What is the starting dose of Haldol (haloperidol) Decanoate and how to convert from oral haloperidol to injection?

Haloperidol Decanoate Starting Dose and Conversion from Oral Haloperidol

The recommended starting dose of haloperidol decanoate is 20 times the daily oral haloperidol dose, administered monthly by intramuscular injection. This conversion factor provides optimal therapeutic levels without requiring oral supplementation in most patients.

Conversion Algorithm from Oral to Depot Haloperidol

1. Calculate total daily oral haloperidol dose

   • Add up all oral doses taken in 24 hours

2. Multiply by conversion factor

   • Multiply daily oral dose by 20 to determine monthly depot dose
   • Example: 10 mg oral daily = 200 mg depot monthly

3. Administration schedule options:

   • Standard approach: Full monthly dose given as single IM injection
   • Loading dose approach: For rapid stabilization
     • Week 1: 50% of calculated monthly dose
     • Week 2: 50% of calculated monthly dose
     • Week 5 onward: Full monthly dose every 4 weeks

Dosage Considerations

Initial Dosage Range

• Moderate symptomatology: Based on oral dose of 0.5-2 mg BID/TID
• Severe symptomatology: Based on oral dose of 3-5 mg BID/TID
• Geriatric/debilitated patients: Based on oral dose of 0.5-2 mg BID/TID

Maximum Dose

• Do not exceed 300 mg monthly injection without specialist consultation
• FDA label indicates oral doses up to 100 mg daily may be necessary in resistant cases 1

Monitoring After Conversion

• Assess clinical response and side effects 2 weeks after first injection
• Plasma levels reach steady state after the second injection
• Expect plasma levels approximately twice as high as during oral treatment 2
• Monitor for extrapyramidal symptoms, though these may actually decrease after conversion

Clinical Pearls and Pitfalls

• Important safety consideration: Haloperidol decanoate is ONLY for IM administration, never for oral or IV use 3
• No oral supplementation is typically needed with the 20x conversion factor 4
• Antiparkinson medications can often be reduced or discontinued after conversion to depot 2
• Lower conversion factors (10-15x) may be appropriate for elderly or medically compromised patients
• Higher conversion factors may be needed for patients with high metabolism or poor response

Special Populations

• Elderly patients: Start with lower conversion factor (10-15x) and titrate as needed
• Patients with hepatic impairment: Use lower conversion factor due to decreased metabolism
• Treatment-resistant patients: May require higher doses, but always start with standard conversion and titrate up

The 20x conversion factor has been validated in multiple studies and provides therapeutic plasma levels by the third week of treatment 5, making it the most reliable approach for converting patients from oral to depot haloperidol therapy while maintaining symptom control and minimizing side effects.