What is the conversion from oral Haloperidol (Haldol) to Haloperidol Decanoate (Haldol Decanoate)?

Conversion of Oral Haloperidol to Haloperidol Decanoate

The recommended conversion ratio from oral haloperidol to haloperidol decanoate is 10:1 to 15:1, meaning that the monthly haloperidol decanoate dose should be 10-15 times the daily oral haloperidol dose. 1

Conversion Algorithm

1. Calculate the total daily oral haloperidol dose
2. Multiply by 10-15 to determine the appropriate monthly haloperidol decanoate dose
3. Consider using a loading dose strategy for initial conversion

Detailed Conversion Process

• The average conversion ratio from daily oral haloperidol to monthly intramuscular haloperidol decanoate is 14.1:1 (range 9.4:1 to 15:1) 1
• For example, a patient taking 10mg oral haloperidol daily would require approximately 100-150mg of haloperidol decanoate every 4 weeks 1
• When converting, plasma concentration data shows that haloperidol decanoate provides lower peak plasma concentrations but more stable levels compared to oral administration 1

Loading Dose Strategy

• A loading dose strategy can be used when initiating haloperidol decanoate to rapidly achieve therapeutic levels 2
• This approach involves administering approximately 20 times the daily oral dose in divided injections during the first two weeks 2
• The dose can then be gradually reduced to approximately 10 times the oral dose by the third and fourth months 2
• This strategy has been shown to maintain therapeutic response without requiring supplemental oral medication 2

Alternative Approach

• Another effective method is to administer double the calculated monthly dose for the first injection, followed by the standard calculated dose for subsequent injections 3
• This approach helps achieve relatively stable plasma levels with the first injection that correspond to those observed with oral medication 3

Clinical Considerations

• Extrapyramidal side effects may initially increase during the first two months of conversion but typically become less pronounced by the third month compared to oral administration 3
• The depot formulation offers several advantages over oral haloperidol including better compliance, more predictable absorption, more controlled plasma concentrations, and fewer extrapyramidal side effects 4
• Careful monitoring during the transition period is essential to ensure therapeutic efficacy and manage potential side effects 2

Practical Example

For a patient taking 10mg oral haloperidol daily:

• Standard conversion: 10mg × 10-15 = 100-150mg haloperidol decanoate monthly 1
• Loading dose strategy: Initial dose of approximately 200mg (20 × 10mg) divided over the first two weeks, then gradually reducing to 100mg monthly 2
• Alternative approach: First injection of 200-300mg, followed by maintenance doses of 100-150mg monthly 3