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HelpTest Code HALO Haloperidol, Serum
Reporting Name
Haloperidol, SUseful For
Optimizing haloperidol dosage
Monitoring patient compliance
Assessing toxicity
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Draw blood immediately before next scheduled dose.
2. Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
Haloperidol:
5-17 ng/mL
Reduced Haloperidol:
10-80 ng/mL
Day(s) Performed
Tuesday
CPT Code Information
80173
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| HALO | Haloperidol, S | 87550-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 80339 | Haloperidol, S | 3669-9 |
| 169 | Reduced Haloperidol | 38364-6 |
Clinical Information
Haloperidol (Haldol) is a member of the butyrophenone class of neuroleptic drugs used to treat psychotic disorders (eg, schizophrenia). It is also used to control the tics and verbal utterances associated with Tourette syndrome and in the management of intensely hyperexcitable children who fail to respond to other treatment modalities.
The daily recommended oral dose for patients with moderate symptoms is 0.5 to 2.0 mg; for patients with severe symptoms, 3 to 5 mg may be used. However, some patients will respond only at significantly higher doses.
Haloperidol is metabolized in the liver to reduced haloperidol, its major metabolite.(1,2)
Use of haloperidol is associated with significant toxic side effects, the most serious of which include tardive dyskinesia, which can be irreversible, extrapyramidal reactions with Parkinson-like symptoms, and neuroleptic malignant syndrome. Less serious side effects can include hypotension, anticholinergic effects (blurred vision, dry mouth, constipation, urinary retention), and sedation. The risk of developing serious, irreversible side effects seems to increase with increasing cumulative doses over time.(1,3)
Interpretation
Studies show a strong relationship between dose and serum concentration(4); however, there is a modest relationship of clinical response or risk of developing long-term side effects to either dose or serum concentration.
A therapeutic window exists for haloperidol, but some patients may respond to concentrations outside of this range. Patients who respond at serum concentrations between 5 ng/mL and 17 ng/mL show no additional improvement at concentrations between 18 ng/mL and 20 ng/mL.(3,5) Some patients may respond at concentrations less than 5 ng/mL, and others may require concentrations significantly greater than 20 ng/mL before an adequate response is attained.
Due to interindividual variation, the serum concentration should only be used as one factor in determining the appropriate dose and must be interpreted in conjunction with the clinical status.
Although the metabolite, reduced haloperidol, has minimal pharmacologic activity, evidence has been presented suggesting that an elevated ratio of reduced haloperidol-to-haloperidol (ie, >5) is predictive of a poor clinical response.(3,6) A reduced haloperidol-to-haloperidol ratio of less than 0.5 indicates noncompliance; the metabolite does not accumulate except during steady-state conditions.
Cautions
Potentially interfering drugs include hydroxyzine (interferes with haloperidol), tiagabine (interferes with reduced haloperidol), and quetiapine (interferes with internal standard resulting in artificially low haloperidol).
Method Description
Haloperidol and reduced haloperidol, its major metabolite, are extracted from serum utilizing protein precipitation and diluted by the addition of internal standard (haloperidol-d4 and reduced haloperidol-d4). Analysis of the supernate is performed on a liquid chromatography tandem mass spectrometry system.(Unpublished Mayo method)