factors: Metabolism primarily involves CYP2D6; poor metabolizers may require dose adjustments.

Lab Test Interference: May cause false-positive tests for ketones in urine.

Overdose Management

Signs/Symptoms: Severe hypotension, respiratory depression, extrapyramidal symptoms, coma, myocarditis, QT prolongation, arrhythmias.

Treatment: Supportive care, continuous cardiac monitoring, activated charcoal if ingestion recent, sedation with benzodiazepines for agitation, equipped resuscitation equipment for life-threatening arrhythmias.

Storage and Handling

Storage: Store at room temperature, away from light and moisture.

Stability: Stable under proper storage conditions for shelf life specified by manufacturer.