What is the proper dosage and usage of Thorazine (chlorpromazine)?

Chlorpromazine (Thorazine) Dosage and Usage Guidelines

The proper dosage of chlorpromazine (Thorazine) should be individualized based on the condition being treated, with initial doses starting at 25 mg three times daily for most adult psychiatric conditions, gradually increasing to an effective maintenance dose, typically 200-400 mg daily, while minimizing adverse effects. 1

Adult Dosing Guidelines

Psychiatric Disorders

• Initial dosage: 25 mg three times daily, gradually increasing until symptoms are controlled 1
• Maintenance dosage: 200 mg daily is typical, though some patients may require higher doses 1
• Maximum dosage: Up to 800 mg daily is not uncommon for hospitalized patients with acute schizophrenia or mania, though there is little therapeutic gain beyond 1000 mg daily 1

Hospitalized Patients with Acute Psychiatric Conditions

• Initial treatment often begins with injectable form until the patient is controlled 1
• Once stabilized (usually within 24-48 hours), transition to oral doses 1
• 500 mg daily is generally sufficient for most hospitalized patients 1
• Dosages should be lower in elderly, emaciated, or debilitated patients 1

Outpatient Management

• Less severe cases: 10 mg three or four times daily, or 25 mg twice or three times daily 1
• More severe cases: Begin with 25 mg three times daily, with increases of 20-50 mg at semi-weekly intervals 1

Non-Psychiatric Indications

• Nausea and vomiting: 10-25 mg every 4-6 hours as needed 1
• Presurgical apprehension: 25-50 mg, 2-3 hours before surgery 1
• Intractable hiccups: 25-50 mg three or four times daily 1
• Acute intermittent porphyria: 25-50 mg three or four times daily 1

Pediatric Dosing (6 months to 12 years)

• Important: Should generally not be used in children under 6 months except in potentially life-saving situations 1
• Severe behavioral problems (outpatient): 0.25 mg/lb body weight every 4-6 hours as needed 1
• Hospitalized patients: Start with low doses and increase gradually; in severe behavior disorders, 50-100 mg daily (older children may require 200 mg daily or more) 1
• Nausea and vomiting: 0.25 mg/lb body weight every 4-6 hours 1
• Presurgical apprehension: 0.25 mg/lb body weight 2-3 hours before operation 1

Special Populations

Elderly Patients

• Use lower dosages as elderly patients are more susceptible to hypotension and neuromuscular reactions 1
• Increase dosage more gradually 1
• Monitor response carefully and adjust dosage accordingly 1

Adverse Effects and Monitoring

Common Adverse Effects

• Extrapyramidal symptoms: More common at higher doses 2, 3
• QT interval prolongation: Monitor ECG, especially when combined with other QT-prolonging medications 4
• Orthostatic hypotension: Particularly concerning in elderly patients 4
• Anticholinergic effects: Dry mouth, constipation, urinary retention, blurred vision 4
• Sedation: May be beneficial or problematic depending on the clinical situation 4

Monitoring Requirements

• Cardiovascular: Monitor for QT prolongation, especially when combined with other QT-prolonging medications 4
• Neurological: Watch for extrapyramidal symptoms, tardive dyskinesia, and neuroleptic malignant syndrome 4
• Vital signs: Regular monitoring for orthostatic hypotension 4

Clinical Considerations and Precautions

• Drug interactions: Chlorpromazine may interact with many medications, including those that prolong QT interval 4
• Anticholinergic properties: May worsen conditions like glaucoma, prostatic hypertrophy, or constipation 4
• Sedation: Can be beneficial in agitated patients but may be problematic in other settings 4
• Palliative care use: Effective for terminal restlessness and dyspnea in advanced cancer at doses of 12.5-25 mg every 4-12 hours 5

Common Pitfalls to Avoid

• Excessive dosing: Higher doses increase risk of extrapyramidal symptoms without necessarily improving efficacy 2
• QT prolongation risk: Avoid combining with other QT-prolonging medications when possible 4
• Pediatric use: Carefully consider risks and benefits in children; use only when clearly indicated 6
• Anticholinergic burden: Be cautious when combining with other medications having anticholinergic properties 4
• Abrupt discontinuation: Gradually reduce dosage to avoid withdrawal symptoms 1

Route of Administration

• Oral: Most common for maintenance therapy 1
• Intramuscular: Useful for acute management when oral administration is not feasible 1
• Rectal: Alternative route when oral or parenteral routes are unavailable 4
• Intravenous: Used in specific circumstances, particularly in palliative care settings 5