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Test Code LAB10390 Haloperidol, Serum

Reporting Name

Haloperidol, S

Useful For

Optimizing haloperidol dosage

 

Monitoring patient compliance

 

Assessing toxicity

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum Red


Specimen Required


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. Centrifuge and aliquot serum into plastic vial within 2 hours of collection.


Specimen Minimum Volume

0.3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reference Values

HALOPERIDOL:

5-16 ng/mL

 

REDUCED HALOPERIDOL:

10-80 ng/mL

Day(s) Performed

Tuesday

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

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 to 16 ng/mL show no additional improvement at concentrations greater than 16 to 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.

Method Description

Liquid-liquid extraction with liquid chromatography-tandem mass spectrometry detection.(Unpublished Mayo method)

Report Available

2 to 8 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.